Preparation and characterization of anionized and cationized gelatin derivatives and their microspheres for drug delivery system

Gelatin is a protein derived from collagen by an acid treatment (type A gelatin, GA) or an alkaline treatment (type B gelatin, GB). In this study, GA and GB were chemically modified by introducing functional groups on their structures to obtain cationized (GE) and anioized gelatin derivatives (GS), respectively. Conjugation of ethylenediamine resulted in the higher positive charge and free amino group content of GE. Various gelatin derivatives GA, GB, GE and GS were fabricated into microspheres using water in oil emulsion and dehydrothermal crosslinking techniques. All gelatin microspheres had a round shape with average size around 40-50 mu m in the dry state. In the swollen state, sizes of GA, GB, and GS microspheres were increased to 73-89 mu m while that of GE microspheres was up to 150 mu m. The highly hydrophilicity of strong positive charged GE may be attributed to its high swelling ability (swelling ratio similar to 3.1) and solubility after immersed in water at 37 degrees C for 24 h although it had high crosslinking degree. On the other hand, GA, GB, and GS had swelling ratio only 1.7-1.9 and less water-solubilized. These gelatin microspheres having different properties will be introduced as carrier for delivery of drug in which the release rate of drug can be controlled. This drug delivery system will be applied for the localized treatment of disease like osteoarthritis with minimal invasion.