Heterogeneous nucleation of calcium phosphates on solid surfaces in aqueous solution.

The heterogeneous nucleation of calcium phosphates on solid surfaces of poly(methyl methacrylate) (PMMA), poly-(tetrafluoroethylene-co-hexafluoropropylene) (FEP), silicone rubber, mica, and radiofrequency glow discharge (RFGD)-treated PMMA, FEP, and silicone rubber has been studied in solutions supersaturated with respect to hydroxyapatite. The surface properties of the substrates were characterized by contact angle measurements. For the RFGD-treated surfaces, the Lifshitz-Van der Waals surface tension component changes very little, but the Lewis acid-base surface tension parameters vary greatly depending upon the materials. With scanning electron microscopy, nucleation of calcium phosphates was observed only on the surfaces: mica, RFGD-treated PMMA and FEP, with relatively high values of the Lewis base surface tension parameter. The more hydrophobic surfaces having low Lewis acid-base surface tensions, untreated PMMA and FEP, silicone rubber, and even RFGD-treated silicone rubber showed no nucleation.