biodegradable nanoparticles thesis

Biodegradable Nanoparticles: A Recent Approach and Applications

Affiliation.

• 1 Department of Pharmaceutics, Faculty of Pharmacy, Parul institute of Pharmacy, Parul University P.O.Limda, Ta.Waghodia, Vadodara, Gujarat 391760 Gujarat, India.
• PMID: 32938346
• DOI: 10.2174/1389450121666200916091659

Biodegradable nanoparticles (NPs) are the novel carriers for the administration of drug molecules. Biodegradable nanoparticles have become popular recently because of their special features such as targeted delivery of drugs, improved bioavailability, and better therapeutic effectiveness to administer the drug at a constant rate. Polymeric NPs are very small-sized polymeric colloidal elements in which a drug of interest may be encapsulated or incorporated in their polymeric network or conjugated or adsorbed on the layer. Various polymers are employed in the manufacturing of nanoparticles, some of the frequently employed polymers are agents, chitosan, cellulose, gelatin, gliadin, polylactic acid, polylactic-co-glycolic acid, and pullulan. Nanoparticles have been progressively explored for the delivery of targeted ARVs to cells of HIV-infected and have performed the prolonged kinetic release. Drug embedded in this system can give better effectiveness, diminished resistance of drugs, reduction in systemic toxicity and symptoms, and also enhanced patient compliance. The present review highlights the frequently employed manufacturing methods for biodegradable nanoparticles, various polymers used, and its application in anti-retroviral therapy. Also, common evaluation parameters to check the purity of nanoparticles, ongoing and recently concluded clinical trials and patents filled by the various researchers, and the future implication of biodegradable NPs in an innovative drug delivery system are described. The biodegradable NPs are promising systems for the administration of a broad variety of drugs including anti-retroviral drugs, and hence biodegradable nanoparticles can be employed in the future for the treatment of several diseases and disorders.

Keywords: Anti-Retroviral therapy; biodegradable nanoparticles; clinical study; future implication; manufacturing methods; patents; polymers employed.

Copyright© Bentham Science Publishers; For any queries, please email at [email protected].

Publication types

• Research Support, Non-U.S. Gov't
• Acquired Immunodeficiency Syndrome / drug therapy
• Biodegradable Plastics / chemistry*
• Biodegradable Plastics / metabolism
• Biodegradable Plastics / therapeutic use*
• Clinical Trials as Topic
• Drug Delivery Systems / methods
• Nanoparticles / chemistry*
• Nanoparticles / metabolism
• Polymers / chemistry
• Polymers / therapeutic use
• Surface-Active Agents / chemistry
• Surface-Active Agents / therapeutic use
• Biodegradable Plastics
• Surface-Active Agents

Grants and funding

• 6-180/RIFD/RPS(POLICY-1)}/2018-19/AICTE RPS

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• Review Article
• Open access
• Published: 19 August 2022

Recent advances in biodegradable polymers for sustainable applications

• Aya Samir 1 ,
• Fatma H. Ashour 1 ,
• A. A. Abdel Hakim 2 &
• Mohamed Bassyouni   ORCID: orcid.org/0000-0002-8711-6019 3 , 4  

npj Materials Degradation volume  6 , Article number:  68 ( 2022 ) Cite this article

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• Pollution remediation

The interest in producing biodegradable polymers by chemical treatment, microorganisms and enzymes has increased to make it easier to dispose after the end of its use without harming the environment. Biodegradable polymers reported a set of issues on their way to becoming effective materials. In this article, biodegradable polymers, treatment, composites, blending and modeling are studied. Environmental fate and assessment of biodegradable polymers are discussed in detail. The forensic engineering of biodegradable polymers and understanding of the relationships between their structure, properties, and behavior before, during, and after practical applications are investigated.

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Introduction.

Disposal of plastic wastes is a serious environmental problem that we face today. Mass production and increased use of plastics in wide applications in our daily life 1 , 2 have resulted in environmental impact. Consequently, these issues lead to the growing threat of global warming resulting from carbon dioxide emission due to burning of non-biodegradable conventional polymers such as polyethylene, polypropylene, and polyvinylchloride 3 . Biodegradable polymers are being developed to be used as an alternative for non-biodegradable polymer materials in a variety of applications 4 . The best option for managing non-biodegradable plastic waste is to replace the use of uneconomical non-biodegradable materials for recycling or reuse with biodegradable polymers as they are environmentally friendly 5 . Because of the environmental pollution resulting from the use of non-biodegradable materials, studies and developments have increased about biodegradable materials 6 .

Biodegradable polymers are materials that can work for a limited time before degrading into readily discarded products through a regulated procedure 7 . They might be made from a variety of wastes or/and bioresources, such as wastes of food, animal, agro-waste as well as other sources such as starch, and cellulose. Bioplastics made from renewable resources are often less expensive than those made from microbial resources prompting producers to concentrate on making bioplastics from renewable resources 8 . The use of biodegradable polymers has environmental benefits such as regeneration of raw materials, biodegradation and reduction of carbon dioxide emissions that are led to global warming 9 . Microorganisms such as bacteria and fungus may consume biodegradable polymers and convert them to H 2 O, CO 2 , and methane. The biodegradation process depends on the material’s composition 10 . The polymer morphology, polymer structure, chemical and radiation treatments, and polymer molecular weight are all parameters that influence the biodegradation process 11 . Biodegradable polymers are also called biopolymers 12 . There are two reasons to use the polymers from renewable resources; (i) environmental concerns in terms of increasing plastic waste and global warming as a result of releasing of carbon dioxide when burning waste, and (ii) petroleum resources are limited and ended 11 .

The biodegradable plastics industry is highly promising. However, they need to be developed in tandem thorough examination of end-of-life processes of treatment and a worldwide integration with organic management of waste as selective biowaste collection expands. Biodegradable plastics have the benefit of being able to be handled biologically at the end of their lives (composting or anaerobic digestion). Composting of biodegradable plastics is thoroughly documented and recognized on a global scale. Product’s biodegradability can be conducted under home or industrial composting conditions. In the absence of oxygen, anaerobic digestion transforms organic waste into biogas (a mixture of CO 2 and CH 4 ), which may then be additionally valorized through heat and power generation 13 . Developing alternative and targeted waste management solutions are also a major challenge to encourage the integration of biopolymers into the circular economy 14 . Biodegradable polymers may be categorized in step with their origin 11 . To manage non-degradable waste and reduce its accumulation in the environment, biodegradable materials have been replaced nonbiodegradable materials in several uses such as plastic bags and packaging. In the field of human health care, biodegradable polymers are also used in various vital applications like soft tissue engineering, gene therapy and soft tissue engineering 15 .

The required properties and performance can be provided at a reasonable cost by mixing the matrix of polymers with natural fibers to form natural fiber-reinforced composites (NFRCs). Natural fibers can provide many environmental and economic advantages including being renewable and accessible in large quantities and reduce the cost of raw materials. They can be recycled, biodegradable, achieve a large stiffness to weight ratio and high thermal insulation. Natural fibers are as inexpensive as synthetic fibers such as carbon and glass fibers. Producing 1 tonne of continuous filament glass fiber products from raw materials for factory export emits between 1.4 and 2.2 tonnes CO 2 -eq, with an average of 1.8 tonnes CO 2 -eq. Compared to natural fibers which emit between 0.3 and 0.7 tonnes of CO 2 -eq per tonne of natural fiber 16 . Natural fibers may be categorized in step with their origin into plant fibers such as flax and cotton. Animal fibers can be extracted from wool and hair. Mineral fibers consist of silicates such as asbestos, inosilicates, and clay 17 , 18 . Although mineral fibers are obtained from nature, they are non-renewable materials 17 . Because of the hydrophobic polymers character and hydrophilic character of the natural fibers, the compatibility between them is very low and a major challenge 19 . Therefore, many techniques are applied to treat and modify the natural fiber surfaces to decrease absorption of moisture and enhance adhesion to the matrix of polymers. These treatments can be chemical, physical, or biological treatments. There are many factors that affect the changes in the chemical composition, properties, and structural aspects of fibers such as the origin of growth, the age of the fiber plant, climatic conditions, and different extraction patterns 17 . For clarification, some properties and chemical composition of several fibers will be mentioned in this research.

In this article some properties of biodegradable polymers, natural fibers, and biocomposites were defined. These properties include mechanical properties, thermal properties, visco-elastic behavior, acoustic properties, surface morphology and chemical composition of materials. The thermal properties of materials were examined by using thermal gravimetric analysis. The visco-elastic behavior was reported using dynamic mechanical analysis. The chemical composition of the composite and the functional groups which are responsible for the reaction within natural fibers and provide information about covalent bonding were identified by using Fourier-transform infrared spectroscopy.

Synthetic polymers have become necessary for several applications in daily life. They are non-biodegradable materials, so they accumulate in the environment causing serious problems. Biodegradable polymers are now gaining attention as an alternative to conventional polymers. Biodegradable polymers are materials that can be degraded naturally by the action of microorganisms producing eco-friendly and useful materials such as CO 2 and CH 4 . Blending two or more biopolymers and mixing with natural fibers surface modification are used to improve the mechanical and physical properties of biodegradable polymers. Biopolymers can be used in a wide range of applications such as plastic bags, parts for automotive and medical applications. Biodegradable materials have the advantage of being able to be composted with organic waste or utilized to generate biomass at the end of usage of these materials. Also, biodegradable materials can be recycled to produce useful monomers and oligomers by microorganisms and use to produce the origin products. Biopolymer failures have been explained according to forensic engineering to try to avoid or reduce these failures during the manufacture and use.

Definition of biodegradation

The biodegradation of biodegradable polymers is defined as chemical decomposition of substances, which is accomplished through the enzymatic work of microorganisms that lead to a change in chemical composition, mechanical and structural properties and forming metabolic products, which are environmentally friendly materials such as methane, water and biomass and carbon dioxide. Figure 1 shows biodegradation steps of polymers 3 . Extracellular enzymes and abiotic agents such as oxidation, photo-degradation, and hydrolysis depolymerize long-chain polymers and create shorter chains (oligomers) in the first stage 20 , 21 . The biomineralization process, in which oligomers are bio-assimilated by microorganisms and then mineralized, is the second stage. Either aerobic and anaerobic degradation can occur. Aerobic degradation takes place in the presence of oxygen producing CO 2 , H 2 O, biomass and residue. Anaerobic degradation is carried out in absence of oxygen producing CO 2 , H 2 O, CH 4 , biomass and residue 20 .

Biodegradation steps of polymers.

Factors affecting biodegradation

The biodegradation process is affected by various factors including polymer morphology, structure, chemical treatment and molecular weight. (1) Polymer structure: biodegradable polymers have hydrolyzable linkages along the chain of polymer that are exposed to degradation in the presence of microorganisms and hydrolytic enzymes. Polymers with both hydrophobic and hydrophilic structures are more degradable than polymers containing either hydrophobic or hydrophilic structures 11 . (2) Polymer morphology: enzymes attack the amorphous regions in polymers easily than crystalline regions as amorphous regions molecules are far apart from each other which makes it susceptible to degradation. The enzymatic degradation of polymers is also affected by the melting temperature ( T m ) of polymers. Biodegradation of polymers decreases by increasing the melting point of polymers 22 .

Where, ΔH is the enthalpy changes on melting and and ΔS is the entropy changes on melting 22 . (3) Radiation and chemical treatments: cleavage and crosslinking of polymers caused by radicals and/or ions produced by photolysis of polymers with UV and γ-rays irradiation. Oxidation additionally takes place complicating the situation that changes the polymer’s capability for biodegradation 11 . (4) Molecular weight: the biodegradability of the polymer reduces as the polymer molecular weight increases 22 .

Biodegradable polymers

The environment suffers from serious problems from the increasing difficulties of disposing of plastic waste that resist microbial degradation 23 . Therefore, the researchers tried to produce biodegradable, non-polluting, and environmentally friendly materials 24 . In recent times, the natural and synthetic origin of biodegradable polymers was produced with good compatibility and biodegradability 11 . As the biodegradable polymers receive great attention because they degrade into non-toxic and environmentally friendly materials 24 . Mechanical strength, thermal and electrical properties of common biodegradable polymers and their composites are shown in Fig. 2a–c . Polyglycolide (polyglycolic acid, PGA) has high tensile strength (70–117 MPa). Thermoplastic starch showed low tensile strength (16–22 MPa).

a Density vs. tensile strength. b Themal expansion vs. electrical resistivity. c Young’s modulus vs. melting temperature.

Polylactide (PLA)—glass fiber composites have high electrical resistivity (2.5 × 10 22 –4.9 × 10 22 ) µohm.cm as shown in Fig. 2b . Melting temperature of biodegradable polymers is variant. Polyglycolide has high melting temperature (220–231 °C) and high Young’s modulus (6.1–7.2 GPa) as shown in Fig. 2c .

Classification of biodegradable polymers

Biodegradable polymers may be categorized based on their origin and synthesis method, their chemical composition, economic importance, processing method and applications. They are categorized in this study based on their origin 24 . Biodegradable polymers are classified into two groups based on their origin as indicated in Fig. 3 . Natural biopolymers and synthetic biopolymers are made from natural resources and oil, respectively 11 , 18 . Natural biopolymers are derived from renewable or biological sources such as animal, plant, marine, and microbial sources, while synthetic biodegradable polymers are manufactured chemically 25 .

Schematic shows biodegradable polymers classification based on their origin and method of production.

Natural biodegradable polymers

All organisms’ growth cycles result in the formation of biopolymers in nature. Polymerization reactions with a chain of enzyme-catalyzed growth from active monomers generated within cells through complicated metabolic processes are included in its production 23 . They are naturally biodegradable and have good biocompatibility 26 .

Biopolymers directly extracted from biomass

Agricultural waste is a major source for the production of bioplastics, plasticizers and antioxidant additives. The main source of polysaccharides is plant-based agricultural waste where biopolymers such as cellulose, starch, and pectin are produced 27 , 28 . The use of agro-waste as a feedstock for biodegradable polymer synthesis can reduce both the cost of producing biodegradable polymers and the waste treatment cost. Biopolymers are produced through several methods, namely microbial methods, blending of biopolymers, and chemical methods 27 . Biopolymers produced from agricultural plant waste have biodegradability, bio-functionality, biostability, and biocompatibility. They have wide range of chemical and mechanical properties that may be employed in several applications such as food packaging, biomedical applications, skincare, electrical electronics, vehicles and wastewater treatment 28 .

Polysaccharides

Polysaccharides, proteins, and lipids are found in numerous applications in biodegradable products. Potatoes, corn, and rice are basic sources of starch production, where the chemical composition and granules size of starch varies according to the source of production 11 . As shown in Fig. 4a , starch is a combination of linear (amylose) and branching (amylopectin) poly-(1,4) -α-glucose 29 . The ratio of amylose to amylopectin has a substantial impact on the physicochemical characteristics of starch 30 . Starch has poor mechanical properties, low impact resistance, water sensitivity, and brittleness properties. The properties can be improved by reinforcing the starch matrix with fibers or modifying the starch chemically or physically with other biodegradable polymers to enhance its properties 24 , 31 . Starch is not completely soluble in water. It is partially soluble in water at room temperature, depending on the proportions of amylose and amylopectin 32 , 33 , 34 . There are many advantages to starch biopolymers, such as high biodegradation, renewability, and good oxygen barrier properties that make them suitable in some commercial applications such as packaging applications, bags, cosmetics, adhesives, medical applications, and agricultural mulch films 3 , 30 , 35 .One of the most common biopolymers is cellulose 29 . It contains reactive OH groups in the backbone 31 . Cellulose is a polysaccharide with a molecular structure that is similar to starch. However, d-glucose units are attached to β-glycosidic bonds in cellulose. In starch, d-glucose units are linked to -α-glycosidic bonds. As illustrated in Fig. 4b , cellulose consists of polymer chains made up of unbranched β (1 → 4) connected D-glucopyranosyl units 29 . Cellulose is the primary component of lignocellulosic plant cell walls. Hemicellulose, lignin, and other carbohydrate polymers are components of a gel matrix embedded with cellulose which exists in the lignocellulosic materials 11 . Cellulose and cellulose derivatives are ecologically friendly materials that are widely utilized due to their ability to decay, compatibility with other materials, and regenerate. Because of cellulose’s hydrophilic nature, moisture absorption causes the material’s mechanical characteristics to deteriorate. As a result, cellulose derivatives are created through chemical modification, in which bonds are formed between the reagents and the OH groups in the cellulose improving solubility and mechanical characteristics by reducing cellulose’s hydrophilicity 31 . Cellulose and its derivatives are used in different applications such as fiber industries, wood products, textile, and pharmaceutical industries 3 .

a starch, b cellulose.

Chitin is a polysaccharide can be produced by fungal fermentation processes or found in marine crustaceans such as shrimps, insects, the shells of crabs and lobsters. Chitosan is a deacylated chitin derivative that makes up the exoskeleton of arthropods 11 . Chitosan is a derivative of glucan that is produced by repeated monomers of chitin. Biodegradability, high strength, and nontoxicity are among the chemical and physical properties of chitosan and chitin 36 . They have several applications in the field of medical and pharmaceutical sciences, tissue engineering applications, absorption of heavy metal ions, membrane barriers, the cosmetic industry and food packaging material 3 , 36 .

Polypeptides (Proteins)

Proteins are natural polymers produced from various vegetables and animals. Collagen is a protein found in both vertebrate and invertebrate connective tissue. It accounts for around half of all human protein. Collagen has a hydrophilic nature as a result of the enormous substance of essential, acidic, and hydroxylated amino corrosive buildups that lipophilic deposits 11 . Collagen properties are exceptionally compelling in many fields, for example, leather chemistry, surgery, pharmaceutical industries like capsule production, etc. 3 , 37 .

Biopolymers derived directly from naturally occurring or genetically engineered organisms

Microorganisms are a source for research on bioplastic materials and biopolymers that use agricultural wastes as a medium for growth. Example of microbiological compounding plastic is polyhydroxyalkanoate (PHA), which is produced from various groups of bacteria and cheap renewable resources. It is completely aerobic decomposed by microorganisms 30 . polyhydroxyalkanoates are produced from a biodegradable aliphatic polyester family. They are formed in nature and produced directly by bacterial metabolism 38 , 39 . They are genuinely biodegradable and profoundly biocompatible thermoplastic materials and can be developed from a variety of renewable resources. Polyhydroxyalkanoate is the potential alternative to the non-degradable polyethylene and polypropylene. Poly(3-hydroxybutyrate) (PHB) is the most representative member of this family 11 , 38 , 39 . It is a natural polymer that formed by various chains of bacteria. It is produced from low-cost, renewable feedstock and without causing much impact on the environment. It is degraded in anaerobic and aerobic conditions and it doesn’t produce any poisonous materials from its degradation 22 . Copolymer of hydroxybutyrate (PHB) and hydroxyvalerate (HV) is known as poly(3-hydroxybutyrate)- hydroxyvalerate (PHBV). It is a highly crystalline polymer. By increasing the HV unit content, the melting point, the glass transition temperature, the crystallinity and the tensile strength decrease but the impact strength increases. The copolymer PHBV is less brittle than PHB. The degradation rate of PHBV is higher than PHB 40 , 41 .

Synthetic biodegradable polymers

Synthetic biodegradable polymers are produced by conventional polymerization procedures such as aliphatic polyesters, polylactide, aliphatic copolymer 42 . Due to the appropriate degradation time and their production in industrial scale, the degradable polyesters are considered as the most potential materials utilized comparing to conventional plastics. They are produced in several forms such as polylactic acid, polycaprolactone and polybutylene succinate. They have low ecological contamination 43 . More than 90% of the biopolymers are polyester as they contain easily hydrolyzable bonds of esters. Synthetic biodegradable polymers may be categorized into bio-based polymers like PLA and oil-based monomers such as PCL 12 , 42 .

Aliphatic polyester synthesized from bio-derived monomers (water-based monomers)

The most significant biodegradable polymer is polylactic acid (PLA) 3 . It is well-known for being biodegradable and biocompatible polymer 29 . It is synthesized from renewable materials such as potato starch, wheat, rice bran corn and biomass 22 , 31 . Polylactic acid is linear aliphatic polyester thermoplastic polymers 22 . Polycondensation and ring-opening polymerization of lactic acid monomers are two processes that may be used to synthesize PLA 3 . PLA’s high molecular weight is achieved by polymerization of ring-opening. The final properties of the polymer can be controlled using this method 44 . Lactic acid monomer exists in three diastereoisomeric structures which are D-lactide, L-lactide, and meso-lactide (DL-lactide) 11 . Mechanical, thermal and biodegradable properties of PLA dependen on the selection of stereoisomers distribution within the polymer chain. PLA is used in many applications such as interference screws, sutures, dental, ligating clips, bone pins and rods 3 .

Polyglycolic acid (PGA) is a linear aliphatic polyester that is synthesized by polymerization of ring-opening of cyclic glycolide monomers 12 . It is a thermoplastic and biodegradable polymer. The degradation process of this polymer takes place in two stages. In the first one, water is dispersed in the amorphous regions of the polymer matrix where the ester bonds are separated. In the second stage, crystalline segment of the polymer gets vulnerable to hydrolytic attack 11 . This polymer is used in several applications such as tissue engineering, medical devices, and drug delivery 3 . Glycolic acid monomers (GA) are copolymerized with L-lactide and LD-lactide (LA) generating poly(lactide-co-glycolide) (PLGA). The rate of degradation decreases when the L/G proportion increased 45 . Mechanical and chemical properties are controlled by adjusting the ratio of monomers in the combined polymerization of the PLA and PGA without affecting the compatibility and biodegradability. The degradation of the PLGA takes place by hydrolysis of the ester bond and to form LA and GA which are eco-friendly materials 31 .

Aliphatic polyester synthesized from synthetic monomers (petroleum-based monomers)

Polycaprolactone (PCL) is a biodegradable synthetic linear aliphatic polyester. It can be synthesized by polymerization of ring-opening of caprolactone monomers within the sight of metal alkoxides catalysts. Aluminum isopropoxide and tin octoate are common catalysts used in polymerization process 22 , 46 . Polycaprolactone is dissolved in numerous solvents such as methylene chloride 46 . The melting point of PCL is between 58-60 °C. It is degraded by the activity of anaerobic and aerobic microorganisms. The degradation rate of PCL depends on the level of crystallinity and its molecular weight 22 . This polymer is used in medical fields such as tissue engineering, long-term drug and vaccine delivery vehicles 3 . The biodegradability of PCL can be improved by copolymerization with aliphatic polyesters. PLA and PGA copolymer has lower crystallinity and melting point compared with the homopolymer 22 , 45 , 46 .

Polybutylene succinate (PBS) can be prepared by polycondensation of 1,4 butanediol with aliphatic dicarboxylic acid succinic acid 47 . It is a thermoplastic aliphatic polyester that has a melting point between 90–120 °C 11 , 47 . It is decomposed by a hydrolysis mechanism 22 . Because PBS is crystalline materials, it degrades slowly 11 . It is normally blended with different materials such as adipate copolymer which acquiring polybutylene succinate adipate (PBSA) 22 . This copolymer has a higher degradation rate than PBS 11 .

Biodegradable polymer blends and composites

The main characteristics of biodegradable polymers are their primarily hydrophilic nature, high rate of decomposition, and potentially undesirable mechanical qualities. These properties could be improved by mixing natural and synthetic polymers 11 , 48 . Blending polymers is a category of substances where two polymers at least are mixed collectively to produce a new material with various physical properties. The purpose of mixing two or more polymers is to develop a blend that combines each polymer’s preferred properties 49 . The preparation of biodegradable polymer blends is normally associated with the blending of a thermoplastic resin with biodegradable one. These types of blends are expected to be more biodegradable than conventional plastics 50 . After the degradation process of the biodegradable materials, the residuals components are more ecologically friendly and do not cause environmental pollution 3 .

Natural fibers

Natural fibers are perfect reinforcing materials for polymer composites (thermoplastics, thermosets, and elastomers). Natural fiber-reinforced polymer composites are gaining popularity due to their excellent mechanical properties and considerable manufacturing benefits, as well as the fact that they provide a solution to environmental contamination. Composites based on natural fibers have better impacts in the industry due to these fibers have high specific properties and low density. They don’t have health hazards because of they are non-toxic 51 . Natural fibers are renewable materials, relatively high in tensile strength, low-cost, and light 52 . Natural fibers have become a substitute for non-renewable and expensive synthetic fibers (glass, carbon and kevlar fibers) 53 in different applications because of environmental aspects and their properties as shown in Fig. 5 54 . Natural fibers contain some desirable properties, including high specific strength and modulus, flexibility during treatment, and excellent corrosion resistance 53 . However they show some limitations such as high anisotropy, moisture absorption, limited compatibility with conventional resins, and inferior homogeneity when compared to glass and carbon fibers 55 , 56 . For centuries, natural fibers used in several applications such as clothing, making baskets, ropes and various parts of automobiles 54 .

Natural fiber vs. glass fiber 54 .

Classification of natural fibers

Natural fibers may be categorized based on their sources 57 . Natural fibers come from three main sources namely; animal, plant, and mineral materials 58 . Plant fibers include bast (stem) fibers, seed fibers, leaf fibers, fruit fibers, core fibers, cereal straw fibers, wood fibers and other grass fibers. Animal fibers include hair and wool. Mineral fibers such as asbestos and glass fiber. Figure 6a, b presents the classifications of the different natural fibers and cell wall of natural plants repectively 55 , 57 , 58 , 59 .

a Classification of natural fibers. b The schematic picture shows the cell wall of natural plants 55 .

The plant fibers can be categorized into bast fibers, fruit fibers, leaf fibers, grass fibers, seed fibers, wood fibers, and stalk fibers. Bast fibers like ramie, hemp and flax. They come from the skin and bast around the plant stem. Fruit fibers that are collected from fruits such as coconut and palm. Leaf fibers that are extracted from leaves such as sisal, pineapple, abaca and banana. Seed fibers that are developed from seeds and seed shell such as kapok and cotton. Stalk fibers which are generated from the stalks of the plants such as wheat, rice, and corn. Grass fibers include bamboo and bagasse. Finally, wood fiber (hardwood and softwood) 58 , 59 , 60 , 61 .

Cotton fiber

The purest form of cellulose is cotton. Cotton is hydrophilic. It has high elastic, flexibility and elongation at break. It is degraded by acids but it has resistance to alkalis. Cotton has low microbial resistance however the fibers are highly resistant to beetles and moths. Cotton is burning very fast 57 . Although cotton fibers are widely used, their mechanical performance suffers behind other natural fibers, notably different types of bast fibers. This can be attributed to the low degree of fiber orientation 59 .

Coir is developed from the coconut fruit 62 . It is found between the outer shell of the coconut and its husk 60 . Among several natural fibers, coconut fiber has many desirable properties such as durability, high hardness, acoustic resistance, resistance to fungi and moths, and hardly burns. Also, this fiber is more moisture resistant than other natural fibers. It was reported that the coir fiber has saltwater and heat resistance 63 .

Flax fiber is the strongest fiber comparing with the other natural fibers 64 . It is a renewable, and biodegradable material. Great attention increased for flax fiber-reinforced plastic composites because of its great toughness, high strength, stiffness, low density, and bio-degradability. When compared to E-glass fiber, flax fiber has a higher specific tensile strength 63 . Flax fiber is widely used in several applications such as towels, carpets, ropes and fabrics. Also, flax fiber has been used in biocomposites fabrication 65 .

Kenaf fiber

The outer (bast) and inner (core) fibers of the kenaf plant are used to produce kenaf fiber 57 . Kenaf fibers are used in polymer matrix composite as reinforcement materials. It is non-abrasive during manufacturing, has a low density, and good specific properties. It is also biodegradable 63 . On the other hand kenaf fibers are rough, brittle, and hard to process. It is widely used in textiles, paper materials, ropes, absorbents, and building materials 66 .

Hemp fiber belongs to the bast fiber family 63 . It is used in polymer composites reinforcement 67 . It consists of 55-72% cellulose, 8–19% hemicellulose, 2–5% lignin, 4% minerals and less than 1% wax 63 . It has excellent mechanical strength, elastic modulus and moisture resistance 46 , 52 . Hemp fiber has chemical composition comparable to flax fibers, however flax is less resistant to moisture than hemp. Hemp fiber has a toughness that is roughly 20% greater than flax, although they have a poor elongation 59 . Hemp fiber is used to produce paper, fabrics, construction materials, plastic and composites 68 .

Jute fiber is extracted from the ribbon of the stem. Jute fiber has wood-like properties. It has good mechanical and thermal properties, high aspect ratio, high strength to weight ratio and good properties of insulation 63 . Jute has a microorganism’s resistance, but it is sensitive to photochemical and chemical attacks. Jute fiber is brittle because of high content of lignin and a small extension to break. It has tensile strength lower than flax or hemp. Exposure to sunlight causes loss of the tensile strength of the fiber and has little resistant to acid and moisture. Jute is the plant fiber with the highest hygroscopicity. Jute is silky texture, biodegradable material and resistant to fire and heat which makes it adequate for use in industries. It is used in travel luggage, fashion, furnishings, carpets and other floor coverings. Jute fibers may be used to strengthen polymer composites (thermoset and thermoplastic) 69 .

