Effect of methyl and hydroxyl functional group surfaces on crystallization of hydroxyapatite coating

The effect of chemical functional groups and condition of supersaturated solutions are two important factors to induce the nucleation of hydroxyapatite onto the substrates. Two kinds of self-assembled monolayers were prepared to create functionalized surfaces by grafting thioalcohol molecular containing hydroxyl and methyl as terminal groups respectively onto single silicon chips. Atomic force microscopy and X-ray photoelectron spectroscopy were used to analyze the topography of the surfaces and estimate the surface density. The results provided the evidences that our experiments were made with almost the same density of chemical functional groups. The surfaces were incubated in the supersaturated solutions (37 °C, pH = 7.4) whose Ca2 + and PO43 − ion concentrations were 1.5 times higher than in simulated body fluid. With the condition mentioned above, this study demonstrates that the growth process and morphology of HAp crystals present great differences.

► Apatite crystallizations were regulated by CH3 and OH surfaces. ► The CH3 and OH surfaces had the same surface density. ► The surfaces behaved different of hydroxyapatite formation in 1.5SBF. ► The OH surface could promote the crystallization of calcium phosphates.