THIOLATED CHITOSANS: A NOVEL MUCOADHESIVE POLYMERS: A REVIEW

Abstract

Chitosan is a natural polycationic copolymer consisting of glucosamine & N-acetylglucosamine units. The polymer has valuable properties as a biomaterial because it is considered to be biocompatible, biodegradable and non-toxic. The purpose of this review article is to provide detailed information about thiolated chitosan which are gaining popularity because of their high mucoadhsiveness and extended drug release properties. The derivatization of the primary amino groups of chitosan with coupling reagents bearing thiol functions leads to the formation of thiolated chitosans or designated as thiomers which posses high mucoadhesion which display thiol bearing side chains. Based on thiol/disulfide exchange reactions and/or a simple oxidation process disulfide bonds are formed between such polymers and cysteine-rich subdomains of mucus glycoprotein’s building up the mucus gel layer. Therefore thiomers mimic the natural mechanism of secreted mucus glycoprotein, which are also covalently anchored in the mucus layer by the formation of disulfide bond which is same as bridging structure commonly encountered in biological systems.