Ramie fiber

Ramie fiber is white in color, very fine and silk-like. Ramie fiber is naturally resistant to germs, insects, and mildew. Ramie fiber is not harmed by mild acids and stable in alkaline media 57 . The physical properties of ramie fiber showed high tenacity, high luster and brightness 70 . The fiber has an exceptional strength which slightly increases when wet. Ramie fiber is gaining attention as a polymer matrix reinforcement in composites 57 . Natural fiber has much less density than that of synthetics fibers 63 .

Sisal fiber

The sisal fiber comes from the sisal plant leaves which is a hard fiber 46 . As compared to glass fiber, sisal fiber has a higher strength and stiffness 71 . Sisal fibers include a number of environmentally friendly benefits such as low density, excellent specific modulus, and strength. These advantages make them appropriate for use as reinforcement in composites 72 . When the temperature of the sisal fiber increased, the tensile strength, modulus, and toughness for fiber decrease. It is smooth, yellow, straight and degraded easily in saltwater 56 . The fiber increases the toughness of polymer than increasing the modulus and strength. The sisal fiber composites had maximum toughness than other fibers 73 .

Pineapple leaf fiber (PALF)

PALF is made from the leaves of the pineapple plant 51 . It’s a cheap waste product from pineapple farming 57 . PALF consists of high content of cellulose about 70-82%, polysaccharide, and lignin 51 , 57 . PALF has superior mechanical properties because of the high content of cellulose 53 . As compared to cotton, dyes faded more quickly due to the high content of lignin and wax materials in pineapple leaf fiber. Also, dyes difficult to penetrate due to the high coarseness of PALF 51 .

The abaca is a banana species. that comes from the leaf sheaths of the banana plant 57 , 59 , 63 . It is yellowish-white in color and lustrous fiber. It is the strongest fiber among all other plant fibers. Abaca tensile strength is twice times higher than sisal and three times higher than cotton 57 . It is resistant to degradation in saltwater than other fibers, so it is preferred to use in marine applications 63 . Abaca fibers are used in many applications such as manufacturing ropes, bags, slippers, placemats and doormats. Also, abaca fiber is used as a reinforcement of composites 74 .

Bagasse and bamboo

After sugar is extracted from the sugarcane stalk, bagasse is a fibrous residue that remains 63 . It is used in many applications like biofuel in the production of renewable energy and used as a natural fiber-reinforced polymeric composite 63 , 75 . Bamboo fiber is a kind of cellulosic fiber 75 . It has eco-friendly characteristics such as high growth rate, lightweight, high strength and it is a biodegradable material. It is used in many applications such as flooring to ceiling and transportation, furniture manufacturing, etc. Also, it is used as a reinforcement of composites 72 .

It is biodegradable, compostable, and has the potential to break down into its essential parts and return to the environment naturally. Palm fiber has five times the tensile strength of structural steel and is comparable to flax, hemp, and sisal. It has better vibration dampening and acoustic insulation than glass and carbon fiber as well as better heat insulation than carbon 60 . Palm fiber has a cellulose purity of up to 70% and a thermal stability of up to 226 °C.

Animal fibers

Animal fibers are the most significant natural fibers after plant fibers. They are employed in composites as reinforcement 57 . Animal fibers include mainly three types: hair, avian and silk fibers. Animal hair fibers are obtained from animals and hairy mammals such as horses, sheep, and goats. Silk fibers are obtained from insects while preparing cocoons or from dried saliva from insects. Avian fibers are produced from bird feathers 58 .

Structure and composition of natural fibers

Natural fiber cell walls are made up of three layers: a main cell wall, a secondary cell wall, and an intermediate cell wall known as lumen 59 . Fig. 6b depicts the structural organization of a natural fiber cell wall 52 , 59 , 76 . This structure is known as microfibril 63 . During cell formation, the wall of the primary cell is the first layer formed. Secondary walls S1, S2, and S3 are the three layers that make up the second cell wall 77 . The lumen layer is responsible for the transportation of water 78 . The cell walls are formed of a semi-crystalline cellulose microfibril, hemicellulose, lignin, wax, pectin and water-soluble compounds 63 , 77 .

The physical properties of the fiber are connected to the inner structure and components of the plant material that is being used. The fiber of plants is lignocellulosic structures which are consist of hemicelluloses, cellulose, and lignin, as well as pectin, protein, wax, ash, tannins, and inorganic salts 59 . These components are vary according to the fibers sources, growth conditions, age of plant and processes of digestion 59 , 63 . The chemical composition of some of the common natural fibers are presented in Table 1 59 , 77 , 79 . Cellulose content of fibers is the most important factor in determining their characteristics and mechanical performance when utilized as reinforcement in composites. In contrast to cellulose, an increase in non-cellulose components causes a decrease in fiber strength and modulus, which has severe consequences for composites reinforced with natural fibers 59 .

Surface modification of natural fibers

Natural fibers have a variety of drawbacks in reinforcement composites, including poor compatibility with the polymer matrix due to the hydrophobic character of the polymer matrix and the hydrophilic character of the fibers. Their moisture absorption, and dimensional stability are considered as main limitations 63 , 80 . The high wettability can be attributed to the existence of OH groups, and polar groups. The mechanical properties of natural fibers decreased when the moisture content in natural fiber increased. This led to a loss in dimensional stability and degradation. This causes weak adhesion between the polymer matrix and the natural fiber when the natural fibers used as reinforcement in composites 17 . Surface adhesion is a key factor in describing component mechanical and physical characteristics 80 , 81 . These problems can be solved by surface modification treatment such as chemical, physical and biological treatments 17 .

Chemical treatment

Since natural fibers are hydrophilic and polymer matrix is hydrophobic, there is an inherent incompatibility between them, this results at the interface in weak bonding. Chemical treatment methods will reduce the fiber’s hydrophilic nature by removing hydrophilic OH groups from reinforcing fiber 81 . This treatment strengthens the adhesion of the polymer matrix to the fiber via chemical reactions 53 , 60 .

Alkaline treatment or mercerization

This method of treatment is the simplest, most cost-effective, and efficient for improving the adhesive capabilities between polymer matrix and natural fibers 53 . In this chemical treatment, aqueous sodium hydroxide (NaOH) is used. Natural fibers are soaked in a predetermined concentration of NaOH for a certain time and temperature. Non-cellulosic components like lignin, hemicellulose, oils, and wax are removed during this process 60 . The following reaction shows alkali treatment in below equation 80 .

The removal of non-cellulosic components modifies the polymerization degree and structural orientation of cellulose crystallites, altering the chemical composition of the fibers. Also, this treatment has a permanent effect on mechanical fibers behavior, particularly on their stiffness and strength. Various alkaline treatment studies indicated that mercerization would increase the amorphous cellulose amount at the crystalline cellulose expense and remove hydrogen bonds in the network structure 80 . Neutralizing the fibers can be achieved by using acetic acid to end the reaction by removing the rest of the hydroxyl groups after washing the fibers with distilled water 82 .

Silane treatment

Saline is a molecule of multifunctional. It is used as a binding agent to adjust the surface of fibers. Saline coupling agent develops a siloxane bridge chemical bond between the polymer matrix and the fiber. Silanols form when moisture and a hydrolysable alkoxy group are present. One silanol end reacts with the matrix functional group during condensation, whereas the other end reacts with the cellulose hydroxyl group 81 . The following reactions show silane treatment in below equations 83 .

The number of hydroxyl groups in natural fibers is decreased during this treatment, which leads to a reduction in absorption of moisture and improves the fiber’s mechanical properties 82 . The saline treatment increases the composite’s tensile strength while also reducing the influence of moisture on its characteristics. It also enhances fiber-polymer matrix adhesion 80 .

Acetylation treatment

In acetylation treatment, acetyl groups are grafted to the cellular structure of the fibers by using acid catalyst 84 . The fibers are firstly soaked in acetic anhydride. They are processed for 1-3 h in acetic anhydride at an elevated temperature (70–120 °C) in order to accelerate the reaction. This process is known as esterification method for plasticizing natural fibers with the formation of acetic acid as byproduct. The hydrophilic hydroxyl groups of the natural fiber react with the acetyl group (CH 3 CO). To swell the cell wall and activate the reaction, a small amount of acetic acid is required in the reaction mixture. Equation ( 4 ) shows the acetylation treatment of natural fiber 80 .

When the natural fiber’s moisture content decreases, the fiber’s hydrophilic nature decreases 60 . The removal of non-cellulosic components from the fiber improves moisture resistance 81 . The dimensional stability and degradation of composites are also enhanced by this procedure 80 .

Benzoylation treatment

Benzoyl chloride is utilized in this procedure. This treatment reduces the fiber’s hydrophilic nature, improves fiber-polymer adhesion, and increases composite strength. Alkaline treatment is used while treating benzoylation. Non-cellulose compounds are removed during the alkaline treatment process. The amount of reactive OH groups on the fiber’s surface likewise increases. After that, the fibers are exposed to benzoyl chloride treatment. The hydroxyl groups are replaced by benzoyl groups and found in the cellulose during benzoylation treatment 81 . This treatment minimizes the absorption of moisture and enhances the thermal stability of the fiber.

Equations ( 5 ) and ( 6 ) describe the steps of benzoylation treatment 85 , 86 .

Peroxide treatment

The connection between the natural fiber and the matrix can be enhanced by peroxide treatment 81 . Peroxide is a specific functional group with function group RO—OR´ which contains divalent ion O—O. Peroxide tends to decompose to free radical in the form of 2 RO • 86 . The peroxide decomposition is completely achieved by heating the solution at high temperature 81 , 86 . The hydrogen group of the cellulose fiber and the matrix react with the free radical RO • . Benzoyl peroxide and dicumyl peroxide are used in the modification of natural fiber surface. In this treatment, dicumyl peroxide or benzoyl peroxide is used to coat the fibers in acetone solution for about 30 min at a temperature of 70° C 81 , 87 after pre-treatment of alkali. The concentration of peroxide solution is about 6% and saturated peroxide solution is used in acetone 86 . The following reactions show the peroxide treatment in below equations 81 .

R = the functional group of peroxide

Pretreatment on the fiber with benzoyl peroxide or dicumyl peroxide produces high mechanical properties of the composition 81 . After treatment, the treated fiber should be washed with distilled water 87 . This treatment increases moisture resistance and improves thermal stability 86 .

Maleated coupling agents

Efficient interaction between the polymer and the fiber can be achieved by maleated coupling agent 81 . Maleic anhydride is commonly used to treat the surface of the fibers as well as the polymeric matrix to enhance the compatibility between polymer and natural fiber. This treatment differs from other chemical treatment methods as it is used to treat both the fibers’ surface and the polymeric matrix. The mechanical properties of polymer matrix-natural fiber composites are improved by this treatment 60 . hydroxyl groups in the amorphous region of the cellulose structure interact with maleic anhydride during grafting, eliminating hydroxyl groups from the fiber. This treatment decreases the hydrophilic tendency 53 .

Acrylation and acrylonitrile grafting

This treatment is used to improve the bonding between the polymer matrix and the fiber by using acrylic acid (CH 2  = CHCOOH). It reacts with hydroxyl groups of the fiber 53 . The chemical reaction between the carboxylic acids in the coupling agent and the cellulose OH groups form linkage of ester. Equation ( 9 ) shows acrylation treatment 88 .

This treatment reduces the fiber’s hydrophilic character and increased its moisture resistance. As a result, peroxide radicals are employed to start the grafting of acrylic acid on the matrix. Peroxide’s O—O bonds remove hydrogen atoms from the tertiary carbon of the polymer chain. The stress transfer capacity at the interface between the fiber and the polymer matrix is enhanced by acrylic acid and therefore improves composite properties 81 . After 1 h of fiber immersion in various concentrations of acrylic acid at elevated temperatures, alkali-pretreated fibers are washed with an aqueous alcohol solution and then oven-dried 84 , 88 .

Fiber grafting with acrylonitrile (AN) (CH 2  = CH-C ≡ N) is a method for modifying the surface of the fibers. Free radicals are initiated by acrylonitrile and reacted with the molecules of cellulose in fibers and the matrix monomer. The interlocking efficiency at the interface is improved as a result of the copolymerization process between the polymer matrix and the fiber 81 . It was reported that sisal fibers showed 25% lower tendency to absorb water, high tensile strength, and modulus characteristics of the polymer composite as a result of acrylation treatment 84 .

Isocyanate treatment

Isocyanate is a coupling agent used to enhance and modify the surface of natural fibers 81 . In this treatment, the reaction between the functional group of isocyanate (-N = C = O) and the OH groups of cellulose and lignin components of the fibers forms a urethane group 81 , 89 , 90 . Equation ( 10 ) shows the isocyanate treatment of natural fiber 24 .

The bonding properties between the polymer matrix and the fibers are improved by forming strong covalent bonds 53 , resulting in high compatibility with the binder resin in the composites 89 , 90 . Also, urea is formed because of the reaction between the moisture content that exists on the surface of the fiber and isocyanate. This urea can react with the celluloses’ OH groups 81 . The second reaction results in a fiber with a stronger moisture resistance property as well as a good bonding with the polymer matrix. As a result, mechanical properties and compatibility of polymer composites are improved 53 , 81 .

Permanganate treatment

The chemical crosslinking at polymer matrix and the natural fibers interfaces can be improved by treating the natural fibers using permanganate 53 . Permanganate treatment is conducted using potassium permanganate (KMnO 4 ) in a solution of acetone. Reactions between highly reactive permanganate ions (Mn +3 ) and the OH groups of cellulose are carried out in this treatment. This treatment forms cellulose-manganate which improves thermal stability. The alkaline treatment is required included with this treatment 81 . Chemical reactions using the permanganate treatment are given in below equations 85 .

Also, the hydrophilic character and water absorption of the fiber-reinforced composites decrease 85 , 86 . This procedure improves the adherence of the polymer matrix to the fiber 53 . A high concentration of KMnO 4 (more than 1%) leads to a decrease in the hydrophilic tendency of the fiber 91 and causes excess delignification inside the cellulosic structure and reduces the properties of the fibers. According to Sheng et al., reported that treatment of natural fiber using potassium permanganate increased the surface area and made it coarser during the oxidation reaction, which improved mechanical entanglement with the matrix 81 .

Physical methods

Natural fibers can be physically treated to improve the mechanical interaction between the polymer matrix and the fibers while maintaining their chemical properties 60 . Physical treatment includes the use of plasma, corona, ultrasound and UV light 17 . These procedures are only utilized and applied to change the surface qualities of natural fibers 53 . Plasma treatment is the most common physical treatment because it stimulates the substrate surface when employed in the treatment of natural fibers 92 , 93 . Surface contaminants are the cause of changes in surface qualities including dyeability, wettability, and flammability, hence plasma treatment can be employed to reduce surface contamination 17 . Generally, the hydrophobicity of the natural fiber is increased as a result of plasma treatment 16 . Plasma treatment would increase surface roughness resulting in good binding to the polymer and the adhesion between the polymer matrix and natural fiber 17 . Corona treatments can be employed as a stand-alone surface modification or as a pre-treatment to activate cellulose in preparation for future chemical treatments like grafting 59 , 94 . Corona treatment improves the compatibility of hydrophobic polymer matrix with hydrophilic fibers. 60 , 95 . Ultraviolet treatment is also used in surface fiber modification which leads to an increase in the fiber’s thermal stability 96 .

Biological treatment

Natural fibers are commonly treated using chemical and physical processes. However, they have some drawbacks such as usage of large volumes of solvents and hazardous chemicals, generation of wastes and pollutants, energy waste, and required costly equipment and chemicals. Microorganisms like fungi, enzymes and bacteria could be used in natural fibers treatment 17 . Biological treatment is an eco-friendly method 97 , more economical than other treatments, less energy waste and improves the thermal stability of the fibers. It was also found to be selective in removing pectin and hemicellulose 98 . Fungal treatment is a new biological treatment that removes of non-cellulose components of the fiber surface by using specific enzymes, increased fineness of the fiber, and fiber individualization can be achieved 98 , 99 . Extracellular oxidizing enzymes produced by white-rot fungus react with lignin and aid in its elimination, as well as enhancing hemicellulose solubility and lowering the fiber’s hydrophobicity. Furthermore, fungi generate hyphae, which causes fine pores on the surface of fiber as well as a rough surface to improve fiber/matrix interaction. Without the use of fungus, enzymes might be applied directly to natural fibers. By increasing cellulose content and eliminating lignin and hemicellulose, enzymes like xylanase and laccase increase hardness, tensile, and flexural strength 100 .

Applications of biodegradable polymer

The use of biodegradable polymers is rapidly growing with a global industry worth many billions of dollars annually. Biodegradable polymers are used in a variety of applications, including food packaging, computer keyboards, automotive interior parts, and medical applications like implantable large devices, medical delivery and tissue engineering 101 , 102 , 103 , 104 . Figure 7 shows various applications of biopolymer materials 101 .

Snapshot of the main fields of application 101 .

Environmental fate and assessment

Biodegradable polymers have been designed and developed over the past 20 years. They are used in applications that advantage biodegradation. Biodegradation is a biological process in which bacteria digest dead organic matter and convert it to microbial energy and biological mass while releasing inorganic compounds as by-products. Biodegradation is used in waste management to convert biowaste into compost for soil fertilization through organic recycling. Anaerobic digesters are another type of organic recycling system that produces biogas and digestate, which is subsequently transformed into compost. Biopolymers are developed to be reused in composting facilities and anaerobic digesters with bio-wastes. Biopolymers are also utilized in agricultural plastics that are made to be left in the field and biodegrade after usage. The environmental effect of compounds produced during polymer biodegradation and composting, which might then be dispersed into the environment by compost fertilization or directly diffused during their biodegradation in soil, is a recurring subject. End-of-life possibilities for biodegradable polymers are represented in Fig. 8 .

End-of-life scenarios of biodegradable polymers.

Biodegradation end products

Chemical elements can be found in nature as components of organic molecules (such as polysaccharides, and so on) as well as in inorganic substances (such as NH 3 , CO 2 , and so on). Microorganisms transform lifeless organic materials into inorganic chemicals during biodegradation. Glucose molecules, for example, are converted back into the inorganic compounds that plants used to create glucose via aerobic biodegradation. This process is termed as mineralization as it leads in the transformation of organic material molecules into inorganic compounds and minerals. Organic molecules, like natural polymers and certain man-made polymers, are affected by the biodegradation process. Biopolymers are used in the manufacture of plastic materials that are designed to decompose in the soil or compost plants. Biodegradation of a polymeric compounds in which part of the original carbon (C polymer ) is mineralized (CO 2 ), part is consumed by microorganisms for their own development and reproduction (C biomass ), and the rest remains as polymeric residue (C residue ). Other kinds of microorganisms are engaged in the biodegradation process under anaerobic circumstances. As a result, products such as CO 2 and CH 4 are produced.

Biodegradation during organic recycling

Organic recycling is a treatment process of bio-waste that results in the generation of compost (stabilized organic matter) that is utilized as a soil fertilizer in agriculture. Organic recycling is standardized and industrial biotechnology that involves a multistep biodegradation process in anaerobic digesters or aerobic composting plants. Organic recycling involves three strategies namely; industrial composting, home composting, and anaerobic digestion.

Industrial composting

This technique can be used to handle bio-waste obtained by home, industrial, and agricultural processes. In addition, bio-waste from sewage treatment, park and garden upkeep are used. Composting refers to organic matter recycling method that turns waste into compost. Biodegradable plastic materials that have been used before are an ideal feedstock for industrial composting. Bio-waste is collected in industrial composting plants, where a variety of elements come together to provide a perfect environment for microorganisms to improve the composting process: temperature, moisture, and pH change over time. During the process, O 2 should be available. Microorganisms get energy and chemical ingredients for their own survival, development, and reproduction through this mechanism. Microbial metabolism generates heat, which leads to increase pile temperature. As the temperature of the mass increases, quicker reactions take place, speeding up the biodegradation process.

Home composting

When compared to industrial composting, home composting is applied to a lower amount of bio-waste created through domestic activities or garden upkeep and is done in a much more varied manner. As a result, home composting can provide different results due to the fact that numerous elements influence the process such as moisture, temperature and types of microorganisms. Because the compact dimensions of the composting masses may not be allowed for high temperatures to be attained, home composting is frequently slower than industrial composting.

Anaerobic digestion

Bio-waste is decomposed by a bacterial population in the absence of oxygen, resulting in the formation of biogas (methane and carbon dioxide) and digestate, with little or no exothermic heat released. A two-step method is used by most commercial anaerobic digestion systems. Anaerobic fermentation is the initial process, followed by aerobic composting in the second step.

Biodegradation in soil

Several biopolymer-based applications that end up in the soil after use are fast growing in the market. Furthermore, it is used to improve soil quality, mature industrial compost, which is made from a feedstock containing biopolymers, ends up in the soil. Soil is a heterogeneous material governed by a mix of environmental and seasonal elements that tightly control the microbial population’s creation and activity. For example, bacteria colonize an alkaline-neutral humid soil, however fungi require acid dry soil to thrive and operate.

Soil texture and structure

Soil texture is formed based on the percentages of clay, sand, and silt particles that make up the soil. The size of clay particles is less than sand and silt particles. Microbial colony development is influenced by soil texture and structure: sandy, dry, and well-aerated soil. It promotes fungal colonization. Clay compact soil with inadequate aeration supports facultative aerobic or microaerophilic bacterial colonies.

Water content

The texture, structure, and organic material concentration of the soil contribute to the soil’s water retention, which has a big influence on microbial selection. The formation of bacterial colonies is aided by humidity, whereas the growth of fungal colonies is aided by dryness.

Organic matter

Organic matter is the preferred substrate for the formation and expansion of microbial colonies since it is the major fuel source for biodegradation. It also acts as a soil buffer, contributes to soil aeration and humidity, and has a good impact on the preservation of microbial habitat.

Microorganisms display varying degree of sensitivity at different pH values. Therefore, pH changes have a significant impact on microorganisms growth. As a result, soil pH is an important factor in restricting microbial colonization. Bacteria prefer a slightly alkaline neutral pH, whereas fungi prefer an acidic pH.

Temperature

The temperature has an impact on microbial activity and presence because it permits microbe colonies to form. Warm temperature speeds up the chemical processes of microbial metabolism and the enzymatic degradation of polymers.

The amount of oxygen in the soil distinguishes between aerobic and anaerobic biodegradation by stimulating the growth of microorganisms that can live with or without oxygen. The amount of oxygen in the air is usually inversely related to the amount of water and carbon dioxide in the air.

Microbial development on the soil surface is inhibited by ultraviolet radiation. As a result, biodegradation takes place within a few millimeters under the soil surface with the highest concentration in the first 10 cm. Temperature, organic matter content, aeration, moisture, and oxygen need to be adjusted to meet optimal values for microbial activity. Mulch films are agricultural biodegradable plastic films that are not removed after cropping. They remain on or in the soil where they are diced up and mixed with the most biologically active soil layer by milling and ploughing activities promoting material biodegradation 97 .

Recycling of plastics and biopolymer

All possible recycling techniques should be investigated to optimize the environmental advantages of these materials 105 . There are four different recycling paths as shown in Fig. 9 . They are involved after collection, separation, and purification of plastic garbage 106 . They are primary recycling, secondary recycling (mechanical recycling), tertiary recycling (feedstock or chemical recycling), and quaternary recycling (energy recovery) 107 .

Different types of plastic waste recycling and their impact on plastic quality 106 .

Because of its simplicity and low cost, primary recycling is the most used method 107 . Primary recycling is mechanical recycling which is a closed-loop recycling technology that can only be used on high-quality plastic trash with a known history 105 . This method entails reusing things in their original form. The disadvantage of this method is that there is a certain limit on the number of cycles for each material 107 . Primary recycling allows the recycled material to be utilized in applications that have the same properties and performance as virgin plastics. It is usually not linked to post-consumer plastics rather to the conversion of uncontaminated plastic waste (e.g., production leftovers) into its original pellet or resin form within the same manufacturing facility. Hence, it does not need sorting and cleaning.

Secondary recycling is the mechanical reprocessing of waste and plastics after consumption. Materials recycled through secondary recycling have lower mechanical properties compared to the mechanical properties of the original product. The lower mechanical propertied of secondary materials recycled are attributed to lower material purity and deterioration processes that result during the life of the product. Secondary recycling may be economically inexpensive if the amount of waste is small or/and contaminated. Otherwise, the cost of recycling increases due to the separation and purification steps. Although mechanical recycling is a well-established recycling approach for conventional plastics, it should be used with caution when it comes to biodegradable plastics 105 . This is due to the sensitivity of biodegradable materials to heat 108 . One of the advantages of this method over chemical recycling is that mechanical recycling is lower in cost processing, less potential for global warming, and less use of non-renewable energy 106 .

Chemical recycling is the process of converting polymers into monomers and partially depolymerizing them into oligomers by chemical processes that modify the polymer’s chemical structure. The resulting monomers can be utilized to recreate the original or a related polymeric product by new polymerizations. Starting with monomers, oligomers, or combinations of various hydrocarbons, this process is capable of reducing the plastic substance into smaller particles appropriate for use as raw material 107 . Chemical recycling provides the following benefits over mechanical recycling: the ability to create valuation products and the potential for a circular polymer manufacturing economy, since recovered virgin monomers may be repolymerized for an endless number of recycles. However, one of the downsides of this technology is that it is both economically and environmentally expensive 106 .

Quaternary recycling is the process of recovering energy from low-grade plastic garbage by incineration 106 , 107 . This method is considered to be the best method for reducing the volume of organic matter and producing large energy from polymers 107 . However, this method of waste recycling should be used as a last resort 106 . This method is not environmentally acceptable because of the resulting pollutants and health risks from toxic materials that are transmitted through the air, such as dioxins 107 . Chemical recycling is the only approach permitted under the principles of sustainable development since it results in the production of the monomers from which the polymer is created 107 . Table 2 lists the benefits and drawbacks of the various approaches 108 , 109 , 110 , 111 , 112 .

Natural fiber reinforced composites

Natural fiber polymer composite (NFPC) is a composite substance comprising of a matrix of polymer reinforced with natural fibers with good strength properties 113 . The natural polymer reinforced composite has taken great interest in many applications. This is because natural fibers offer more and good benefits and qualities than synthetic fibers. Natural fibers have low weight, low cost, renewable and available materials. They are considered less harmful to processing equipment. It also has relatively good mechanical properties like flexural modulus and tensile modulus, as well as an enhanced surface finish of the molded parts composite 114 , stability during manufacturing, biological degradation, and limited health risks. Natural fiber polymer composites with excellent mechanical strength and stiffness may be made by integrating a light-weight and durable natural fiber into a polymer matrix (thermoset and thermoplastic) 115 . They are used in many applications which are rapidly increased in various engineering fields. The different types of NFPCs have got great attention in various automotive applications. Also, the other natural fiber composites are found in various applications like building and construction industry, window frame, panels, sports, aerospace, and bicycle frame 116 .

Characterization of natural fibers, biodegradable polymers and biocomposites

Mechanical properties.

Natural fibers have good mechanical strength, modulus of elasticity and they are tough. The composites from natural fibers are served for commercial purpose and become a good substitute of synthetic fibers in various applications 117 . When comparing natural fibers with glass fibers, the most important features of natural fibers are inexpensive, good mechanical properties due to lower density of them, easy processing and handling, renewable resources, recyclable, and has good acoustic and thermal insulation ability 118 . Kim et al. 119 reported that natural fiber-reinforced composites with high-strain rates absorb more energy than glass-fiber-reinforced composites. Natural fibers have drawbacks such as low strength, variation in quality, high absorption of moisture, treatment temperatures are limited, low durability and less resistance to combustion 117 , 118 . In general, bast fibers are distinguished for having the better properties for structural applications. Among these, flax fibers give the best possible properties between low cost, lightweight, hardness and high strength. Jute is more common. However, it is not as stiff or strong as flax. Overall, natural fibers are characterized by a low density and renewable materials and can be obtained cheaper than glass fiber. Conversely, the strength of natural fibers is much less than synthetic fibers. In situations where stiffness and weight are crucial, natural fibers outperform synthetic fibers. Natural fibers have various unique features, such as biodegradability, renewability, and eco-friendliness, that make them good candidates for serval applications 118 . Mechanical and physical properties of some different natural and synthetic fibers are listed in Table 3 118 , 120 , 121 , 122 , 123 , 124 .

When comparing the mechanical properties of biodegradable polymers and non-biodegradable polymers such as polystyrene (PS), polyethylene (PE), polypropylene (PP), there is a wide values range for the strength of both materials, but conventional polymers are generally stronger than biodegradable polymers. These biodegradable polymers have relatively lower strength than conventional polymers 125 . Among these biodegradable polymers, PLA is considered as one of the most important polymers due to its good mechanical properties that make them suitable for several applications 125 , 126 . The mechanical and physical properties of several biodegradable and non-biodegradable polymers are listed in Table 4 120 , 127 , 128 , 129 , 130 , 131 .

