A novel approach to fabricate hydroxyapatite coating on titanium substratein an aqueous solution

3-Aminopropyltriethoxysilane (APTS) thin membranes with amino groups (posit ive surface) were successfully fabricated on pure titanium surfaces by the method of liquid phase processing. A two-step soaking procedure was employe d to prepare HAp coating on the titanium surface modified with an APTS thin membrane. At the first step the negatively charged microparticles of calci um phosphate (CP) homogeneously formed in the supersaturated solution (1.5 SBF, pH = 7.6) at 50 degreesC were attracted to attach to the modified tita nium substrate (positive) due to the electrostatic interaction (attractive) , while no CP microparticles were observed on the unmodified titanium subst rate. At the second step, after the growth of microparticles through consum ption of Ca2+ and PO43- in the solution (1.0 SBF, pH = 7.25, 37 degreesC) t he 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 po sitive surface potential.