Mechanisms of polymer-Ca2+ interaction and their effects on the characteristics of alginate microspheres and films

Abstract

This study investigates the effects of polymer-Ca2+ interaction on the alginate matrix. Alginate films and/or microspheres were produced using different grades of sodium alginate with/without pectin, carrageenan and gellan gum. Alginate viscosity was found to exert a greater effect on the encapsulation efficiencies and drug release rates of the microspheres than alginate composition. However, the latter affected matrix strength to a greater extent. Different mechanisms of cross-linking were also studied. Internally cross-linked alginate films had rougher surfaces, lower tensile strengths and lower drug permeabilities than the externally cross-linked ones. Comparable extents of cross-linkage were produced by the two gelation methods but with difference in the distributions of cross-linkages. The properties of the alginate matrix were also significantly affected by incorporation of the co-polymers. In conclusion, modification of alginate matrix properties could be brought about by judicious choice of sodium alginate, co-polymers and cross-linking method, through their effects on polymer-Ca2+ interaction.