Pseudo single domain NiZn-γFe₂O₃colloidal superparamagnetic nanoparticles for MRI-guided hyperthermia application

Magnetic resonance imaging (MRI)-guided magnetic nanofluid hyperthermia (MNFH) is highly desirable in cancer treatment because it can allow for diagnosis, therapeutics, and prognosis simultaneously. However, the application of currently developed iron-oxide based superparamagnetic nanoparticles (IOSPNPs) for an MRI-guided MNFH agent is technically limited by the low AC heat induction power at the physiologically tolerable range of AC magnetic field (H_AC,safe), and the low transverser₂-relaxivity responsible for the insufficient heating of cancers, and the low resolution of contrast imaging, respectively. Here, pseudo single domain colloidal NiZn_1--γFe₂O₃(x = 0.6) superparamagnetic nanoparticle (NiZn-γFe₂O₃PSD-SPNP) physically and theoretically designed at theH_AC,safe, specifically by the applied frequency, is proposed for a highly enhanced MRI-guided MNFH agent application. The NiZn-γFe₂O₃PSD-SPNP showed the superparamagnetic characteristics, significantly enhanced AC heat induction performance (ILP = 6.3 nHm²kg^-1), highly improved saturation magnetization (M= 97 emu g^-1Fe, 3.55 × 10⁵A m^-1) andr₂-relaxivity (r₂ = 396 mM^-1s^-1) that are desirable for highly efficient MRI-guided MNFH agent applications. According to the analyzed results, the remarkably enhanced effective relaxation time constant and its dependent out-of-phase magnetic susceptibility, as well as the DC/AC magnetic softness optimized by the PSD-SPNP at theH_AC,safewere revealed as the main physical reason for the significance. All the fundamentalin vitroandin vivoexperimental results demonstrated that the physically designed NiZn-γFe₂O₃PSD-SPNP is bio-technically feasible for a highly efficient MRI-guided MNFH agent for future cancer nanomedicine.