Comparative study in physico-chemical properties of gelatin derivatives and their microspheres as carriers for controlled release of green tea's extract

Two types of gelatin derivatives were prepared from type A and type B gelatin, respectively. Cationized gelatin was produced by conjugation of ethylenediamine into type A gelatin using carbodiimide reaction. Anionized gelatin was produced by conjugation of succinic anhydride to type B gelatin. Characteristics of four gelatin types and their microspheres fabricated by water-in-oil emulsion and glutaraldehyde crosslinking were evaluated. Cationized gelatin showed the highest positive charge and free amino group concentration due to the ethylenediamine conjugation, resulting in the highest crosslinking percentage and slowest degradation rate of cationized gelatin microspheres. Type A, B and anionized gelatin which had lower concentration of free amino groups produced the low crosslinking and fast-degrading microspheres. These gelatin microspheres were introduced as carrier for controlled release of epigallocatechin 3-gallate (EGCG), a high antioxidant green tea's extract. The cationized gelatin microspheres showed prolonged release of EGCG due to the slow degradation and ionic attraction with the negative-charged EGCG. The release of EGCG from type A, B and anionized gelatin microspheres was accelerated as a result of diffusion and microsphere's swelling mechanisms. These EGCG-loaded gelatin microspheres can be further studied as injectable drug for localized treatment of inflammation-related diseases with minimal invasion.