Natural fibers are used to enhance mechanical properties of biodegradable polymers. Dong et al. 132 examined the coir fiber/PLA composite mechanical properties. Figure 10a–d shows that flexural and tensile moduli of PLA biocomposites at the fiber loading from 5 to 20 wt% are moderately improved when compared with neat PLA. It was found that the tensile modulus of untreated coir fiber biocomposites improved to 25.6%, and the flexural modulus was enhanced by 13.4% in the presence of 5 wt% and 20 wt% coir fiber respectively. Increased coir fiber loading to 10 wt% resulted in lower tensile and flexural modulus, which became obvious at 30%. Treated fibers may not improve the modulus of biocomposite particularly at higher fibers loading (20 and 30 wt%). This is because the condition of adhesion between the polymer matrix and the fiber, which has less influence on the tensile modulus of biocomposites than tensile strength.

The treated and untreated PLA/coir fiber composites flexural and tensile properties. a Tensile modulus, b tensile strength, c elongation at break, d flexural modulus, and e flexural strength 132 .

As shown in Fig. 10a, b , biocomposites have lower flexural and tensile strengths than neat PLA. Biocomposites with treated natural fibers have better strength levels than biocomposites with untreated fibers. Biocomposites have lower elongation at break than PLA at fiber loading 5–20 wt%, as illustrated in Fig. 10c . It was found that the brittleness of PLA composites is higher than that of neat PLA. This is because of the rigid nature of the reinforcement of wet coir fibers with the PLA matrix. When fiber loading reaches 30% in the composite, these composites have a high elongation at break compared to polylactic acid. The increase in elongation at break for PLA biocomposites reinforced with coir fiber up to 30 wt% coir fiber can be attributed to the presence of bundles of excessive non-wet fibers, as shown in Fig. 10d, e . This helps biocomposites deform longitudinally under tensile loading. The alkali treatment of fibers works to remove pectin and lignin from the coir fiber. Thus, increase the cellulose content improves the elasticity and flexibility of coir fibers.

Thermal properties

Thermal analysis is used to examine chemical, physical, and structural response as a result of a temperature change. Temperature is a basic state variable that impacts the majority of chemical processes, physical qualities, and structural changes. Thermal analysis may be defined as any scientific or technical assessment of a material in which temperature is manipulated 133 . This term, however, has long been restricted to approaches using thermogravimetric and calorimetric effects 134 . The basic techniques used in thermal analysis are TGA thermogravimetry analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The difference in temperature between a sample and a reference is carried out by differential thermal analysis (DTA). The loss of weight measured by thermogravimetry is measured by thermogravimetry analysis (TGA). The determination of heat flow done by differential scanning calorimetry (DSC) 53 , 134 . Thermogravimetry analysis is widely used to describe the thermal stability of natural fiber and polymer composites. The thermal stability of natural fiber and polymer biocomposites has been thoroughly characterized using TG/DTG research. The lignocellulosic fibers are affected by temperature 134 .

Yao et al. 135 selected ten natural fibers including wood, bamboo, agricultural residues and bast fibers to study thermal decomposition kinetics. The complete thermogravimetric degradation process of natural fibers at a rate of 2 °C/min is shown in Fig. 11a, b . A clear DTG peak with a noticeable shoulder (arrow) is formed due to cellulose thermal breakdown, which is generally the outcome of hemicellulose thermal decomposition in an inert environment. However, since the shoulder peaks of low-temperature hemicelluloses were overlapping with the cellulose main peaks, they were no longer visible in some situations as shown in Fig. 11b . The high-temperature (tails) is usually presented by the degradation of lignin as proven in Fig. 11a, b . Because natural fibers are lignocellulosic materials, the TG and DTG curves for various are very comparable, indicating that natural fibers have similar thermal breakdown characteristics.

a Natural fibers with obvious hemicellulose shoulders and b not obvious hemicellulose shoulders 135 c TGA for PCL, PLA, and PHB d DTGA for PCL, PLA, and PHB 136 .

Herrera-Kao et al. 136 studied the thermal degradation of three common biodegradable polyesters (polycaprolactone (PCL), polylactic acid (PLA) and polyhydroxybutyrate (PHB)) by using TGA. Degradation curves for each PCL and PLA showed that they have only one decomposition level. Whereas TGA of PHB displayed two degradation. The TGA mass loss curve and the related derivate curve (DTGA) for the examined biopolymers (PHB, PCL, and PLA) are shown in Fig. 11c, d . The maximum rate of breakdown temperature differs according to polymer type. However, both PCL and PLA showed only one phase of mass loss with an initiation temperature higher than 300° C as displayed in Fig. 11c, d . This temperature was 430° C for PCL and 395° C for PLA. At 303° C and 410° C, PHB showed two different deterioration phases, the first stage is the major transition since it accounts for over 90% of the total mass loss.

Dynamic mechanical analysis

Dynamic mechanical analysis (DMA) is used on advanced materials with a rheometer to examine their viscoelastic behavior based on storage modulus (Gʹ), loss modulus (Gʺ) and damping factor (tan Δ). Also, DMA is applied on the advanced composite material to understand the glass transition temperature ( T g ) 137 . Manral et al. 138 studied the viscoelastic behavior of neat PLA and natural fibers reinforcing PLA by using DMA at different temperature range 30–100 °C. Samples were exposed to twisting load during DMA test.

Storage modulus (Gʹ)

The storage modulus of a composite material is a measure of storage energy in terms of elasticity when subjected to cyclic load. The quantity of energy absorbed in step with the cycle during oscillatory load on the material is known as Gʹ 139 . Figure 12a displays the storage modulus fluctuation with relation to temperature at a steady cycle loading frequency of 1 Hz. Results confirmed that polymer reinforced with natural fibers improved the Gʹ or the stiffness of polymer composites. Storage modulus curves showed that flax/PLA has the highest value by obtaining the value of 2524 MPa when compared to other composites 138 . The high Gʹ value indicates that flax/PLA composites are stiffer. When the temperature increases, the value of Gʹ decreases for all composites. As the temperature increased, the storage modulus of the composite decreased due to a decrease in stiffness. The decrease in Gʹ refers to viscous behavior of polymer in addition to low stored energy 138 .

a Storage modulus. b Loss modulus c damping factor 138 .

Loss modulus (Gʺ)

The loss modulus(Gʺ) and storage modulus (Gʹ) are interrelated. When polymer shows viscous behavior, it has the potential to dissipate energy in the form of heat due to intermolecular friction among molecules under loading. Further energy could be dissipated by stiff materials and showing higher Gʺ value. Thus, increasing fiber loading in the presence of biodegrdable polymer such as PLA led to increase in friction force and energy dissipation as shown in Fig. 12b 18. Flax fiber reinforcement enhanced the stiffness of neat PLA and resulted in a greater loss modulus. It was reported that flax/PLA composites have higher strength than other natural fiber/PLA biocomposites 138 .

Damping factor (Tan Δ)

The ratio between the loss modulus and the storage modulus is defined as Tan Δ. The ratio refers to the damping behavior of the substance with different temperatures. Figure 12c shows the damping behavior variation with respect to temperature. Neat PLA reinforced with the fibers reduces its damping behavior. The Tan Δ value of neat PLA is found to be higher than all developed composites. It is found that Jute/PLA has a lower damping factor value (0.65). The glass transition temperature ( T g ) of material also determined using damping factor curve where the polymer mobility is about to begin. From Fig. 12c , it was found that the damping curve showed that flax/PLA has the highest value of ( T g ) of 68.68 °C compared to other biocomposites. This proves that the flax/PLA requires a higher temperature to start molecules mobility 138 .

Acoustic properties

Natural fiber-reinforced materials have advantages such as better acoustic properties. Because of the great potential of natural fibers to absorb sound, several studies were reported in the literature showing the possibility of using natural fiber rather than synthetic fiber for sound acoustic absorbers. Natural fibers as sound-absorbing materials have an essential consideration in the fabrication of sound-absorbing materials for buildings in today’s environment. Most natural fibers function as porous absorbers when it comes to sound absorption. Porosity appears to be one of the factors that define the absorption properties of any fibrous material. Also, density and thickness of fiber are other factors. The porous material with sound absorption is characterized by a very weak absorption coefficient in the small frequency range but with better acoustic properties in the high-frequency range 118 .

Natural fibers have good acoustic properties and are utilized in various applications such as vehicles, soundboards, and thermal and acoustic panels 140 . Values of acoustic absorption coefficients of selected natural fibers are listed in Table 5 141 , 142 , 143 , 144 . Chin et al. 145 have made a PLA as a polymer matrix reinforced with kenaf fiber. They found that when the kenaf fiber content is 30%, the maximum sound absorption coefficient 0.987 appears at 1521 Hz frequency, and the mechanical properties also improved 141 .

Surface morphology

Polymers and fiber testing and analysis using surface morphology is one of the areas that need a unique method for creating fully prepared samples. The fibers are tested before and after various processes, including fracture surface. Results are accurate and reliable. Surface analysis can measure dispersed phase at all scales, from micro to nano scale. Scanning electron microscopy provides information on the interaction between matrix and dispersed phase 146 .

In order to study the PLA and natural fiber biocomposites, Xia et al. 147 used alkaline treatment, maleic anhydride (MA) grafting treatment, aminopropyl triethoxysilane treatment, and corona discharge treatment to modify the surface of flax fibers 17 , 148 . Lignin, hemicelluloses, waxes, and oils were successfully removed from the fiber surface using an alkali treatment. The fiber surface hydrophobic character was increased. Morphological changes resulting from the various treatment methods are shown in Fig. 13a–e 147 . It was noticed that the alkaline treatment increased the surface roughness leading to more contact points and an improvement in the mechanical interaction between PLA and fiber as shown in Fig. 13a . Maleic anhydride (MA) and silane act as coupling agents. Figure 13d, e shows the surface of the fibers coated with a layer of MA and silane where increased the interaction between the natural fiber and PLA 17 , 147 .

SEM pictures of a untreated fiber, b alkali-treated fiber, c coronatreated fiber, d MA-grafted fiber, and e silane-treated fiber 147 .

Fracture surface of neat PLA and PLA/flax composites were studied by Xia et al. Figure 14a, b shows that the neat PLA fracture surface is smooth compared with the PLA/flax biocomposites. This refers to brittle fracture. After tensile test, flax fibers were pulled-out from the PLA matrix, leaving a substantial number of fragments 147 . Also, the remaining fibers showed smooth and clean surface and does not contain any layers of polymer matrix. Furthermore, there are numerous holes in the PLA matrix/fiber interfaces, resulting from a relatively poor interface strength between the untreated fiber and PLA 147 , 148 , 149 . The tough fracture morphology is significantly different from the neat PLA and PLA/untreated fiber composite fracture as shown in Fig. 14c–e . Inside the matrix, fibers are well dispersed, and between the fiber and matrix there are no gaps. The remaining of flax fibers were coated with PLA matrix, indicating that the treated flax fibers and PLA have better interfacial force. The results are in a good agreement with toughness results that are obtained by mechanical testing.

SEM pictures of impact fracture surface of a neat PLA, b PLA/untreated, c PLA/alkali-treated, d PLA/MA-grafted, and e PLA/silane-treated composites 147 .

Spectroscopic characterization

The functional groups of polymer composites that might be responsible for the polymer/natural fiber interaction are determined using effective approach of Fourier transform infrared spectroscopy (FTIR) 150 , 151 , 152 , 153 . The FTIR analysis peaks for various untreated natural fibers are listed in Table 6 53 , 154 , 155 , 156 , 157 . The spectroscopic properties of treated sisal fibers by benzylated were studied. It was that peaks at 1250 cm −1 and 1363 cm −1 which are assigned to lignin and hemicellulose. They were successfully removed in the treatment process of sisal fiber. Mofokeng et al. 158 studied the interaction of random and oriented PLA/sisal fiber composite using FTIR analysis as shown in Fig. 15 . Peaks at 1780–1680 cm −1 are assigned to C = O stretches, 3600–3000 cm −1 corresponding to O–H stretches, and 1180 cm −1 referred to C– O–C stretches. Due to the existence of free OH groups in the fiber, the presence of the O–H bonds in the composites became more apparent and wider as the fiber loading increases. They also found that hydroxyl groups developed a new peak at 1650 cm −1 , which is assigned to the absorbed water molecules 53 .

FTIR spectra of random-oriented sisal fiber/PLA composite manufactured by a technique of injection molding 158 .

Using infrared spectra, Xia et al. 145 investigated the untreated flax (UF), alkali-treated fiber, corona-treated fiber, MA grafted fiber, and silane-treated fiber. The samples were analyzed with a spectral resolution of 2 cm −1 and a spectrum of 4000 cm −1 to 500 cm −1 . The FTIR spectra of treated and untreated flax fibers are shown in Fig. 16 . The components of flax fiber are cellulose, hemicelluloses, and lignin. These components can be identified using FTIR spectra. C–O and C–O–C looked stretched at 1170 and 1030 cm −1 , respectively. The –C = O stretching of aliphatic carboxylic acid and ketone groups in the cellulose chain showed the peak at 1654 cm −1 . The absorption of –C–H in flax fiber cellulose showed a peak at around 2900 cm −1 . The largest peak was the –OH stretching of D-pyran glucose in the cellulose chain at 3400 cm −1 . It was noticed that the band at 1735 cm −1 (–C = O) stretching of aldehyde carbonyl is assigned to lignin and hemicellulose. Figure 16b shows that the band at 1735 cm −1 was vanished in the alkali-treated fiber indicating that the lignin and hemicellulose of flax fiber were removed by NaOH solution treatment. Due to the alkali treatment, the band at 1735 cm −1 was not visible in the MA-grafted treated fiber, corona-treated fiber, and silane-treated fiber spectra, as shown in Fig. 16c–e 147 .

FTIR spectra of (a) untreated fiber, (b) alkali-treated fiber, (c) MA grafted fiber, (d) corona-treated fiber, and (e) silane-treated fiber 147 .

Theoretical modeling of mechanical properties of biocomposites

Several studies were conducted to explore if natural fiber composites are applicable for structural and non-structural applications. The tensile properties of synthesized composites are frequently measured using a variety of mechanical tests. Young’s modulus and strength of discontinuous and continuous fiber composites were reported using micromechanical models. The fundamental rule of mixtures is often used to calculate Young’s modulus and strength of reinforced composites by unidirectional continuous fiber in longitudinal and transverse loading. However, rule of Mixtures model is no longer obeyed if the fibers are discontinuous. The tensile characteristics of discontinuous fiber composites are influenced by the fiber’s length, dispersibility, orientation, and the interfacial force between the matrix and natural fiber. The orientation of the fibers and stress transfer are strongly correlated with tensile properties of polymer composites. Several models were developed to estimate composite tensile characteristics while accounting for the aforementioned conditions. Nevertheless, there is a wide range of results 159 .

The rule of Mixtures model was modified for fibers parallel to the loading direction by including Kelly and Tyson. Various ways for predicting young’s modulus and strength of non-continuous fiber composites were applied. It is based totally on the distribution of stress of the dispersed fibers in the plastic matrix. It is supposed that shear forces on the fiber-matrix interface shift the applied load to the fibers, as defined in the Cox model. Shear stress at the interface is expected to keep constant until the fiber strain equals the matrix strain where the average fiber stress and the shear stress at the interface will be zero. In this model, the critical fiber length ( L c ) is defined as the average fibers’ length relative to the fiber length, which is known as the shortest possible length to carry the load. It could be obtained by experimentation or micromechanics, like a model suggested by Bowyer-Bader. The fiber fragmentation test and a pull-out test are the most popular techniques used to determine the critical fiber length, which could be obtained using below equation:

Where D is the average fiber diameter and τ is the interfacial shear strength.

It is clear that the decrease in critical fiber length makes an improvement to the interfacial shear strength. If the fiber length is equal to L c (critical fiber), the ultimate fiber tensile stress is achieved only at the center of the fiberIf the fiber length exceeds L c , reinforcement of fiber becomes more efficient and ultimate tensile stress within the fibers can be achieved along a greater length. And finally, if the fiber length is less than (subcritical fiber), it would ultimately pull-out from the matrix.

Efendy et al. 159 investigated the tensile properties of a PLA composite reinforced with harakeke and hemp mats of fiber. They compared experimental results with predicted values using different models. Results are displayed in Fig. 17a, b . For Hirsch, it is found that, when the fitting parameter x = 0.13, it gave a better correlation with the experimental strengths. When the fiber content increased up to 30 wt%, Modified Cox models were shown to demonstrate logical agreement with experimental tensile strength as shown in Fig. 17a, b . The fitted, predicted, and experimental young’s modulus of the two fiber polymer composites with different fiber loading are shown in Fig. 17c, d The modified Halpin-Tsai and Cox models, which take into consideration the interconnection integrity between the polymer matrix and the fibers are the best models for predicting Young’s modulus at fiber loading up to 25% by weight 159 .

Variation of actual and predicted a tensile strength of PLA/harakeke Biocomposites, b tensile strength of PLA/hemp fiber biocomposites, c Young’s moduli of PLA/harakeke biocomposites, and d Young’s moduli of PLA/hemp fiber 159 .

Future perspective of biodegradable polymer

The need to develop sustainable alternatives to oil-based polymers has sparked a lot of study. Biodegradable polymers are also appealing materials for biomedical applications due to their unique physicochemical, biological, and degrading features. They help in reducing greenhouse gas emissions and fossil resource depletion 160 , 161 . Currently, biopolymers are being used and produced in small quantities around the world. They are used mainly for food packaging and bioplastic industries. In the future, studies need to be conducted to improve the polymeric properties of these biodegradable materials by combining different types of polymers in varying ratios to see how they affect the physical and chemical properties of biomaterials. The medical industry will benefit greatly since biopolymer-based bio-implants and drug carriers’ agents are now being developed. More advancements in the future might result in a revolution in medical implants in terms of economic effectiveness.

The United Nations General Assembly approved 17 sustainable development goals (SDGs) to be implemented by 2030. The SDGs objectives reflect a comprehensive approach to achieving a society that is both healthy and sustainable. Bioplastic production establishes a foundation for environmentally friendly product development. Most of sustainable development goals are made possible by the plastic industry and polymers, which are widespread and adaptable materials 162 . Materials science helps to achieve a variety of goals, according to report maps of the most recent sustainability research and activities namely; SDG 2: zero hunger, SDG 3: good health and well-being, SDG 6: clean water and sanitation, SDG 7: affordable and clean energy, SDG (9): industry, innovation, and infrastructure, SDG 11: sustainable cities and communities, SDG 12: responsible consumption and production, SDG 13: climate action, and SDG 14: life below water are among the 17 SDGs 162 . The carbon footprint of both the raw and final product is minimized since bioplastics are made from monomers derived from agricultural waste. Through its sourcing, manufacture, marketing, consumption, and removal, the recyclable characteristic of bioplastics assures that the commodity is commercially, socially, and ecologically acceptable. As a result, consumers’ lives are enhanced, and the community as whole benefits 163 . Energy, waste disposal, and operating costs may all be reduced by adopting sustainable materials 164 . It is clear that biopolymers will open up new possibilities in the effort to establish a better environment devoid of hazardous substances and products.

Forensic engineering of advanced biodegradable polymer systems

The study of failure in polymer products is the focus of traditional forensic polymer engineering. This branch of science deals with the breaking of plastic items, as well as any other reason for the product’s inability to function or meet its standards 165 . Ex-post analyses of classic polymeric materials or their thermoplastic composites have been the focus of most forensic polymer engineering case studies 166 .

One of the major drawbacks of biodegradable polymers derived from renewable sources is their rapid rate of degradation due to the hydrophilic nature and, in certain circumstances, low mechanical properties, especially in water environment. Despite their drawbacks, biodegradable polymers have a number of benefits due to the fact that they are made from a variety of plant components 167 . Bio-polyesters have recently gained prominence as a result of their biodegradability and possible medical uses. Specific aspects such as biodegradation methods, biocompatibility, processing conditions, and prospective uses in medicine, environmental protection, and agro-chemistry have received a lot of attention. The bio-safety of such advanced biodegradable polymers as well as the nano-safety of their composite continues to be negligible. This new perspective focuses on predicting, evaluating and indicating possible issues associated with advanced polymer usage. The approach created by forensic engineering of advanced polymeric materials (FEAPM) would be used to analyze associations between polymeric materials’ structures, characteristics, and behaviors before, during, and after actual applications. This should aid in the development of new sophisticated polymeric materials, reducing the number of product flaws that occur during manufacture and use. The economic and societal effect of FEAMP investigations is projected to be significant, allowing for the identification of safe advanced polymers in a future sustainable society. Failure modes are well reported for several applications and laboratories scales. These studies do not only study failures but also work on reducing the possibility of their causes.

Mechanical failure

Mechanical failure is easy to be realized if the loads and dimensions of a product are known at specific time over its life 168 . Fracture is one of the most prevalent failure modes 169 . It could take place under various conditions such as overload, creep, stress relaxation, fatigue, and wear 170 , 171 , 172 .

Loading patterns

Tension, compression, bending, shear, torsion, and impact are all examples of how the polymer is exposed to stress. Loading patterns are commonly result from one or more factors.

When evaluating loading patterns, it is notably that forces must be coupled in a chain via a product to produce a path. When there are many distinct components along a path, the load takes on diverse shapes as it travels along with it. The compressive local load on the flat surface would decrease from the point of contact until it reaches zero. To counteract the compressive force, a tension force would be generated to the surface.

Stress concentrations

They are localized form deviations caused by the product’s stress lines being pressed together and amplified. Cracks in or at the edges of bodies, holes in flat sheets, voids inside materials, corners and fillets, change in the profile of shafts, and screw threads are just a few simple examples of stress concentration.

Chemical attack

If mechanical failure occurred in a complex process, a chemical attack on a product would begin as a complicated problem. The fact that materials may be attacked in variable ways reflects the complex process. Polymers might be exposed to chemicals in service, beginning with the atmospheric air. When the product is loaded or has in-built forces that can be alleviated through fracture development, the situation becomes much more significant. Although hydrolysis is a prominent degradation process for one type of polymer, oxidation may be the most prevalent kind of assault in its many varied incarnations.

The main active element is oxygen (O 2 ) in the air (around 21% by volume), although there are numerous additional chemicals that breakdown polymers as well (degraded many thermoplastics). Ozone gas is one of the most powerful oxidizing agents. Because oxidizing chemicals are ubiquitous in our environment, oxidation must always be considered a potential attack vector.

Alkali and acids break down polymers by hydrolysis, where the polymer chain is broken by the cleavage of functional groups that bind the chains together. Dramatic decrease in the molecular weight is found as the chains are reduced in length at each stage. Water have a negative impact on most polymers due to its widespread presence. Hydrolysis step of polymers are direct or indirect process. When high temperatures enhance the risks of hydrolysis during processing or shaping, the issue appears. Because most processing temperatures exceed 100°C, any liquid water in the feedstock will evaporate and cause undesirable bubbles in the final product.

Ultraviolet radiation

Exposure to UV radiation from the sun is a typical cause of failure in many polymers. Polymers containing double bonds or other absorbing functional groups are the most vulnerable to UV deterioration. UV damage can cause cracking and the creation of a damaged layer on the surface, as well as the bleaching of pigments, a process known as whitening.

Stress corrosion cracking

Stress corrosion cracking (SCC) is a common failure mechanism caused by a chemical assault on polymers. Microcracks can be caused by trace concentrations of strong chemicals, which further increase slowly over applied stresses or by an issue known as frozen-in strain. Other types of SCC in polymers include attacks by oxygen, ozone, and chlorine, which need a low stress or strain threshold for crack formation 173 .

Environmental stress cracking (ESC)

Among the most common prevalent causes of abrupt brittle breaking of thermoplastic polymers is environmental stress cracking (ESC). The chemical composition of the polymer, bonding, crystallinity, surface roughness, molar mass, and residual stress are all variables that impact the rate of ESC. There is no long-term chemical alteration, although the symptoms are similar to those of SCC. Srisa et al. 174 studied antifungal bioplastic films, developed based on PLA and poly(butylene adipateco- terephthalate) (PBAT) blends with incorporated trans-cinnamaldehyde. Mold was discovered on bread that were preserved in ordinary PP films. According to PP’s forensic engineering, additional storage resulted in the development of fungal growth over the entire loaf on day 4 as shown in Fig. 18 , 1 a. Mold mycelium expansion was successfully reduced by PLA/PBAT films and microbiological growth was not detected in any of the films containing trans-cinnamaldehyde (Fig. 18a ). This is because the bacteria were successfully suppressed by large levels of trans-cinnamaldehyde release.

a Appearance of packaged bread stored in (1) PP and (2) PLA and PBAT blend films with different concentrations of transcinnamaldehy, and b stress–strain curves of PLA samples with various porosity and 3D printed design deformed in three-point bending (top). Comparison of failure modes of specimens 174 , 175 .

Juraj Svatík et al. 175 studied the mechanical strength and toughness of neat PLA and PLA bamboo biocomposites. It was found that the solid specimen and uniform porosity specimens were brittle and was broken up catastrophically. However, the gradient porosity specimens were quasi-ductile with no catastrophic breakdown and much greater strain at break as shown in Fig. 18b.

Data availability

The data that support the findings of this study are available from the corresponding author upon request.

Pan, D., Su, F., Liu, C. & Guo, Z. Research progress for plastic waste management and manufacture of value-added products. Adv. Compos Hybrid. Mater. 3 , 443–461 (2020).

Article   CAS   Google Scholar  

Moharir, R. V. & Kumar, S. Challenges associated with plastic waste disposal and allied microbial routes for its effective degradation: A comprehensive review. J. Clean. Prod. 208 , 65–76 (2019).

Luckachan, G. E. & Pillai, C. K. S. Biodegradable polymers- a review on recent trends and emerging perspectives. J. Polym. Environ. 19 , 637–676 (2011).

Zhong, Y., Godwin, P., Jin, Y. & Xiao, H. Biodegradable polymers and green-based antimicrobial packaging materials: A mini-review. Adv. Ind. Eng Polym. Res. 3 , 27–35 (2020).

Google Scholar  

Ernesto D. M., & Salvatore I. Biodegradable composites. wiley encyclopedia of composites, 1–18. https://doi.org/10.1002/9781118097298.weoc013 (2011).

Rigolin, T. R., Takahashi, M. C., Kondo, D. L. & Bettini, S. H. P. Compatibilizer acidity in coir-reinforced PLA composites: matrix degradation and composite properties. J. Polym. Environ. 27 , 1096–1104 (2019).

Peng, X., Dong, K., Wu, Z., Wang, J. & Wang, Z. L. A review on emerging biodegradable polymers for environmentally benign transient electronic skins. J. Mater. Sci. 56 , 16765–16789 (2021).

Taha, T. H. et al. Profitable exploitation of biodegradable polymer including chitosan blended potato peels’ starch waste as an alternative source of petroleum plastics. Biomass Convers. Biorefinery https://doi.org/10.1007/s13399-021-02244-9 (2022).

Zhu, J. & Wang, C. Biodegradable plastics: Green hope or greenwashing? Mar. Pollut. Bull. 161 , 111774 (2020).

Künkel, A., et al. Polymers, Biodegradable”. Ullmann’s encycl. ind. chem. 1–29 https://doi.org/10.1002/14356007.n21_n01.pub2 (2016).

Ghanbarzadeh, B. & Hadi A. Biodegradable polymers. Biodegradation-life of science, 141–185, https://doi.org/10.5772/56230 (2013).

Zhang, L., Jing, Z., & Xiaofeng, R. Natural fiber-based biocomposites. Green biocomposites. 31–70 (Springer, Cham, 2017).

Cazaudehore, G. et al. Can anaerobic digestion be a suitable end-of-life scenario for biodegradable plastics? A critical review of the current situation, hurdles, and challenges. Biotechnol. Adv. 56 , 107916 (2022).

Payne, J., McKeown, P. & Jones, M. D. A circular economy approach to plastic waste. Polym. Degrad. Stab. 165 , 170–181 (2019).

Kalia, Susheel, B. S. Kaith, Inderjeet Kaur, eds. Cellulose fibers: bio-and nano-polymer composites: green chemistry and technology. Springer Science & Business Media. https://doi.org/10.1007/978-3-642-17370-7 (2011).

Balla, V. K., Kate, K. H., Satyavolu, J., Singh, P. & Tadimeti, J. G. D. Additive manufacturing of natural fiber reinforced polymer composites: Processing and prospects. Compos Part B Eng. 174 , 106956 (2019).

Ferreira, D. P., Cruz, J. & Fangueiro, R. Surface modification of natural fibers in polymer composites. Green Composites for Automotive Applications (Elsevier Ltd). https://doi.org/10.1016/B978-0-08-102177-4.00001-X (2018).

Ho, M. P. et al. Critical factors on manufacturing processes of natural fibre composites. Compos. Part B Eng. 43 , 3549–3562 (2012).

Yang, J., Ching, Y. C. & Chuah, C. H. Applications of Lignocellulosic Fibers and Lignin in. Polym. (Basel) 11 , 1–26 (2019).

