Structural and microstructural interpretations of Zn-doped biocompatible bone-like carbonated hydroxyapatite synthesized by mechanical alloying

Abstract

Single-phase nanocrystalline biocompatible Zn-doped A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized via mechanical alloying of a stoichiometric mixture of CaCO₃, CaHPO₄·2H₂O and ZnO powders in open air at room temperature by 10 h of milling. The A-type carbonation in HAp (A-cHAp) is confirmed by Fourier transform IR analysis. The structural and microstructural parameters of the as-milled powders are revealed by Rietveld powder structure refinement analysis and transmission electron microscopy. Zn substitution along with mechanical alloying causes partial amorphization of crystalline A-cHAp, analogous to native bone mineral. Zn²⁺ cations substitute into the ninefold-coordinated Ca²⁺ sites in the A-cHAp unit cell. An assay test using MTT [3-(4,5-dimethyl­thiazol-2-yl)-2,5-diphenyl­tetrazolium bromide] reveals a high percentage of cell viability and hence confirms the biocompatibility of the sample. The overall results indicate that the processed A-cHAp has a chemical composition very close to that of natural biological apatite.