The role of biocompatible coatings of magnetic nanorods on their thermal response in hyperthermia. Consequences on tumor cell survival

There are so many hopes for nanoscience as a tool in the fight against various diseases, notably cancer, that the problem can be approached from many different points of view. In this paper, we focus on two essential aspects. One is the preparation of non-spherical and superparamagnetic magnetic particles, with the right size to be able to exit the blood vessels and be incorporated by cells. The second is their use as agents of hyperthermia. For the first purpose, a two-step method was followed, in which hematite templates with the desired shape and size were first prepared, and these were subsequently reduced by heat treatment. As a result, nanorods with a length of 40 nm and an axis ratio of 1:8 were obtained. The bare particles were coated with a triple layer of cationic/anionic/cationic polymers. Electrophoretic mobility, thermogravimetric analysis, x-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy evaluations confirmed the presence of the coating and the positive charge of the last polymeric layer, while x-ray diffraction and micro-Raman spectroscopy indicated that the crystal structure of the core particles was magnetite/maghemite. The magnetization cycles of the particles showed that they were superparamagnetic, with a saturation magnetization of 82 emu/g in the case of the bare particles. For concentrations up to 300 μg/mL, they were found to be compatible with MCF7 (Michigan Cancer Foundation-7) breast cancer cell line, for cell uptakes higher than 80 %. Both bare and polymer-coated particles produced heating by magnetic hyperthermia and laser-light irradiation. Finally, cytotoxicity against the cancer cells was evaluated, and it was found that photothermia and, above all, magnetic hyperthermia applied to the coated particles could induce more than 50% cell death.