Synergistic effects of glucose and ultraviolet irradiation on the physical properties of collagen.

Our objective was to strengthen and stabilize collagen films without the introduction of cytotoxic chemical crosslinkers. We hypothesized that collagen could be rapidly crosslinked with glucose with ultraviolet (UV) irradiation as a catalyst. In theory, UV-generated free radicals can expedite collagen crosslinking with glucose via the formation of reactive, linear glucose molecules. The mechanical properties of glucose-incorporated, UV-exposed collagen films and appropriate controls were determined under various conditions: (1) hydration in phosphate-buffered saline, (2) heat-denaturation, (3) incubation in a collagenase solution, and (4) incubation in a trypsin solution. Without exposure to UV, the incorporation of glucose into the films had no effect. Without glucose, exposure to UV increased the strength but caused significant denaturation. The combination of glucose and UV, however, synergistically improved the mechanical properties and enzyme resistance of collagen films, indicative of increased crosslinking without significant denaturation effects. The addition of thiourea, a potent free-radical scavenger, or aminoguanidine, an inhibitor of glucose-derived crosslinking, to the collagen films markedly hindered these synergistic effects. These data strongly suggest that free-radical-dependent, glucose-derived crosslinks provide the enhanced strength and enzyme resistance observed in glucose-incorporated, UV-exposed collagen films. Further studies are required to explore biomaterial applications of this novel collagen crosslinking method. Copyright 2002 Wiley Periodicals, Inc.