Chitosan is a marine-based polysaccharide deacetylated chitin that is characterized by versatility, biocompatibility, biodegradability, and controllable physicochemical characteristics. Sulfation, phosphorylation, carboxymethylation, quaternization, and guanidinylation are structural changes that increase the solubility, bioadhesion, antimicrobial activity, and biological performance of physiological conditions. Depolymerized derivatives, such as chitosan oligomers, have enhanced permeability, antioxidant, and immunomodulatory properties and physically engineered forms, such as nanoparticles, hydrogels, and electrospun fibers provide superior platforms to targeted drug delivery, tissue scaffolds, and controlled drug delivery. Together, these multifunctional derivatives have demonstrated potential in a variety of biomedical applications such as wound healing, antimicrobial therapy, gene delivery and regenerative medicine and in food preservation, agriculture and environmental remediation. The recent advances of selective O-/N-substitution and green chemistry-based synthesis have enhanced reproducibility, scalability and regulatory compliance, but it is still difficult to achieve standardized production, high quality, and whole biocompatibility inspection. This review presents a systematic synthesis of the synthesis pathways, structural-functional interaction, and the general application scope of the chitosan derivatives, whereas the essential translational issues and emerging opportunities are outlined. It combines the approach of chemistry, biology, and engineering to emphasize the future potential of chitosan derivatives as the next generation biomaterials in clinical, pharmaceutical, agricultural, and environmental practices.
Divya Vijayakumar (Sat,) studied this question.