Case for applying subnanosecond high-intensity, electrical pulses to biological cells

The Action of the Pulsed Electric Field of the Subnanosecond Range on Human Tumor Cells

The action of the pulsed electric field of the subnanosecond range on Jurkat, HEK 293, and U-87 MG human cell lines was studied. The cells were treated in a waveguide in 0.18 ml electrodeless Teflon cuvettes. The electric field strength in the cell culture medium was ~2 kV/cm, the pulse duration was ~1 ns, the leading edge was 150 ps, the frequency was 100 Hz, and the treatment time was 5 min. According to estimates, the change of the transmembrane potential during the pulse was ~20 mV and we assume that it was insufficient for electroporation. Jurkat and HEK 293 cells appeared to be more resistant to the treatment than U-87 MG cells. We have observed that the impulses with the above-mentioned parameters can cause a noticeable change in the mitochondrial activity of U-87 MG cells. © 2022 Bioelectromagnetics Society.

Nonlinear dispersive cell model for microdosimetry of nanosecond pulsed electric fields

For applications based on nanosecond pulsed electric fields (nsPEFs), the underlying transmembrane potential (TMP) distribution on the plasma membrane is influenced by electroporation (EP) of the plasma membrane and dielectric dispersion (DP) of all cell compartments which is important for predicting the bioelectric effects. In this study, the temporal and spatial distribution of TMP on the plasma membrane induced by nsPEFs of various pulse durations (3 ns, 5 ns unipolar, 5 ns bipolar, and 10 ns) is investigated with the inclusion of both DP and EP. Based on the double-shelled dielectric spherical cell model, the Debye equation describing DP is transformed into the time-domain form with the introduction of polarization vector, and then we obtain the time course of TMP by solving the combination of Laplace equation and time-domain Debye equation. Next, the asymptotic version of the Smoluchowski equation is included to characterize the EP of plasma membrane in order to observe more profound electroporation effects with larger pore density and electroporated areas in consideration of both DP and EP. Through the simulation, it is clearer to understand the relationship between the applied nsPEFs and the induced bioelectric effects.

A Microdosimetric Study of Electropulsation on Multiple Realistically Shaped Cells: Effect of Neighbours

Over the past decades, the effects of ultrashort-pulsed electric fields have been used to investigate their action in many medical applications (e.g. cancer, gene electrotransfer, drug delivery, electrofusion). Promising aspects of these pulses has led to several in vitro and in vivo experiments to clarify their action. Since the basic mechanisms of these pulses have not yet been fully clarified, scientific interest has focused on the development of numerical models at different levels of complexity: atomic (molecular dynamic simulations), microscopic (microdosimetry) and macroscopic (dosimetry). The aim of this work is to demonstrate that, in order to predict results at the cellular level, an accurate microdosimetry model is needed using a realistic cell shape, and with their position and packaging (cell density) characterised inside the medium.

Microdosimetric study for nanosecond pulsed electric fields on a cell circuit model with nucleus

Recently, scientific interest in electric pulses, always more intense and shorter and able to induce biological effects on both plasma and nuclear membranes, has greatly increased. Hence, microdosimetric models that include internal organelles like the nucleus have assumed increasing importance. In this work, a circuit model of the cell including the nucleus is proposed, which accounts for the dielectric dispersion of all cell compartments. The setup of the dielectric model of the nucleus is of fundamental importance in determining the transmembrane potential (TMP) induced on the nuclear membrane; here, this is demonstrated by comparing results for three different sets of nuclear dielectric properties present in the literature. The results have been compared, even including or disregarding the dielectric dispersion of the nucleus. The main differences have been found when using pulses shorter than 10 ns. This is due to the fact that the high spectral components of the shortest pulses are differently taken into account by the nuclear membrane transfer functions computed with and without nuclear dielectric dispersion. The shortest pulses are also the most effective in porating the intracellular structures, as confirmed by the time courses of the TMP calculated across the plasma and nuclear membranes. We show how dispersive nucleus models are unavoidable when dealing with pulses shorter than 10 ns because of the large spectral contents arriving above 100 MHz, i.e., over the typical relaxation frequencies of the dipolar mechanism of the molecules constituting the nuclear membrane and the subcellular cell compartments.

Novel passive element circuits for microdosimetry of nanosecond pulsed electric fields

Microdosimetric models for biological cells have assumed increasing significance in the development of nanosecond pulsed electric field technology for medical applications. In this paper, novel passive element circuits, able to take into account the dielectric dispersion of the cell, are provided. The circuital analyses are performed on a set of input pulses classified in accordance with the current literature. Accurate data in terms of transmembrane potential are obtained in both time and frequency domains for different cell models. In addition, a sensitivity study of the transfer function for the cell geometrical and dielectric parameters has been carried out. This analysis offers a new, simple, and efficient tool to characterize the nsPEFs' action at the cellular level.