Control of Cell Adhesion on Titanium Dioxide by Light Irradiation

Abstract

Several techniques have been employed to attach/detach cells to/from a substrate. Cells cultured on a substrate are generally detached from the substrate into a sheet by the destruction of protein between the cells and the substrate using enzymes such as trypsin. However, the enzymes also damage the adhesion molecules among the cells. TiO2 is an n-type semiconductor with an energy band gap of 3.0-3.2 eV, which displays a photocatalytic activity under ultraviolet (UV) light. The purpose of this work was to fabricate photo-responsive cell culture vessel using TiO2 film and to investigate adhesion behaviour of cells on it. TiO2 films were prepared on SiO2 plates by a sol-gel method using titanium tetraisopropoxide. Primary osteoblasts were seeded on the vessels and then incubated at 37 °C. During the incubation, UV irradiation was performed continuously from back-side of the vessels. Basically the number of cells monotonically increased with incubation periods under darkness. Previous light irradiation promoted the cell adhesion on the surface. The formation of Ti-OH groups on the TiO2 seems to be facilitated by the UV irradiation. In contrast, the cells decreased under continuous light irradiation. The cells were not exposed to UV in the vessels since it was completely absorbed by the TiO2 layer. It might be due to generated photocurrent or hydroxyl radicals on the TiO2 surface. These results imply that the adhesion/proliferation/detachment behaviours of cells can be controlled by the photocatalytic reaction of TiO2 and the irradiation patterns.