Trilemma of magnetic hyperthermia “field - frequency - size” by the example of ZnMn ferrite nanoparticles

The efficiency of conversion of electromagnetic energy into heat is a key factor for magnetic nanoparticles (MNPs) utilization in magnetic hyperthermia and many other emerging medical technologies, such as treating Parkinson's disease and MNP-based nerve interface. At present, in order to increase the release of heat, the concentration and/or EM field of the MNPs in tumors increased, which increases the weight, size and power consumption of the field source, and the increase in the adverse effects of the health organization. In this review, we first proposed the dilemma of magnetic hyperthermia for the first time. The best balance between the frequency, amplitude and MNP size of the electromagnetic field is determined. The purpose of the work is to try to use MnZn iron oxygen MNP as an example to solve this dilemma. That is to find the best combination of MNP features and external parameters, and develop a new strategy that uses MnZn iron oxygen -based MNP to improve heat dissipation efficiency at a lower frequency. Research in the field of magnetic hyperthermia will be focused on the new range of magnetic field amplitude and MNP sizes. The paper shows the extraordinary dependence of EM field in $Zn_{0,2}Mn_{0,8}Fe_{2}O_{4}$ MNP (nearly five, not well-known the second-power one). Our study challenges the traditional approach based on minimizing the magnetic field and increasing the frequency (in some cases up to 300-500 kHz or even higher) and suggests an improved strategy: increasing the amplitude while decreasing the frequency as much as possible. This will make it possible to effectively use the presence of a superquadratic dependence of the specific absorption of EM energy on the field amplitude in MNPs. The results of the study may have a significant impact on the development strategy of other advanced biomedical technology using MNPs.