Chemical Synthesis and Magnetic Properties of Monodisperse Nickel Ferrite Nanoparticles for Biomedical Applications

With the aim of improving the response in magnetic hyperthermia treatments and other biomedical applications, a nanoparticle system based on nickel ferrites has been investigated. Monodisperse ferrite nanoparticles with different proportions of Ni2+ ions and sizes have been produced by an optimized synthesis based on the thermal decomposition method and the seed-growth technique. All samples were chemically and structurally characterized by different methods, and the magnetic behavior has been analyzed by means of field and temperature dependent magnetization measurements and electronic magnetic resonance. It has been proved that low proportions of Ni2+ cation in the structure favors high saturation magnetization values and a reduction of the magnetic anisotropy constant. The optimized nanoparticles were transferred to water. Such nanoparticles are innocuous at concentrations up to 0.5 mg/mL and are convenient MRI contrast agents. Those samples with lower percentages of Ni2+ atoms and bigger particle sizes presented the highest specific absorption rate, and, for instance, they are the most adequate for magnetic hyperthermia applications.