Chitosan-based Drug Delivery Systems

The most important characteristics of chitosans, which make them useful as delivery vectors for drugs and therapeutic proteins, are their excellent mucoadhesive and absorption enhancing properties [1-3]. The mucoadhesion is due to the electrostatic interaction between the positive charge on the chitosan polymer and the negatively charged sialic acid residues on the mucosal surface [4]. Because of the bioadhesive characteristics of chitosan, the rate of clearance of drugs from the nasal cavity and thereby the bioavailability increases [5]. In addition, chitosan is biocompatible with living tissues and it possesses antimicrobial properties. It absorbs toxic metals such as cadmium, lead, mercury and so on from the body. Chitosan is biodegradable and it degrades under the action of human enzymes, especially lysozymes, into harmless products that are completely absorbed by the human body [6]. Chitosan also has good adhesion, coagulation ability and immuno-stimulating activity. Other interesting biopharmaceutical characteristics of chitosan are its ability to control the release of active agents, the availability of primary amino groups for modification, and the use of aqueous acidic solvents instead of the use of hazardous organic solvents while fabricating particles. Chitosan in clinical applications can be sterilised by methods such as ionising radiation, heat, steam and chemical methods.