A Novel Approach to Fabricate Hydroxyapatite Coating on Titanium Substrate in an Aqueous Solution

Abstract

3-Aminopropyltriethoxysilane (APTS) thin membranes with amino groups (positive surface) were successfully fabricated on pure titanium surfaces by the method of liquid phase processing. A two-step soaking procedure was employed to prepare HAp coating on the titanium surface modified with an APTS thin membrane. At the first step the negatively charged microparticles of calcium phosphate (CP) homogeneously formed in the supersaturated solution (1.5SBF, pH=7.6) at 50°C were attracted to attach to the modified titanium substrate (positive) due to the electrostatic interaction (attractive), while no CP microparticles were observed on the unmodified titanium substrate. At the second step, after the growth of microparticles through consumption of Ca²⁺ and PO₄^3- in the solution (1.0SBF, pH=7.25, 37°C) the dense coating of hydroxyapatite was formed on the modified Ti substrate. The results verified our expectation that CP microparticles formed in the solution dominated the formation of hydroxyapatite on the substrate with positive surface potential.