Abstract
The enzyme-free crosslinking of gelatin was developed by the use of caffeic acid in a neural aqueous phase. In the presence of copper(II) acetate under an oxygen atmosphere at 40°C, the mixture was turned to the brown hydrogel which was thermally stable and mechanically strong. The gel was physicochemically examined to suggest that the basic amino acid residues (lysine, hyroxylysine and histidine) of the protein were mainly modified by the quinone, an oxidation product of caffeic acid, to form 2-8 crosslinks per protein. These results indicated that the natural phenolic compound and the simple copper(II) salt are potentially useful as a crosslinking agent for fabricating new proteinous materials.
