Fe-based nanoparticles as tunable magnetic particle hyperthermia agents

Magnetic hyperthermia, an alternative anticancer modality, is influenced by the composition, size, magnetic properties, and degree of aggregation of the corresponding nanoparticle heating agents. Here, we attempt to evaluate the AC magnetic field heating response of Fe-based nanoparticles prepared by solar physical vapor deposition, a facile, high-yield methodology. Nanoparticle systems were grown by evaporating targets of Fe and Fe₃O₄ with different stoichiometry. It is observed that Fe₃O₄ nanoparticles residing in the magnetic monodomain region exhibit increased heating efficiency together with high specific loss power values above 0.9 kW/g at 765 kHz and 24 kA/m, compared with that of 0.1 kW/g for zero-valent Fe nanoparticles under the same conditions. The enhanced performance of Fe₃O₄ nanoparticles under the range of field explored (12–24 kA/m) may be attributed to the activation of a magnetic hysteresis loss mechanism when the applied AC field surpasses the particle anisotropy field at H ≥ 0.5H_A. This is also illustrated by the smaller coercivity of Fe₃O₄ nanoparticles compared with that of their Fe counterparts. Therefore, understanding the interconnection between intrinsic parameters (composition, size and magnetic properties), the dosage (concentration, volume) and the intensity and frequency of the AC field can lead to essential design guidelines for in vitro, in vivo, and clinical applications of magnetic nanoparticles for hyperthermia.