Cathodic Silver and Carbon Nanotube containing Hydroxyapatite Coatings

Objectives: Calcium phosphate ceramics have been used as biomaterials and coatings because of their similarity in composition to the bone mineral. Among their several forms, hydroxyapatite (HA; chemical formula Ca10(PO4)6(OH)2; Ca/P ratio of 1.67) is widely used in clinical applications. HA is brittle and is therefore applied as coatings on metallic implants. Studies have shown Ag to be more effective in reducing bacterial adhesion. Carbon nanotube (CNT) increases the fracture toughness and wear-resistance of HA and also assists the mineralization of apatite. This paper proposes to achieve a HA coating containing Ag and CNT by simple, inexpensive cathodic deposition. Methods: The electrolyte contained NaCl, CaCl2, K2HPO4 and AgNO3. This solution was adjusted to have an initial pH of 7.2. 0.05 wt.% CNT was added to this electrolyte. Using a platinum anode deposition was carried out on cathodic titanium for 30 minutes from the bath maintained at 60°C. Three current densities, namely, 30, 45 and 65 mA/cm2 were used. Results: XRD indicated the presence of HA and Ag in all the coatings and the HA crystal sizes were in the range of 10–17 nm. Coating surface was completely covered by CNT particles. Roughness values (Ra) of the coatings were lower than 0.2 µm and increased with current density. Water contact angles for these coatings were more than 100°. Conclusions: Nano-crystalline HA coating containing Ag and CNT is successfully produced by cathodic method. Besides the presence of CNT, nano-crystalline HA is also reported to improve the cell activity. In vitro cell culture tests are being done to establish this. Acknowledgement: The authors thank BK21 project for the financial assistance.