Cobalt-ferrite nano-cubes for magnetic hyperthermia applications

Highly crystalline superparamagnetic nano-cubes of CoFe2O4 with size of about 15 nm were prepared by the thermal decomposition method. The structure, morphology, magnetic properties, magnetothermal response, and cytotoxicity study were used to investigate the CoFe2O4 nano-cubes for magnetic hyperthermia. Diffraction methods (employing X-ray and transition electron microscope) confirm the presence of an inverted spinel structure of cobalt ferrite. The presence of a spin-disordered magnetically dead layer that has been confirmed both by X-ray diffraction and magnetometry data. The average crystallite size DXRD - 12 nm has been found smaller than the average physical edge of the nano-cube observed by transition electron microscope DTEM 15 nm. The analysis of the isothermal magnetization data by assuming a cubic instead of spherical shape of the prepared nanoparticles yielded conclusive values of relevant parameters. The effective magnetocrystalline anisotropy constant K = 2.3x105 J/m3 determined by the Law of approach and by the fitting of coercivity data is in excellent correspondence with collected zero-field cooled magnetization data for nano-cube system of crystallite size - 12 nm. In-vitro cytotoxicity tests on U87MG (cancer model) and HDF (non-cancer models) confirm the good biocompatibility and very low cytotoxicity. One of the our mail contributions is, that we provide exact analysis of relaxation processes responsible for heat generation in our nano-cube system and we obtained higher SAR and IPL coefficients than 30 commercial iron-oxide nanoparticle systems designed for magnetic hyperthermia. This, along with the promising results of the magneto-thermal response, indicates the suitability of using the prepared nano-cubes for applications in magnetic particle hyperthermia.