Naturally Occurring Chitosan and Chitosan Derivatives: A Review

Chitosan, a polymer obtained by deacetylation of chitin is widely studied for its pharmaceutical and nonpharmaceutical applications. Recommendations about uses of this polymer although could not be always realized due to limited solubility. Chitosan has been extensively evaluated for its mucoadhesive and absorption enhancement properties. The positive charge on the chitosan molecule gained by acidic environment in which it is soluble seems to be important for absorption enhancement. However chitosan is not soluble in medium except below pH 5.6. This limits its use as permeation enhancer in body compartments where pH is high. In this regard there is a need for chitosan derivatives with increased solubility, especially at neutral and basic pH values. This review introduces the physical background of the special properties of the various chitosan derivatives and their application. Chitosan derivatives with different physicochemical properties especially water solubility at neutral and basic values are of interest. Chemical modification of chitosan is useful for the association of bioactive molecules to polymerize and controll the drug release profile. From the studies reviewed it is concluded that chitosan derivatives are promising materials for controlled drug and nonviral gene delivery.