Changes in Cell Adhesiveness and Physicochemical Properties of Cross-Linked Albumin Films after Ultraviolet Irradiation.

We discovered the unique cell adhesive properties of ultraviolet (UV)-irradiated albumin films. Albumin films prepared using a cross-linking reagent with epoxy groups maintained native albumin properties, such as resistance to cell adhesion. Interestingly, the cell adhesive properties of films varied depending upon the UV irradiation time; specifically, cell adhesiveness increased until 2 h of UV irradiation, when the cell number attached to the film was similar to that of culture dishes, and then cell adhesiveness decreased until 20 h of UV irradiation, after which the surface returned to the initial non-adhesive state. To elucidate the molecular mechanisms underlying this phenomenon, we examined the effect of UV irradiation on albumin film properties. The following changes occurred in response to UV irradiation: decreased α-helical structure, cleavage of albumin peptide bonds, and increased hydrophilicity and oxygen content of the albumin film surface. In addition, we found a positive correlation between the degree of cell adhesion and the amount of fibronectin adsorbed on the film. Taken together, UV-induced changes in films highly affect the amount of cell adhesion proteins adsorbed on the films depending upon the irradiation time, which determines cell adhesion behavior.