Chitosan as mucoadhesive polymer in drug delivery

Abstract Amongst various drug delivery approaches, mucoadhesive approaches for drug delivery have achieved great interest as these are capable of prolonging the residence period of the dosage forms at the absorption sites or at the site of action; and thus mucoadhesive drug delivery systems facilitate sustained release of loaded drug candidates with significant minimization of drug degradations. For the development of different mucoadhesive drug delivery systems, various natural, semisynthetic, and synthetic polymers have been exploited. Amongst these, natural polymers like chitosan have been extensively exploited for the design of different kinds of mucoadhesive drug deliveries with effective therapeutics. Chitosan is a naturally occurring biopolysaccharide, which has been used in mucoadhesive systems due to its high mucoadhesive characteristics. However, the inadequate aqueous solubility of chitosan at basic as well as neutral pHs are the major limitations of its use as a biopolymer in the design of mucoadhesive systems. To curtail this drawback, various chemical modifications of chitosan have been investigated and successfully employed. In this chapter, we describe the mucoadhesive characteristics of chitosan and its chemically modified derivatives like thiolated chitosan, trimethyl chitosan, hydrophobically modified chitosans, etc., for their uses in the design of mucoadhesive drug delivery.