Table 4.

Application of biomolecules in the production of natural fiber-based composites for potential biomedical applications and respective properties. Most of the selected combinations have already been established for biomedical uses. However, there are a few that, even though the publications do not state those as potential applications, the authors feel that the combinations or the principles described may be of interest for biomedical uses and as such were included. This table compiles examples of natural fiber-reinforced composites modified with multiple biomolecules reported in the last 10 years.

Category	Specific Biomolecule		Natural Fiber-Reinforced Composites	Biofunctionalized Fibers/Fabric/Composite Production and Properties	References
	Name	Characteristics
Drugs/Antibiotics	Amoxicillin	Penicillin-type antibiotic that works by stopping the growth of bacteria. Used to treat several bacterial infections like, middle ear infection, strep throat, pneumonia, skin and urinary infections, etc.	Woven cotton fabric/polylactic acid composite	Drug-loading capacity increased with decreasing fabric porosity. Degradation of the fabric composites influenced drug release rate. Water absorption decreased with increasing PLA concentrations. The mechanical properties of the composites were consistent with the fabric’s density and weight.	[14]
	Tigecycline	FDA approved glycylcycline antibiotic used in the treatment of skin tissue infections.	Sericin (outer layer of silk fibers)/poly(vinyl alcohol) composite	Composite fibers showed a smooth and uniform morphology with suitable porosity, mechanical stability and water vapor transmission rate. They also revealed antibacterial activity against Escherichia coli and Bacillus subtilis. In vivo testing showed this composite to accelerate wound healing.	[78]
	Diclofenac	Nonsteroidal anti-inflammatory drug used to treat pain and inflammation associated with arthritis.	Keratin/hydrotalcite NPs composite	Keratin extracted from wool and filled with hydrotalcite NPs intercalated with anionic diclofenac gave rise to a new composite. These showed a less pronounced swelling, porosity and degradation and a greater thermal stability compared to pure keratin films. Diclofenac release profile was more stable on the modified composites, which were also able to support fibroblast-like cells adhesion.	[79]
	Dimethyl phthalate	Colorless liquid soluble in organic solvents, commonly used as an insect repellent and ectoparasiticide.	Sugarcane bagasse/starch granules composite	Cellulose nanofibers derived from waste sugarcane bagasse were mixed with starch granules to produce a low porosity biocomposite with enhanced water uptake. The initial dimethyl phthalate release burst was reduced, gaining a superior controlled release efficiency overtime.	[80]
Nanoparticles (NPs)	Silver (Ag)	Inorganic particles endowed with superior antimicrobial activity. Their mechanism of action is not yet completely understood but it is clear it is significantly affected by the particles’ nanoscale dimensions.	TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) selectively oxidized jute fiber	AgNPs, averaging 50.0 ± 2.0 nm, were formed in situ and deposited on the surface of jute cellulose fibers by microwave heating. The versatile jute-AgNPs nanocomposites demonstrated superior thermal stability and high crystallinity.	[81]
			Silk fibers/polyhexamethylene biguanide (PHMB) fabric	Regenerated silk fibers were fabricated through the dry–wet spinning process and modified via master batch or dipping process with different concentrations of PHMB and AgNPs. The bactericidal efficiency of the master batch treated fabrics was dependent on the concentration of the antibacterial agent as well as particle size. In the dipping process, a compromise was made between the good inhibition effect and the least amount of color change on the bio-fibers.	[82]
			Sugarcane bagasse/acrylamide/glycidyl methacrylate composites	Sugarcane bagasse was successfully grafted with acrylamide and glycidyl methacrylate and further modified in a colloidal suspension of AgNPs, gaining superior antimicrobial action against Escherichia coli, Staphylococcus aureus, Aspergillus flavus and Candida albicans.	[83]
			Linen (from flax family)/chitosan composite	Linen fabrics coated with chitosan and modified with AgNPs via in situ synthesis with tamarind seed coat extract showed efficient multifunctional properties, with bacterial reduction of 100%, UPF rating of 50+ and antioxidant activity of 97%. Except for flame retardancy, all properties were retained to a satisfactory level even after 50 washing cycles.	[84]
