Characteristics and application of chitosan in pharmaceutical/biomedical preparations

Chitosans are binary linear heteropolysaccharides derived from chitin by its partial deacetylation. Due to unique cationic nature these biopolymers have enormous potential in pharmacy and biomedicine. This potential is improved by their chemical versatility (molecular mass and degree of deacetylation) and possibility of chemical derivatisation. Numerous biological activities of chitosans such as mucoadhesivity, hemostatic, hypocholesterolemic and antimicrobial activity are based on their specific polycationic nature. Gel-forming, cross-linking and polyelectrolyte complex forming ability make chitosans suitable for design of colloidal drug delivery systems, such as dendrimers, liposomes, micelles, micro- and nanoparticles. Chitosans as well as their derivates are used in commercially available wound dressings due to their hemostatic activity and ability to stimulate cell proliferation, tissue regeneration process and mild local analgesic effect. The use of chitosans as dietary supplements has been approved in many countries since their effect on maintenance of normal blood LDL cholesterol concentrations has been confirmed. Chitosan derivatives, such as N-carboxymethyl chitosan are commonly used in cosmetics, due to their gel and film forming ability, pleasant, hydrating, softening, and protecting effect on skin. There is a special interest for use of chitosans in tissue engineering due to their ability to form biocompatible porous tridimensional gel networks, whose porosity and in vivo degradation can be controlled. Lack of registered chitosan based products is a consequence of its unsolved regulatory status. Namely, its chemical versatility may affect biodistribution, biodegradation and toxicological profiles, thus making regulatory approval of chitosans as GRAS materials quite difficult.