Nucleation of biomimetic Ca-P coatings on Ti6Al4V from a SBF x 5 solution: influence of magnesium

Biomimetic Calcium-Phosphate (Ca-P) coatings were applied by using 5 times concentrated Simulated Body Fluid (SBF x 5) using Carbon Dioxide gas. This process allows the deposition of a uniform Ca-P coating within 24 h. A previous study of our process emphasized the importance of hydrogenocarbonate ions (HCO3-), a crystal growth inhibitor. The aim of the present study 3 was to investigate the role of the other crystal growth inhibitor present in SBF x 5. Magnesium (Mg2-). on the Ca-P coating formation. Several SBF x 5 solutions were prepared with various Mg2+ and HCO3- contents. No Ca-P deposits were detected on Ti6Al4V substrate soaked for 24 h in a Mg-free SBF x 5 solution. whereas by increasing HCO3- content in a Mg-free SBF x 5 solution. a Ca-P coating developed on Ti6Al4V substrate. Therefore. it appeared that Mg2+ has a stronger inhibitory effect on apatite crystal growth than HCO3-. Nevertheless. Mg2+ plays also another important role as suggested by depth profile X-ray Photoelectron Spectroscopy (XPS) of the Ca-P coating obtained from SBF x 5 solution. Ca2+ and Mg2+ Contents increased significantly at the titanium,coating interface. Therefore, Ca2+ and Mg2+ initiated Ca-P coating from SBF x 5 solution. The relatively high interfacial concentration in Mg2+ favors heterogeneous nucleation of tiny Ca-P globules onto the substrate. So physical adhesion is enhanced at the early stage of the coating formation. (C) 2002 Elsevier Science Ltd. All rights reserved.