Karthika, M. et al. Biodegradation of Green Polymeric Composites Materials. Bio Monomers Green Polym. Compos. Mater . 141–159, https://doi.org/10.1002/9781119301714.ch7 (2019).

Engineer, C., Parikh, J. & Raval, A. Review on hydrolytic degradation behavior of biodegradable polymers from controlled drug delivery system. Trends Biomater. Artif. Organs 25 , 79–85 (2011).

Saini, R. D. Biodegradable polymers. Int. J. Appl. Chem. 13 (2), 179–196 (2017).

Shivam, P. Recent Developments on biodegradable polymers and their future trends. Int. Res. J. Sci. Eng. 4.1 , 17–26 (2016).

Jha, K., Kataria, R., Verma, J. & Pradhan, S. Potential biodegradable matrices and fiber treatment for green composites: A review. AIMS Mater. Sci. 6 , 119–138 (2019).

Balaji, A. B., Pakalapati, H., Khalid, M., Walvekar, R. & Siddiqui, H. Natural and synthetic biocompatible and biodegradable polymers. Biodegradable and Biocompatible Polymer Composites: Processing, Properties and Applications. https://doi.org/10.1016/B978-0-08-100970-3.00001-8 (2017).

Niemelä, T. & Kellomäki, M. Bioactive glass and biodegradable polymer composites. Bioactive Glasses: Materials, Properties and Applications (Woodhead Publishing Limited). https://doi.org/10.1533/9780857093318.2.227 (2011).

Maraveas, C. Production of sustainable and biodegradable polymers from agricultural waste. Polym. (Basel) 12 (2020).

Bassyouni, M., Zoromba, M. S., Abdel-Aziz, M. H. & Mosly, I. Extraction of Nanocellulose for Eco-Friendly Biocomposite Adsorbent for Wastewater Treatment. Polym. (Basel) 14 (2022).

Jiang, L. & Zhang, J. 7 Biodegradable and Biobased Polymers. Applied Plastics Engineering Handbook (Elsevier Inc.). 127–143. https://doi.org/10.1016/B978-0-323-39040-8/00007-9 (2017).

Kumar, Satish & Thakur, K. S. Bioplastics-classification, production and their potential food applications. J. Hill Agric 8 , 118–129 (2017).

Article   Google Scholar  

Shah, T. V. & Vasava, D. V. AL-Self-dual Leonard pairs A glimpse of biodegradable polymers and biomedical applications. E-Polym. 19 , 385–410 (2019).

Biduski, B. et al. Starch hydrogels: The influence of the amylose content and gelatinization method. Int. J. Biol. Macromol. 113 , 443–449 (2018).

Perez-Rea, D., Bergenståhl, B. & Nilsson, L. Development and evaluation of methods for starch dissolution using asymmetrical flow field-flow fractionation. Part I: Dissolution of amylopectin. Anal. Bioanal. Chem. 407 , 4315–4326 (2015).

Zhang, Z., Ortiz, O., Goyal, R. & Kohn, J. Biodegradable Polymers. Handbook of Polymer Applications in Medicine and Medical Devices. https://doi.org/10.1016/B978-0-323-22805-3.00013-X (Elsevier Inc., 2014).

Mülhaupt, R. Green polymer chemistry and bio-based plastics: Dreams and reality. Macromol. Chem. Phys. 214 , 159–174 (2013).

Asghari, F., Samiei, M., Adibkia, K., Akbarzadeh, A. & Davaran, S. Biodegradable and biocompatible polymers for tissue engineering application: a review. Artif. Cells, Nanomed. Biotechnol. 45 , 185–192 (2017).

CAS   Google Scholar  

Vasiljevic, Ljubica, and Stefan Pavlović. Biodegradable polymers based on proteins and carbohydrates. Advances in Applications of Industrial Biomaterials. 87–101 (Springer, Cham, 2017).

Soleymani Eil Bakhtiari, S., Karbasi, S. & Toloue, E. B. Modified poly(3-hydroxybutyrate)-based scaffolds in tissue engineering applications: A review. Int. J. Biol. Macromol. 166 , 986–998 (2021).

Tebaldi, M. L., Maia, A. L. C., Poletto, F., de Andrade, F. V. & Soares, D. C. F. Poly(-3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV): Current advances in synthesis methodologies, antitumor applications and biocompatibility. J. Drug Deliv. Sci. Technol. 51 , 115–126 (2019).

Perveen, K., Masood, F. & Hameed, A. Preparation, characterization and evaluation of antibacterial properties of epirubicin loaded PHB and PHBV nanoparticles. Int. J. Biol. Macromol. 144 , 259–266 (2020).

Yeo, J. C. C., Muiruri, J. K., Thitsartarn, W., Li, Z. & He, C. Recent advances in the development of biodegradable PHB-based toughening materials: Approaches, advantages and applications. Mater. Sci. Eng. C. 92 , 1092–1116 (2018).

Mangaraj, S., Yadav, A., Bal, L. M., Dash, S. K. & Mahanti, N. K. Application of biodegradable polymers in food packaging industry: a comprehensive. Rev. J. Packag. Technol. Res. 3 , 77–96 (2019).

Tian, K. & Bilal, M. Research progress of biodegradable materials in reducing environmental pollution. Abatement of Environmental Pollutants: Trends and Strategies. https://doi.org/10.1016/B978-0-12-818095-2.00015-1 (Elsevier Inc., 2019).

Balla, E. et al. Poly(lactic acid): A versatile biobased polymer for the future with multifunctional properties-from monomer synthesis, polymerization techniques and molecular weight increase to PLA applications. Polym. (Basel) 13 (2021).

Gentile, P., Chiono, V., Carmagnola, I. & Hatton, P. V. An overview of poly(lactic-co-glycolic) Acid (PLGA)-based biomaterials for bone tissue engineering. Int. J. Mol. Sci. 15 , 3640–3659 (2014).

Sisson, A. L., Ekinci, D. & Lendlein, A. The contemporary role of ε-caprolactone chemistry to create advanced polymer architectures. Polym. (Guildf.) 54 , 4333–4350 (2013).

Rafiqah, S. A. et al. A review on properties and application of bio‐based poly(Butylene succinate). Polym. (Basel) 13 , 1–28 (2021).

Shaikh, S., Yaqoob, M. & Aggarwal, P. An overview of biodegradable packaging in food industry. Curr. Res. Food Sci. 4 , 503–520 (2021).

Makhijani, K., Kumar, R. & Sharma, S. K. Biodegradability of blended polymers: A comparison of various properties. Crit. Rev. Environ. Sci. Technol. 45 , 1801–1825 (2015).

Ibrahim, N. I. et al. Overview of bioplastic introduction and its applications in product packaging. Coatings 11 , 1423 (2021).

Kumar, K. P. & Sekaran, A. S. J. Some natural fibers used in polymer composites and their extraction processes: A review. J. Reinf. Plast. Compos. 33 , 1879–1892 (2014).

Kalia, S. et al. Cellulose-based bio- and nanocomposites: A review. Int. J. Polym. Sci. 2011 , 1–35 (2011).

Gholampour, A. & Ozbakkaloglu, T. A review of natural fiber composites: properties, modification and processing techniques, characterization, applications. J. Mater. Sci. vol. 55 (Springer US, 2020).

Ahmad, F., Choi, H. S. & Park, M. K. A review: Natural fiber composites selection in view of mechanical, light weight, and economic properties. Macromol. Mater. Eng. 300 , 10–24 (2015).

Rong, M. Z., Zhang, M. Q., Liu, Y., Cheng Yang, G. & Min Zeng, H. Effect of fiber treatment on the mechanical properties of unidirectional sisal-reinforced epoxy composites. Compos. Sci. Technol . 61 , 1437–1447 (2001).

Jawaid, M. & Abdul Khalil, H. P. S. Cellulosic/synthetic fibre reinforced polymer hybrid composites: A review. Carbohydr. Polym. 86 , 1–18 (2011).

Bassyouni, M. & Waheed Ul Hasan, S. The use of rice straw and husk fibers as reinforcements in composites. Biofiber Reinforcements in Composite Materials. https://doi.org/10.1533/9781782421276.4.385 (2015).

Bassyouni, M., Sherif, S. A., Sadek, M. A. & Ashour, F. H. Synthesis and characterization of polyurethane - Treated waste milled light bulbs composites. Compos Part B Eng. 43 , 1439–1444 (2012).

Hussain, A. et al. Pyrolysis of Saudi Arabian date palm waste: A viable option for converting waste into wealth. Life Sci. J. 11 , 667–671 (2014).

Bassyouni, M., Taha, I., Abdel-Hamid, S. M. S. & Steuernagel, L. Physico-mechanical properties of chemically treated polypropylene rice straw bio-composites. J. Reinf. Plast. Compos. 31 , 303–312 (2012).

S, S. K. & Hiremath, S. S. Natural Fiber Reinforced Composites in the Context of Biodegradability: A Review. Encyclopedia of Renewable and Sustainable Materials. 322 (Elsevier Ltd., 2020).

Verma, D., Gope, P. C., Shandilya, A., Gupta, A. & Maheshwari, M. K. Coir fibre reinforcement and application in polymer composites: A review. J. Mater. Environ. Sci. 4 , 263–276 (2013).

Rohit, K. & Dixit, S. A review - future aspect of natural fiber reinforced composite. Polym. Renew. Resour. 7 , 43–60 (2016).

Saxena, M., Pappu, A., Sharma, A., Haque, R. & Wankhede, S. Composite Materials from Natural Resources: Recent Trends and Future Potentials. Adv. Compos. Mater. - Anal. Nat. Man-Made Mater . https://doi.org/10.5772/18264 (2011).

Kilinç, A. Ç., Durmuşkahya, C. & Seydibeyoğlu, M. Ö. Natural fibers. Fiber Technol. Fiber-Reinforced Compos . 209–235 https://doi.org/10.1016/B978-0-08-101871-2.00010-2 (2017).

Arjmandi, R. et al. Kenaf fibers reinforced unsaturated polyester composites: A review. J. Eng. Fiber. Fabr . 16 (2021).

Gohil, P., Patel, K. & Chaudhary, V. Natural fiber-reinforced polymer composites: A comprehensive study on machining characteristics of hemp fiber-reinforced composites. Biomass, Biopolymer-Based Materials, and Bioenergy: Construction, Biomedical, and other Industrial Applications (Elsevier Ltd). https://doi.org/10.1016/B978-0-08-102426-3.00002-3 (2019).

Crini, G., Lichtfouse, E., Chanet, G. & Morin-Crini, N. Applications of hemp in textiles, paper industry, insulation and building materials, horticulture, animal nutrition, food and beverages, nutraceuticals, cosmetics and hygiene, medicine, agrochemistry, energy production and environment: a review. Environ. Chem. Lett. 18 , 1451–1476 (2020).

Shahinur, S., Hasan, M., Ahsan, Q., Saha, D. K. & Islam, M. S. Characterization on the Properties of Jute Fiber at Different Portions. Int. J. Polym. Sci. 2015, (2015).

Kalita, B. B., Gogoi, N. & Kalita, S. Properties of ramie and its blends. Int. J. Eng. Res. Gen. Sci. 1 , 1–6 (2013).

Fink, J. K. Unsaturated polyester resins. reactive polymers: fundamentals and applications, 1–69. https://doi.org/10.1016/B978-0-12-814509-8.00001-4 (2018).

Puttegowda, M. et al. Potential of natural/synthetic hybrid composites for aerospace applications. Sustainable Composites for Aerospace Applications (Elsevier Ltd). https://doi.org/10.1016/B978-0-08-102131-6.00021-9 (2018).

Benítez-Guerrero, M., Pérez-Maqueda, L. A., Artiaga, R., Sánchez-Jiménez, P. E. & Pascual-Cosp, J. Structural and chemical characteristics of sisal fiber and its components: effect of washing and grinding. J. Nat. Fibers 14 , 26–39 (2017).

Simbaña, E. A. et al. Abaca: Cultivation, obtaining fibre and potential uses. Handb. Nat. Fibres Second Ed. 1 , 197–218 (2020).

Keya, K. N. et al. Natural fiber reinforced polymer composites: history, types, advantages, and applications. Mater. Eng. Res. 1 , 69–87 (2019).

Lotfi, A., Li, H., Dao, D. V. & Prusty, G. Natural fiber–reinforced composites: A review on material, manufacturing, and machinability. J. Thermoplast. Compos. Mater. 34 , 238–284 (2021).

Sood, M. & Dwivedi, G. Effect of fiber treatment on flexural properties of natural fiber reinforced composites: A review. Egypt. J. Pet. 27 , 775–783 (2018).

Latif, R. et al. Surface treatments of plant fibers and their effects on mechanical properties of fiber-reinforced composites: A review. J. Reinf. Plast. Compos. 38 , 15–30 (2019).

Komuraiah, A., Kumar, N. S. & Prasad, B. D. Chemical composition of natural fibers and its influence on their mechanical properties. Mech. Compos. Mater. 50 , 359–376 (2014).

Ali, A. et al. Hydrophobic treatment of natural fibers and their composites—A review. J. Ind. Text. 47 , 2153–2183 (2018).

Sheng, K., Qian, S. & Wang, H. Influence of potassium permanganate pretreatment on mechanical properties and thermal behavior of moso bamboo particles reinforced PVC composites. Polym. Compos. 35 , 1460–1465 (2014).

Ouarhim, W., Zari, N., Bouhfid, R. & Qaiss, A. E. K. Mechanical performance of natural fibers-based thermosetting composites. Mech. Phys. Test. Biocomposites, Fibre-Reinforced Compos. Hybrid Compos. 43–60 https://doi.org/10.1016/B978-0-08-102292-4.00003-5 (2018).

Sonar, T., Patil, S., Deshmukh, V. & Acharya, R. Natural Fiber Reinforced Polymer Composite Material-A Review. 142–147 (2015).

Silva, N. G. S, T. F Maia, and D. R Mulinari. effect of acetylation with perchloric acid as catalyst in sugarcane bagasse waste. J. Nat. Fibers , 1–15. (2021).

Jena, P. K., Mohanty, J. R. & Nayak, S. Effect of surface modification of vetiver fibers on their physical and thermal properties. J. Nat. Fibers 19 , 25–36 (2022).

Godara, S. S. ScienceDirect Effect of chemical modification of fiber surface on natural fiber composites: A review. Mater. Today Proc. 18 , 3428–3434 (2019).

Vinayagamoorthy, R. Influence of fiber surface modifications on the mechanical behavior of Vetiveria zizanioides reinforced polymer composites. J. Nat. Fibers 16 , 163–174 (2019).

Punyamurthy, R., Sampathkumar, D. & Bennehalli, B. Influence of Fiber Content and Effect of Chemical Pre-Treatments on Mechanical Characterization of Natural Abaca Epoxy Composites. 8 (2015).

Tanas, F. Modified hemp fibers intended for fiber-reinforced polymer composites used in structural applications — A review. I. Methods of modification. 1–27 https://doi.org/10.1002/pc.25354 (2019).

Anbupalani, M. S. & Venkatachalam, C. D. Influence of coupling agent on altering the reinforcing efficiency of natural fibre-incorporated polymers – A review. https://doi.org/10.1177/0731684420918937 (2020).

Imoisili, P. E. & Jen, T. Mechanical and water absorption behaviour of potassium permanganate (KMnO 4) treated plantain (Musa Paradisiacal) fibre / epoxy bio-composites. Integr. Med. Res. 9 , 8705–8713 (2020).

Amiandamhen, S. O., Meincken, M. & Tyhoda, L. Natural fibre modification and its influence on fibre-matrix interfacial properties in biocomposite. Materials 21 , 677–689 (2020).

Zille, A., Oliveira, R. & Souto, P. Plasma treatment in textile industry. 1–34 https://doi.org/10.1002/ppap.201400052 (2014).

Adekomaya, O. & Majozi, T. Sustainability of surface treatment of natural fibre in composite formation: challenges of environment-friendly option. Int J. Adv. Manuf. Technol. 105 , 3183–3195 (2019).

Koohestani, B., Darban, A. K., Mokhtari, P., Yilmaz, E. & Darezereshki, E. Comparison of different natural fiber treatments: a literature review. Int. J. Environ. Sci. Technol 16 , 629–642 (2019).

Carada, P. T. D., Fujii, T., & Okubo, K. Effects of heat treatment on the mechanical properties of kenaf fiber. In AIP Conference Proceedings AIP Publishing LLC (Vol. 1736, p. 020029). (2016).

Kalia, Susheel et al. Surface modification of plant fibers using environment friendly methods for their application in polymer composites, textile industry and antimicrobial activities: A review. J. Environ. Chem. Eng. 1 , 97–112 (2013).

Liu, L. et al. Enzymatic treatment of mechanochemical modified natural bamboo fibers. Fibers Polym. 13 , 600–605 (2012).

Siakeng, R. et al. Natural fiber reinforced polylactic acid composites: a review. 1–18 https://doi.org/10.1002/pc.24747 (2018).

Kenned, J. J., Sankaranarayanasamy, K. & Kumar, C. S. Chemical, biological, and nanoclay treatments for natural plant fiber-reinforced polymer composites: A review. https://doi.org/10.1177/0967391120942419 (2021).

Yin, G. Z. & Yang, X. M. Biodegradable polymers: a cure for the planet, but a long way to go. J. Polym. Res 27 , 38 (2020).

Kunduru, K. R., Basu, A., & Domb, A. J Biodegradable polymers: medical applications. Encyclopedia of Polymer Science and Technology, 1–22 (2016).

Manavitehrani, I. et al. Biomedical applications of biodegradable polyesters. https://doi.org/10.3390/polym8010020 (2016).

Farachi, F. & Ardisson, G. B. 3 Environmental fate and ecotoxicity assessment of biodegradable polymers. Handbook of biodegradable polymers. De Gruyter, 45–74 (2020).

Fredi, G. & Dorigato, A. Advanced industrial and engineering polymer research recycling of bioplastic waste: a review. Adv. Ind. Eng. Polym. Res. 4 , 159–177 (2021).

Lamberti, F. M., Román, L. A. & Joseph, R. Recycling of bioplastics: routes and benefits. J. Polym. Environ. 28 , 2551–2571 (2020).

Grigore, M. E. Methods of recycling, properties and applications of recycled thermoplastic. Polym. Recycling 2 , 24 (2017).

Niaounakis, M. Recycling of biopolymers—The patent perspective ☆ . Eur. Polym. J. 114 , 464–475 (2019).

Ragaert, K., Delva, L. & Van Geem, K. Mechanical and chemical recycling of solid plastic waste. Waste Manag 69 , 24–58 (2017).

Chanda, M. Advanced industrial and engineering polymer research chemical aspects of polymer recycling. Adv. Ind. Eng. Polym. Res. 4 , 133–150 (2021).

Francis, Raju, ed. Introduction. Recycling of polymers: methods, characterization and applications. John Wiley & Sons, 1–10 (2016).

Dimitris, S. & Achilias, L. A. Recent advances in the chemical recycling of polymers (PP, PS, LDPE, HDPE, PVC, PC, Nylon, PMMA). Mater. Recycl. Trends Perspect. 3 , 64 (2014).

Shesan, O. J., Stephen, A. C., Chioma, A. G., Neerish, R., & Rotimi, S. E. Fiber-Matrix Relationship for Composites Preparation. In Renewable and Sustainable Composites. IntechOpen. 9–38. (2019).

Shalwan, A. & Yousif, B. F. In State of Art: Mechanical and tribological behaviour of polymeric composites based on natural fibres. J. Mater. 48 , 14–24 (2012).

Mohammed, L., Ansari, M. N. M., Pua, G., Jawaid, M. & Islam, M. S. A Review on Natural Fiber Reinforced Polymer Composite and Its Applications. 2015 (2015).

Ngo, T-D. Natural fibers for sustainable bio-composites. Natural and artificial fiber-reinforced composites as renewable sources, 107–126 (2018).

Taiwo, E M, Khairulzan Y & Zaiton H. Potential of using natural fiber for building acoustic absorber: A review. Journal of Physics: Conference Series. 1262. (IOP Publishing, 2019).

Dittenber, D. B. & Gangarao, H. V. S.Composites: Part A critical review of recent publications on use of natural composites in infrastructure. Compos Part A 43 ,1419–1429 (2012).

Kim, W. et al. High strain-rate behavior of natural fiber-reinforced polymer composites. J. Compos. Mater. 46 , 1051–1065 (2012).

Khan, M. Z., Srivastava, S. K. & Gupta, M. K. Tensile and flexural properties of natural fiber reinforced polymer composites: a review. J. Reinf. Plast. Compos., 37 , 1435–1455 (2018).

Jeyapragash, R., Srinivasan, V. & Sathiyamurthy, S. Mechanical properties of natural fiber/particulate reinforced epoxy composites - A review of the literature. Mater. Today Proc. 22 , 1223–1227 (2020).

Pickering, K. L., Efendy, M. G. A. & Le, T. M. A review of recent developments in natural fibre composites and their mechanical performance. Compos. Part A Appl. Sci. Manuf. 83 , 98–112 (2016).

Sanjay, M. R., Arpitha, G. R. & Yogesha, B. Study on mechanical properties of natural - glass fibre reinforced polymer hybrid composites: a review. Mater. Today Proc. 2 , 2959–2967 (2015).

Sathishkumar, T. P., Satheeshkumar, S. & Naveen, J. Glass fiber-reinforced polymer composites - A review. J. Reinf. Plast. Compos. 33 , 1258–1275 (2014).

Song, Y. S. et al. Viscoelastic and thermal behavior of woven hemp fiber reinforced poly(lactic acid) composites. Compos. Part B Eng. 43 , 856–860 (2012).

Luyt, A. S. & Malik, S. S. Can biodegradable plastics solve plastic solid waste accumulation? Plastics to Energy: Fuel, Chemicals, and Sustainability Implications (Elsevier Inc.). https://doi.org/10.1016/B978-0-12-813140-4.00016-9 (2018).

Plackett, D. & Siró, I. Polyhydroxyalkanoates (PHAs) for food packaging. Multifunct. Nanoreinforced Polym. Food Packag. 498–526 https://doi.org/10.1533/9780857092786.4.498 (2011).

Biron, M. EcoDesign. Material selection for thermoplastic parts: practical and advanced information. William Andrew. pp. 603–653 (2015).

Nair, N. R., Sekhar, V. C., Nampoothiri, K. M. & Pandey, A. Biodegradation of Biopolymers. Current Developments in Biotechnology and Bioengineering: Production, Isolation and Purification of Industrial Products (Elsevier B.V.). https://doi.org/10.1016/B978-0-444-63662-1.00032-4 (2016).

Jordan, J. L. et al. Mechanical properties of low density polyethylene. J. Dyn. Behav. Mater. 2 , 411–420 (2016).

Kobayashi, S., & Müllen, K. (Eds). Encyclopedia of polymeric nanomaterials. 1509–2129.2 (Springer Berlin Heidelberg, Berlin Heidelberg, 2015).

Dong, Y. et al. Polylactic acid (PLA) biocomposites reinforced with coir fibres: Evaluation of mechanical performance and multifunctional properties. Compos. Part A Appl. Sci. Manuf. 63 , 76–84 (2014).

Sagar, S. et al. Fabrication and thermal characteristics of functionalized carbon nanotubes impregnated polydimethylsiloxane nanocomposites. J. Compos. Mater. 49 , 995–1006 (2015).

Monteiro, S. N., Calado, V., Rodriguez, R. J. S. & Margem, F. M. Thermogravimetric behavior of natural fibers reinforced polymer composites-An overview. Mater. Sci. Eng. A 557 , 17–28 (2012).

Yao, F., Wu, Q., Lei, Y., Guo, W. & Xu, Y. Thermal decomposition kinetics of natural fibers: Activation energy with dynamic thermogravimetric analysis. Polym. Degrad. Stab. 93 , 90–98 (2008).

Herrera-Kao, W. A. et al. Thermal degradation of poly(caprolactone), poly(lactic acid), and poly(hydroxybutyrate) studied by TGA/FTIR and other analytical techniques. Polym. Bull. 75 , 4191–4205 (2018).

Bassyouni, M. Dynamic mechanical properties and characterization of chemically treated sisal fiber-reinforced polypropylene biocomposites. J. Reinf. Plast. Compos. 37 , 1402–1417 (2018).

Manral, A., Ahmad, F. & Chaudhary, V. Static and dynamic mechanical properties of PLA bio-composite with hybrid reinforcement of flax and jute. Mater. Today Proc. 25 , 577–580 (2019).

Gupta, M. K. Thermal and dynamic mechanical analysis of hybrid jute/sisal fibre reinforced epoxy composite. Proc. Inst. Mech. Eng. Part L J. Mater. Des. Appl. 232 , 743–748 (2018).

Shanmugam, D. & Thiruchitrambalam, M. Static and dynamic mechanical properties of alkali treated unidirectional continuous Palmyra Palm Leaf Stalk Fiber/jute fiber reinforced hybrid polyester composites. Mater. Des. 50 , 533–542 (2013).

Sekar, V., Fouladi, M. H., Namasivayam, S. N. & Sivanesan, S. Additive Manufacturing: A Novel Method for Developing an Acoustic Panel Made of Natural Fiber-Reinforced Composites with Enhanced Mechanical and Acoustical Properties. J. Eng. (United Kingdom, 2019).

Oldham, D. J., Egan, C. A. & Cookson, R. D. Sustainable acoustic absorbers from the biomass. Appl. Acoust. 72 , 350–363 (2011).

Fouladi, M. H, et al. Utilizing Malaysian natural fibers as sound absorber. Modeling and measurement methods for acoustic waves and for acoustic microdevices, 161–170 (2013).

Yang, W. D. & Li, Y. Sound absorption performance of natural fibers and their composites. Sci. China Technol. Sci. 55 , 2278–2283 (2012).

Chin, D. D. V. S., Yahya, M. N. B., Che Din, N. B. & Ong, P. Acoustic properties of biodegradable composite micro-perforated panel (BC-MPP) made from kenaf fibre and polylactic acid (PLA). Appl. Acoust. 138 , 179–187 (2018).

Kala, T. F., & Kavitha, S. Bamboo fibre analysis by scanning electron microscope study. IJCIET 7 , 234–241 (2016).

Xia, X. et al. Modification of flax fibersurface and its compatibilization in polylactic acid/flax composites. Iran. Polym. J. 25 , 25–35 (2016).

Kiruthika, A. V. A review on physico-mechanical properties of bast fibre reinforced polymer composites. J. Build. Eng. 9 , 91–99 (2017).

Kaiser, M. R. et al. Effect of processing routes on the mechanical, thermal and morphological properties of PLA-based hybrid biocomposite. Iran. Polym. J. 22 , 123–131 (2013).

Guerrero-Pérez, M. O. & Patience, G. S. Experimental methods in chemical engineering: Fourier transform infrared spectroscopy—FTIR. Can. J. Chem. Eng. 98 , 25–33 (2020).

Mohamed, M. A., Jaafar, J., Ismail, A. F., Othman, M. H. D. & Rahman, M. A. Fourier Transform Infrared (FTIR) Spectroscopy. Membrane Characterization. https://doi.org/10.1016/B978-0-444-63776-5.00001-2 (Elsevier B.V., 2017).

Alamri, H. & Low, I. M. Mechanical properties and water absorption behaviour of recycled cellulose fibre reinforced epoxy composites. Polym. Test. 31 , 620–628 (2012).

Ramírez-Estrada, A., Mena-Cervantes, V. Y., Mederos-Nieto, F. S., Pineda-Flores, G. & Hernández-Altamirano, R. Assessment and classification of lignocellulosic biomass recalcitrance by principal components analysis based on thermogravimetry and infrared spectroscopy. Int. J. Environ. Sci. Technol. 19 , 2529–2544 (2022).

Zhou, F., Cheng, G. & Jiang, B. Effect of silane treatment on microstructure of sisal fibers. Appl. Surf. Sci. 292 , 806–812 (2014).

Zafar, M. T., Maiti, S. N. & Ghosh, A. K. Effect of surface treatment of jute fibers on the interfacial adhesion in poly(lactic acid)/jute fiber biocomposites. Fibers Polym. 17 , 266–274 (2016).

Sawpan, M. A., Pickering, K. L. & Fernyhough, A. Effect of various chemical treatments on the fibre structure and tensile properties of industrial hemp fibres. Compos. Part A Appl. Sci. Manuf. 42 , 888–895 (2011).

Arrakhiz, F. Z. et al. Mechanical properties of high density polyethylene reinforced with chemically modified coir fibers: Impact of chemical treatments. Mater. Des. 37 , 379–383 (2012).

Mofokeng, J. P., Luyt, A. S., Tábi, T. & Kovács, J. Comparison of injection moulded, natural fibre-reinforced composites with PP and PLA as matrices. J. Thermoplast. Compos. Mater. 25 , 927–948 (2012).

Aruan Efendy, M. G. & Pickering, K. L. Comparison of strength and Young modulus of aligned discontinuous fibre PLA composites obtained experimentally and from theoretical prediction models. Compos. Struct. 208 , 566–573 (2019).

