Drug-Releasing Gelatin Coating Reinforced with Calcium Titanate Formed on Ti-6Al-4V Alloy Designed for Osteoporosis Bone Repair

Ti-6Al-4V alloy has been widely used in the orthopedic and dental fields owing to its high mechanical strength and biocompatibility. However, this alloy has a poor bone-bonding capacity, and its implantation often causes loosening. Osteoporosis increases with the aging of the population, and bisphosphonate drugs such as alendronate and minodronate (MA) are used for the medical treatment. Reliable and multifunctional implants showing both bone bonding and drug releasing functions are desired. In this study, we developed a novel organic-inorganic composite layer consisting of MA-containing gelatin and calcium-deficient calcium titanate (cd-CT) with high bone-bonding and scratch resistance on Ti-6Al-4V alloy. The alloy with the composite layer formed apatite within 7 days in a simulated body fluid and exhibited high scratch resistance of an approximately 50 mN, attributable to interlocking with cd +/- CT. Although the gelatin layer almost completely dissolved in phosphate-buffered saline within 6 h, its dissolution rate was significantly suppressed by a subsequent thermal crosslinking treatment. The released MA was estimated at more than 0.10 mu mol/L after 7 days. It is expected that the Ti alloy with the MA-containing gelatin and cd-CT composite layer will be useful for the treatment of osteoporosis bone.