Microstructural, mechanical, and osteocompatibility properties of Mg2+/F(-)-doped nanophase hydroxyapatite

Pure as well as Mg(2+)- and F(-)-doped nanophase (i.e., grain sizes in the nanometer regime in at least one dimension) hydroxyapatite (HA) samples were synthesized by a precipitation method followed by sintering at 1100 degrees C for 1 h to determine their microstructural, mechanical, and osteoblast (bone-forming cell) adhesion properties pertinent for orthopedic applications. Different amounts of Mg(2+) and F(-) ions (specifically from 0 to 7.5 mol %) were doped into the HA samples. X-ray diffraction was used to identify the presence of crystalline phases, lattice parameters, and crystal volumes of the samples. Fourier transform infrared (FTIR) was further used to chemically characterize HA, and thus FTIR patterns revealed the characteristic absorption bands of HA. Microhardness measurements were also performed to assess mechanical properties of the novel formulations. Results of this study showed an improvement in sample density for some of the samples, which was a consequence of the molar percentage variation of the dopants. Moreover, in most of the samples doped with Mg, beta-tricalcium phosphate was observed as a second phase to HA. In addition, 1% Mg- and 2.5% F-doped HA had the highest microhardness values. Lastly, results demonstrated the highest osteoblast densities when the HA samples were doped with 2.5-7.5% Mg(2+) and F(-). Thus, the results of this study suggest that decreasing the grain size of HA into the nanometer regime and doping HA with Mg(2+) and F(-) can potentially increase the efficacy of HA for orthopedic applications.