Narancic, T., Cerrone, F., Beagan, N. & O’Connor, K. E. Recent advances in bioplastics: Application and biodegradation. Polym. (Basel) 12 (2020).

Tarazona, N. A. et al. Opportunities and challenges for integrating the development of sustainable polymer materials within an international circular (bio)economy concept. MRS Energy Sustain 9 , 19–25 (2022).

Rai, P., Mehrotra, S., Priya, S., Gnansounou, E. & Sharma, S. K. Recent advances in the sustainable design and applications of biodegradable polymers. Bioresour. Technol. 325 , 124739 (2021).

Andreeßen, C. & Steinbüchel, A. Recent developments in non-biodegradable biopolymers: Precursors, production processes, and future perspectives. Appl. Microbiol. Biotechnol. 103 , 143–157 (2019).

Lewis, P. R, Introduction, Forensic Polymer Engineering: Why polymer products fail in service. 1–31 https://doi.org/10.1016/B978-0-08-101055-6.00001-X (Woodhead Publishing, 2016).

Rydz, J. et al. Forensic engineering of advanced polymeric materials. Part 1 - Degradation studies of polylactide blends with atactic poly[(R,S)-3-hydroxybutyrate] in paraffin. Chem. Biochem. Eng. Q 29 , 247–259 (2015).

Kowalczuk, M. M. Forensic engineering of advanced polymeric materials mathews. J. Forensic Res. 1 , 1–2 (2017).

Čolnik, M., Hrnčič, M. K., Škerget, M. & Knez, Ž. Biodegradable polymers, current trends of research and their applications, a review. Chem. Ind. Chem. Eng. Q 26 , 401–418 (2020).

Elhenawy, Y., Fouad, Y., Marouani, H. & Bassyouni, M. Performance analysis of reinforced epoxy functionalized carbon nanotubes composites for vertical axis wind turbine blade. Polym. (Basel) 13 , 1–16 (2021).

Elhenawy, Y., Fouad, Y., Marouani, H. & Bassyouni, M. Simulation of glass fiber reinforced polypropylene nanocomposites for small wind turbine blades. Processes 9 , 1–16 (2021).

Bassyouni, M. & Gutub, S. A. Materials selection strategy and surface treatment of polymer composites for wind turbine blades fabrication. Polym. Polym. Compos. 21 , 463–472 (2013).

Bassyouni, M., Javaid, U. & Ul Hasan, S. W. Bio-based hybrid polymer composites: A sustainable high performance material. Hybrid Polymer Composite Materials: Processing (Elsevier Ltd). https://doi.org/10.1016/B978-0-08-100789-1.00002-2 (2017).

Bassyouni, M. I., Abdel-Hamid, S. M.-S., Abdel-Aziz, M. H. & Zoromba, M. S. Mechanical and viscoelastic study of functionalized MWCNTs/epoxy/Kevlar composites. Polym. Compos. 39 , E2064–E2073 (2018).

Robeson, L. M. Environmental stress cracking: A review. Polym. Eng. Sci. 53 , 453–467 (2013).

Srisa, A. & Harnkarnsujarit, N. Antifungal films from trans-cinnamaldehyde incorporated poly(lactic acid) and poly(butylene adipate-co-terephthalate) for bread packaging. Food Chem. 333 , 127537 (2020).

Svatík, J. et al. PLA toughening via bamboo-inspired 3D printed structural design. Polym. Test 104 , 1–9 (2021).

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The corresponding author would like to acknowledge the assistance provided by the Academy of Scientific Research and Technology (ASRT)—Joint ASRT/ Bibliotheca Alexandrina (BA) Research Grants Program for funding the project, No. 1348.

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Samir, A., Ashour, F.H., Hakim, A.A.A. et al. Recent advances in biodegradable polymers for sustainable applications. npj Mater Degrad 6 , 68 (2022). https://doi.org/10.1038/s41529-022-00277-7

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Biodegradable polymers are expected to be an alternative to plastics. Because of its high biocompatibility, poly (lactic-co-glycolic acid) (PLGA) is widely used in medicine. It has been reported that micro-nano plastics can be accumulated in the circulatory system and cause tissue injury. With the increasing environmental exposure of degradable polymer nanoparticles (NPs), the impact of this risk factor on cardiovascular disease deserves attention. Thus, we aim to study the harmful effect of PLGA NPs on the process of vascular stenosis which is a typical pathological feature of cardiovascular diseases. We establish a mouse vascular stenosis model with intravenously injecting of PLGA NPs for 2 weeks. This model leads to a significant narrowing of the left common carotid artery which is characterized by the increasing intima area and focal stenosis. We observe that PLGA NPs accelerate stenosis progression by inducing inflammation and impairing vascular function. It promotes the proliferation of smooth muscle cells and causes abnormal collagen distribution. The combination of wall shear stress and PLGA NPs uptake speed up endothelial cell damage, decrease endothelial permeability and cell migration capacity. Our results suggest that PLGA NPs may pose a risk in cardiovascular stenosis which inspire us to concern the biodegradable polymeric materials in our living especially the clinic applications.

Graphical Abstract

Degradable materials have been expected as an alternative to plastic. Among them, biodegradable materials can be decomposed by enzymes or micro-organisms, and some can be degraded in the human body, finally form harmless products, which is considered to be environmentally friendly materials [ 1 ]. It has been widely used in catering products, packaging, automotive, consumer electronics, textiles, agriculture and other fields [ 2 ]. Plastics release micro- or nano-plastics (MNPs) along with the degradation process, which are washed away by water and preferentially enter aquatic organisms to cause damage [ 3 ]. MNPs damage the survival and reproduction of the organism, which can be detected in human blood [ 4 , 5 ]. Biodegradable materials such as PLGA has been widely employed in medical therapy and diagnosis, therefore, the potential harm of degradable MNPs in the human body is attracting attention.

The impact of metal oxide nanoparticles on human health has always been concerned, it mainly leads to organic inflammation, genotoxicity and major cellular organelle dysfunction [ 6 ]. Cui et al. found both high dose and low dose of metal oxide nanoparticles caused severe cytotoxicity on metabolomics [ 7 ]. Sun et al. evaluated toxicity differences among varying size of SiO 2 NPs on the cornea, which led to increased cell death and mitochondrial dysfunction in primary human corneal epithelial cells [ 8 ]. Kong found that Ni NPs had an apoptotic effect on Sertoli-germ cells of rats [ 9 ]. Furthermore, nickel (Ni) NPs injected intravenously in Sprague Dawley rats induced liver and spleen injury, lung inflammation, and caused cardiac toxicity [ 10 , 11 ]. Toxicological studies on degradable biomaterials are limited, for instance Green et al. reported that in the salt-water organisms, like flat oyster Ostrea edulis and Arenicola marina L., high levels of poly lactic acid (PLA) in sandy sediments induce stress and elevate respiration rates [ 12 , 13 ]. PLGA NPs were injected 0.5 mg under the skin of rats would have a probability caused pale kidneys and pyelectasis [ 14 ]. Thackaberry et al. reported that intravitreal administration of PLGA microspheres would cause a serious immune response of nonhuman primates and rabbits [ 15 ]. Grabowski et al. found PLGA NPs with negative charge induced higher cytokine secretions in human lung epithelial cells [ 16 ]. However, the current research cannot clarify the harmful effects of NPs of degradable materials on the circulation.

As a common cardiovascular disease, atherosclerosis (AS) is a main cause of death in the world. The incidence of vascular stenotic diseases represented by atherosclerosis increase by years, and the patients tend to be younger [ 17 ]. Fat streaks that form in blood vessels are the initial stage of the disease, which can happen as early as infants. For a long time before entering the advanced stage, they are in the incubation period and asymptomatic state [ 18 ]. Arterial stenosis is one of the typical pathological features of AS, and an important indicator of cardiovascular diseases risk. Furthermore, percutaneous coronary intervention also puts the patient at risk of developing in-stent stenosis, which is the slow renarrowing of a stented coronary artery lesion due to arterial injury, followed by the development of neointimal tissue [ 19 , 20 ].

PLGA can be hydrolyzed into lactic acid and glycolic acid which can then be metabolized by humans [ 21 ]. Due to its biocompatibility and biodegradability properties, PLGA is certified by the US Food and Drug Administration (FDA) and the European Medicine Agency (EMA), which has been developed for use in nano-pesticides, food preservation, surgical sutures, bone and oral prosthetics, drug delivery, nanomedicine diagnostics, and intravascular stent [ 22 , 23 ]. The industrial application of degradable materials such as PLGA also releases a large number of polymers into the environment. As it is mostly used in the biomedical field, it makes PLGA more accessible to the human body. Although degradable polymers are metabolically broken down after a period of time, before degradation, the polymers remain in the circulation in the form of nanometers. During this time, few studies on the impact of PLGA polymers on people have been published. The NPs were prone to accumulated in the main organs like liver, lung, spleen where they can be metabolized by macrophages [ 24 , 25 ]. In previous studies, we reported that macrophages in the plaque phagocytized PLGA NPs accelerated the progression atherosclerosis in ApoE −/− mice [ 26 ]. Also, the polymeric nanomicelles were considered to be a potential hazard for the cardiovascular disease [ 27 ]. Thus, taking the PLGA as an example, we study the effect of degradable material NPs on vascular stenosis in pre-atherosclerosis and vascular stenosis after interventional therapy.

In this research, we constructed an in vivo vascular stenosis model to investigate the effect of PLGA NPs on the stenosis progress [ 28 , 29 ]. First, we prepared PLGA NPs and examined the influence of PLGA NPs on vessels with different degrees of stenosis, including intimal thickness, the distribution of smooth muscle cells (SMCs) and collagen. Next, since PLGA NPs directly contacted the vascular endothelium, we tested the effect of PLGA NPs on vascular endothelial function and vascular inflammation. To observe its role on endothelial cell phagocytosis and cell migration, we co-cultured vascular endothelial cells with PLGA NPs. Blood stream would produce abnormal shear stress at the branches and stenosis of blood vessel, which have been proven that it promoted AS [ 30 ]. To mimic the environment of disturbed flow in narrow locations, we treated endothelial cells with a mechanical loading device and found increased accumulation of PLGA NPs under disturbed flow [ 31 , 32 ]. We revealed the potential risk of PLGA NPs in cardiovascular stenosis from the aspects on vascular inflammation and function. Moreover, PLGA NPs damaged endothelium under the disturbed blood flow at the stenosis site. This study can provide new perspectives for the design and application of polymeric nanomaterials in diagnosis and treatment. It reveals the potential cardiovascular risk of biodegradable PLGA polymer in our living environment on the human beings.

ApoE −/− mice and C57 BL/6 mice (8 weeks, male) were purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd. (Beijing, China). PLGA polymer powder: molecular weight 90,000, 50/50; the ingredients of High-fat diet (HFD) contained 20% protein, 40% carbohydrate, 40% lard and 0.15% cholesterol. The human umbilical vein endothelial cells (HUVECs) were purchased from ATCC cell bank (Manassas, VA, USA).

Preparation and characterization of PLGA NPs

PLGA NPs were produced by nanoprecipitation process and labelled the PLGA NPs with DiI. Briefly, 50 mg PLGA was completely mixed into 5 mL dimethyl sulfoxide (DMSO) to obtain a PLGA stock solution. The PLGA mixture solution (5 mL) was taken and transferred into a 50 mL beaker. Adding 10 mL of distilled water drop by drop in the PLGA mixture with gentle stirring, after that PLGA mixture was dialyzed using dialysis bag (3.5 kDa, Solarbio, Beijing, China) to remove DMSO. The volume was replenished to 20 mL to obtain a concertration of 2.5 mg mL −1 PLGA NPs solution, stored at 4 °C. The protocols for the characterization of NPs were detailed in previous studies [ 26 ].

Animal experiment

All animal procedures were approved by Laboratory Animal Welfare and Ethics Committee of Chongqing University for Animal Protection. Twenty ApoE −/− male mice were randomly divided into five groups after an adaptive feeding week. Local left common carotid artery (LCCA) stenosis was created as manipulation with ~ 30% and ~ 70% stenosis estimation by calculation that have been determined by placing 9–0 nylon suture around the artery using an external blunt needle on middle or distal location of LCCA, which was removed subsequently [ 28 ]. We fixed mice by mouse tail vein injecting fixator (Zhenhuabio, China), and injected NPs at a dose of 10 mg kg −1 every two days to each group through tail vein. The control group was injected with 100 μL PBS. In the period of experiment, all the animals were fed with western diet, freely water, and the conditions of experimental animals were observed and recorded every day, which were lasted for 2 weeks.

After 2 weeks the mice were harvested. The blood was collected from the mice and preserved at 4 °C, after 6 h, centrifuged at 4000 rpm for 15 min to obtain serum. We measured the lipid profile using an automated biochemical analyzer (Shenzhen Redu Life Technology) according to previous studies [ 26 ]. We collected fresh vein blood from healthy C57 BL/6 mice. The experimental procedures for detecting hemolysis rate were carried out according to our previous studies [ 26 ].

HE and IHC staining

Hematoxylin–eosin (HE) and Immunohistochemistry (IHC) staining of the carotid artery was performed as previously researches [ 26 ]. After dewaxing, MASSON, MOVAT, EVG, α-SMA, CD31, vWF, Ki67, P120 and Thrombomodulin (TM) staining were used to observe the vascular function, pathological feature and the distribution of collagen. Sections of the main organs were also analyzed by HE staining.

HUVECs cell viability assay

HUVECs were cultured with medium containing 10% fetal bovine serum (FBS). At exponential growth stage, HUVECs were seeded in 96-well plates during phase log-growth. After 12 h, the medium was changed to serum-free medium. The cells were starved overnight, then treated with different concentrations (0, 50, 100, 200, 300 and 400 μg mL −1 ) of PLGA NPs. After incubating for 3, 6, and 12 h, MTS assay solution was added to each well and fetched out after 60 min. To mix colors, gently shake the culture plate for 15 s before testing. The OD value was measured at 490 nm by microplate reader (BioTek Instruments Inc., USA).

PLGA NPs uptake by HUVECs

HUVECs were seeded into 24-well plate (contained glass coverslips) with a density of 2 × 10 5  mL −1 and 10% FBS added into each well. After 12 h, the medium was changed to fresh medium containing 100 μg mL −1 of DiI@PLGA. HUVECs were treated for different time points (0.5, 2, 4, 8 and 12 h) to observe the PLGA NPs uptake. Then they were fixed and permeabilized. The nuclear were colored with DAPI. Each step was followed by washing with PBS three times. The cells on glass coverslips were observed and analyzed via confocal laser scanning microscopy.

PLGA NPs influence to the VE-Cadherin

Monolayer HUVECs formed in 24-well plate were exposed to PLGA NPs. After 24, 48, and 72 h, the cells were fixed and permeabilized. Then the cells were blocked with blocking buffer for 1 h. HUVECs were incubated with VE-Cadherin (Santa Cruz, sc52751) and secondary antibody 1 h at room temperature separately. Then the same steps were repeated according to “ PLGA NPs uptake by HUVECs ” part.

PLGA NPs influence to the HUVECs migration

HUVECs were seeded on a 6-well plate to 90% confluency, the scratches were made on the bottom of the 6-well plate. Then cells were treated with 100 μg mL −1 PLGA NPs for 24, 48 and 72 h and cultured with medium serum-free. Optical microscopy (Olympus Optical Co., Ltd.) was used to take photograph.

Actin rearrangements induced by PLGA NPs exposure

The HUVECs were seeded into 6-well plate, after the cells adherence we put it on the horizontal platform of an orbital shaker (DS-5000, VWR International, West Chester, Penn) in the incubator for shaking 24 h and 72 h [ 31 ]. Each incubation time consisted of a control group and a group with PLGA NPs exposure. Then HUVECs were fixed and washed, for staining of the cell cytoskeleton, F-actin was used. Then the same steps were repeated according to “ PLGA NPs uptake by HUVECs ” part.

Statistical analysis

All results were presented as mean ± standard deviation. For image data analysis and processing, Image J software was used and statistical procedures were performed using the Graphpad Prism 6. The significance of the variable of the detections and results were tested statistically by using the one-way ANOVA and Student’s t-test followed by Tukey’s Multiple Comparison Test. P < 0.05 was considered significantly.

To start with, PLGA NPs were prepared by nanoprecipitation (Fig.  1 A). Then, the characterization of the as-prepared PLGA NPs was carried out by a dynamic light scattering (DLS) experiment, resulting in an average size of 85.7 ± 3.09 nm with a zeta potential of -26.6 ± 1.0 mV. The result proved that the NPs were in the normal nano size and properties (Fig.  1 B, C). It has been proved that when the particles are smaller than 100 nm, they could be easily taken up by the tissue. Besides, the result of the transmission electron microscope (TEM) showed that NPs had a regular round shape and a similar size to the previously reported data (Fig.  1 D) [ 26 ]. It also showed that the NPs were well distributed in an aqueous solution with an appropriate hemolysis rate (< 5%) (Fig.  1 D, E). In brief, we successfully prepared PLGA NPs and tested the physicochemical properties of the NPs.

PLGA NPs preparation and administration accelerate intimal thicken after stenosis operation. A The illustration of PLGA NPs preparation (upper) and animal stenosis operation (lower). B PLGA nanoparticle size distribution (n = 3). C Measurement of PLGA NPs zeta potential (n = 3). D Hemolysis rate (%) of the nanoparticle dispersions (2 mg/mL), n = 3. E TEM image of PLGA NPs. Scale bars, 100 nm. F Transversal and longitudinal sections of the HE staining of ApoE −/− mice carotid artery, which showed the changes in the structure of vessel walls after NPs treatment and SO. Scale bars, upper, 50 μm, lower, 20 μm. Quantitative analysis of intimal area of carotid artery in transversal section ( G ) and longitudinal section ( H ). Scale bars, upper, 100 μm, lower, 50 μm, n = 5, *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001

PLGA NPs accelerate stenosis progression

A stenosis operation (SO) experiment was designed to investigate the influence of PLGA NPs on the progression of arterial stenosis. At first, the LCCA of a 12-week-old ApoE −/− mouse was partially ligated (shown in Fig.  1 A). Then, a short rod was tied to the LCCA with sutures. The rod had a diameter of 30% and 70% of the average size of the mouse carotid artery, respectively. After the short rod was removed, the local area of the blood vessel lost 70% and 30% correspondingly, resulting in stenosis. Next, the mice were on an HFD, followed by several injections of PLGA NPs every other day for two weeks. As shown in the HE staining results of the transversal and longitudinal sections of the blood vessel (Fig.  1 F), the SO induced a corresponding reduction in the lumen area, suggesting that the SO model was feasible for further study. Compared to only the 30% SO group, the lumen area in the corresponding group treated with PLGA became smaller. Besides, the 70% SO groups treated with/without PLGA NPs showed similar results, which demonstrated that the NPs promoted the progress of stenosis. At the same time, the microscopic analysis showed that the morphology of the vascular wall had changed greatly by NPs. According to Fig.  1 G and H, the intima area was increased by only SO with HFD. However, PLGA NPs exacerbated this effect. The media area and adventitia area of the vascular wall were also affected by SO and PLGA NPs injection, although there was no distinct statistical difference (Additional file 1 : Fig. S1A–D). We calculated the inner diameter of the vessels in transversal section and longitudinal section (Additional file 1 : Fig. S1E and F). When treated with PLGA NPs, the inner diameter would decrease significantly both in 30% stenosis and 70% stenosis group. In short, PLGA NPs promoted intimal hyperplasia in the stenosis and led to the decrease of the lumen area.

Extracellular matrix are deposited in the stenosis vascular wall accompanied with the PLGA NPs administration

It has been known that for the purpose of vessel wall healing, vascular smooth muscle cells (VSMCs) tend to become proliferative in response to injury. Excessive proliferation and migration of VSMCs from the media into the intima, however, results in the formation of neointima and vascular occlusion [ 33 ]. Based on that, the effect of PLGA NPs on the VSMCs of the blood vessels in the stenosis was tested. As shown in Fig.  2 A, we observed the alpha-smooth muscle actin (α-SMA) that is a marker of VSMCs was expressed in both media and neointima. The percentage of α-SMA are enhanced after 70%SO, indicating that VSMCs were proliferated. After PLGA injection, the corresponding areas further expanded, and the intima became thicker (Fig.  1 F–H, Fig.  2 C). The inner diameter of blood vessels has decreased after treated with PLGA NPs in SO group, though no significant difference between SO 30% and SO 30% + PLGA group (Additional file 1 : Fig. S1E and F). These results demonstrated that PLGA NPs would enhance the proliferation of VSMCs and induced diffuse intimal thickening in the narrow area. Then, the MASSON, EVG, and MOVAT staining were used to observe the distribution of extracellular matrix (ECM) in the stenosis sites, such as collagen fibers, elastic fibers, and muscle fibers (Fig.  2 B). In the sham group, the collagen fibers were thin and slightly curved. However, after SO, the blood vessel wall was thickened, the elastic plate was bent irregularly, and collagen fibers were deposited. Moreover, with SO and PLGA NPs injection, the blood vessel wall was even thicker, while collagen fiber deposition further increased and fractures appeared. Intimal hyperplasia occurred in the 70% SO group and 70% SO + PLGA group. In general, SO together with PLGA NPs injection had thicker blood vessel walls, worse fiber integrity, and more severe intimal hyperplasia than SO alone (Fig.  2 D–F). Thus, it showed that the injection of PLGA NPs accelerated the proliferation of VSMCs and tended to break the collagen and elastic fibers in the blood vessel wall.

The distribution of VSMCs and ECM in blood vessel wall is changed by stenosis operation and NPs administration in the stenosis area. A IHC staining for α-SMA of carotid artery longitudinal sections after stenosis operation and PLGA NPs treatment (n = 4, scale bars, 50 µm). B Masson’s trichrome (MASSON) staining (upper), collagen fiber (red), muscle fiber (blue); MOVAT staining (middle), collagen fiber (black), muscle fiber (red); EVG Staining of carotid artery longitudinal sections (lower) (scale bars, 500 µm; 50 µm); elastic fiber (black/purple); muscle fiber (red); A: Adventitia; M: Media; and I: Intima; SO: stenosis operation. C The quantification of α-SMA expression (n = 4). Quantification of D collagen of MASSON staining, E collagen percentage of MOVAT staining and F elastin integrity of EVG staining, *p < 0.05; **p < 0.01; ***p < 0.001 (n = 5)

PLGA NPs decrease the endothelium function of blood vessels in stenosis sites

To evaluate the effect of SO with/without PLGA NPs treatment on the endothelium function of blood vessels, a panel of markers of endothelial function was profiled using IHC (Fig.  3 A). The expression of CD31 was used to indicate the re-endothelialization in injured vessels as described in the previous study was investigated [ 34 , 35 ]. In the SO group without PLGA NPs injection, the CD31 expression was higher than in other groups. It indicated that the increase of CD31 expression enhanced re-endothelialization and endothelial proliferation in response to injured vessels. Interestingly, the SO combined with the PLGA NPs group had a lower CD31 expression level compared to the group with no PLGA NPs injection. It suggested that PLGA NPs could decrease the CD31 expression and might lead to endothelium dysfunction (Fig.  3 B). Only megakaryocytes and endothelial cells (ECs) generate Von Willebrand factor (vWF), which is a large multimeric glycoprotein. By mediating platelet adherence to active and damaged vessels, it aids in hemostasis and thrombosis [ 36 ]. In addition, inflammation- induced vWF secretion can enhance the interaction between vWF and platelets, promoting thrombosis [ 37 ]. As a result, the expression of vWF was increased after PLGA NPs treatment, suggesting the promotion of the stenosis inflammation (Fig.  3 C). However, the Ki67 expression, which indicate the endothelial proliferation, did not change significantly between the groups (Fig.  3 D). Furthermore, the effect of PLGA NPs on cell adhesion and atherosclerotic thrombosis was also investigated. The p120 expression is normally related to the VE-Cadherin in ECs [ 38 ]. Additionally, thrombomodulin (TM), which is related to the occurrence of thrombosis, is expressed in normal vascular arteries [ 37 ]. It was found that intercellular adhesion of blood vessels at stenosis was decreased after PLGA NPs treatment. The expression of TM was decreased demonstrating an increased risk of thrombosis (Fig.  3 E, F). Overall, with the treatment of PLGA NPs, the secretion of vWF in the stenosis area increased, endothelial cell function was dysregulated, intercellular adhesion and the expression of TM was decreased. As a result, these effects on blood vessels would boost the risk of AS.

PLGA NPs administration influence the function of vascular wall in stenosis area. A IHC staining for CD31, vWF, Ki67, p120 and TM of carotid artery longitudinal sections. Scale bars, 50 µm. B – G And the quantification of percentage of CD31 expression ( B ); percentage of vWF positive expression ( C ); percentage of Ki67 positive expression ( D ); percentage of p120 positive expression ( E ); percentage of TM positive expression ( F ) in different groups, *p < 0.05; **p < 0.01; ***p < 0.001 (n = 5)

PLGA NPs accumulate in stenosis sites and promote the secretion of inflammatory factors

Inflammation can cause AS by changing the function of the cells in the arterial wall [ 39 ]. At the beginning of the atherosclerotic process, pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) are released, followed by the anti-inflammatory cytokine interleukin-10 (IL-10) [ 40 , 41 ]. The TNF-α and IL-6 expression levels in blood vessels were measured in this investigation. The up-regulation of inflammatory factors was discovered to be triggered by SO, and the expression of inflammatory factors was directly proportional to the degree of SO. At the same time, the SO + PLGA NPs group showed an enhanced expression of inflammatory factors compared with the SO group. Also, the expression of anti-inflammatory factor IL-10 in blood vessels was tested, showing similar trends (Fig.  4 A, C–E). These results proved that PLGA NPs could promote vascular inflammation, inferring that the treatment of NPs could influence the ECs and VSMCs. It was also found that the deposition of PLGA NPs in the site of vascular stenosis was increased in comparison to a control group. After NPs injection, a lot of NPs had entered blood vessels through ECs in the SO + PLGA NPs group after 24 h, indicating that abnormal shear stress induced by vascular stenosis promoted the deposition of NPs. (Fig.  4 B, F, G).

PLGA NPs deposition at stenosis sites promote inflammatory factors secretion. A IHC staining for TNF- α, IL-6, and IL-10 (scale bars, 20 µm). B Comparison of deposition of NPs in blood vessels. And the quantification of percentage of IL-10 positive expression ( C ); percentage of TNFα positive expression ( E ) and percentage of IL-6 positive expression ( F ) in different groups. D The quantification of NPs and CD31. *p < 0.05; **p < 0.01; ***p < 0.001 (n = 5)

PLGA NPs are phagocytized by ECs decreasing cell viability and cell migration

ECs are located in the inner lining of vascular walls. They’re also vital for preserving and absorbing cell detritus and foreign materials, which makes it a crucial concern when evaluating the safety of PLGA NPs. At 0.5 h, the percentage of PLGA NPs uptake by HUVECs was 2.036 ± 0.252% (Fig.  5 A and C). At 2 h, it increased greatly by 5 folds compared to that of 0.5 h incubation. With a longer incubation time, the uptake of PLGA NPs consistently showed a higher percentage. Furthermore, the stability of ECs is important during injury, especially when foreign materials like NPs try to enter and affect the stability of the ECs. According to the experimental results, the PLGA NPs could inhibit cell migration over time (Fig.  5 B and D). According to ISO guidelines for the biological evaluation of medical devices, non-toxic or mildly cytotoxic materials are clinically acceptable. In a previous study, up to a concentration of 300 µg mL −1 of PLGA NPs, no substantial fatal toxicity was observed [ 42 ]. Herein, the cell viability of HUVECs was tested at high concentrations (assuming the cytotoxic concentrations: 50, 100, 200, 300, and 400 µg mL −1 ) which was higher than 70–80% of the control group (Fig.  5 E). The viability of HUVECs was considerably influenced by PLGA NPs at higher concentrations. At the highest concentration, the percentage of cell viability was even higher than 70% as previously reported. Conclusively, PLGA NPs phagocytosis by ECs was positively correlated with incubation time. PLGA NPs decreased the progress of endothelial cell migration. The high concentration of PLGA NPs influenced ECs viability in a time- and dose-dependent manner, even if the viability of HUVECs remains above 70%.

