Hipertermia magnética de nanopartículas à base de ferrita de manganês: efeito do recobrimento superficial de nanopartículas por moléculas de citrato

Abstract

This work investigated the magneto-thermal properties of manganese ferrite-based nanoparticles. The nanosctructures were synthesized by the coprecipitation method. Three samples were studied, namely: non passivated (2A), passivated (2B), and passivated with citrate coating molecules (2B cit). The particles were characterized by x-ray diffraction (XRD), transmission eléctron microscopy (TEM), vibrating sample magnetometer (VSM) and electron magnetic resonance (EMR). The non-coated samples showed similar diameter and saturation magnetization values, while the citrate-coated sample showed striking diferente values. In particular, the 2B cit sample showed lower values of particle size (determined from Scherrer relation), saturation magnetization and magnetic anisotropy. Those results corroborate with a core-shell nanoparticle model. The magnetic hyperthermia studies, perfomed around 300kHz, revealed that sample 2B had a higher magneto-thermal effiency when compared with the 2B cit one. Dynamic hysteresis curves, obtained within the linear response regime, were capable to explian qualitatively the experimental data. The phenomena was related to a lower magnetic anisotropy for the 2B cit nanoparticles. In addition, the biocompatible magnetic colloid (2B cit) showed SAR values around 50 W/g of MnFe 2 O 4 at the high field limit. However, differently from results reported in the literature, based upon magnetite/maghemite nanoparticles, saturation is achieved at a lower magnetic field amplitude. This suggest that this type of material has great biomedical potential for low-field magnetic hyperthermia applications, which might be necessary in order to inhibit harmful eddy currents inside the patient’s body.