Improving the osteogenic and angiogenic properties of synthetic hydroxyapatite by dual doping of bivalent cobalt and magnesium ion

The present study delineates improvement in the osteogenic and angiogenic properties of synthetic hydroxyapatite by dual doping of bivalent magnesium (Mg+2) and cobalt (Co+2) ions. The doped samples were prepared by ammoniacal precipitation method and characterized by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Thermo Gravimetric Analysis (TGA). The study revealed that the extent of cobalt doping (ICP-OES analysis) was higher in comparison to magnesium. Doping of metal ions caused a slight distortion in the crystal structure (XRD analysis), increased apatite-water interaction (FT-IR) and decreased thermal stability (TGA analysis) of the hydroxyapatite. A preliminary evaluation showed that the doped samples had a significantly higher protein absorption capacity in comparison to pure hydroxyapatite. A detailed analysis pertaining to the bone cell (MG-63) compatibility and differentiation revealed that the doping significantly promoted cell proliferation and differentiation, as verified by Runt-related transcription factor 2 (Runx2) expression and in vitro nodule formation. When treated with doped samples, significant increase in intracellular hypoxia inducible factor 1 alpha (HIF-1 alpha) expression was observed. That resulted in higher expression of vascular endothelial growth factor (VEGF), a key molecule that promotes angiogenesis. In conclusion, dual doping of magnesium and cobalt improves the osteogenic and angiogenic properties of hydroxyapatite and makes it a better biomaterial for bone tissue engineering. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.