A Biomimetic Synthesis Process for Sr2+, HPO42−, and CO32− Substituted Nanohydroxyapatite

Abstract

Hydroxyapatite (HA) that occurs in nature containssignificant amounts of Sr2+, , and . In the present investigation, a biomimetic synthesis process was applied to incorporate Sr2+, , and into HA crystals without high-temperature calcination. CaCl2, SrCl2, and NaH2PO4 were used as the Ca, Sr, and P sources, respectively. The substitution of into the HA lattice was achieved by controlling the pH of the reaction environment. The substitution of into the HA lattice was due to the reactive absorption of CO2 from the air during mineral precipitation. The chemical characteristics phase and crystal morphology as a function of Sr2+ substitution were evaluated using inductively coupled plasma-atomic emission spectrometry (ICP-AES), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). A dose-dependent relationship was found between the relative amount of Sr2+ in the final solid products and the Sr/(Ca+Sr) molar ratio in the initial (Ca+Sr)-containing solutions. The lattice parameters increased as the Sr2+ incorporation increased. The addition of Sr2+ produced distortions in the apatite crystal structure at sites. Less than 4.14 at% incorporation of Sr2+ ions in the HA crystals did not restrain the crystal growth of HA, whilst 7.69 at% incorporation of Sr2+ ions in the HA crystals restrained the crystal growth of HA.