Co-Sr doped carbonated hydroxyapatite: A biomaterial with enhanced mechanical and bioactivity properties

Abstract

The present study is aimed at investigating the role of two biologically important cations, cobalt (Co2+) and strontium (Sr2+) doped into carbonated hydroxyapatite (CHA) crystal structure. Four different compositions of Co-Sr CHA powders were synthesized via nanoemulsion method at ambient temperature. Among the as-synthesized powders, Co-Sr CHA 1 (0.0082wt% Co, 0.0547wt% Sr) and Co-Sr CHA 2 (0.0085wt% Co, 0.0261wt% Sr) were chosen as the optimum compositions and used for fabrication of dense products. Sintering was then performed on the Co-Sr CHA compacted samples at 900°C in air, followed by cooled down in dry CO2 atmosphere at temperature of 200°C. Regardless of their compositions, the sintered samples remained as single phase B-type CHA. Co-Sr CHA 1 has the optimum mechanical properties where the relative density and diametral tensile strength (DTS) values obtained were 89.15% and 7.67 MPa, respectively. In vitro bioactivity test revealed that the formation of apatite layer were detected on the surface of all sintered samples after soaking in SBF solution for 7 days, with Co-Sr CHA 1 showing the fastest apatite formation as compared to CHA and Co-Sr CHA 2. Results obtained indicate that simultaneous doping of Co2+ and Sr2+ into CHA structure gives rise to improved mechanical strength as well as enhanced the bioactivity of the apatite.