Pseudo single domain NiZn- γ Fe 2 O 3 colloidal 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 transverse r 2 -relaxivity responsible for the insufficient heating of cancers, and the low resolution of contrast imaging, respectively. Here, pseudo single domain colloidal Ni x Zn 1- x - γ Fe 2 O 3 ( x  = 0.6) superparamagnetic nanoparticle (NiZn- γ Fe 2 O 3 PSD-SPNP) physically and theoretically designed at the H AC,safe , specifically by the applied frequency, is proposed for a highly enhanced MRI-guided MNFH agent application. The NiZn- γ Fe 2 O 3 PSD-SPNP showed the superparamagnetic characteristics, significantly enhanced AC heat induction performance (ILP = 6.3 nHm 2 kg -1 ), highly improved saturation magnetization ( M s = 97 emu g -1 Fe, 3.55 × 10 5 A m -1 ) and r 2 -relaxivity ( r 2  = 396 mM -1 s -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 the H AC,safe were revealed as the main physical reason for the significance. All the fundamental in vitro and in vivo experimental results demonstrated that the physically designed NiZn- γ Fe 2 O 3 PSD-SPNP is bio-technically feasible for a highly efficient MRI-guided MNFH agent for future cancer nanomedicine.