Induction of fiber-like aggregation and gelation of collagen by ultraviolet irradiation at low temperature.

Ultraviolet (UV) irradiation is a common method of molecular crosslinking and sterilization of collagen. In this study, UV irradiation at low temperature conditions was investigated as an induction and regulation method for fiber-like aggregation and gelation of collagen. Differences between gelation processes induced by UV irradiation and by traditional temperature-induced methods as well as differences in the properties of the gelation products were systematically analyzed. We found that UV irradiation can induce fiber-like aggregation and gelation of bovine tendon collagen at lower temperatures (<17 °C) than the usual temperature of 37 °C. During UV irradiation, cross-linking and degradation of collagen molecules occurred along with typical collagen fiber formation. The collagen fibers, together with the grafted collagen molecules and the degraded collagen peptides, formed a gel product that had a unique, multi-layered network structure. Collagen gels induced by UV irradiation at low temperatures displayed improved thermal stability, mechanical strength, and cell-growth promoting ability compared with collagen gels that were induced at 37 °C. Our results open up new avenues for the production of collagen-based biomaterials.