			Cotton/carboxymethyl chitosan/L-cysteine composite	Cotton fabric grafted with carboxymethyl chitosan and immobilized with AgNPs, via amidation reaction with the L-cysteine groups available at the fabric surface, demonstrated enhanced antibacterial functions, sustained even after 180 cycles of washing. Cytotoxicity assays showed insignificant effects on human immortalized keratinocyte cells, revealing the safety of the material for contact with the human skin.	[13]
			Cotton/polypyrrole-silver nanocomposites	Polymer–AgNPs nanocomposites modified cotton fabrics prepared by in situ chemical oxidative polymerization, displayed enhanced conductivity. AgNPs were also responsible for the increased antibacterial activity of the composite against Staphylococcus aureus and Escherichia coli.	[85]
	Silver and copper (Ag/Cu bimetallic NPs)	Inorganic particles with exceptional antimicrobial and antifungal properties.	Cotton/polyester composite	Cotton–polyester textiles were successfully impregnated during washing and ironing processes with five impregnation solutions containing Ag/Cu in the form of bimetallic NPs (alloy and core-shell) as well as ionic species. The antimicrobial activity of the fabrics was observed and did not become compromised after 20 washing cycles. Surfaces treated with solutions containing Ag+/Cu2+ and AgNPs/Cu2+ inhibited fungi growth significantly.	[86]
	Copper oxide (CuO)	Inorganic particles with antimicrobial properties. CuO has unique optical, catalytic and chemical properties at nanoscale.	Polycotton-based fabric	CuO-modified cotton fabrics revealed excellent resistance to microorganisms (bacteria and fungi) at different concentrations.	[87,88]
	Calcium carbonate (CaCO3)	Inorganic particles endowed with an ultra-fine solid structure and high economic value that play an important role in reinforcing and toughening materials and enhancing electrostatic attraction.	Kenaf fiber/polyester composite	Kenaf fiber–polyester composites produced via vacuum-assisted resin infusion process followed by CaCO3 NPs impregnation exhibited increased modulus of elasticity, modulus of rapture, tensile modulus and tensile strength, and a reduced swelling capacity and moisture absorption.	[89]
			Kenaf bast fibers-polyolefin matrices/polypropylene composite	CaCO3 was incorporated within the composite via the inorganic nanoparticle impregnation method. The tensile modulus and strength of the fibers increased significantly after NPs incorporation, as the compatibility of the modified kenaf fibers and polypropylene was significantly improved.	[90]
			Bamboo fiber/polypropylene composite	Impregnation of the bamboo fibers with CaCO3 increased the fiber density, filling the morphological voids and creases, and improving the interfacial compatibility of the composite. The modified composites exhibited improved tensile strength, modulus of elasticity, and elongation at break.	[91,92]
	Silver chloride (AgCl)	Like AgNPs, these inorganic particles are capable of great antimicrobial activity, by acting as leaching antibiotics.	Wool/polyester composite	Composites were prepared by pad-dry-cure method which generated a functional silica matrix that induced the in situ synthesis of AgCl NPs. Ag-modified surfaces were successful against bacteria and fungi at concentrations superior to 0.5 mM AgNO3.	[93]
	Silver zeolites (SZs)	Zeolites are crystalline aluminosilicates that exhibit adsorption properties and ion-exchange capabilities. By encapsulating silver, they allow an optimized release of the NPs and ensure antimicrobial activity without adverse effects.	Cotton/chitosan composites	Cotton fabrics were modified with a film of chitosan or by a conventional pad–dry–cure process in which chitosan–zeolite composites were immobilized onto the fabric surface. The altered fabrics displayed improved antibacterial properties against Escherichia coli, Staphylococcus aureus, Candida albicans and Trichophyton rubrum. Evidences of thermoregulating properties were also found.	[94]
	Zeolitic imidazolate framework-8 (ZIF-8)	Inorganic particles endowed with a large surface area, and strong hydrophobicity.	Cotton/ZIF-8-polydimethylsiloxane fabric	The modified cotton fabric showed superhydrophobic properties and excellent antibacterial action against Escherichia coli and Staphylococcus aureus. Fabrics retained their excellent antibacterial property and superhydrophobicity after 300 cycles of abrasion and 5 cycles of washing.	[95]
