Physical and chemical properties of superparamagnetic Fe-incorporated nano hydroxyapatite.

Nano hydroxyapatite (n-HA) crystals carrying incorporated Fe ions were designed and synthesized by a co-precipitation method. The microstructure and morphology as well as magnetic property of the Fe-incorporated n-HA crystals (denoted as n-Fe-HA) were characterized by TEM, XRD and VSM. The results showed that lattice substitution or incorporation had occurred between Fe ions and n-HA, which was quite different from the mechanical mixture of Fe3O4 nanoparticles and n-HA crystals. The n-Fe-HA with a synthetic molar ratio of 1:2 (calculated by Fe3O4:HA) exhibited a needle like crystal shape and relatively good crystallinity. However, when the molar ratio was up to 1:1, some Fe3O4 nanoparticles were separated from n-Fe-HA crystals. The magnetization measurements showed that n-Fe-HA crystals were in superparamagnetic state, proving that the existence of Fe ions in n-HA crystals contributed to the magnetic properties of n-Fe-HA crystals. As one component of biomedical composite, n-Fe-HA has a potential to promote bone regeneration.