Effects of degree of deacetylation and cross-linking on physical characteristics, swelling and release behavior of chitosan microspheres

The effect of N-deacetylation in chitosan was studied by preparing chitosan samples with 48%, 62%, and 75% degree of deacetylation (DDA). The degree of deacetylation in prepared samples of chitosan was estimated by infrared and potentiometric methods of analysis. The degree of deacetylation was further verified by a method based on elemental analysis. The degree of deacetylation obtained by these methods was found to be almost the same, hence providing support that the methods used in determination of degree of deacetylation in chitosan samples are complementary. The degree of cross-linking, swelling and controlled release characteristics of microspheres showed dependence on degree of deacetylation and cross-linking in chitosan. The microspheres prepared with 62% degree of deacetylation and 6% (w/w) degree of cross-linking show an optimum degree of swelling, releasing 70% (w/w) of loaded centchroman in a controlled manner within a sustained period of 60 h. Varying the concentration of glutaraldehyde changed the degree of cross-linking in microspheres. The degree of deacetylation and cross-linking has controlled the loading and release profile of centchroman from prepared microspheres. The centchroman from microspheres was released in two stages. In the first stage, the centchroman was released in rapidly, in a burst, while in second stage the centchroman was released in a controlled manner. The centchroman release was diffusion controlled with zero order kinetics.