Modified MgFe₂O₄ ferrimagnetic nanoparticles to improve magnetic and AC magnetically-induced heating characteristics for hyperthermia

A ferrimagnetic nanoparticle with a smaller size, a narrower size distribution, and a higher ac heat generation ability has been still studied for intra-arterial or intra-tumoral hyperthermia. In this study, we manipulate the calcining temperature in the range of 400∼600 °C to modify MgFe₂O₄ ferrimagnetic nanoparticles (FMNPs) during modified sol-gel process. The modified MgFe₂O₄ FMNPs have well controlled with small size and narrow size distribution, so that their magnetic and ac magnetically-induced heating characteristics are significantly improved. In particular, MgFe₂O₄ nanoparticles synthesized at the calcining temperature of 600 °C and sintering temperature of 700 °C show the most suitable size (58 nm±13 nm) and its distribution (22%) resulting in the highest ac magnetically-induced heating temperature (T_{AC, mag,} ΔT = 93 °C) and SLP (Specific Loss Power, 600 W/g) at the biologically tolerable range of magnetic field (H_appl = 140 Oe) and frequency (f_appl = 110 kHz). It is found to be due to the improvement of magnetic softness and saturation magnetization resulting in the largest hysteresis loss power. All the results in this work clearly demonstrate that calcining process is one of the key parameters to control the proper size and size distribution for improving magnetic and ac magnetically-induced heating characteristics of MgFe₂O₄ FMNPs, which can be applicable to hyperthermia agents in nanomedicine.