	Aluminum hydroxide (Al(OH)3)	Hydrophilic, inorganic particles, non-toxic and odorless that exhibit good dispersion and can generate very easily hydrogen bonds with cellulosic fibers.	Kenaf fibers/polyester composite	Kenaf fiber reinforced composites were produced via vacuum-assisted resin transfer molding process and impregnated with Al(OH)3 NPs. The NPs addition increased the composite modulus of elasticity, modulus of rupture, tensile modulus and tensile strength, while the water thickness of swelling was reduced.	[96]
	Titanium dioxide doped with iron and nitrogen atoms (TiO2)	Inorganic particles with photocatalytic activity, self-cleaning properties and base substrate-dependent superhydrophilicity/superhydrophobicity.	Cotton/reduced graphene oxide composite	Cotton fabrics treated with reduced graphene oxide were successfully decorated with two types of TiO2 NPs doped with 1% iron and nitrogen atoms and synthesized in different hydrothermal conditions. NPs-modified fabrics were found harmless for human skin cells and capable of inhibiting the growth of Staphylococcus aureus and Enterococcus faecalis.	[97]
	Iron oxide (magnetite, Fe3O4)	Inorganic particles with photocatalytic activity and antimicrobial properties.	Cotton/polyester composite	Sonosynthesis and sonofabrication of Fe3O4 NPs was accomplished on cotton/polyester composite fabrics, with appropriate saturation magnetization. Composites demonstrated a 95% antibacterial efficiency against Staphylococcus aureus and a 99% antifungal effect against Candida albicans, along with enhanced mechanical properties.	[98]
	Cerium oxide (CeO2)	Inorganic particles with outstanding catalytic, electronic and magnetic properties. They are also highly efficient in absorbing UV radiation and protecting against corrosion.	Chitosan/linen (from flax family) composite	Linen fabric was modified with chitosan followed by in situ synthesis of CeO2 NPs. The modified fabric displayed effective antibacterial activity against Staphylococcus aureus and Escherichia coli bacteria. They were also endowed with properties like wrinkle resistance, UV-protection and flame retardancy, which were maintained after 5 washing cycles.	[99]
	Platinum (Pt)	Inorganic particles very stable and effective for antimicrobial applications. PtNPs have high activity and selectivity for catalytic reaction, good recyclability, and can enhance the cleansing function of the skin surface.	Silk-based fabrics	PtNPs were synthesized in situ on silk-based fabrics through heat treatment. Color strength increased with the concentration of the Pt ions. The modified fabrics exhibited good washing fastness and excellent rubbing color fastness. They also demonstrated significant catalytic functions and a significant antibacterial effect against Escherichia coli.	[100]
	Bamboo	Biocompatible, organic particles endowed with superior mechanical properties, namely ultimate tensile, toughness and Young’s modulus.	Woven-nonwoven kenaf fiber/unsaturated polyester composite	Due to the high surface area of the bamboo NPs, incorporation allowed for a strong bond between kenaf and polyester to be generated with improved wettability and excellent mechanical and thermal properties.	[101]
Enzymes	Laccase	Laccases are multi-copper glycoproteins that catalyze the mono-electronic oxidation of phenols and aromatic or aliphatic amines to reactive radicals and reduce molecular oxygen to water in a redox reaction.	Lignocellulosic jute/polypropylene composite	Lignocellulosic jute fabrics were treated with laccase and then used as reinforcement materials to prepare polypropylene-based composites. Laccase-treated jute/polypropylene composites exhibited high breaking strength, storage modulus, and melting temperature. Data suggests a good interfacial adhesion between the jute and the polypropylene.	[102]
				Grafting of dodecyl gallate onto jute fibers via laccase was investigated as a reinforcement of polypropylene-based composites. The composite hydrophobicity and breaking strength increased after grafting, and the composite fracture section became neat and regular.	[103]
				Alkyl gallates with different aliphatic chain lengths, such as propyl gallate, octal gallate and dodecyl gallate, were enzymatically grafted onto jute by laccase and then incorporated onto polypropylene matrices. After modification, the tensile and dynamic mechanical properties of the composites improved, while water absorption and swelling decreased.	[104]
