Current Trends in Chitosan Functionalization Methods and Their Applications

Growing concerns about the harmful impact of synthetic polymers on the environment and living organisms have shifted the attention towards biopolymers which are environment‐friendly and biocompatible. Biopolymers represent attractive sustainable and biodegradable alternatives for replacing commercial synthetic polymers. Chitosan is one of the most prevalent biopolymers available on Earth. Chitosan is an alkaline cationic polymer, the deacetylated form of chitin. Chitosan possesses excellent physicochemical properties such as biocompatibility, biodegradability, nontoxic, nonallergenic, and biologically active molecules. During recent years, there has been a surge in the demand for chitosan in various fields, however, due to poor water solubility and mechanical properties, chitosan applications are limited to some extent. Strong inter and intramolecular hydrogen bonds in the chitosan matrix make it highly crystalline, reducing its water solubility. Chemical modification of the chitosan matrix by various technologies is reported to improve its solubility and other physicochemical characteristics, expanding the application areas. Details on various chemical reactions involved in chemical modification and other available technologies have been focused in this paper. The role of chitin deacetylase enzyme in chitosan modification has been discussed. This review aims to provide insight into recent developments in chitosan functionalization, and the development of chitosan derivatives for various applications.