SOLUBILIZATION AND BIODEGRADATION OF CROSS-LINKED GELATINS BY ALKALINE PROTEINASE

Abstract

This investigation involves the chemical modification of gelatin, a biomaterial which has been widely studied because of its environmental friendliness, its ready availability from waste products, and its biodegradability. The focus was on cross-linking because it has been shown that the mechanical properties of gelatin can be improved by a sequence of processing steps involving cross-linking, swelling, orientation, and, finally, drying in the oriented state. Because cross-linking is required in this technique, the present study characterizes its possible effects on gelatin biodegradability, as gauged by the time required to solubilize the material. A series of cross-linking agents having various alkylene sequence lengths was used. The resulting cross-linked gelatins were relatively insoluble in phosphate buffer (pH = 8.2) at room temperature, but at higher temperatures, they became partially soluble. Full solubilization of cross-linked gelatins was successfully obtained, however, by the action of an alkaline proteinase, specifically subtilisin. Both the rate of the partial solubilization in buffer and the full solubilization with alkaline proteinase showed dependences on the type, concentration, and chain lengths of the cross-linking agent.