NANOPHASE HYDROXYAPATITE COATINGS ON TITANIUM FOR IMPROVED OSTEOBLAST FUNCTIONS

In order to improve orthopedic implant performance, the objective of this in vitro study was to synthesize nanocrystalline hydroxyapatite (HA) powders and use such powders to coat titanium. HA was synthesized through a wet chemical process. The precipitated powders were either sintered in order to produce UltraCap (or traditionally-used microcrystalline size). HA powders or they were treated hydrothermally to produce nanocrystalline size HA powders. Some of the UltraCap and nanocrystalline HA powders were doped with yttrium (Y) because previous studies demonstrated that Y-doped HA in bulk improved osteoblast (or bone-forming cell) function over undoped HA. These powders were deposited onto titanium by a novel room-temperature process, called IonTite(TM), which provides the advantage of retaining properties of the starting HA powders. The original HA particles were characterized using XRD, ICP-AES, BET, a laser particle size analyzer, and SEM. The properties of the resulting HA-coatings were compared to properties of the original HA powders. The results showed that the chemical and physical properties of the original HA powders were retained when coated on titanium by IonTite(TM),as determined by XRD, SEM, and AFM analysis. In addition, results showed increased osteoblast adhesion on the nanocrystalline HA IonTite(TM) coatings compared to traditionally used plasma-sprayed HA coatings. Results also demonstrated greater amounts of calcium deposition by osteoblasts cultured on Y-doped nanocrystalline HA coatings compared to either UltraCap IonTite(TM) coatings or plasma-sprayed coatings. These results encourage further studies on nanophase IonTite(TM) HA coatings for orthopedic applications.