Preparation, thermal stability and biocompatibility studies of gelatin-induced hydroxyapatite co-substituted with essential physiological trace elements

Abstract

Gelatin-induced hydroxyapatite with combined substitution of essential physiological trace elements (G-FAP) was prepared by a precipitation method. Pure hydroxyapatite (HAP) and ion-substituted hydroxyapatite (FAP) were also prepared for comparison. The characteristics of the precipitated powders were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), specific surface area measurement (SSA), X-ray fluorescence spectroscopy (XRF), and thermogravimetric (TG) analysis. The biocompatibility was also determined by an in vitro investigation with MC3T3-E1 cells. SEM and TEM results showed that the G-FAP powders were composed of dense aggregates of agglomerated whisker-like crystals of 200–300 nm in length and 10–20 nm in width. XRD and FT-IR analyses indicated the formation of pure apatite phase, and the substituted ions and gelatin did not change the diffraction pattern of the precipitated powders. The SSAs of the precipitated powder were 64.741, 72.492, and 107.745 m2/g, for HAP, FAP, and G-FAP, respectively. XRF analysis showed that Na+, Mg2+, and F− were substituted into the crystal lattice. TG results showed a reduced thermal stability of the precipitated G-FAP powders, with an advanced phase transformation beginning at 800 °C and a serious phase transformation from hexagonal apatite phase to rhombohedral β-TCP phase at 1,200 °C in comparison with HAP and FAP. In vitro biological tests showed non-cytotoxic effects for all powders. However, G-FAP stimulated the proliferation of MC3T3-E1 cells earlier than HAP and FAP. The present G-FAP will therefore be a promising primary biomaterial for bone regeneration, tooth filling, or as a coating for metal artificial limbs.