Electric Field Redistribution due to Conductivity Changes during Tissue Electroporation: Experiments with a Simple Vegetal Model

Electroporation, or electropermeabilization, is the phenomenon in which cell membrane permeability to ions and macromolecules is increased by exposing the cell to short high electric field pulses. In living tissues, such permeabilization boost can be used in order to enhance the penetration of drugs (electrochemotherapy) or DNA plasmids (electrogenetherapy) or to destroy undesirable cells (irreversible electroporation). During the application of the high voltage pulses required for in vivo electroporation treatments, the conductivity of the involved tissues increases due to the electroporation phenomenon. This alteration results in a redistribution of the electric field magnitude that should be taken into account at treatment planning in order to foresee the areas that will be treated by electroporation. In the last five years some authors have indeed started to include such conductivity alteration in their simulation models. However, little experimental evidence has been provided to support the fact that conductivity changes really have a significant role on the electric field distribution. By reporting experiments on potato tuber, here we show that conductivity increase due to electroporation has indeed a significant physiological effect on the result of the application of the pulses. For instance, we noticed that by taking into account such conductivity alteration during simulations the error in electroporated area estimation went down from 30 % to 3 % in a case in which electroporation was performed with two parallel needles. Furthermore we also show that the field redistribution process occurs in two stages: an immediate and fast (< 5 μs) redistribution after the pulse onset, probably only held up by the cell membrane charging process, and a slower, and less significant, redistribution afterwards probably related to slow, and moderate, changes in tissue conductivity during the pulse.