Chitosan is a polysaccharide with structural characteristics similar to glycosamines, obtained by alkaline deacetylation of chitin, and derived from the exoskeleton of crustaceans. Studies on chitin and chitosan have been performed because these polymers show excellent biological properties such as biodegradation in the human body, and immunological, antibacterial, and wound-healing activity. Moreover, chitosan possesses excellent properties when included into drug delivery systems and once used for tissue engineering applications.

Most of the commercial use of chitin and chitosan has been confined to the unmodified forms. For an advance in its utilization, chemical modification to introduce a variety of functional groups to chitosan has been established, aiming the improvement of its properties.

Chemical modification can be used to attach various functional groups and to control hydrophobic, cationic, and anionic properties. Moreover, chemical modification of chitosan provides derivatives that are soluble at neutral and basic pH. Still, most of the new derivatives are in the beginning of their development, and more fundamental studies on chemical modification are required to attest the safety, security, and efficacy of their use.

We are particularly interested in articles describing the synthesis, characterization, and biological applications of chitosan derivatives. Special importance is expected on the role of individual functional groups in applications of modified chitosan. Potential topics include, but not limited to:

• Graft copolymerization for chemical modification of chitosan
• Chitosan derivatives developed to overcome chitosan solubility drawbacks
• Chitosan derivatives developed to overcome chitosan biocompatibility drawbacks
• Enzymatic Modifications of chitin and chitosan
• Chitosan-based systems with temperature-responsive behavior
• Dietary fiber and alteration of bile composition of chitosan and derivatives
• Recent advances in drug delivery systems based on chitosan derivatives
• Recent advances in tissue engineering systems based on chitosan derivatives
• Chitosan functionalization with cell ligands and antibodies

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