Chitosan and its Derivatives in Biomedical and Pharmaceutical Sciences: From Fundamentals to Advanced Applications

Chitosan, a naturally derived polysaccharide obtained by the deacetylation of chitin, has emerged as a versatile biomaterial in biomedical and pharmaceutical sciences. Its unique combination of biocompatibility, biodegradability, mucoadhesiveness, and antimicrobial activity has led to widespread exploration in drug delivery, wound healing, tissue engineering, and anticancer therapy. Structural features such as reactive amino and hydroxyl groups allow for a range of chemical modifications, yielding derivatives with improved solubility, stability, and targeted functionality. This review presents a comprehensive synthesis of chitosan’s physicochemical properties, including degree of deacetylation, molecular weight, and pH-dependent solubility, and their implications in biomedical formulations. Emphasis is placed on nanoparticles, hydrogels, nanofibers, and scaffolds, along with their use in oral, ocular, nasal, and injectable drug delivery systems. Chitosan’s role in tissue regeneration is examined through applications in bone, skin, nerve, and soft tissue engineering. Moreover, it’s antimicrobial and anticancer mechanisms—including membrane disruption, gene silencing, and targeted cytotoxicity—are discussed. The review also covers biocompatibility, enzymatic degradation, and regulatory considerations, highlighting approved medical devices and commercial products. While limitations such as poor solubility at neutral pH and batch variability remain, recent innovations in chemical modification, stimuli-responsive systems, and green production methods offer promising solutions. Keywords: Chitosan, hydrogel, nanofibers, biocompatibility, stimuli-responsive systems.