PLGA NPs are phagocytized by ECs in time-dependent manner, decreasing cell viability and cell migration. A HUVECs uptake of PLGA NPs on 0.5, 2, 4, 8, and 12 h. Scale bars, left, 20 µm, right, 5 µm. B The HUVECs migration morphology influenced by PLGA NPs. Scale bar, 100 µm. C The quantification of PLGA NPs uptake by HUVECs (n = 5). D Cell migration area of HUVECs influenced by PLGA NPs (n = 5). E Different concentrations of PLGA NPs and time points impact on the viability of HUVECs. (n = 3) *p < 0.05; **p < 0.01; ***p < 0.001

PLGA NPs induce endothelial leakiness

To determine VE-Cadherin expression of the ECs after the incubation with PLGA NPs, experiments for VE-Cadherin detection were carried out using 100 µg mL −1 NPs with different incubation periods (0, 24, 48, and 72 h). As a result, the percentage of VE-Cadherin expression increased to 46.127 ± 5.234% at 24 h. However, VE-Cadherin expression decreased gradually at 48 and 72 h with the exposure to PLGA NPs, resulting in 23.017 ± 1.461% and 16.309 ± 2.291% (P < 0.05), respectively (Fig.  6 A, D and E). For the detection of endothelial cell phagocytosis induced by PLGA NPs, more than 40% of ECs had swallowed NPs at 24 h. With the time increasing, the number of ECs that swallowed NPs had a certain increase at 48 and 72 h. However, there was no statistical difference in the percentage of ECs that swallowed PLGA NPs between 48 and 72 h, which indicated that the NPs phagocytosis of ECs reached a saturated state. These results suggested that the PLGA NPs might cause damage to the endothelial barrier, thus promoting phagocytosis. To investigate whether the exposure to PLGA NPs dysregulated endothelial barrier by altering cytoskeletal structure, a previously reported mechanical loading model was applied in this study [ 31 ]. The orbital shaker was subjected to low shear stress loading in the middle of the six-well plate at 150 rpm, mimicking the mechanical conditions at the plaque of AS and vascular stenosis. HUVECs were exposed to low shear stress and NPs for 24 and 72 h. The fractal dimension in the actin cytoskeleton was then analyzed with Image J (Fig.  6 C). Actin rearrangement in response to the shear stress exposure was observed in HUVECs treated with PLGA NPs (Fig.  6 B and F) at different incubation times. Cytoskeletal of HUVECs was immuno-stained, and the protein expression and distribution in ECs were analyzed. The quantification of actin alignment which was presented by fractal dimension did not show a significant difference within the control group. However, fractal dimension in PLGA NPs with 72 h incubation time showed a significant difference and higher than others (P < 0.05), which proved that those NPs could destroy cytoskeletal under low shear stress after a long time. At 24 h, even the PLGA NPs group showed no significant difference of statistical analysis in fractal dimension compared to the control group. Moreover, the quantification of PLGA NPs uptake by HUVECs (Fig.  6 G) (P < 0.01) represented a significant difference between 24 and 72 h incubation time.

PLGA NPs can impair the function of vascular ECs. A The expression of VE-cadherin and NPs uptake of HUVEC in 24, 48, and 72 h. Scale bar, 20 µm. B Cytoskeleton and NPs uptake of HUVEC under low shear stress in 24 and 72 h. Scale bar, 50 µm. C Schematic illustration of a mechanical experimental device by mimicking shear stress using an orbital shaker of a 6-well plate and approximate low shear stress range in the center area. D , E The quantification analysis of VE-Cadherin and PLGA NPs uptake on HUVECs (n = 5). F , G Changes of fractal dimension in cytoskeleton and PLGA NPs uptake of HUVECs under low shear stress (n = 5), *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. H Illustration of the negative effect of PLGA NPs on the site of stenosis

According to the above description, PLGA NPs might disturb the endothelial barrier of HUVECs, which led to endothelial dysfunction. Then, the down-regulated expression of VE-cadherin followed by increased ECs engulfment of PLGA NPs interfered with the integrity of the endothelial barrier and contributed to the endothelial leakiness.

The effects of SO and PLGA NPs administration on plasma lipid levels were also investigated. The TC, TG, and HDL-C test showed a substantial distinction (P < 0.05) in the manipulated stenosis group accompany by PLGA NPs injection compared to the group with no PLGA NPs treatment (Additional file 1 : Fig. S2A). However, this significant difference did not always occur in the same manipulated stenosis setting level in each test, which suggested that it did not represent a definite trend line. Thus, the results revealed that the formation of stenosis would not cause obvious changes in plasma lipids. According to morphological images, there were no aberrant changes in the primary organs of mice in all groups (Additional file 1 : Fig. S2B). It was evidenced that PLGA NPs did not influence the plasma lipids and they had no toxicity in the main organs.

It can be concluded that the PLGA NPs could be more easily phagocytized by ECs in the disturbed flow area and could enter the interior of the vessel wall, which would induce ECs dysfunction, increased permeability, and further promote the accumulation of PLGA NPs. It led to inflammation and abnormal distribution of internal elastic lamina, affecting the physiological activity of SMCs. Pathologically, PLGA NPs could accelerate the progress of stenosis. (Fig.  6 H).

With the potential harm of NPs to the human body, the cardiovascular system has been recognized as one of the targets of nanotoxicity. We have explored the PLGA NPs effects on the cardiovascular diseases, stenosis progression, and possible related mechanisms. For detecting the effect of NPs on the progress of vascular stenosis, we performed surgery for focal stenosis of the left carotid artery in ApoE −/− mice. This method could reduce the luminal area and induce ECM deposition (Figs.  1 F–H, 2 B, D–F). Consequently, neointimal hyperplasia with distinct morphologic characteristics in the artery wall was found after two weeks, which indicating stenosis. The model was developed based on earlier techniques that LCCA blood flow was disrupted in mice by total ligation or flow limitation via outflow branch ligation [ 29 ]. To investigate the effects of NPs on the progression of stenosis and atherosclerotic lesions, the ApoE −/− mice were performed in two degrees of stenosis: ~ 30% and ~ 70% in LCCA, then were fed HFD and injected with PLGA NPs. We found that plaques would be formed after carotid stenosis surgery two weeks. We focused on stenosis and the pathological changes of early AS. In order to discuss endothelial function clearly, we expect to reduce the impact of plaques.

We found that the involvement of HFD and PLGA NPs promoted stenosis development in the vessel walls. In the narrow site after the NPs injection, factors that have been shown to promote stenosis were observed, including the increased proliferation of VSMCs, endothelial damage, thrombosis risk, inflammation, changes in collagen distribution, and accelerated deposition of PLGA NPs. With the increased uptake of PLGA NPs by HUVECs, endothelial permeability and cell migration ability decreased, proving that the PLGA NPs might cause endothelial dysfunction. Under shear stress, PLGA NPs were found to affect actin rearrangement. Lactic and glycolic acids are PLGA degradation products that can enter the citric acid cycle and be metabolized, which might increase vascular inflammation. Chen et al. reported that the lactic acid generated by the PLLA degradation process could induce human aortic endothelial cells inflammation [ 43 ]. Therefore, we inferred that the polymers with similar compositions would have a similar effect.

PLGA NPs absorbed the protein in serum formed NPs with protein corona. Also, the degradation process of nanometer and its surface charge would affect the biophysical characteristics. Our previous research detected the physicochemical properties and morphology of PLGA NPs with protein corona, meanwhile, PLGA NPs with protein corona promoted the formation of foam cells was found [ 26 ]. The chemical composition of PLGA NPs was detected in previous work [ 44 ]. Meanwhile, we considered that the application research on carbon nanotubes and CuS NPs is popular, so the safety assessment of these materials would be challenging [ 45 , 46 , 47 ]. Different ratios of lactic acid and glycolic acid have different degradation rates of PLGA. PLGA (50:50) has the fastest degradation rate in the same molecular weight [ 48 , 49 ]. It takes 8 weeks for PLGA (50:50) to be completely hydrolyzed and can be retained in the human body for a period of time [ 50 ]. It had reported that PLA/PLGA could accelerate the degradation rates under weakly acidic condition [ 51 ]. Zeng et al. found the 50:50 PLGA NPs acidified the solution at a faster rate than 75:25 PLGA NPs and PLA NPs [ 52 ]. PLGA NPs with negative charge are more likely to be phagocytized, which can be conducive to observation [ 53 ]. Furthermore, PLGA usually needs PEG modification or biomimetic membrane coating in practical applications in order to prolong the circulation time. Therefore, the harm of polymers such as PLGA to the human body needs further investigation.

The result of cell viability revealed the relative viability of PLGA group was higher than 70–80% of the control group. It is considered as non-toxic or slight cytotoxic and clinically acceptable according to the guidance of ISO 10993-5 for the biological evaluation of medical devices, and in previous study has been explored up to a concentration of 300 μg mL −1 PLGA NPs did not cause significant lethal toxicity [ 42 ]. Considering the weight and blood content of mice, we designed the dose of 10 mg kg −1 for treatment, the average NPs concentration in each mouse would lower than 300 μg mL −1 . Therefore, this reflects the PLGA NPs could impair blood vessels despite at the safe dosage. In clinical, PLGA is the form of microparticle made for drug loading. Park et al. summarized the PLGA-based injectable depot formulations clinically, which have introduced the dose of each PLGA-based microparticle [ 54 , 55 ]. The research of the biomedical application of PLGA is almost nanoscale, but these studies are mainly conducted on small rodents. The dose of PLGA NPs used in our research helps to provide safety evaluation for future drug design.

ECs in blood vessels are the first barrier to contact NPs in blood circulation. However, the effect of ECs that have phagocytized NPs on VSMCs is worthy of further consideration. At the same time, the mechanism of NPs on VSMCs after entering the media is also interesting. In this study, the distribution of collagen in the stenosis model and the effect of NPs on VSMCs were examined. It was found that the area of collagen was increased. Collagen is mainly synthesized by VSMCs in vessels. The result indicated that NPs could stimulate VSMCs to secrete the amount of collagen in the stenosis area, suggesting the transfer of VSMCs from contractile to synthetic VSMCs. In addition, the NPs promoted the expression of α-SMA in the stenosis, showing the proliferation of VSMCs under the stimulation of the NPs, which was in line with the past investigations [ 56 ]. However, the mechanism of VSMCs interplaying with ECs which were impaired by NPs under abnormal shear stress still need to be studied.

It is worth noting that in the arterial circulation, abnormal hemodynamics not only exists in vascular stenosis and plaque areas, but also appears in the branches and bends of the aorta. The effect of NPs on these parts in the application of diagnosis and treatment has been rarely studied, which is of significance to investigate.

Conclusions

We studied on the negative effects and mechanism of the accumulation of biodegradable PLGA NPs in the cardiovascular system, especially in the area of abnormal hemodynamics. In the area of disturbed flow, PLGA NPs were prone to be engulfed by ECs and deposited in vascular wall, which led to abnormal distribution of ECM, promoted the proliferation of VSMCs. We found that PLGA NPs were more likely to aggregate at area of stenosis, reduced endothelial function and promoted inflammation, which aggravated the process of stenosis. In addition, we proved PLGA NPs influence to the endothelial cell leakiness leads to endothelial cell dysfunction in vitro. PLGA NPs enhanced the endothelial permeability and reduced cell migration ability, and affected actin rearrangement under shear stress application which prove that PLGA NPs might cause endothelial dysfunction. The neglected hazard for polymeric NPs and potential risk in cardiovascular stenosis were revealed. The PLGA NPs were found to accumulate in the stenosis area, inducing endothelium dysfunction and inflammation, thus increasing the vascular stenosis. The application of biodegradable polymeric materials in our living environment especially in the cardiovascular field is proposed to require more in-depth and detailed research on safety and evaluation.

Availability of data and materials

All data generated or analyzed during this study are included in this published article and its additional information files.

Change history

16 march 2023.

A Correction to this paper has been published: https://doi.org/10.1186/s12951-023-01839-w

Abbreviations

Poly (lactic-co-glycolic acid)

Nanoparticles

Micro- or nano-plastics

Poly lactic acid

Atherosclerosis

Food and drug administration

European medicine agency

Smooth muscle cells

High-fat diet

Human umbilical vein endothelial cells

Dimethyl sulfoxide

Local left common carotid artery

Hematoxylin–eosin

Immunohistochemistry

Thrombomodulin

Fetal bovine serum

Dynamic light scattering

Transmission electron microscope

Stenosis operation

Vascular smooth muscle cells

Alpha-smooth muscle actin

Extracellular matrix

Endothelial cells

von willebrand factor

Interleukin-6

Tumor necrosis factor-αlpha

Interleukin-10

Kamaly N, Yameen B, Wu J, Farokhzad OC. Degradable controlled-release polymers and polymeric nanoparticles: mechanisms of controlling drug release. Chem Rev. 2016;116:2602–63.

Article   CAS   PubMed   PubMed Central   Google Scholar  

Rai P, Mehrotra S, Priya S, Gnansounou E, Sharma SK. Recent advances in the sustainable design and applications of biodegradable polymers. Bioresour Technol. 2021;325:124739.

Article   CAS   PubMed   Google Scholar  

Junaid M, Liu S, Chen G, Liao H, Wang J. Transgenerational impacts of micro(nano)plastics in the aquatic and terrestrial environment. J Hazard Mater. 2023;443:130274.

Gao D, Liu X, Junaid M, Liao H, Chen G, Wu Y, et al. Toxicological impacts of micro(nano)plastics in the benthic environment. Sci Total Environ. 2022;836:155620.

Leslie HA, van Velzen MJM, Brandsma SH, Vethaak AD, Garcia-Vallejo JJ, Lamoree MH. Discovery and quantification of plastic particle pollution in human blood. Environ Int. 2022;163:107199.

Medici S, Peana M, Pelucelli A, Zoroddu MA. An updated overview on metal nanoparticles toxicity. Semin Cancer Biol. 2021;76:17–26.

Cui L, Wang X, Sun B, Xia T, Hu S. Predictive metabolomic signatures for safety assessment of metal oxide nanoparticles. ACS Nano. 2019;13:13065–82.

Sun D, Gong L, Xie J, Gu X, Li Y, Cao Q, et al. Toxicity of silicon dioxide nanoparticles with varying sizes on the cornea and protein corona as a strategy for therapy. Sci Bull. 2018;63:907–16.

Article   CAS   Google Scholar  

Kong L, Hu W, Gao X, Wu Y, Xue Y, Cheng K, et al. Molecular mechanisms underlying nickel nanoparticle induced rat Sertoli-germ cells apoptosis. Sci Total Environ. 2019;692:240–8.

Magaye RR, Yue X, Zou B, Shi H, Yu H, Liu K, et al. Acute toxicity of nickel nanoparticles in rats after intravenous injection. Int J Nanomedicine. 2014;9:1393–402.

PubMed   PubMed Central   Google Scholar  

Wu Y, Kong L. Advance on toxicity of metal nickel nanoparticles. Environ Geochem Health. 2020;42:2277–86.

Green DS, Boots B, Blockley DJ, Rocha C, Thompson R. Impacts of discarded plastic bags on marine assemblages and ecosystem functioning. Environ Sci Technol. 2015;49:5380–9.

Green DS, Boots B, Sigwart J, Jiang S, Rocha C. Effects of conventional and biodegradable microplastics on a marine ecosystem engineer ( Arenicola marina ) and sediment nutrient cycling. Environ Pollut Barking Essex. 1987;2016(208):426–34.

Google Scholar  

Fodor-Kardos A, Kiss ÁF, Monostory K, Feczkó T. Sustained in vitro interferon-beta release and in vivo toxicity of PLGA and PEG-PLGA nanoparticles. RSC Adv. 2020;10:15893–900.

Thackaberry EA, Farman C, Zhong F, Lorget F, Staflin K, Cercillieux A, et al. Evaluation of the toxicity of intravitreally injected PLGA microspheres and rods in monkeys and rabbits: effects of depot size on inflammatory response. Invest Ophthalmol Vis Sci. 2017;58:4274–85.

Grabowski N, Hillaireau H, Vergnaud J, Santiago LA, Kerdine-Romer S, Pallardy M, et al. Toxicity of surface-modified PLGA nanoparticles toward lung alveolar epithelial cells. Int J Pharm. 2013;454:686–94.

Song P, Fang Z, Wang H, Cai Y, Rahimi K, Zhu Y, et al. Global and regional prevalence, burden, and risk factors for carotid atherosclerosis: a systematic review, meta-analysis, and modelling study. Lancet Glob Health. 2020;8:e721–9.

Article   PubMed   Google Scholar  

Libby P, Buring JE, Badimon L, Hansson GK, Deanfield J, Bittencourt MS, et al. Atherosclerosis. Nat Rev Dis Primer. 2019;5:56.

Article   Google Scholar  

Giacoppo D, Alfonso F, Xu B, Claessen BEPM, Adriaenssens T, Jensen C, et al. Drug-coated balloon angioplasty versus drug-eluting stent implantation in patients with coronary stent restenosis. J Am Coll Cardiol. 2020;75:2664–78.

Giustino G, Colombo A, Camaj A, Yasumura K, Mehran R, Stone GW, et al. Coronary in-stent restenosis. J Am Coll Cardiol. 2022;80:348–72.

Machatschek R, Lendlein A. Fundamental insights in PLGA degradation from thin film studies. J Controlled Release. 2020;319:276–84.

Yin T, Du R, Wang Y, Huang J, Ge S, Huang Y, et al. Two-stage degradation and novel functional endothelium characteristics of a 3-D printed bioresorbable scaffold. Bioact Mater. 2022;10:378–396.

Zare EN, Jamaledin R, Naserzadeh P, Afjeh-Dana E, Ashtari B, Hosseinzadeh M, et al. Metal-based nanostructures/PLGA nanocomposites: antimicrobial activity, cytotoxicity, and their biomedical applications. ACS Appl Mater Interfaces. 2020;12:3279–300.

Zhang G, Cong Y, Liu F-L, Sun J, Zhang J, Cao G, et al. A nanomaterial targeting the spike protein captures SARS-CoV-2 variants and promotes viral elimination. Nat Nanotechnol. 2022;17:993–1003.

Tsoi KM, MacParland SA, Ma X-Z, Spetzler VN, Echeverri J, Ouyang B, et al. Mechanism of hard-nanomaterial clearance by the liver. Nat Mater. 2016;15:1212–21.

Yin T, Li Y, Ren Y, Fuad ARM, Hu F, Du R, et al. Phagocytosis of polymeric nanoparticles aided activation of macrophages to increase atherosclerotic plaques in ApoE − / − mice. J Nanobiotechnol. 2021;19:121.

Wang Y, Wang G. Polymeric nanomicelles: a potential hazard for the cardiovascular system? Nanomed. 2017;12:1355–8.

Yoon J-K, Kim D-H, Kang M-L, Jang H-K, Park H-J, Lee JB, et al. Anti-atherogenic effect of stem cell nanovesicles targeting disturbed flow sites. Small Weinh Bergstr Ger. 2020;16:e2000012.

Tao M, Mauro CR, Yu P, Favreau JT, Nguyen B, Gaudette GR, et al. A simplified murine intimal hyperplasia model founded on a focal carotid stenosis. Am J Pathol. 2013;182:277–87.

Article   PubMed   PubMed Central   Google Scholar  

Souilhol C, Serbanovic-Canic J, Fragiadaki M, Chico TJ, Ridger V, Roddie H, et al. Endothelial responses to shear stress in atherosclerosis: a novel role for developmental genes. Nat Rev Cardiol. 2020;17:52–63.

Driessen R, Zhao F, Hofmann S, Bouten C, Sahlgren C, Stassen O. Computational characterization of the Dish-In-A-Dish, a high yield culture platform for endothelial shear stress studies on the orbital shaker. Micromachines. 2020;11:E552.

Filipovic N, Ghimire K, Saveljic I, Milosevic Z, Ruegg C. Computational modeling of shear forces and experimental validation of endothelial cell responses in an orbital well shaker system. Comput Methods Biomech Biomed Eng. 2016;19:581–90.

Wang Y, Xu Y, Yan S, Cao K, Zeng X, Zhou Y, et al. Adenosine kinase is critical for neointima formation after vascular injury by inducing aberrant DNA hypermethylation. Cardiovasc Res. 2021;117:561–75.

Setyawati MI, Tay CY, Bay BH, Leong DT. Gold nanoparticles induced endothelial leakiness depends on particle size and endothelial cell origin. ACS Nano. 2017;11:5020–30.

Edsfeldt A, Osterlund J, Sun J, Pan M, Tengryd C, Nitulescu M, et al. Circulating CD31 reflects endothelial activity and is associated with a lower risk for cardiovascular complications. Eur Heart J. 2022;43:ehac544.3054.

de Maat S, Clark CC, Barendrecht AD, Smits S, van Kleef ND, El Otmani H, et al. Microlyse: a thrombolytic agent that targets VWF for clearance of microvascular thrombosis. Blood. 2022;139:597–607.

Giri H, Panicker SR, Cai X, Biswas I, Weiler H, Rezaie AR. Thrombomodulin is essential for maintaining quiescence in vascular endothelial cells. Proc Natl Acad Sci USA. 2021;118:e2022248118.

Fang J, Zhang Z, Shang L, Luo Y, Lin Y, Yuan Y, et al. Hepatoma cell-secreted exosomal microRNA-103 increases vascular permeability and promotes metastasis by targeting junction proteins. Hepatology. 2018;68:1459–75.

Libby P. Inflammation in atherosclerosis—No longer a theory. Clin Chem. 2021;67:131–42.

Xu J, Wang J, Qiu J, Liu H, Wang Y, Cui Y, et al. Nanoparticles retard immune cells recruitment in vivo by inhibiting chemokine expression. Biomaterials. 2021;265:120392.

Mohammadpanah M, Heidari MM, Khatami M, Hadadzadeh M. Relationship of hypomethylation CpG islands in interleukin-6 gene promoter with IL-6 mRNA levels in patients with coronary atherosclerosis. J Cardiovasc Thorac Res. 2020;12:221–8.

Xiong S, George S, Yu H, Damoiseaux R, France B, Ng KW, et al. Size influences the cytotoxicity of poly (lactic-co-glycolic acid) (PLGA) and titanium dioxide (TiO(2)) nanoparticles. Arch Toxicol. 2013;87:1075–86.

Chen D, Weng L, Chen C, Zheng J, Wu T, Zeng S, et al. Inflammation and dysfunction in human aortic endothelial cells associated with poly-l-lactic acid degradation in vitro are alleviated by curcumin. J Biomed Mater Res A. 2019;107:2756–63.

Yin Y, Wang J, Yang M, Du R, Pontrelli G, McGinty S, et al. Penetration of the blood-brain barrier and the anti-tumour effect of a novel PLGA-lysoGM1/DOX micelle drug delivery system. Nanoscale. 2020;12:2946–60.

Flores AM, Hosseini-Nassab N, Jarr K-U, Ye J, Zhu X, Wirka R, et al. Pro-efferocytic nanoparticles are specifically taken up by lesional macrophages and prevent atherosclerosis. Nat Nanotechnol. 2020;15:154–61.

Baimanov D, Wang J, Zhang J, Liu K, Cong Y, Shi X, et al. In situ analysis of nanoparticle soft corona and dynamic evolution. Nat Commun. 2022;13:5389.

Gao W, Sun Y, Cai M, Zhao Y, Cao W, Liu Z, et al. Copper sulfide nanoparticles as a photothermal switch for TRPV1 signaling to attenuate atherosclerosis. Nat Commun. 2018;9:231.

Walker J, Albert J, Liang D, Sun J, Schutzman R, Kumar R, et al. In vitro degradation and erosion behavior of commercial PLGAs used for controlled drug delivery. Drug Deliv Transl Res. 2023;13:237–51.

Zeng C-H, Liu L-L, Zhu H-D, Teng G-J. The exploration of a novel biodegradable drug-eluting biliary stent: preliminary work. Cardiovasc Intervent Radiol. 2021;44:1633–42.

Cedervall T, Lynch I, Lindman S, Berggård T, Thulin E, Nilsson H, et al. Understanding the nanoparticle-protein corona using methods to quantify exchange rates and affinities of proteins for nanoparticles. Proc Natl Acad Sci USA. 2007;104:2050–5.

Wang J, Wang G, Shan H, Wang X, Wang C, Zhuang X, et al. Gradiently degraded electrospun polyester scaffolds with cytostatic for urothelial carcinoma therapy. Biomater Sci. 2019;7:963–74.

Zeng J, Martin A, Han X, Shirihai OS, Grinstaff MW. Biodegradable PLGA nanoparticles restore lysosomal acidity and protect neural PC-12 cells against mitochondrial toxicity. Ind Eng Chem Res. 2019;58:13910–7.

Areny-Balagueró A, Mekseriwattana W, Camprubí-Rimblas M, Stephany A, Roldan A, Solé-Porta A, et al. Fluorescent PLGA nanocarriers for pulmonary administration: influence of the surface charge. Pharmaceutics. 2022;14:1447.

Abulateefeh SR. Long-acting injectable PLGA/PLA depots for leuprolide acetate: successful translation from bench to clinic. Drug Deliv Transl Res. 2023;13:520–30.

Park K, Skidmore S, Hadar J, Garner J, Park H, Otte A, et al. Injectable, long-acting PLGA formulations: analyzing PLGA and understanding microparticle formation. J Control Release Off J Control Release Soc. 2019;304:125–34.

Dai Z, Zhu MM, Peng Y, Jin H, Machireddy N, Qian Z, et al. Endothelial and smooth muscle cell interaction via foxm1 signaling mediates vascular remodeling and pulmonary hypertension. Am J Respir Crit Care Med. 2018;198:788–802.

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Acknowledgements

We gratefully thanked the other staff of the Public Experiment Centre of State Bioindustrial Base (Chongqing) for providing technical support and assistance in data collection and analysis.

This research was supported by the National Natural Science Foundation of China (12032007, 32171334, 12272071) and the Key and Postdoctoral Projects of Natural Science Foundation of Chongqing (cstc2019jcyj-zdxmX0009 and cstc2020jcyj-bsh0139).

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Wen Shi and Atik Rohmana Maftuhatul Fuad have contributed equally to this work

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Key Laboratory for Biorheological Science and Technology of Ministry of Education, State and Local Joint Engineering Laboratory for Vascular Implants, Bioengineering College of Chongqing University, Chongqing, 400044, China

Wen Shi, Atik Rohmana Maftuhatul Fuad, Yanhong Li, Yang Wang, Junyang Huang, Ruolin Du, Guixue Wang & Tieying Yin

School of Medicine, Chongqing University, Chongqing, 400030, China

Yazhou Wang

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WS edited and modified the manuscript. WS and ARMF did the data curation, formal analysis, investigation, methodology of this work and wrote original draft. YL, YW, JH and RD assisted the investigation and Methodology of the work. GW provided the funding and reviewed the manuscript. YW provided funding and conceptualization. TY provided the conceptualization and funding, did project administration, writing-review and editing. All authors read and approved the final manuscript.

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Additional file 1: figure s1..

The quantitative of ApoE -/- mice carotid artery HE staining longitudinal and transversal section. Quantitative analysis of media area (A) and adventitia area (B) in carotid artery longitudinal section. The quantitative analysis of media area (C) and adventitia area (D) in carotid artery transversal section. (E) Quantitative analysis of inner diameter in carotid artery longitudinal section. (F) Quantitative analysis of inner diameter in carotid artery transversal section. n= 5 , *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. Figure S2. Biosafety of PLGA NPs administration and restenosis manipulation. (A) The plasma lipid and lipoprotein levels were measured in Sham group, SO 30 % and SO 70 % with or without NPs treatment (n = 5), *p < 0.05. From top to bottom are triglycerides, total cholesterol, HDL-C, LDL-C. (B) The HE staining of main organs from different groups were representative. Scale bars, 50 μm.

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Shi, W., Fuad, A.R.M., Li, Y. et al. Biodegradable polymeric nanoparticles increase risk of cardiovascular diseases by inducing endothelium dysfunction and inflammation. J Nanobiotechnol 21 , 65 (2023). https://doi.org/10.1186/s12951-023-01808-3

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DOI : https://doi.org/10.1186/s12951-023-01808-3

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Green synthesis of nanoparticles from biodegradable waste extracts and their applications: a critical review

V. p. aswathi.

Department of Chemistry, CHRIST (Deemed to Be University), Bangalore, Karnataka 560029 India

C. G. Ann Maria

The contemporary world is concerned only with non-biodegradable waste management which needs more sophisticated procedures as compared to biodegradable waste management. Biodegradable waste has the potential to become useful to society through a simple volarization technique. The researchers are behind sustainable nanotechnology pathways which are made possible by using biodegradable waste for the preparation of nanomaterials. This review emphasizes the potentialities of biodegradable waste produced as a viable alternative to create a sustainable economy that benefits all humans. Volarization results in the utilization of biowastes as well as provides safer and hazard-free green methods for the synthesis of nanoparticles. Starting from different sources to the application which includes therapeutics, food industry and water treatment. The review hovers over the pros and cons of biowaste-mediated nanoparticles and concludes with possible advances in the application. In the present scenario, the combination of green synthesis and biowaste can bring about a wide variety of applications in nanotechnology once the hurdles of bulk-scale industrial production are resolved. Given these points, the review is focused on the cost-effective synthesis of metal and metal oxide nanoparticles.

Introduction

Waste management has evolved into a local and worldwide concern affecting society, wildlife and the environment. In developing countries, garbage generation has increased in tandem with population growth, resulting in increased per capita waste generation and economic growth. Waste generated from numerous human activities, both industrial and household can pose health risks and a harmful influence on the environment without a comprehensive and efficient solid waste management program [ 1 ]. When comparing biodegradable and non-biodegradable waste, both have their drawbacks and ill effects which can dreadfully affect society if the waste is not treated properly or disposed of properly. Biodegradable wastes include both plant waste and animal waste. In most Asian developing countries, the urban population could grow by over 50% by 2025 because waste generation rates are directly tied to a country's population and per capita waste generation. Figure  1 shows the 4R’s of waste management which should be implemented to overcome the hazards of waste degradation.

