Chitosan in Medicine: From Molecular Structure and Biochemical Interactions to Biomedical and Therapeutic Applications

Abstract

Background and Objective: Chitosan is a bioactive polysaccharide mainly derived from the deacetylation of chitin. Due to its biocompatibility, biodegradability, mucoadhesive properties, and chemical modifiability, it has gained an important position in biomedical applications. The biological properties of chitosan are closely associated with its molecular structure, particularly the presence of amino and hydroxyl groups, degree of deacetylation, and molecular weight. This review aimed to examine the relationship between the structure and biochemical properties of chitosan, its mechanisms of biological action, and its medical applications. Method: This study was conducted as a narrative review using a structured search of the scientific literature. Studies related to the structural and biochemical properties of chitosan, its biological mechanisms of action, and medical applications were reviewed. Information on various chitosan-based systems, including films, sponges, nanoparticles, hydrogels, tissue-engineering scaffolds, and injectable responsive systems, was analyzed. Result: Protonation of the amino groups of chitosan under acidic conditions generates a positive charge along the polymer chain, enabling electrostatic interactions with cell membranes, proteins, glycosaminoglycans, and nucleic acids. These interactions contribute to its antimicrobial, hemostatic, and mucoadhesive activities, as well as the regulation of cellular responses and drug and gene delivery. In recent years, the applications of chitosan have expanded from simple forms, such as films and sponges, to more advanced systems, including nanoparticles, smart hydrogels, tissue-engineering scaffolds, and injectable responsive systems. However, low solubility at physiological pH, variability in molecular weight and degree of deacetylation, and standardization challenges remain among its major limitations. In addition, the gap between preclinical findings and clinical applications remains a significant challenge. Conclusion: The ability to engineer the structure of chitosan and translate its molecular properties into controllable biological functions has made this polymer a promising material for the development of novel biomedical systems. Despite its considerable potential, addressing challenges related to standardization, physicochemical properties, and the translation of preclinical findings into clinical applications is essential for its broader utilization.