New ${\rm T}_{\rm c}$ -Tuned Manganese Ferrite-Based Magnetic Implant for Hyperthermia Therapy Application

The aim of this work is to develop a new low-T_c magnetic implant material with high heat generation and self-controlled capability for hyperthermia treatments based on a new class of Mn_1+xTi_xFe_2-2xO₄ spinel ferrite. Magnetic Mn_1+xTi_xFe_2-2xO₄ ferrites were successfully prepared by a coprecipitation technique. The structural and magnetic properties were characterized using X-ray diffraction (XRD), thermomagneto-gravimetric analysis (TMGA), and vibrating sample magnetometer (VSM). The heat generation ability of these magnetic materials was evaluated by calorimetric measurements of specific absorption rate (SAR). XRD results demonstrated an increase in the lattice constant of Mn-ferrites with increasing Ti content, whereas showed a tendency to decrease linearly with increasing Ti content in the Mn-ferrite. T_c was confirmed to be tunable within the therapeutic temperature range by adjusting the Ti⁴⁺ content near x = 0.55. These behaviors could be explained by considering the lattice expansion in the spinel structure of Mn-ferrites, which was accompanied by a decrease in the overlap of orbital and the J_A-B superexchange interaction. The SAR value obtained was about 17.5 W/g with a maximum self-controlled temperature within the safe therapeutic range (42-46°C). MTT (3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay results confirmed that the toxicity of bare ferrite particles was related to the particle concentration. The cell viability showed a decrease from 93% to 66% with increasing particle concentration from 0.05 to 10 mg/ml. The high saturation magnetization and SAR of Mn_1.55Ti_0.55Fe_0.9 along with tunability of its Curie temperature in the therapeutic temperature range, and its relatively low cytotoxicity rendered this new magnetic material attractive for hyperthermia therapy a- plications in comparison with other T_c-tuned spinel ferrites.