Natural decrease of protein adsorption capability of titanium over time

Objectives: The hydrophilic status and protein adsorption capacity of titanium surfaces play a vital role in mediating cell attachment and initiating the function. Surface chemistry, as represented by carbon deposition, has been reported to change over time. In this study, we investigated an initial protein adsorption to titanium with different ages, as well as the effect of ultraviolet (UV) light treatment of the titanium surfaces.

Methods: Machined, acid etched and sandblasted titanium surfaces were prepared. Immediately (fresh), 3 days, 1 week and 1 month after the preparation, the surfaces were examined for hydrophilicity and protein adsorption. Adsorption of albumin and fibronectin to titanium surfaces was evaluated after 1 hour incubation using micro BCA protein kit and a microplate reader at 562 nm wavelength. Additionally, the 1 month-old titanium treated with UV was also tested.

Results: Adsorption rate of both albumin and fibronectin to titanium was significantly lower for the aged surfaces than the fresh ones (2-way ANOVA, p<0.001). For instance, the amount of albumin adsorbed to the 1 month old acid-etched surface was 30% of that for the fresh acid-etched surface. The amounts of protein adsorption of the 1 month-old surfaces were lower by 30% than for the fresh surfaces even after 24 hour incubation. The age-dependent reduction of protein adsorption was correlated with a decrease of titanium hydrophilicity. However, the 1-month old surface, once treated with UV, recovered the protein adsorption capacity to the level equivalent to the fresh surfaces. A similar trend of results was consistently obtained from other titanium surface types.

Conclusions: Protein adsorption capacity of titanium drops over time, and, however, this unfavorable change can be fully restored by the UV treatment. The results raise a novel, crucial concept of biological aging of titanium and, more intriguingly, its rejuvenation as a compelling solution for the problem.