Chitosan and its Derivatives as Chemical Drug Delivery Carriers

Background: Chitosan (CS) is a nontoxic and biocompatible natural polysaccharide with great development potential in the delivery of chemical drugs. However, further applications of CS are limited due to its inherent insolubility in neutral solution. Objective: The chemical modification of CS is of great significance for drug carriers, and the modification would not alter its fundamental skeleton but affords new or improved properties for drug delivery systems. Method: This review is designed to afford an overview of CS and CS derivatives used as drug delivery carriers, with a special stress on chemical modifications of CS to attain specific biomedical purpose. Results: The chemical modification of CS is generally carried out on the primary amine group or on the hydroxyl group. A variety of modifications such as quaternization, acylation, sulfonation, phosphorylation, thiolation, hydrophobization, hydrophilization afford extensive derivatives with improved properties for specific applications in pharmaceutical, biomedical and biotechnological fields. Conclusion: Various drug delivery systems and delivery of different categories of drugs based on CS and CS derivatives have also been illustrated.