Physico-chemical properties of Co-Sr doped carbonated hydroxyapatite powders

Abstract

Abstract The present study aimed to investigate the effects of ionic substitutions on the physico-chemical properties of carbonated hydroxyapatite (CHA) by incorporation of two biologically important cations, cobalt (Co2+) and strontium (Sr2+) ions into the apatite structure. Four different compositions of Co-Sr CHA powders with different combinations of Co2+ and Sr2+ were synthesized via nanoemulsion method at 25°C. The physico-chemical properties of the powders were investigated through several analytical techniques, i.e. X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Carbon, Hydrogen, Nitrogen (CHN) analyzer and Field Emission Scanning Electron Microscopy equipped with Energy Dispersive X-Ray (FESEM/EDX). Regardless of their compositions, the as-synthesized Co-Sr CHA powders remained as B-type CHA and no secondary phase detected. The amounts of carbonate present in the as-synthesized powders were found to be in a range of 1-5 wt%, which relatively close to the carbonate content found in natural human bone. The Ca/P ratios obtained for all the as-synthesized powders were relatively higher than the theoretical ratio of the stoichiometric HA (1.67). This proved that carbonate, strontium and cobalt ions were partially substituted into the apatite structure. All as-synthesized powders showed highly agglomerated nanoparticles when observed under FESEM. Co-Sr CHA 1 with 0.0082 wt% Co and 0.0547 wt% Sr was selected as the best formulation to be used in the next phase of our study in developing three-dimensional porous scaffolds.