Peptides	RGD-peptide	Arginyl-glycyl-aspartic acid (RGD) is the most common and well documented peptide motif responsible for cell recruitment and attachment to the extracellular matrix.	Milkweed/polyethylene/polypropylene composite	A composite of milkweed, polyethylene and polypropylene was made by carding and further treated with atmospheric pressure plasma to functionalize the surface with carboxylic acid groups for RGD-peptide binding. Plasma treatment accelerated the degradation of milkweed. The composite was seen to promote MC3T3 osteoblast-like cells recruitment.	[11]
Antimicrobial Peptides (AMPs)	Cecropin-B/[Ala5]-Tritrp7	Cecropin-B is an antibacterial peptide found in the hemolymph of the pupae of H. cecropia. It is composed of 35–39 a.a. in length and assumes an amphipathic α-helice structure that facilitates microbial penetration. [Ala5]-Tritrp7 is a synthetic peptide that results from the replacement of the first Pro at position 5 in tritrpticin by Ala (Tritrp7). The substitution of Pro-5 to Ala in Tritrp7 leads to the formation of amphipathic α-helices, which stimulates an effective cell leaching and thus bacteria death.	Wool-based materials	AMPs immobilization was accomplished via exhaustion method. The functionalized AMPs reduced significantly the bacterial growth, with Cecropin-B resulting in 71.67% reduction against Staphylococcus aureus and 85.95% against Klebsiella pneumoniae, while [Ala5]-Tritrp7 promoted a 66.74% and 88.65% reduction, respectively.	[12]
Plant Extracts	Baicalin (5,6,7-trihydroxyflavone-7-O-glucuronid)	Major component of the root of Scutellaria baicalensis Georgi. It possesses multiple bioactivities including antibacterial, antioxidant, anticancer, anti-inflammatory, and antiviral activities.	Silk-based fabrics	Baicalin bonded with the silk fabric via electrostatic interactions between the ionized carboxyl groups in the extract and the positively charged amino groups in the fabric. The treated fabric exhibited excellent antioxidant activity, high antibacterial performance against Escherichia coli and Staphylococcus aureus, and very good UV-protection.	[105]
	Propolis	Propolis is a gum gathered by honeybees from various plants. It is not toxic to humans or mammals. Propolis has been reported as anticancer, antioxidant, anti-inflammatory, antibacterial, antifungal and antiviral.	Cotton-based fabrics	Cotton fabrics were treated with propolis at different concentrations using the pad–dry–cure technique. Surfaces were found highly antibacterial, water repellent and capable of protecting against UV-radiation.	[106]
	Psidium guajava Linn. leaf extract	Psidium guajava Linn., from the Myrtacae family, also known as guava, is characterized by its exceptional antidiabetic, anticough, antioxidant, antibacterial and antispasmotic properties.	Cotton-based fabrics	Microcapsules containing Psidium guajava Linn. leaf extract were prepared by in situ polymerization using urea and formaldehyde for encapsulation and applied by direct printing onto cotton fabrics. The extract modified fabrics showed antibacterial activity against Staphylococcus aureus but were not effective against Escherichia coli bacteria.	[107]
	Aloe Vera gel	Aloe Vera is a highly abundant, natural plant that has antimicrobial activity against various pathogens. External application of Aloe Vera gel penetrates the skin directly and produces a soothing, pain-relieving and anti-inflammatory effect on arthritic joints and tendonitis.	Cotton-based fabrics	Bleached cotton fabrics were immersed in the extracted solution for specific periods of time, padded, dried and cured. Modified fabrics became very effective against pathogens, namely Bacillus subtillis, Pseudomonas aeruginosa, Bacillus pumalis and Escherichia coli. The antimicrobial finishing did not affect the physical properties of the fabric.	[108]
	Jatropha curcas leaf extract	Jatropha curca is a plant indigenous of India composed of phenolic, terpenoids, flavonoids, alkaloids, glycosides, steroids, tannin, etc., which endows the extract with antibacterial properties (bactericide and bacteriostatic). It is also known for its anti-cancerous properties.	Cotton-based fabrics	An ecofriendly natural antibacterial finish was applied to cotton-based fabrics via dip coating. Modified fabrics were characterized as bactericides and bacteriostatic against Staphylococcus aureus bacteria.	[109]
