Chitin and chitosan has been used in a wide range of applications in different industrial and medicinal fields such as food packaging, antimicrobial wound healing, water treatment, tissue engineering, drug release, and bleeding control, which are shown schematically in Fig. 1.3.

FIGURE 1.3 Important applications of chitin/chitosan and their blends and composites.

Application of chitin and chitosan composites in food packing

Transparent and colorless citric acid-incorporated fish GL/CS composite films were prepared by the solution casting method, which slowed down the swelling rate and swelling values of the films and maintained their integrity, resulting in flexible hydrated films with a reduction in the growth of Escherichia coli, indicating the combined effect of citric acid and CS as natural antimicrobial compounds. The composite films showed good ultraviolet barrier properties and hydrophobic surfaces, essential properties for food packaging applications, highlighting the potential use of these films as active packaging. Three different types of sulfur NPs were prepared by the solution casting method and used to prepare functional CS/sulfur NPs composite films. Sulfur NPs capped with CS composite film exhibited the strongest antimicrobial activity against food-borne pathogenic E. coli and Listeria monocytogenes bacteria with enhanced hydrophobicity, mechanical strength, and water vapor barrier property. The CS/sulfur NPs composite films. Sulfur NPs capped with CS composite film exhibited the strongest antimicrobial activity against food-borne pathogenic E. coli and Listeria monocytogenes bacteria with enhanced hydrophobicity, mechanical strength, and water vapor barrier property. The CS/sulfur NPs composite films can be used as antimicrobial food packaging films or wound dressings in biomedical applications. Microcrystalline cellulose was surface-modified with urea under microwave irradiation and was then added as filler to a CS matrix to prepare a fully natural polymer composite material through casting the mixture slurry followed by coagulation; the results showed improved mechanical properties, reduced water vapor permeability, and satisfactory visible light transparency, which indicate promising potential as a packaging material.

Application of chitin and chitosan composites in antimicrobial activities

A microfluidic approach for single-step and in situ synthesis of AgNPs-loaded CS microparticles showed enhanced antibacterial ability because of the properties of AgNPs and CS. The synthesized composite microparticles can be used in several future potential applications, such as bactericidal agents for water disinfection, antipathogens, and surface plasma resonance enhancers. The self-assembly approach was used for the synthesis of an AgNPs organized CS nanopolymer which provided a monolayer film with good antimicrobial activity against pathogens, that when applied to a liquid medium or surfaces of edible food products can prevent the growth of microbes.

Application of chitin and chitosan composites in woundhealing activities

Hydrophilic and macroporous composite hydroxybutyl CS sponge was developed via the incorporation of CS into hydroxybutyl CS through the vacuum freeze-drying method. The composite sponge showed high porosity, great water absorption, good softness, and low blood-clotting index without cytotoxicity. The composite sponge had a better ability to promote wound healing and helped faster formation of skin glands and reepithelialization, which encourages the use of this composite sponge for wound dressings.

A CS-COL/organomontmorillonite loaded with Callicarpa nudiflora composite membrane was prepared by a solution mixing method as a wound dressing, combining the excellent properties of each material, such as the biocompatibility and hemostasis effect of CS, the low inflammation of COL, and the antibacterial activity of the leaves of C. nudiflora.

Application of chitin and chitosan composites in water treatment process

Heavy metals removal

Uniform CS nanofiber mats have been prepared by the incorporation of polyacrylic acid sodium into CS through the electrospinning method; they showed significantly improved solvent resistance, mechanical strength, and chelating abilities. The CS/polyacrylic acid sodium composite nanofiber mats can effectively adsorb Cr(VI) ions from dilute aqueous solution, and the higher adsorption performance has been attributed to abundant CS chelating sites, the large surface area of thee nanofiber mats, and the higher stability in acidic water solution. The adsorption abilities of these cross-linked CS/polyacrylic acid sodium nanofiber mats are dependent on the CS contents as well as the N-atom basicity of the CS chain.

Activated carbon from oil palm empty fruit bunch has been produced and used as a filler in PEG diglycidyl ether cross-linked CS/activated carbon composite film preparation. The film showed high adsorption potential for the adsorption of Cd21 due to a good adhesion of the matrix and filler interface.

