Core/Shell Nanoparticles of Non-Stoichiometric Zn–Mn and Zn–Co Ferrites as Thermosensitive Heat Sources for Magnetic Fluid Hyperthermia

We report on the suitability of core/shell nanoparticles (NPs) for magnetic fluid hyperthermia in a self-regulated and theranostic approach. Aqueous magnetic colloids based on core/shell ZnxMnyFezO4@γ-Fe2O3 and ZnxCoyFezO4@γ-Fe2O3 NPs were produced by a three-step chemical synthesis. Systematic deviations from stoichiometry were observed with increasing Zn substitution for both series of samples. We investigated how the chemical composition affects the saturation magnetization, magnetic anisotropy, and thermomagnetic properties of these core/shell NPs. The heating efficiency through specific power absorption (SPA) was analyzed in the framework of the linear response theory. SPA values obtained for NPs present a different contrast of anisotropy between the core and shell materials, indicating no evidence of the contribution of enhanced exchange coupling to the heating efficiency.