Medicinal and Chemosensing Applications of Chitin-Based Materials: A Comprehensive Review.

Chitin, a naturally occurring biopolymer composed of β-(1-4)-linked N-acetyl-D-glucosamine units, has attracted significant attention for its versatile applications in medicine, environmental monitoring, and chemical sensing. Its β-(1-4) glycosidic bonds confer structural rigidity and chemical reactivity, enabling diverse biological and functional activities. Chitin derivatives, obtained through chemical modifications such as deacetylation, carboxymethylation, or grafting, expand the polymer's functional scope, enhancing solubility, bioactivity, and compatibility for specific applications. Chitin-based materials, including films, nanoparticles, and composites, exploit these intrinsic properties for antibacterial, antifungal, anti-inflammatory, anticancer, and antioxidant activities. Furthermore, these materials have been engineered into sensitive and selective colorimetric and fluorimetric chemosensors for detecting heavy metals, anions, and other analytes in biological, environmental, and agricultural contexts. This review provides a comprehensive overview of recent advances in chitin derivatives and chitin-based materials, highlighting how the polymer structure and chemical modifications underpin their diverse biological and sensing applications.