Synthesis of nanogranular Fe3O4 biomimetic hydroxyapatite for potential applications in nanomedicine: structural and magnetic characterization

• Published in: Materials research express 2015-06, Vol.2 (6)
• Main Authors: Bianco, L Del, Lesci, I G, Fracasso, G, Barucca, G, Spizzo, F, Tamisari, M, Scotti, R, Ciocca, L
• Format: Article
• Language: English
• Subjects: biocompatible magnetic material; biomimetic hydroxyapatite; magnetite nanoparticles
• ISSN: 2053-1591
• DOI: 10.1088/2053-1591/2/6/065002

We realized the synthesis of a novel nanogranular system consisting of magnetite nanoparticles embedded in biomimetic carbonate hydroxyapatite (HA), for prospective uses in bone tissue engineering. An original two-step method was implemented: in the first step, magnetite nanoparticles are prepared by refluxing an aqueous solution of Fe(SO4) and Fe2(SO4)3 in an excess of tetrabutilammonium hydroxide acting as surfactant; then, the magnetite nanoparticles are coated with a Ca(OH)2 layer, to induce the growth of HA directly on their surface, by reaction of Ca(OH)2 with HPO42−. Two nanogranular samples were collected with magnetite content ∼0.8 and ∼4 wt%. The magnetite nanoparticles and the composite material were investigated by x-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. These analyses provided information on the structure of the nanoparticles (mean size ∼6 nm) and revealed the presence of surface hydroxyl groups, which promoted the subsequent growth of the HA phase, featuring a nanocrystalline lamellar structure. The magnetic study, by a superconducting quantum interference device magnetometer, has shown that both the as-prepared and the HA-coated magnetite nanoparticles are superparamagnetic at T = 300 K, but the magnetization relaxation process is dominated by dipolar magnetic interactions of comparable strength. In the three samples, a collective frozen magnetic regime is established below T ∼ 20 K. These results indicate that the magnetite nanoparticles tend to form agglomerates in the as-prepared state, which are not substantially altered by the HA growth, coherently with the creation of electrostatic hydrogen bonds among the surface hydroxyl groups.