Nano-crystalline growth of electrochemically deposited apatite coating on pure titanium

Hydroxyapatite (HA) coatings were deposited on commercially pure titanium plates using a hydrothermal–electrochemical deposition method in an electrolyte containing calcium and phosphate ions. The deposition conditions used in this study were the followings: electrolyte temperature (33–80 °C), current density (1–8 mA/cm2), and deposition time (10–120 min). Needle-like and granular crystals of apatite coating were created with different concentrations of calcium (0.0021–0.042 M) and phosphate (0.00125–0.025 M) salts. The size of HA crystals of the coating was considerably changed with different concentration of calcium and phosphate salts, temperature of the electrolyte, and deposition time. The shape of HA crystals of the coating remarkably was altered by changing the concentration of calcium and phosphate salts, and current density. Multivariate analysis revealed that both size and shape of the hydroxyapatite crystals had been regulated accurately by systematic control of those above factors. These results, showed that hydrothermal–electrochemical deposition of apatite coating takes place in two steps: nucleation and crystal growth, which strongly depended on the current density, concentrations of calcium and phosphate salts, the temperature of electrolyte, deposition time. Also it was revealed that preferential growth direction there is along the (0 0 2) planes of nano-scale and columnar structures of the electrochemical deposited apatite coating on titanium substrate. The cell culture experiment showed the cell adherence on the coatings was well. No floating cells were observed after 4 days. The HA deposition was of benefit to the cell proliferation on the surface of titanium substrate.