Chemically modified chitin, chitosan, and chitinous polymers as biomaterials

Chitin and chitosan are polysaccharides usually obtained from animal or microbial sources. Chitosan is the most common chitin derivative that results from the deacetylation of chitin. When extracted from microbial sources, those biopolymers are usually obtained in the form of complexes, in which chitin/chitosan are covalently linked to glucans chains. The biocompatibility, biodegradability, and biological activity of these polysaccharides make them interesting biomaterials for various application areas. However, the insolubility of chitin in aqueous solutions makes its use difficult in a wider range of applications. Hence, the chemical modification of this polysaccharide, and also that of chitosan, has emerged as an alternative to overcome this problem. In this chapter, the most common chemical modification reactions performed to chitin/chitosan and chitinous polysaccharides are reviewed, as well as their applicability as biomaterials in several areas, such as biomedicine, food, agriculture, or wastewater treatment.