A cost-effective magnetic CS composite adsorbent was prepared with magnetic macroparticles and highly porous activated carbon carrier using the sol
gel method for the removal of Cu(II). The magnetic CS composite adsorbent is a promising adsorbent for removing Cu(II) due to its good reusability and convenient magnetic separability.
The CS-coated attapulgite was prepared by a self-assembly method and applied for U(VI) removal from aqueous solutions. The CS-coated attapulgite composite is a potential and suitable candidate for the preconcentration and separation of U(VI) from contaminated natural wastewater and aquifers due to its wide availability, simple synthesis procedure, efficient sorption ability, and good bioacceptability.

Dye removal

Coir pith activated carbon (CPAC), CS, and sodium dodecyl sulfate composites were prepared and used as an effective low-cost adsorbent for the removal of malachite green from wastewater. An efficient photocatalyst, poly(methacrylic acid) cross-linked CS@zinc oxide/CdS quantum dots, was synthesized under microwave irradiation by crosslinking of poly(methacrylic acid) with CS followed by incorporation of ZnO and CdS quantum dots on the cross-linked polymer surface. It showed excellent photocatalytic efficiency toward the degradation of toxic cationic dyes (malachite green and safranin) as well as toxic pollutant 2,4-dichloro phenol in the presence of sunlight.

Arsenic and mercury removal

A novel biomimetic SiO2@CS composite prepared by a hydrothermal method exhibited a high adsorption performance toward heavy metal ions As(V) and Hg(II) in solution due to the availability of many functional groups including amino and hydroxyl groups for adsorbing heavy metal ions. A novel polymer-based adsorbent of hyperbranched polyethylenimine functionalized CMC semiinterpenetrating network composite was fabricated through a facile one-step cross-linking reaction, which exhibited excellent selectivity for removing Hg(II) ions by the interaction between Hg(II) ions and nitrogen functional groups, such as amine and imine groups.

Phosphate, nitrate, and humic acid removal

PEG/CS and PVA/CS were effectively utilized for the removal of phosphate and nitrate due to good affinity of phosphate and nitrate ions toward PEG/CS and PVA/CS composites. A granular CSbased sorbent was fabricated from carbon waste for enhancing removal of nitrate and phosphate.

Fluoride removal

A cerium immobilized CS composite adsorbent was prepared for the removal of fluoride from water. This composite has great potential to remove fluoride by the mechanism of the electrostatic attraction among -NO3+ and Ce3+/4+ with F- ions, the ligand exchange between NO3- and F-, and the formation of the CTS-Ce-F complexation.

Nanofiltration and antibacterial process

The nontoxic, biocompatible PVDF/CS composite was synthesized by an nonsolvent induced phase inversion process to make fouling-resistant nanofiltration membranes which exhibited excellent mechanical and thermal stability and flux recovery ratio.

Tissue engineering

CS and Sr21-modified montmorillonite composite was fabricated into porous three-dimensional scaffolds via a freeze-drying method, and it displayed desirable physicochemical and biological characteristics as a bone tissue engineering construct. This construct may be an ideal biomimetic template for the repair of defective bone with osteoblasts.
Zirconium-based bioceramics nanopowder-CS scaffolds were prepared by a freeze-drying method and utilized for bone tissue engineering application due to their great mechanical strength, cell proliferation nature, cell spreading on the scaffolds, and sufficient water absorption capacities and porosities.

Application of chitin and chitosan composites in drug release

A CS/PVA-based hydrogel composite was prepared using tetraethyl orthosilicate as a cross-linking agent via wet conventional synthesis. The CS/PVA-based hydrogel composite exhibited good properties as a drug delivery system, because its release profile of gallic acid showed high antioxidant activities. Ultrastrong composite film of CS and silicacoated graphene oxide sheets were prepared by a simple solution casting method to utilize more potential applications in biomedical fields. Fe3O4@C NPs were incorporated into carboxymethyl cellulose matrix and coated with a CS layer via a self-assembly technique to form core
- shell polyelectrolyte complexes, which showed a high swelling ratio and prevented a sudden release in phosphate buffer.

Application of chitin and chitosan composites in bleeding control

Incorporation of nanobioglass with silica, calcium and phosphate ions into CS hydrogel by sol-gel method, which is acted simultaneously on mechanisms involved in hemostasis and bring about effective bleeding control might be due to the synergistic effect of CS and nanobioglass when it contact with blood. This composite hydrogel might have good potential in achieving effective bleeding control during major surgeries and traumatic conditions.