The 4 R’s of waste management which needs implementation in every sources of waste generation

In this scenario, a study on waste extracts shows that a decrease in waste generation is observed with increasing income. High-income countries possess 28% biodegradable municipal solid waste, upper-middle-income countries possess 54% biodegradable municipal solid waste, and lower-middle-income countries possess 59% biodegradable municipal solid waste [ 2 ]. Many biodegradable wastes are currently disposed of in hazardous ways, such as by burning, unscientific dumping, or discharge into bodies of water. Furthermore, bio-resources like animal dung cakes, crop residue, and firewood are often used as cooking fuel, polluting interior air. Kitchen wastes such as vegetable peels, fruit peels, spent tea leaves and juices can be decomposed by bacteria or other decomposers. When biodegradable trash is abundant in the ecosystem it can contaminate the environment. They produce a lot of microbial flora in the vicinity of wastes. In humans, plants and animals, these bacteria can cause a variety of infectious diseases. These wastes emit a foul odour when burned due to the production of specific gases and can also lead to the emission of greenhouse gases such as methane and carbon dioxide. Waste dumps serve as breeding sites for disease carriers and vectors such as mosquitos and rodents which spread a variety of diseases. As evidence of the effects of climate change become more widespread, scientists continue to look for ways to mitigate the havoc produced by harmful manufacturing practices [ 3 ].

One way to make use of this biodegradable waste or biomass is to use it as raw material for nanoparticle formation via green synthesis. It is a renewable source which is heterogeneous and can be chemically combined and a suitable option for the generation of desired products since it is easily available, cheap, sustainable and with usual affluence [ 4 ]. Nanotechnology has gotten a lot of attention in recent years. Materials with a diameter of 1–100 nm are classified as nanotechnology. They are used in practically every industry, including electronics, agriculture and the medical field. The use of nanoparticles aids in improving thermal, mechanical and barrier characteristic properties. The fine-tuning of numerous reaction conditions results in nanoparticle with different morphologies which includes spheres, rods, quantum dots and particles which allow for a wide range of applications and perhaps endless technological improvement potential. For the synthesis of nanosized material, classical synthesis methods like the top-down approach were used, which relied on both carcinogenic chemicals and significant energy input. The traditional synthesis method causes pollutants, necessitating the development of environmentally friendly synthesis techniques. As a result, the synthesis of nanoparticles from biodegradable wastes is a means to reduce and reuse the waste that pollutes our ecosystem. Natural biological systems are used to produce nanomaterials in green material synthesis processes [ 3 ].

Green nanoscale particles such as zerovalent metallic NPs are produced via a redox process involving metabolites. Phenolic acids, terpenoids, alkaloids and flavonoids are among the main secondary metabolites found in biowaste [ 5 ]. Primary metabolites are substances which are produced by all plant groups that play a vital part in their normal development, growth and reproduction, whereas secondary metabolites are compounds produced by only a few plant species [ 6 ]. Almost all agro-industrial and food residues contain phenolic compounds (fruits, vegetables, oilseeds, nuts, cereals and drinks) containing specific functional groups which enhance reduction and stabilization properties. The phenolic compound in fruits and vegetables helps to replace synthetic preservatives as they can scavenge free radicals and prevent oxidation reactions in food and also contains other bioactive components which include carotenoids, vitamins, oils, enzymes, etc. Biomass waste generated from fruit residues contains a variety of flavonoids which can chelate and reduce metal ions into NPs. Thus, they are used for nanoparticle production.

Synthesis of nanoparticles using different biogenic wastes

In this review, we mainly focus on the synthesis of nanoparticles from different sources which include banana peel, coconut coir, eggshell, groundnut shell, mango peel, onion peels, pomegranate peel, sapota peel, rice husks, watermelon rind, orange peel, tamarind shell as mentioned below (Fig.  2 ), human hair, algal extract, tea waste, marine waste and slaughterhouse waste.

Commonly used biowastes for the synthesis of nanoparticles a banana peel, b coconut coir, c eggshell, d groundnut shell, e mango peel, f onion peels, g pomegranate peel, h sapota peel, i rice husks, j watermelon rind, k orange peel and l tamarind shell

Out of these, orange peel constitutes between 50 and 65% of total fruit weight and is rich in soluble fibres, proteins, bioflavonoids and insoluble fibres, which have potential applications in the synthesis of NPs. For example, according to Skiba et al. [ 7 ], orange peel extract obtained by plasma chemical extraction technique and methylene blue degradation under solar irradiation used to synthesize silver NPs.

Nuts can act as an environmentally benign resource for the synthesis of nanoparticles. The waste nut residue from different parts of nuts such as shell, kernel and extract are rich in various components such as hemicellulose, lignin and cellulose. It can aid in the synthesis of bionanomaterials as a green reducing agent and bio nanocatalyst, which provides a cheaper catalytic system that can be applied in oxidation reactions, hydrogen evolution reactions, hydrolysis, degradation of pollutants, etc. This is of great advantage as the source is of natural origin, environmentally friendly, economical and reduces waste generation [ 8 ].

One of the agricultural wastes that have garnered attention recently is eggshells. Every day, a large number of eggshells are generated as biowaste all over the world. Not only does the odour of eggshell attract flies and make it abrasive, but it also causes the loss of numerous useful materials [ 9 ]. Eggshell waste is mostly generated from households, restaurants and bakeries. Pure calcium carbonate with low porosity is the major component of eggshells which has the potential to be turned into useful products. Nano-calcium oxide can be synthesized from a waste egg shell by the sol–gel method [ 10 ]. Due to its hierarchical and porous structure, the eggshell membrane is used for the synthesis of magnetic CuFe 2 O 4 nanomaterials with multifunctional properties such as catalytic and and antibacterial functions that have an application in the industrial water treatment [ 11 ].

Volarization, co-pyrolysis, anaerobic digestion and recycling of waste paper biomass can help in saving landfill space and reduce the requirement for incineration, resulting in value-added products with lower air pollution risks [ 12 ]. Cellulose, the world’s most prevalent biopolymer, is widely recycled [ 13 ] and that waste paper can be used to synthesize cellulose nanocrystals [ 14 ]. These synthesized cellulose nanocrystals are used in drug delivery, catalysis, biomedical engineering, material science, etc. Highly porous carbon nanoparticles can be synthesized from a waste paper by isothermal reactions at 1000 °C for 2 h followed by HCl treatment, which results in conversion of the dominant cellulosic component in waste paper into highly porous carbon nanoparticles. These highly porous carbon nanoparticles can be applied in wastewater treatment for the removal of dyes and heavy metals, the studies revealed that the molecule concentration of dye molecule and Pb + 2 ion decreased significantly [ 15 ].

Human hair is also a biowaste which is a complex tissue containing lipids, water, protein and pigments. The traditional practice is to burn human hair which badly affects the environment. Gold and silver nanoparticles can be synthesized using human hair-derived keratin. They are stabilized using a capping agent such as cysteine amino acid with amine and thiol functional groups which are found abundantly in human hair. Both silver and gold NPs exhibited effective antibacterial activity against Pseudomonas aeruginosa , Staphylococcus aureus , Klebsiella pneumoniae and Escherichia coli [ 16 ].

The algal extract (Microalgae and cyanobacteria) serves as a living cell factory for efficient green synthesis of nanoparticles due to their unique characteristics which include the absence of toxic by-products, minimum energy input, the biomolecules (enzymes and pigments) present act as reducing and capping agent, hyperaccumulation of heavy metals, higher growth rate [ 17 ]. For example, silver nanoparticles can be synthesized from aqueous extract of Marine Algae Sargassum myriocystum which have potential application in inhibition of Aedes aegypti and Culex quinquefasciatus mosquito vectors, HeLa cells in anticancer activity, clinical human pathogens. Further studies revealed that it can be used as an effective drug for anticancer and bacterial infections and also shows potential efficiency in photocatalytic degradation of methylene blue dyes [ 18 ].

Tea waste constitutes components such as polysaccharides, caffeine and tannic acid which has the potential to stabilize metal and metal oxide nanoparticles as it can act as a reducing and capping agent. Silver nanoparticles can be synthesized using an aqueous extract of tea waste. It has potential catalytic activity in degrading cationic organic dyes [ 16 ]. Gautam et al. reported that iron nanoparticles can be synthesized from tea waste extract. The synthesized iron nanoparticles exhibited a very high zeta potential of − 45 mV at pH 10 indicating their high stability in an aqueous medium.

According to the reports, the discards from the fisheries exceed 20 million tons per year which corresponds to 25% (approximately) of processed fish waste and total production including by-catch (non-target species). The fish biowaste contains value-added components such as chitin, collagen, bioactive peptides, pigments and gelatin. Carbon dots and nanocarbons can be prepared from fish biowaste using chitosan as the starting material [ 19 ]. Chitosan is a marine waste made of amino polysaccharides that aids in the synthesis of nitrogen-doped carbon nanomaterial with varied applications which include the removal of contaminants from liquid and gas phases, acting as catalysts, sequestration of carbon dioxide [ 20 ]. Another study showed the synthesis of nickel nanoparticles capped on the N-doped carbon obtained via pyrolysis from chitosan as a source of carbon and nitrogen. The formation of closely coupled, extremely stable and uniform nickel nanoparticles is aided by nitrogen doping in the carbon nanotube network, which offers an adsorption site. It also offers a large number of reactive sites for nitroarene adsorption, as well as molecular hydrogen diffusion and dissociation thereby, acts as an efficient, recyclable catalyst and chemoselective hydrogenation of nitroarenes to corresponding amines [ 21 ].

Only a small fraction of animal food (meat) is consumed by humans. A large percentage of meat is discarded as waste. After processing, approximately 50–54% of each cow, 52% of each sheep or goat, 60–62% of each pig, 68–72% of each chicken, and 78% of each turkey end up as meat consumed by humans, with the rest going to waste (Regulations 2003). After evisceration (the removal of the body's interior organs such as the heart, lungs, intestines and kidneys), the difficulty of disposing of them arises. Slaughterhouse trash is mainly biodegradable, but owing to a lack of awareness, it is not properly disposed of and is allowed to fester, producing pollution and becoming a great source of disease-causing bacteria. As a result, the problem is no longer restricted to a single region or country but has grown to enormous proportions all across the world. So, the wastes should be recycled, reused, and redirected towards an efficient and useful product. For example, zinc oxide nanoparticles can be synthesized from goat slaughter waste [ 22 ].

Methods of nanoparticle synthesis

Conventional technologies used a top-down approach to synthesize nanoparticles. The nanoparticles are synthesized from bulk material as the starting material and then it is broken down into smaller pieces using different physical, chemical and mechanical processes [ 23 ]. It includes different techniques such as laser ablation, mechanical milling and sputtering [ 24 ]. Alternatively, a bottom-up approach was developed for the biosynthesis of nanoparticles. This method involves the utilization of a biological system to produce metal nanoparticles at ambient pressure and temperature without using harmful chemicals and reagents in which oxidation–reduction is the main reaction [ 23 ]. Here atoms or molecules act as the starting material in the formation of nanoparticles. It includes different methods such as solid-state methods (physical vapour deposition, chemical vapour deposition), gas-phase methods (sol–gel methods, hydrothermal method, etc.) and liquid state synthesis methods (spray pyrolysis, laser ablation, etc.) [ 24 ]. There are different types of nanomaterials produced from biowaste however we are limiting our study to metal and metal oxide nanoparticles.

Metal and metal oxide nanoparticles

Metallic nanoparticles (MNPs) possess an inorganic metal or metal oxide core that is usually surrounded by a shell made up of organic or inorganic material or metal oxide. The shape of MNPs is an important component that influences biological response. The shapes include metal rods, spheres, ellipsoids, cylinders, triangular, hexagonal and more. The ability of NPs to traverse biological barriers, the process by which NPs enter cells, cycling duration, and targeting effect are all said to be influenced by NP geometry. For example, when compared to rod-shaped gold NPs of identical size, spherical gold NPs had a higher tendency to be taken up by HeLa cells [ 25 ]. MNPs can also exhibit a range of behaviours, including agglomeration or aggregation, interactions with natural organic matter (NOM) in water, and particle adsorption onto surfaces. Physicochemical features are partly responsible for these behaviours [ 26 ]. The properties of MNPs are also influenced by the effect of solubility. MNPs are designed to function as a source of metal ions in cells, continually releasing metal ions into the cytoplasm. The release of the metal ion is determined by its solubility and rate of dissolution. Although some MNPs have poor solubility, they still cause tremendous toxicity in the physiological medium [ 26 ]. Out of the metal nanoparticles, most of the studies are concentrated on noble metal nanoparticles.

Metal oxide nanoparticles (MONPs) are usually made by the hydrolysis of metal salts at ambient temperature or temperatures below 100 °C [ 27 ], because of their small size and high density of corner or edge surface sites, metal oxide nanoparticles can have exceptional physical and chemical properties. Beneficial bioactive substances found in fruits and vegetable waste, such as alkaloids, amino acids, enzymes, phenolics, proteins, polysaccharides, tannins, saponins, vitamins and terpenoids, as well as other compounds, operate as reducing agents in the creation of metal nanoparticles (NPs) [ 28 , 29 ].

It has been reported that metal oxide NPs can be synthesized from the peels of fruits such as banana, Citrus sinensis , jackfruit, lemon, mango, Musa paradisiacal , pomegranate, tangerine, Punica granatum , Garcinia mangostana , Citrus aurantifolia and Nephelium lappaceum [ 30 ]. Agro waste can be employed in the synthesis of nanoparticles. Metal and metal oxide nanoparticles can be synthesized from weeds in an agricultural field, the weeds act as bioreactors for the synthesis of nanoparticles. Copper nanoparticles can be synthesized from Lantana camara , silver nanoparticles can be synthesized from Ipomoea carnea and copper oxide nanoparticles can be synthesized from Gloriosa superba L [ 23 ]. A variety of plant-mediated extracts and various microorganisms such as yeast, fungi and bacteria act as nanofactories for intra and extra-cellular synthesis of metal and metal oxide nanoparticles. This approach was considered a potential alternative for large-scale production of metal and metal oxide nanoparticles as it is eco-friendly, cost-effective and economical. Some of the metal nanoparticles and metal oxide nanoparticles discussed in this review are:

Silver nanoparticles (Ag NPs)

Synthesis of AgNPs from plant extract is considered to be a beginner-level experiment in the nanotechnology world due to the low cost and exciting applications in every field of invention. Proper tuning of the reaction conditions and parameters results in small size (< 10 nm) and different shapes of AgNPs with unique properties instead of spherical shapes. For the preparation of Ag nanoparticles, a variety of methods are available including reduction in solutions, chemical and photochemical processes in reverse micelles, radiation-assisted electrochemical, sonochemical, thermal decomposition and recently via green chemistry routes [ 30 ]. For example, the reducing property of pomegranate peel extract, which contains phenolic compounds, gallic acid and other fatty acids, flavanols, flavones, flavanones, and anthocyanidins, has been used to produce silver nanoparticles [ 31 ]. Additionally, an inexpensive, non-toxic and eco-friendly approach is used to synthesize silver NPs from the fruit shell of Tamarindus indica. The silver NPs synthesized from this fruit shell extract act as a therapeutic agent for human breast cancer treatment [ 32 ]. Furthermore, the geranium leaf residue and terpenoids play an important role in the conversion of silver ions into nanoparticles [ 33 ]. Likewise, banana peel extract is a natural reducing agent that is also high in polymers such as lignin, cellulose, hemicellulose, and pectin, which is why it is used to make silver nanoparticles.

According to Skiba et al., AgNPs were synthesized from orange peel water extract by dissolving AgNO 3 in bidistilled water to make solutions with different concentrations. For 0.1 min, both orange peel extract and silver nitrate solution were mixed with constant stirring. The resulting mixture was then heated to 75 °C. The change in colour of the mixture to brown colour indicates the formation of Ag NPs. The characterization of Ag NPs was done by UV–visible spectra at the range between 400 and 450 nm. A similar method is followed in the synthesis of silver nanoparticles from grape pomace extract. Synthesis of silver nanoparticles from sapota pomace extract was done in which, an aqueous solution of silver nitrate (7 mM) was combined with the extract in a ratio of 1:0.5 (v/v) and vigorously stirred for 20 min. The reaction was centrifuged for 30 min at 20 °C. The AgNPs-containing pellet with attached organic material was re-dispersed in DI water after discarding the supernatant. Furthermore, AgNPs were re-precipitated using acetone to eliminate clinging organic debris and again it was centrifuged for 30 min at 20 °C. The nanoparticles were produced and dried in a 60 °C oven before being recovered in powdered form. The characterization was done using UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD) Analysis, Energy Dispersive X-ray Analysis (EDX), Transmission Electron Microscopy (TEM) [ 34 ].

Synthesis of silver NPs from Bilberry and red currant waste, silver NPs were made in glass vials with a magnetic bar that was thermostated and screw-capped, the phenolic extract and silver nitrate solution were combined and were constantly stirred. The temperature of the reaction varied between 20 and 60 °C, and the pH was controlled between 8 and 12 by adding NaOH as needed. The characterization of Ag Np was done using UV visible spectra at 420 nm, DLS, and Zeta potential [ 35 ]. When the stability of AgNPs is too high the colloidal AgNPs are generated which adds to the list of applications. The description of all the methods of synthesis and application of AgNPs is out of the scope of this review.

Gold nanoparticles (Au NPs)

Gold nanoparticles (Au NPs) are the most stable NPs with tuneable properties in the nanoscale and for their biosynthesis, several fruit peel extracts have been used [ 36 ]. Pomegranate peel extracts have been used as reducing and stabilizing agents in the biosynthesis of AuNPs. Appropriate concentrations of both pomegranate peel extract and chloroauric acid solution (HAuCl4) were mixed. The reaction mixture was held at room temperature for 24 h with periodic shaking and the colour change from gold to pink confirmed the formation of pomegranate extracted-Au NPs [ 37 ]. The synthesis of Au NPs from red and green waste parts of watermelon extract is a simple process that does not need the use of specialized equipment. UV–visible spectroscopy, X-ray diffraction analysis, energy-dispersive spectroscopy (EDS) analysis and scanning electron microscopy (SEM) were used to characterize the Au nanoparticles that were formed. Additionally, the Kirby–Bauer sensitivity technique was used to assess antibacterial activity against E. coli and Staphylococcus epidermidis [ 38 ]. The biological potentials of using a food waste material (aqueous extract of dried onion peels (OP)) to synthesize gold nanoparticles (OP-AuNPs) were studied. UV–Vis spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray (EDX) analysis, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and differential thermogravimetric analysis (DT-TGA) were used to characterize the produced OP-AuNPs [ 39 ]. Even though Au NPs find application in all fields of innovation, the high price demands a good reason for using gold precursor in any experiment.

Palladium nanoparticles (Pd NPs)

The physicochemical features of noble palladium nanoparticles (Pd NPs) are exceptional, including great thermal stability, strong chemical stability, remarkable photocatalytic activity, electrical properties, and optical properties [ 40 ]. Pd NPs have a wide range of applications in organic coupling synthesis, hydrogen storage, fuel cells, sensors, catalysis [ 40 ] and also in making active membranes [ 41 ]. They are photothermal agents, photoacoustic agents, gene/drug carriers, prodrug activators, anticancer agents and antimicrobial agents that have all been identified with Pd NPs [ 40 ]. Palladium NPs can be synthesized by electrochemical or sonochemical, or chemical methods [ 41 ].

According to Bankar et al., banana peel extract (BPE) a non-toxic and environmentally acceptable substance, was also used to make bio-inspired palladium nanoparticles. For the novel-green synthesis of palladium NPs, palladium chloride was reduced using boiled, crushed, acetone precipitated and air-dried peel powder. UV–visible spectroscopy, scanning electron microscope–energy-dispersive spectra (SEM–EDX) and X-ray diffraction (XRD) analysis were used to analyse Palladium NPs. The aqueous extract of watermelon rind, an agricultural waste was tested as a capping agent and reducing agent for palladium NP biosynthesis. The formation of Pd NPs was first observed visually, with the colour changing from pale yellow to dark brown, which was monitored using UV–visible spectroscopy. Further characterization of Pd NPs was done by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), DLS, AFM and TEM techniques. The nanoparticles formed are spherical and exhibit catalytic activity [ 42 ].

Copper nanoparticles (Cu NPs) and copper oxide nanoparticles (CuO–NPs)

Copper nanoparticles have been synthesized using both physical and chemical methods. The most prevalent chemical method is microemulsion; however, it requires a high concentration of surfactant and is expensive [ 43 ]. Although laser ablation, aerosol approaches, and radiolysis are widespread physical methods for synthesizing nanoparticles, their high cost and high energy consumption make them less popular [ 43 ]. Due to its availability, cost-effectiveness, eco-friendly nature and lack of hazardous by-products, biodegradable waste extract (biowaste) can be utilized as a green synthesis source for the production of copper nanoparticles. According to Sharon. et.al, at a dosage of 10 mg/L, copper nanoparticles from Artocarpus heterophyllus killed 100% of Aedes aegypti larvae from the first to fourth instars. Phang et al. reported that CuO NPs synthesized using a nontoxic and sustainable aqueous extract of waste papaya peel exhibit a high photocatalytic efficacy in the degradation of POME (Photocatalytic Degradation of Palm Oil Mill Effluent with low phytotoxicity), making them a suitable photocatalyst for POME wastewater treatment.

The seaweed S. longifolium (brown algae) can act as bionanofactory for the synthesis of copper oxide nanoparticles as it contains a significant amount of reducing agents that aid in the conversion of metal salts into their corresponding metal nanoparticles without producing any harmful by-products. The biosynthesized CuO-NPs exhibit antibacterial and antioxidant activities. CuSO 4 solution was added to water and placed in a beaker. The algal extract was added to this CuSO 4 solution drop by drop with constant stirring and then placed in a rotary shaker (Room temperature, 150 rpm). After 6 h, the colour of the solution has been observed (from green to brown), indicating the formation of CuO-NPs. The solution is then centrifuged at 7000 rpm for 5 min and subjected to further studies.

The absorbance of the CuO-NPs was measured using a UV–visible spectrophotometer as the primary confirmation. The infrared spectrophotometer was used to measure the secondary metabolites functional groups found in S. longifolium extract (resolution: 1 cm −1 ; 4000–400 cm −1 regions). TEM and SEM were used to determine the surface structure, size, and morphology of CuO-NPs. The degree of crystallinity (range 10–90 2Ө) and phase confirmation was measured by XRD [ 36 ].

Din et al. used aqueous extracts of (i) bilberry ( Vaccinium myrtillus L.) waste residues from the production of fruit juices and (ii) non-edible “false bilberry” fruits ( Vaccinium uliginosum L. subsp. gaultherioides), green synthesis of copper nanoparticles (Cu-NPs) was achieved. Because of their high number of phenolic compounds, notably anthocyanins, which are potent reducing agents, these extracts could be potential candidates for the green synthesis of Cu-NPs. For the synthesis, several cupric salts ( CuCl 2 , Cu(C H 3 COO ) 2 and Cu(N O 3 ) 2 ) were utilized. Transmission electron microscopy was used to examine the development of stable nanoparticles (Cu NP), and X-ray photoelectron spectroscopy was used to monitor the oxidation status of copper in these aggregates. The antibacterial activity of the produced Cu-NPs was generally higher than that of equal quantities of cupric salts, and it was effective against Gram-negative and Gram-positive bacteria and fungi.

Zinc oxide nanoparticles (ZnO)

Excess reactive oxygen species (ROS) generation, such as superoxide anion, hydroxyl radicals and hydrogen peroxide production, can be induced by ZnO NPs. Due to its unique qualities, such as high specific surface area and high activity to block a wide range of pathogenic agents, zinc oxide nanoparticles (ZnO NPs) act as an antibacterial material. Zinc oxide nanoparticles have been synthesized from the waste fruit peels of Punica granatum and Musa acuminata . UV–visible spectroscopy, x-ray diffraction analysis, and scanning electron microscopy were used to characterize ZnO nanoparticles. These NPs could also have a role in biology and biomedicine, as well as the environment, industries, food, and agriculture [ 44 ]. The influence of synthesis temperature on the size and shape of zinc oxide (ZnO) nanoparticles (NPs) generated using pineapple peel waste, as well as the antibacterial activity of ZnO NPs in starch sheets, was examined. Pineapple peels are high in phytochemical components, so it is used to extract bioactive chemicals like ZnO. When ZnO NPs were synthesized at 60 °C, they produced a mixture of spherical and rod-shaped structures, whereas when they were synthesized at 28 °C, they produced spherical flower-shaped structures [ 45 ].

The discovery of a unique method for effectively utilizing goat slaughter waste has led to the notion that dead animals and their tissue and/or organ wastes can also be used to synthesize nanoparticles. This work could aid in the control of pollution in the environment and, as a result, many diseases could be prevented. Jha et al. synthesized ZnO NPs from goat slaughter waste. The production of ZnO nanoparticles is investigated using X-ray and transmission electron microscopy [ 22 ]. Aminuzzaman et al. reported the synthesis of zinc oxide nanoparticles from aqueous extract of dragon fruit ( Hylocereus polyrhizus ) peel biowaste which acts as stabilizing and reducing agent. The synthesized zinc oxide nanoparticles are with an average size of 56 nm, spherical in shape and crystalline in nature. ZnO NPs were synthesized using an aqueous extract of dragon fruit peel. In an aqueous solution of zinc nitrate, freshly prepared dragon fruit peel extract was added drop by drop and heated at 70–80 °C with continuous stirring. The reaction solution's colour gradually changed from red to pale yellow, and further heated until a yellow colour paste was formed. The paste was placed in a ceramic crucible and held at 450 °C for 2.5 h in a temperature-controlled muffle furnace (air ambient). The resulting pale white powder was further characterized using different analytical tools. Zinc oxide nanoparticles exhibited a hexagonal wurtzite phase which was detected from XRD and Raman spectroscopic results.

Zinc oxide nanoparticles can be synthesized from longan seeds extract constituting phytochemical extracts such as catechin, vitamin, protein, sugar and flavonoids which act as reducing and capping agents. The longan seeds are obtained from the dried pulp of longan ( Dimocarpus longan  Lour). These seeds due to their continuous disposal serve as a source of pathogens and attract flies causing hygienic and environmental-related problems. For the synthesis of ZnO NPs, zinc acetate (Zn (CH3COO) 2 ·2H 2 O) solution was dissolved in the seed extract to varying concentrations. The reaction was carried out in a microwave oven that was set to various powers (450–800 W) and irradiation cycles. The size of ZnO nanoparticles ranges between 40–60 and 40–80 nm. The pure phase of hexagonal ZnO was measured by powder X-ray diffraction, and the shapes of ZnO nanoparticles were mostly irregular according to TEM results. ZnO nanoparticles aid in photocatalysed decolourization of methylene blue (MB), malachite green (MG), methyl orange (MO), and orange II (OII) thereby useful in wastewater treatment disposed of textile industries [ 46 ].

Titanium dioxide nanoparticles ( T i O 2 )

Different sizes of titanium dioxide nanoparticles have been investigated for various uses. Because of its photocatalyst, high chemical stability, and lack of toxicity, titanium dioxide is environmentally friendly. Titanium dioxide nanoparticles are believed to be the most valuable materials for cosmetics, pharmaceuticals, and most significantly, skin protection from ultraviolet (UV) rays, in papers, food colourants and toothpaste. Ti O 2 NPs have a strong antibacterial effect [ 47 ].

Ajmal et.al synthesized cost-effective, inexpensive eco-friendly titanium dioxide nanoparticles using a methanolic extract of fruits peel agro-waste. TiO 2 NPs were found nanocrystalline from the X-ray diffraction spectrum. Fourier transform infrared revealed the presence of O–H, C=O, C–O and C–H functional groups in the fruit peel, all of which are involved in the formation of Ti O 2 NPs. Plum, Kiwi, and Peach mediated Ti O 2 NPs were found to be cylindrical in SEM images. The antibacterial and antioxidants exhibited by all of the Ti O 2 NPs were size and dose dependant.

Titanium dioxide nanoparticles are synthesized via bacterial cellulose (BC) produced from agricultural wastes, where bacterial cellulose (BC) currently known as biotype is synthesized using sugar cane molasses and also from rotten apple waste. The green process was utilized to reduce titanium tetraisopropoxide into titanium dioxide nanoparticles using bacterial cellulose (BC) produced by Achromobactin sp. M15. Utilizing 3-glycidyloxypropyltrimethoxysilane (GPTMS), titanium dioxide nanoparticles (TiO2NPs) were added to the solution and the process was carried out via the sol–gel method. The produced titanium dioxide NPs were characterized using transmission electron microscopy (TEM), and their particle sizes were within a range of 5–10 nm. Fabrics treated with Ti O 2 -NPs were characterized using FTIR, thermal gravimetric analysis (TGA), mechanical characteristics, scanning electron microscopy (SEM) and EDX [ 48 ]. More examples of different nanoparticles synthesized from vegetable and fruit extract are included in Table ​ Table1 1 and examples of other biowaste-assisted NPs syntheses are included in Table ​ Table2 2 .

