Biophysics and metrology of electroporation in tissues

Abstract

High-voltage pulses change the electrical properties of cells and tissue. The most sensitive targets are membrane structures charging up due to their high resistance. With achievement of a critical transmembrane voltage, structural rearrangements yield conductive, aqueous pores across the lipids able to transport ions but also larger polar molecules. Moreover, due to high current density, Joule heating can induce further reversible or nonreversible changes. Practical applications rely on optimal pulse conditions which require objective measures of the reaction to the stimulus. Since the electrically induced changes and the recovery after exposure to electric pulses take place on a time scale of microseconds up to minutes, only fast measurements are relevant. Postprocessing may be used to measure electroporation yield, time course, and level of recovery or information about localized heating. Here, fast electrical measurement methods before and after but also during the presence of elevated electric field are revised from theory up to basics for data mining. Fast impedance measurement presented here bases on time domain approach with multisinus or step excitation rather than frequency sweep in frequency domain. Spatially resolved temperature measurements with time resolution compatible with millisecond pulse duration are described. Merging electrical and thermal action, a model for synergistic effect, is presented.