Application of chitosan and chitosan derivatives as biomaterials

Chitosan derivatives with targeting ligand (A), thiol group (B) or amino acid (C). A (a): galactosylated chitosan, (b): mannosylated chitosan, and (c): lactosylated chitosan. B (a): thioglycolic acid conjugated chitosan, (b): cystamine modified trimethylated chitosan. C: amino acid modified chitosan. Chitosan is a linear polysaccharide composed of randomly distributed β-(1-4)-linked d-glucosamine and N-acetyl-d-glucosamine. It is one of the major cationic polymers and the second most abundant polysaccharides in nature. It is extensively used to the biomedical and the industrial fields. Specially, chitosan has been studied much in the field of gene therapy during the last decade for its biocompatibility and non-cytotoxicity. However, it has several problems such as solubility, low transfection efficiency, and low specialty on targeted disease. To solve these problems, various strategies have been reported to enhance them. This review briefly introduces various strategies of chitosan carrier.