	Curcumin	Bright yellow compound produced by Curcuma longa plants. It is endowed with many functions, including anti-inflammatory, anticancer, antiviral, antiarthritic and antioxidant properties.	Cotton and non-woven fabrics/diphenylalanine (FF) peptide nanotubes	Cotton and non-woven fabrics were decorated via sonochemical process with FF loaded with curcumin. A sustainable, controlled release of curcumin was attained using this functionalization process, which was modulated by the sonication time, conferring potential antimicrobial and anti-inflammatory properties to the fabric.	[110]
			Sisal fibers/poly(methyl methacrylate) composites	Composite microspheres loaded with curcumin and made of poly(methyl methacrylate) stabilized with cellulose nanocrystals prepared from sisal fibers were produced. Results showed curcumin loaded composites to display long-term photostability and good encapsulating ability.	[111]
	Ocimum sanctum leaf extract	Ocimum sanctum plant is found in India and has antibacterial, antioxidant, antibiotic, antiatherogenic, immunomodulatory, anti-inflammatory, analgesic, antiulcer, chemo-preventive and antipyretic properties. Besides it is very abundant and easily accessible, economically feasible, and possesses minimal side effects.	Cotton/polyester composite	The composite fabric was treated with the herbal extract at different concentrations, using glutaraldehyde as cross-linking agent and sodium hypophosphite as catalyst by the exhaustion method. Modified fabrics inhibited Gram-positive bacteria growth in more than 92%. Although, the treated fabrics showed enhanced crease recovery property, there was a marginal reduction in tensile properties.	[112]
Essential Oils (EOs)	Rosemary, lavender, clove and cinnamon	Bioactive oils endowed with antimicrobial properties.	Cotton/monochlorotriazinylβ-cyclodextin fabric	Cotton fabrics were modified with monochlorotriazinyl β-cyclodextrin, as an eco-friendly encapsulating/hosting compound, to create core-shaped hydrophobic cavities for individual loading of EOs. The modified fabrics revealed improved antibacterial activity and durability. The antibacterial activity of the treated knitted cotton fabrics was superior to that of woven fabrics.	[113]
	Citronella	Biopesticide with a non-toxic mode of action that works as a mosquito repellent due to its eco-friendly and biodegradable nature.	Wool/gelatin and gum Arabic biopolymers	Microencapsulation of citronella oil was done by complex coacervation onto wool fabrics. The multi-core structure of the microcapsules allowed the oil diffusion by a Fickian mechanism in the first release stage and by non-Fickian kinetics on the second stage. The textile structure influenced the release model due to the interaction between the fabric and water.	[114]
	Oregano	Oregano oil comes from the leaves and shoots of the oregano plant and is botanically known as Origanum vulgare. It is a natural antibiotic and antimicrobial agent with antioxidant, anti-inflammatory and anti-cancerous properties. It may also be involved in lowering cholesterol.	Sugarcane bagasse/starch foam composite	Sugarcane bagasse fiber-reinforced starch foam composites were prepared with different oregano essential oil contents. The addition of oregano oil increased the composite antimicrobial properties, particularly against Gram-positive bacteria, but decreases its water absorption capacity and hygroscopicity. The biodegradation rate and flexural strength of the composite slightly decreased with increasing oil content.	[115]
			Coconut fibers/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composite	Green composites were obtained by twin-screw extrusion followed by compression molding. Coconut fibers were impregnated with oregano essential oil by spray coating and then incorporated into PHBV. The green composites displayed enhanced physical performance and superior bacteriostatic effect against Staphylococcus aureus bacteria.	[116]
	Cinnamon	Cinnamon oil is derived from the bark or leaves of several trees, including the Cinnamomum verum tree and the Cinnamomum cassia tree. Possesses antibacterial, antifungal, antidiabetic and antioxidant properties.	Durian skin fiber/polylactic acid composite	Transparent composites were produced via solvent casting and further modified by the incorporation of cinnamon oil. Scanning calorimetry analysis showed that the oil-modified composites were less crystalline than the controls, suggesting their structure was less rigid and flexible. The oils decreased the water vapor permeability and improved the composite antimicrobial activity against Gram-positive and Gram-negative bacteria.	[15]