Effect of trisodium citrate on electrolytic deposition of hydroxyapatite coatings

Hydroxyapatite coatings were deposited on the titanium substrate by using various content Na(3)Cit as an organic modifier in electrolytes. The influence of the Na(3)Cit on the sizes of the HA crystals during electrolytic deposition was investigated under different molar ratio of Na(3)Cit to calcium ions. The experimental results showed that the size of HA crystal was well controlled by the addition of Na(3)Cit. When the molar ratio of Na(3)Cit to calcium ions was equal or greater than five, the obtained HA coating consisted of nanosized crystals. The HA nanoparticles were precipitated without a precursor phase when the molar ratio of Na(3)Cit to calcium ions was five; otherwise, the CaP coating experienced a phase conversion from octacalcium phosphate (OCP) to HA during the ELD. The effect of pH on saturation indexes with respect to hydroxyapatite, OCP, and dicalcium dihydrogen phosphate of these electrolytes was calculated by a computer program PHREEOC. The calculation showed the nucleation of OCP as the precursor during the deposition could be inhibited with increasing Na(3)Cit content in the electrolytes. (C) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 968: 1-8, 2011.