Abstract
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.
Highlights
Quantitative analysis of the cell-death process was performed by flow-cytometry using Annexin V-fluorescein isothiocyanate (FITC) and propidium iodide (PI) staining (Figures 5 and 6) and all calculations and further graphs were based on these data
The careful comparative analysis shows that the U937 cell-line induces significant apoptotic cell-death after the water-bath heating conventional hyperthermia (WHT) treatment at 44oC, like as shown in earlier studies with treatment durations of 15min [41]
The waterbath heats with a macroscopic gradient from the surface of the flask to its middle, while the mEHT starts in depth, heating first the selected membrane rafts and meaning that the heat-flow direction is opposite in mEHT than in the WHT (Figure 1)
Summary
The processes are mostly chemical reactions, where energy absorption-emission is a central point. The energy liberated by metabolic activity appears in the bodytemperature, which is very heterogenic by its sources, but is averaged by natural heat-conduction and the connected temperature equalisation. Hyperthermia is a thermal process, defined by a temperature-elevation in the target [1]. The mass- or volume-specific energy absorption (defined by the specific absorption rate [SAR]) increases the temperature. In the definition of hyperthermia, temperature is the obligatory parameter, used for dosing by considering the time for which it was effective [2]. The treatment has to be identified by temperature, or at least by the specific energy absorption rate (SAR) in the target. The temperature and the energy-deposition must be controlled. PEC (Perfect Electrical Conductor) εr=72.5, μ=1, σ=1.2 S/m εr=72.5, μ=1, σ=0.3 S/m εr=2, μ=1, σ=3*10-7 S/m εr=40, μ=1, σ=3*10-6 S/m εr=1, μ=1, σ=0 S/m
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
