Hydrophilic chitosan: modification pathways and biomedical applications

Chitosan, a natural and abundant polysaccharide, offers several advantageous properties, such as excellent biocompatibility, biodegradability, and antimicrobial activity, making it a highly versatile material. However, its extensive application is hindered by its insolubility in water and most organic solvents, due to numerous intramolecular/intermolecular hydrogen bonds. To overcome this limitation and optimize its benefits, chitosan is often chemically modified to enhance its utility in various industries. Biomedical materials, environmental management, biological papermaking, food preservation, and the daily chemical industry are a few examples. Modified chitosan retains the inherent properties of chitosan and acquires new physicochemical characteristics as a result of introduced functional groups. Hydrophilic modifications typically include carboxylation, phosphorylation, and quaternary ammonium modification reactions. The specific properties and applications of chitosan derivatives depend on the grafted groups. This review summarizes the reaction conditions, properties, and applications of hydrophilic chitosan derivatives in drug delivery and food preservation, serving as a reference for the development and use of chitosan-based biomaterials.