紫外線照射チタンの親水性の経時的変化が細胞接着タンパク質吸着に与える影響

抄録

Ultraviolet (UV) treatment of titanium produces a hydrophilic surface on the titanium and enhances osteoblast attachment, proliferation and differentiation. It is reported that differences in storage conditions influence the sustainability of hydrophilicity of titanium surfaces after ultraviolet treatment. However, there are no reports regarding the relationship between the change of hydrophilicity of titanium surfaces during storage and biological properties. In the present study, the influence of time-dependent changes of hydrophilicity of ultraviolet treated titanium on protein adsorption was investigated. As protein, fibronectin, which is a cell adhesive protein, was used. Titanium was stored in a desiccator under atmospheric conditions for 1 day, 3 days, 1 week, 2 weeks and 1 month after ultraviolet treatment. As a control, a titanium surface immediately after UV treatment (0-day) was employed.
First, contact angles against water at different storage periods were measured. Fibronectin adsorption behavior was monitored by the quartz crystal microbalance (QCM) method. Amounts of fibronectin adsorbed onto the titanium sensor and apparent adsorption rate were obtained using QCM measurements.
The contact angle after 1-day storage was almost seven times higher than that of the 0-day titanium surface (p＜0.05). The contact angle gradually increased with the storage period. After 1-week storage, the degree of increase of contact angle became smaller.
A significantly large degree of frequency decrease by fibronectin adsorption was observed at 0-day by QCM measurement (p＜0.05). Longer storage periods of UV treated titanium resulted in a smaller degree of frequency decrease. Calculation of adsorption amounts of fibronectin by the frequency decrease curve revealed that the adsorbed amount at only 1-day storage was significantly less than that at 0-day (p＜0.05). The adsorbed amounts of fibronectin to 1-day or 3-day stored titanium were significantly greater than that to 1-month stored titanium (p＜0.05). The apparent adsorption rate was obtained by curve fitting of the frequency decrease curve. The apparent adsorption rate of 1-day and 3-day storage significantly reduced to less than half of that of 0-day storage (p＜0.05).
In conclusion, atmospheric storage of UV treated titanium changed the hydrophilic titanium surface to a hydrophobic surface and significantly reduced the adsorption amounts and apparent adsorption rates of fibronectin to titanium even for only 1-day storage.