The influence of simultaneous divalent cations (Mg2+, Co2+ and Sr2+) substitution on the physico-chemical properties of carbonated hydroxyapatite

Abstract

Bone is generally known as calcium-apatite which contains considerable amounts of various trace elements, mainly carbonate. Thus, bone is usually referred as carbonated hydroxyapatite (CHA). The incorporation of dopants into calcium-apatite has been proposed. This approach provides a safer and efficient platform for enhancing bone remodelling. However, reports that emphasize on the influence of multi-dopant substitutions into the CHA structure particularly in the form of as-synthesized powders are limitedly available. The present study investigates the influence of simultaneous substitution of divalent cations, Mg2+, Co2+ and Sr2+ into CHA structure by a nanoemulsion method. Several combinations of ions were doped into the CHA structure. The XRD and FTIR results confirmed that the phase purity and crystallinity were not affected by the simultaneous incorporation of multi-doped ions; all powders remained as amorphous B-type CHA. Despite the small amount of dopants used, all the three cations were successfully substituted into the Ca2+ site of CHA structure. The crystallite size of the as-synthesized powder decreased as the amount of incorporated dopants increased. Interestingly, the particle shape showed the transformation from near spherical structures into needle-like structures with increasing amount of dopants. Our finding highlights that the incorporation of these cations into the CHA structure results in crystal imperfections, which cause a substantial dislocation of the crystal lattice, as seen by the alteration of the lattice parameters, crystallite and particle sizes of the as-synthesized powders.