Nanoheating without artificial nanoparticles Part II. Experimental support of the nanoheating concept of the modulated electro-hyperthermia method, using U937 cell suspension model

There are intensive debates about the effects and mechanisms of radiofrequency (RF) hyperthermia in oncology. We theoretically modelled the mechanism of the nanoheating effect of the RF current at the cellular and subcellular level. Then, we experimentally investigated the mechanism of heating in comparison with selective modulated electrohyperthermia and water-bath heating conventional hyperthermia (WHT) using the U937 suspension cell line model. The two heating-processes resulted in different distributions of energy-absorption, causing different mechanisms of the thermal processes. Both of the mechanisms are thermal (fit to Arrhenius plot) but the selectively absorbed energy by the plasma membrane rafts and the cell-cell contacts of the cells results in earlier cell-destruction than in case of unselective homogeneous heating. This thermal effect is used for the characterisation of selective heating. The experimental results clearly support the previous theoretical considerations; the cell killing effect can be realised at lower temperature ranges in the case of the modulated electro-hyperthermia (mEHT, trade-name: oncothermia) method than with WHT.