Synthesis and characterization of cobalt-substituted hydroxyapatite powders

Abstract The crystal structure of hydroxyapatite lends itself to a wide variety of substitutions and ion doping, which allows for tailoring of material properties. Magnetic properties are one area of interest in which substitutions can be used to tailor hydroxyapatite properties. Pure HA is diamagnetic, but metal ion doping may lead to a magnetic apatite. In this study, cobalt doped hydroxyapatite was synthesized via two methods: a simple ion-exchange procedure and wet synthesis. The resulting materials were characterized thoroughly for crystal structure and phase purity using X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Magnetic properties were studied using vibrating sample magnetometer and superconducting quantum interference device analysis. The degradation behavior and cobalt release of pure HA and CoHA in simulated body fluid was also examined. The results showed that after both cobalt substitution methods the powder retained characteristic apatite crystal structure and functional groups. Cobalt substituted samples displayed paramagnetic properties, as opposed to the diamagnetism of pure HA. Degradation studies showed that CoHA did not display markedly different degradation behavior from pure HA and the amount of cobalt released over the course of a month was extremely low, alleviating toxicity concerns. Cobalt substituted hydroxyapatite nanoparticles, a biomaterial with magnetic properties, could be a promising material to be used in a variety of biomedical applications, including magnetic imaging, drug delivery, or hyperthermia based cancer treatments.