Age-dependent degradation of the protein adsorption capacity of titanium

Reported bone-implant contact percentages are far below the ideal 100%. We tested a hypothesis that the protein adsorption capability of titanium, which is critical to the process of osseointegration, changes over time before its use. Machined, acid-etched, and sandblasted surfaces were prepared and stored under dark ambient conditions for 3 days, 1 week, or 4 weeks. For all surfaces, protein adsorption decreased as the storage time increased, and their decreasing rates were dependent on titanium topography. After 4 weeks, the amounts of albumin and fibronectin adsorbed by the acid-etched surface were only 20% and 35%, respectively, of that adsorbed by the fresh surface after 2 hours of incubation, and remained substantially low even after 24 hours. This time-dependent degradation in protein adsorption of titanium correlated with its naturally decreasing hydrophilicity, which was not observed for the nickel and chromium surfaces, indicating a titanium-specific biological aging.