Different types of vegetable and fruit peel extracts derived nanoparticles

Different types of nanoparticles derived from biodegradable waste extracts other than vegetable and fruit peel extracts, synthesis methods and their application

Silica nanoparticles

Numerous studies have documented the use of waste as a silica source, with the majority of them focusing on the abundant agricultural waste such as rice husk, corn cob and sugarcane bagasse. According to Mohamed. et.al, banana peel ash was used to make mesoporous silica nanoparticles (MSN), which were tested for their ability to adsorb methyl orange (MO) and phenol under a variety of conditions, including pH, adsorbent dosage, starting concentration and temperature. As a result, the synthesized MSNs have the potential to be used as a low-cost adsorbent in the treatment of wastewater contaminated with dyes [ 60 ]. According to Araichimani et al., amorphous silica nanoparticles with sizes ranging from 50 to 80 nm have been synthesized via rapid microwave-assisted combustion from rice husk biowastes. A powder X-ray diffractometer was used to measure the crystalline property of the synthesized nanoparticles and an FTIR spectrometer with a range of 4000–400 cm −1 was used to determine the chemical composition of the produced sample. A scanning electron microscope (SEM) with an energy-dispersive X-ray (EDX) analyser was used to study the morphological features and elemental composition of the synthesized sample. From sugarcane bagasse, amorphous silica nanoparticles with spherical morphology with an average size of 30 nm, and a specific surface area of 111 m 2 /g −1 have been synthesized using the extraction and precipitation method. The confirmation of the silica nanoparticles in the sample was obtained from the IR spectra which showed the vibration peak of Si–O–Si. The morphology and particle size of synthesized nanoparticle was obtained by scanning electron microscope (SEM). X-ray powder diffraction confirms the structural characteristics of the produced silica nanoparticles (XRD). While the functional group's vibration is obtained by Fourier transform infrared (FTIR) spectroscopy and a BET surface area analyser was used to estimate the surface area of silica nanoparticles.

Hydroxyapatite nanoparticles

Eggshells are usually discarded since they have no nutritional value and they promote microbial growth if discarded untreated, However, CaO can be used as a source for the commercial synthesis of hydroxyapatite nanoparticles. According to Aal et al., hydroxyapatite nanoparticles were synthesized by chemical precipitation method using chicken eggshell as biowaste and phosphoric acid solution as starting material. Hydroxyapatite nanoparticles can be synthesized from fish scales. The scales of fish ( Lethrinus lentjan ) could be used to make hydroxyapatite bio-precursors at a low cost. Organic (collagen, proteins and lipids) and inorganic (hydroxyapatite) compounds can be found in fish waste. So, these substances present in fish scales are converted to hydroxyapatite nanoparticles (solid form) by a hydrothermal method which is carried out at 280 °C. The physiochemical characteristics of fish scale-derived hydroxyapatite nanoparticles can be characterized by using different techniques such as high-resolution transmission electron microscope (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer and thermogravimetric analyser (TGA). Sharifianjazi et.al used the ball milling method for the preparation of hydroxyapatite nanoparticles, after annealing waste pigeon bones at 850 °C, cold-pressing the nanoparticles and re-sintering at 850, 950, 1050 and 1150 °C. The typical particle size of the ball-milled pigeon-derived nano-hydroxyapatite (PHA) was 50–250 nm.

Nano-cellulose crystals

Lei et al., introduced a new approach for the synthesis of cellulose nanocrystals (CNCs) from recycled office waste papers. This approach has a lot of significance as every year, a massive volume of office waste paper (OWP) is wasted, polluting the environment. OWP being cellulose-rich biomass was employed for the production of cellulose nanocrystals (CNCs) by acid hydrolysis with different acid concentrations but without subjecting OWP to alkali and bleaching treatments. CNCs produced with a 65% acid concentration coated on a PET sheet not only had improved water vapour barrier properties but also had the same transparency as PET. CNCs are a potential new material with unique qualities such as nanoscale size, high specific strength and modulus, high surface area, high crystallinity and distinctive optical properties, among others.

Mehanny et al. synthesized CNCs from palm wastes (fronds, leaves and coir) by the chemical extraction method in which amorphous regions of cellulosic structure are attacked by acid leaving cellulose nanocrystals. Further characterization was done by scanning electron microscope (SEM) to determine the morphological structure, transmission electron microscopy (TEM), particle size analyser was used to measure the average diameter, size distribution and the zeta potential of the sample, FTIR spectrometer was used to determine infrared spectroscopy with the range between 4000 and 400 cm −1 , and for XRD analysis X-ray diffractometer is used with radiation at 30 kV and 10 mA. Zheng et al. synthesized nanocrystals from walnut shells and also highlights a few sustainable and environmentally friendly approaches based on recyclable chemicals that have been emerged as a result of recent technological advancements. Hydrolysis using solid acids (for example, phosphor tungstic acid) or treatment with ionic liquids or deep eutectic solvents are two examples. The most often utilized acid for synthesizing sulfonated cellulose nanocrystals with good water dispersibility is sulfuric acid. The Para crystalline or disordered regions of cellulose are hydrolysed and dissolved in the acid solution during the hydrolysis process; however, the crystalline parts of cellulose are chemically resistant to the acid and stay intact. As a result, the cellulose fibrils are cleaved transversely, resulting in short cellulose nanocrystals with high crystallinity.

Application of biosynthesized nanoparticles

Green nanotechnology-based approaches based on biowaste have been accepted as an environmentally friendly and cost-effective approach with a variety of applications as depicted in Fig.  3 .

Various applications of green synthesized nanoparticles derived from biogenic waste extracts [ 80 ]

In therapeutics

Anticancer activity.

Cancer is a group of diseases characterized by uncontrolled cell division [ 81 ]. Cancer has resulted in 8.2 million deaths per year. Nearly 200 different forms of cancer have been identified. Nanotechnology and immunology have been combined to form nano-immune-chemotherapy, which is effective in cancer treatment. Various metal and metal oxide nanoparticles exhibit cytotoxicity against cancerous cells without affecting the normal cell thereby working efficiently in anticancer activities. Das et al. synthesized Ag NPs from pineapple peel waste extract which exhibited antioxidative, antidiabetic, and cytotoxic activity against HepG2 cancer cells, as well as antibacterial activity. It is effective in the treatment of acute ailments as well as in the development of drugs to cure diseases like cancer and diabetes. It also has uses in wound dressing and the treatment of bacterial infections. MgONPs were synthesized from aqueous extracts of brown seaweed Sargassum wightii . They are rich in constituents such as polyphenols, carotenoids, amino acids, vitamins and polysaccharides which help them act as a capping agent and reducing agent in the synthesis of MgONPs. These biosynthesized MgONPs lead to apoptosis of cancerous cells thereby exhibiting potential cytotoxic activity against lung cancer cell line A549 by increasing ROS generation [ 82 ]. Another study reported the synthesis of bimetallic nanoparticles from Trapa natans peel extract. Silver (Ag) (15 nm) and gold (Au) (25 nm) nanoparticles have been synthesized using Trapa peel extract, with potential cytotoxic activity against various cancer cells. Bimetallic nanoparticles are more advantageous than unimetallic nanoparticles as it combines the features of both Ag and Au nanoparticles. The studies have shown that the bimetallic composites NPs can be a potential alternative for p53 as they can induce mitochondrial stress and apoptosis, thereby exhibiting ROS-mediated p53-independent apoptosis in cancer cells. Bimetallic composite NPs have the potential to be used in nanomedicine for cancer treatments in the future as it is an efficient, cost-effective and easy method [ 83 ].

Antibacterial activity

The antibacterial activity of metal and metal oxide nanoparticles commonly involves the formation of reactive oxidative species (ROS); superoxide radicals (O −2 ), hydroxyl radicals (OH −1 ), singlet oxygen (O −2 ), etc., are a few short-lived oxidants of ROS. It can lead to inhibition of transcription, translation, enzymatic activity and the electron transport chain, and second, it involves protein inactivation and DNA destruction leads to the destruction of bacterial cells [ 84 ]. Metal and metal oxide nanoparticles have shown potential efficiency in bacterial growth inhibition and to tackle antibacterial resistance. Basumatari et al. reported the synthesis of ZnO NPs from aqueous extract of Musa balbisiana  Colla pseudostem biowaste of size ranges between (45 and 65 nm). It exhibited efficient antibacterial activity against both gram-positive and gram-negative bacteria including E. coli , S. aureus , Bacillus subtilis and P. aeruginosa by the release of Zn 2+  ions from ZnO NPs, which binds to the bacterial cell membrane and produce reactive oxidative species (ROS) that stops the cellular function inside the bacterial cell and leads to proteins, lipids, DNA denaturation. ZnO NPs can also exhibit antibiofilm activity against P. aeruginosa thereby can also be used as a water disinfectant in the drug industry and food conservation.

Various types of agri-food by-products such as rapeseed pomace, sugar beet pulp, fodder radish cake, grape pomace and pomegranate peels or bio waste extracts were used to produce nanoparticles which were prepared by the ultrasound-assisted water extraction with subsequent oxidation by oxygen purge and characterized by liquid chromatography-mass spectroscopy (LC–MS), and these Ag NPs synthesized from oxidized aqueous black currant, apricot, grape pomace and pomegranate peel extracts exhibited antimicrobial activity against common pathogenic bacteria E. coli and B. subtilis [ 85 ].

Grape pomace extract (GPE)-synthesized AgNPs demonstrated significant antibacterial activity against E. coli and S. aureus . The antibacterial response mechanism was investigated by detecting bacterial cell membrane rupture and cytoplasmic contents, which included nucleic acid, proteins and reducing sugars. The antibacterial potential and synergistic efficacy of GPE-AgNPs in combination with traditional antibiotics were demonstrated against human pathogenic bacterial infections. The potential of GPE as a novel source for the biosynthesis of AgNPs has been demonstrated in this study, which could open up new vistas in nanomedicine [ 53 ].

Yuvakumar et al. reported the Antibacterial action of ZnO nanocrystals against pathogenic microorganisms synthesized from rambutan peel waste extract and also applicable in biomedical nanotechnology. AgNPs can also be synthesized from rambutan peel waste extract which has antibacterial efficacy against Salmonella parathypi A ., with a 4 mm inhibitory zone, where Salmonella parathypi A . is prone to cause paratyphoid fever (enteric fever) [ 86 ].

Antiviral activity

In the last decade, the importance of nanotechnology in virology has grown at an exponential rate. Various metal and metal oxide nanoparticles are exhibiting virucidal properties which can act against different viruses such as Human immunodeficiency virus (HIV), hepatitis (type A, B, C and E) and herpes simplex virus (HSV-1&2). Metal nanoparticles exhibit antiviral activity when it interacts with viral cell surfaces, metallic nanomaterials may diffuse into the cell and affect the cell by destroying the viral genome (DNA or RNA), in addition, to directly interacting with the viral cell surface glycoproteins. Metallic nanoparticles interact with the genomic components of the cell and inhibit replication thereby preventing the spread of infection.

According to the reports, Ag and Au are the most common metallic nanoparticles exhibiting antiviral activities against enveloped viruses. Algae-mediated silver nanoparticles exhibit antiviral activity and also can be extensively applied in different nano-silver products, AgNp-coated wound dressings, comprising surgical instruments, implants, etc. [ 87 ]. There are varied applications found for the metal nanoparticle, on considering silver nanoparticles according to the relevant studies the usage of silver nanoparticles has intensified importance, especially in the covid pandemic situation as the Ag NPs has been reported to exhibit antiviral properties used to inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [ 88 ], by utilizing Ag NPS which inhibits the virus nucleotide replication. It binds to electron donor groups present in the microbe's enzymes, such as sulphur, oxygen and nitrogen. As a result, the enzymes are denatured, thus incapacitating the cell's energy supply, and the microbe dies quickly [ 89 ]. Another study reported the efficient antiviral property of CuO-NPs in the treatment of herpes simplex virus (HSV-1) infection, wherein the CuO-NPs interfere with the entry and attachment of HCV infectious virions in hepatic host cells thereby inhibiting HSV-1 infection in the Vero cell culture system [ 90 ].

Antioxidant activity

Any compound or substance capable of preventing the oxidation of a suitable substrate even at low concentrations exhibits antioxidant activity. In general, because of their scavenging activities, these antioxidants either prevent or postpone cellular damage [ 91 ]. Rajamanikandan et al. reported that carbon quantum dots (CQDs) exhibit antioxidant activity synthesized from Biowaste Ananas comosus by facile hydrothermal treatment. The pineapple peel extracts constitute sugar, high fibre and phenolic compounds as well as antioxidant properties. Antioxidant assay of the CQDs was assessed against DPPH (2, 2-diphenyl-1picrylhydrazyl), hydroxyl radical scavenging, superoxide anion radical scavenging and hydrogen peroxide radical scavenging activities. The CQDs extracted showed fluorescence spectra which displayed blue emission radiation at 438 nm that can be used for photonic devices. The silver nanoparticles of particle size of 40–60 nm and spherical shape synthesized from the aqueous extract of black currant pomaces (BCPE) exhibited antioxidant activity.

The antioxidant activity of the biosynthesized nanoparticles was characterized using different techniques such as total antioxidant capacity, DPPH radical scavenging activity and iron (III) reducing capacity. The antioxidant compounds such as flavonoids, stilbene, aldehyde and phenolic acids contribute to the total antioxidant activity of black currant pomace extract which is found essentially high. These synthesized silver nanoparticles also have the property to inhibit pathogenic organisms such as Gram-negative bacteria [ 92 ] The silver nanoparticles synthesized from aqueous and methanol fruit extracts of Nauclea latifolia (African peach) exhibit potent antioxidant activity by their ability to scavenge DPPH radicals. The DPPH scavenging activity of the methanolic fruit extract of Nauclea latifolia and a standard antioxidant (ascorbic acid) range between 6.1 and 23.9% at a concentration of 100–1000 µg/ mL, their antioxidant property results from their ability to donate hydrogen groups and chelate metal ions involved in generating free radicals. These biosynthesized silver nanoparticles can be applied in various antimicrobial control systems, water treatments and medical processes [ 93 ]. Another study reported the synthesis of chitosan nanoparticles (ChNP) from chitosan, which was found to have scavenging activity against free radicals and the ability to chelate metal ions thus making it a potent antioxidant. These ChNP can act as excellent vegetable and fruit coating material as it is non-toxic, biodegradable and have the potential to control the decay of many fruits such as strawberries, papaya cucumber, carrot, apple, citrus, kiwifruit, peach, pear, strawberry and sweet cherry and to extend storage life. The edible coatings made of ChNP prevent the weight loss in many vegetables such as brinjal and chilly by controlling the water vapour transmission and by reducing the water loss [ 94 ].

Waste water treatments

The wastewater discharge from textiles and industries is inevitable; however, its treatment is highly necessary. It is a major crisis across the globe. Introduction to nanotechnology in waste treatment has improved its efficiency. The incorporation of biosynthesized nanoparticles from biowaste in wastewater treatment provides an environmentally friendly, toxic-free and sustainable approach, it also prevents the deposition of biowaste causing harmful effects to the environment. A study reported the synthesis of Cu2O nanoparticles from sugarcane bagasse. The sugarcane bagasse extract is rich in reducing carbohydrates which can act as a reducing and stabilizing agent and aid in the synthesis of Cu2O nanoparticles. By utilizing the catalytic efficiency of Cu2O NPs and their reusability, it can be employed in photocatalytic degradation of organic, toxic dyes such as methyl orange (MO), methyl blue (MB), methyl red (MR) and Congo red (CR) present in wastewater. The degradation efficiency of the toxic dyes is in the following order MR < CR < MB < MO. In the future, further improvement in this method will have the potential to remove chemical warfare reagents to toxic heavy metals in wastewater and also aid in the absorption of pollution from the atmosphere [ 95 ]. According to Doan et al., an eco-friendly, cost-effective method was introduced for the synthesis of silver and gold nanoparticles from aqueous extract of waste corn-cob and these biosynthesized metallic noble nanoparticles exhibited potential catalytic properties used in the reduction of nitrophenols and degradation of organic dyes, as a result, it can act as an efficient catalyst in the treatment of water. Methylene blue is a cationic thiazine dye which is water-soluble and is widely used in the photographic, printing and textile industries. Methylene blue is toxic to humans and animals, causing permanent eye burns, nausea, profuse sweating, mental confusion, methemoglobinemia and vomiting. It was reported that Green-synthesized ZnO NPs from dragon fruit peel extract under solar irradiation exhibited 95% degradation of Methylene blue dye in 120 min. This approach is an economical, favourable, renewable method for the removal of organic pollutants from an aqueous solution under solar irradiation [ 44 ].

Iron nanoparticles from tea extract with an average particle size of 98.79 nm exhibited a zeta potential of − 45 mV at pH 10. The studies have proven that iron nanoparticles from tea extract have the potential to remove phenol red from an aqueous solution by efficient adsorption of phenol red at alkaline pH (pH 8) [ 96 ]. Silver nanoparticles made from cauliflower waste have a wide range of applications, including photocatalytic degradation of methylene blue dye and Hg2 + biosensing. AgNPs with the right size and shape have a high surface area-to-volume ratio, making them ideal dye degrading catalysts [ 56 ].

Food packaging

Food packaging always leads to food safety. It is a healthy way of preserving food and beverages. Packaging helps to protect the food from disease-prone pathogens. Food packaging involves primary and secondary levels of packaging. Secondary packages are usually concerned with transportation, storage and delivery [ 97 ]. Nowadays, “Nano food packaging” (food packages were made using nanoparticles) gained a lot of interest in the food industry. But the level of toxicity associated with nanoparticles is of major concern. Debate is still going on among researchers about the safety issues in nanofood packaging.

Nanotechnology-based novel and efficient polymeric materials for food packaging can bring solutions to food industry issues such as product safety and material performance, and economic and also it includes environmental benefits. The use of suitable packaging materials and processes prevents food losses and they always offer safe and healthy food products. Metal and metal oxide NPs as a potential replacement for traditional antibiotics in food processing and medicine [ 98 ]. Various industries, including food processing and packaging, may profit from the use of these nanoparticles as antimicrobial materials deposited onto surfaces. ZnO is used in the food industry as a source of zinc, which is an essential micronutrient that plays a crucial and critical role in human and animal well-being [ 99 ]. By adding ZnO (obtained by spray pyrolysis) to the polylactic acid matrix, it is investigated that new films based on polylactic acid (PLA) can be used for possible applications in the food packaging sector with improved properties, such as barrier and mechanical properties, and majorly antibacterial activity [ 100 ]. Zinc oxide and titanium dioxide NPs are the most commonly used nano-sized antimicrobial metal oxides in active packaging.

Beneficial bioactive chemicals found in fruits and vegetable waste, such as alkaloids, amino acids, enzymes, phenolics, proteins, polysaccharides, tannins, saponins, vitamins and terpenoids, operate as reducing agents in the formation of metal nanoparticles (NPs) [ 101 , 102 ]. According to Biswal et al., silver nanoparticles (Ag NPs) were synthesized using an aqueous extract of Mahua ( Madhuca latifolia ) oil cake as a reducing and capping agent. According to the study, Mahua oil cake extract could be used for the biogenic production of AgNPs with antibacterial and antioxidant properties that could be used in commercial food packaging, which also aids in waste utilization. Fruit and vegetable peel waste can be used as edible coatings. These edible coatings are thin films added to the surface of the food to extend its shelf life and preserve its features, attributes, and functionality at a low cost [ 103 ]. By increasing the shelf life, reducing microbial deterioration, and functioning as a carrier matrix for antimicrobial compounds, all these applications can improve their functionality. AgNPs were synthesized using a Soxhlet extraction system from extract of the sugar industry waste, sugar cane bagasse, which can act as capping and reducing agent with potential application in food, cosmetics, electronics and biomedical applications due to their physical and chemical properties [ 104 ]. Titanium, silver, zinc oxide, selenium, copper, magnesia and gold are common antibacterial agents. Various industries, including food processing and packaging, may profit from the use of these nanoparticles as antimicrobial materials deposited onto surfaces [ 105 ].

Various other applications

Cuk et al., synthesized silver nanoparticles (in-situ) on cotton fabric from waste extracts of plant food waste (green tea leaves, avocado seed and pomegranate peel) and alien invasive plants (Japanese knotweed rhizome, goldenrod flowers and staghorn sumac fruit) which can act as reducing agents. Such cotton fabrics provide protection against UV radiation and pathogenic bacteria which is very much beneficial in today’s world. In an alkaline medium, silica nanoparticles with sizes ranging from 90 to 10 nm were effectively produced from sugarcane bagasse ash by the sol–gel method, which can be used as a filler in natural rubber composites [ 106 ]. A method for producing fluorescent carbon nanoparticles (CNPs) from discarded rice husk using thermally-assisted carbonization in the presence of strong sulphuric acid. The CNPs' interfacial interaction with metal ions allows them to be used for sensing applications. This might be used to replace some existing fluorescent dyes or quantum dots that are less environmentally friendly due to their toxicity and production methodology [ 107 ]. Nanoparticles synthesized were also used in a wide range of environmental applications, including water treatment, the detection of persistent contaminants and soil/water remediation. Photocatalysis, superconductivity, solar energy harvesting, energy storage (lithium-ion batteries) and antimicrobial devices are only a few of the disciplines where green synthesized CuO Np has found broad use [ 108 ]. Copper nanoparticles could be used in optics, electronics, and medicine, as well as in the production of lubricants, nanofluids, conductive coatings and antibacterial agents. They are preferred over silver nanoparticles because of their lower cost, physical and chemical stability, and ease of combining with polymers [ 43 ]. The use of these low-cost waste horticulture wastes to create a value-added product is an innovative step toward their long-term sustainability [ 109 ].

Merits and demerits of biosynthesized nanoparticles from biowaste

Synthesis of nanoparticles from biowaste offers potential benefits over the chemical-based synthesis approach. This approach is eco-friendly, cost-effective and easy. Here the precursor of natural sources can be reused, recycled and reduced. Furthermore, the abundance of natural precursors aids in the development of large-scale-up technologies. The green synthesis approach eliminates the need for extra capping or stabilizing agents, thereby lowering the cost and simplifying the synthetic process as the natural precursor itself constitutes polyphenols, proteins and pigments which can act as reducing and capping agents. There are varied applications for biosynthesized nanoparticles in energy sectors, it aids in improving the efficiency of solar cells, fuel cells and batteries, in manufacturing sectors which will require materials such as aerogels, nanotubes and nanoparticles to produce desired products, is another area that might profit from nanotechnology. These materials are often more durable, stronger, and lighter. Biosynthesized nanoparticles have efficient application in drug delivery, as the nanoparticles are synthesized from biodegradable materials that aid in sustained release of drug in the target region over days or weeks and effective drug accumulation at the target site is due to the small size of nanoparticles that can penetrate through narrow capillaries that are taken up by the cells thereby increasing the therapeutic efficiency [ 110 ].

The major challenge is to scale up the synthesis of nanoparticles from biowaste at the industrial level. In the case of industrial-scale environmental applications, the monodispersity, size, and shape of the NPs should also be considered. Identification of particular biomolecules responsible for the stabilization and reduction of metal NPs from their precursor is another challenge. It is easy to maintain optimum conditions for the synthesis of nanoparticles from biowaste at the small-scale laboratory level, while it is a challenging task to maintain optimum for the synthesis of nanoparticles from biowaste at the large-scale level, wherein the degradation of biowaste is a problem to be addressed [ 111 ]. The biowaste-mediated M/MO-NPs sometimes exhibit non-uniform size and indefinite shape which is unfit for various applications as it fails to meet the required criteria. Another problem related to biomedical applications, for example, for cancer therapy is the low toxicity of biosynthesized nanoparticles which makes them incapable to achieve the desired results, also the safety of metal oxide NPs in smart food packaging is one of the main problems, therefore migration from the packaging and cytotoxicity are major concerns for their future use in smart food packaging [ 112 ].

Summary and future prospects

As discussed in this review, biowaste generation is inevitable and if not treated and disposed of properly it can lead to many other environmental impacts it is hazardous to human health as it has the potential to cause a variety of diseases. In agriculture, post-harvest waste is about 80% of the total biomass, which is usually discarded by burning it, and it leads to massive volumes of green gas emission, smog and other pollutants resulting in serious health consequences, air pollution, global warming, climate change, etc. Alternatively, the synthesis of nanoparticles from biowaste can act as a potential source, thereby aiding in the long-term use of resources, improving sustainability and reducing high energy demand waste deposits. Biowaste is recognized as an alternative source as it is regenerative, recyclable, reusable, and economical. Out of the many nanoparticles discussed biowaste-mediated synthesis of noble metal nanoparticles has gained a lot of prominence due to their antiviral and antimicrobial activities against pathogens in therapeutics. More study needs to be implemented in improving the toxic properties of nanoparticles against cancerous cells in cancer treatments. Further research is needed to synthesize nanoparticles of desired uniform size and shape without the expenditure of high energy.

One of the major drawbacks in dealing with biowaste is that the chemical composition of different biowaste obtained in different parts of the world will vary resulting in a non-uniform synthesis of nanoparticles at a large scale. Further studies are needed on the time taken for degradation of different biowaste so that timely collection of different biowaste can be implemented or techniques to prevent deterioration of different biowastes before it can be subjected to different methods for nanoparticle synthesis. However, in recent years tremendous effort has been put into tackling the synthesis of nanoparticles from biowaste. Biowaste-mediated nanoparticles have the potential to be used extensively in the medical field, for therapeutic drugs, antimicrobial activity, antioxidant activity, water treatments and food packaging. It also shows recent advances in utilizing biowaste-mediated nanoparticles in energy storage technology, which has the potential to act as a renewable resource for energy applications. Further research is initiated for the application of biowaste-mediated nanoparticles in wearable technology. The synthesis of nanoparticles from biowaste has paved a pathway to developing an eco-friendly process that limits the usage of hazardous chemical substances. Because of the widespread availability of biowaste and biologically active biomolecules, synthesis of nanoparticles from biowaste could act as an alternate potential precursor or source.

On the whole, this brief review explores the recent advances of the last decade in the utilization of biowaste for the sustainable fabrication of NPs with numerous applications in the medical industry, drug delivery, cancer treatments, food industry and water treatment. Cumulatively, a study on the last two decades shows an exponential increase in the pace of biowaste-assisted nanomaterials synthesis owing to its easy availability, better stability and dispersion in aqueous solutions. In the final analysis, the use of biowaste is found to be more advantageous over other raw materials in terms of zero contamination, simple procedures, low toxicity, high stability and cost-effectiveness in the NPs synthesis. On the contrary, the interaction between the metal precursor and biowaste, mechanism of interaction in reduction of metal precursor, techniques for isolation or purification of the interesting component from biowaste, functionalization, cytotoxicity, bulk industrial production, shape-selective synthesis of nanoparticle synthesis still need extensive investigation to expand eco-friendly implementation of nanomaterials in biomedicine, bio-sensing, battery storage, energy, crop production, edible packaging and wearable devices. Taking everything into account, biowaste-assisted nanosynthesis has the potential to be scaled up with proper policy-making from the government or concerned authority to meet sustainable green applications which open new horizons and better tomorrow.

Acknowledgements

The authors thank the department of chemistry CHRIST (Deemed to be University) Bangalore, India, for the support and encouragement.

Declarations

The authors declare no conflict of interest.

This review emphasizes the biowaste-assisted synthesis of metal and metal oxide nanoparticles. Contrary to the recent reviews on the same topic, authors have included many applications other than a single application or antibacterial and antiviral studies alone. Authors have also listed many sources which are neglected by other review papers. Moreover, advances in the recent innovations are included with 129 articles on the specified field, which not only gives a broader prospect about the topic but also a comprehensive review for beginners in the field of nanotechnology.

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Analytical Methods

Unravelling the potential of magnetic nanoparticles: a comprehensive review of design and applications in analytical chemistry.

Nanoparticles have emerged as a prominent research field, offering a wide range of applications across various disciplines. With their unique physical and chemical properties within the size range of 1-100 nm, nanoparticles have garnered significant attention. Among them, magnetic nanoparticles (MNPs) exemplify promising super-magnetic characteristics, especially in the 10-20 nm size range, making them ideal for swift responses to applied magnetic fields. In this comprehensive review, we focus on MNPs suitable for analytical purposes. We investigate and classify them based on their analytical applications, synthesis routes, and overall utility, providing a detailed literature summary. By exploring the diverse range of MNPs, this review offers valuable insights into their potential application in various analytical scenarios.

• This article is part of the themed collection: Analytical Methods Review Articles 2024

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S. Cicek, I. Kaba and F. A. ozdemir olgun, Anal. Methods , 2024, Accepted Manuscript , DOI: 10.1039/D4AY00206G

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