Synthesis and cytocompatibility of manganese (II) and iron (III) substituted hydroxyapatite nanoparticles

Manganese (II) and iron (III) substituted hydroxyapatite (HA, Ca10(PO4)6(OH)2) nanoparticles were synthesized using wet chemical method. All samples were single-phase, non-stoichiometric and B-type carbonated hydroxyapatite. Compared with pure HA, Mn2+ substituted (MnHA) and Fe3+ doped HA (FeHA) did not demonstrate significant structure deviation. Since ion exchange mechanism was applied for the synthesis process, the morphology and particle size were not significantly affected: all samples were elongated spheroids of around 70 nm. The presence of Fe and Mn was confirmed by energy dispersive X-ray spectroscopy (EDX) while the concentrations were quantified by inductively coupled plasma (ICP). Fe3+ ions were more active than Mn2+ ions in replacing Ca2+ ions in HA lattice structure. The magnetic property of HA was modified by substitution with Fe. The Fe5 (Feadded/Caadded = 5% by molar ratio) was paramagnetic while pure HA was diamagnetic. Results of extraction assay from cells cultured in extracted medium for 72 h suggested that both MnHA and FeHA were non-cytotoxic to osteoblast cells. Meanwhile, the presence of Fe3+ ions in HA demonstrated significant positive effect on osteoblast cells, where the cell number on Fe5 pellets was twice that of pure HA and MnHA samples.