Nucleation and growth of hydroxyapatite on an amino organosilane overlayer

An amino organosilane overlayer (NH2-overlayer) was successfully processed on Si/SiO2 substrates. Remarkable nucleation and growth of hydroxyapatite w ere found to take place on an NH2-overlayer after Si/SiO2 substrates covere d with the NH2-overlayer were soaked in supersaturated solutions with respe ct to Ca2+ and PO43- ions [1.0SBF (simulated body fluid), which contains si milar compositions to that in a living body and 1.5SBF in which only Ca2+ a nd PO43- concentrations are 1.5 times than that in 1.0SBF]. The experimenta l results demonstrated that HAp nucleation on an NH2-overlayer is related t o the electrostatic attractive force between positive NH2-overlayer surface and negative incipient HAp microparticles homogeneously nucleated in 1.5SB F solution at 50 degreesC. On the contrary, fewer HAp particles were observ ed on negatively charged "OH" terminated self-assembled monolayer (SAM) bec ause of the repulsive interaction. The Ca/P molar ratios of HAp particles i ncreased from 0.92 at the beginning of nucleation in 1.5SBF to 1.63 in 14 d ays after growth in 1.0SBF at 37 degreesC. After 14 days of soaking in 1.0S BF, a dense HAp film with the thickness up to 8.6 mum was formed on the NH2 -overlayer. (C) 2001 John Wiley & Sons, Inc.