Modulation of biological responses to 2 ns electrical stimuli by field reversal

High-voltage 10 ns delayed paired or bipolar pulses for in vitro bioelectric experiments

“…Consistently with previous studies [2], [9], the bipolar pulse with no delay showed less YP uptake than the unipolar pulse, i.e., bipolar cancellation. Reduction of this cancellation has been observed when a delay is introduced between the two phases of the pulse, however delays of µs duration still result in less uptake than a unipolar pulse [1], [4], [8].…”

“…It was shown that bipolar pulses in the nanosecond range produce cancellation of the bioeffects classically observed when applying unipolar pulses [1]- [6]. This phenomenon was largely assessed with pulse durations from 60 ns [1], [3], [7] to 900 ns [8], and more recently for 2 ns [9], for different cell lines (CHO, Jurkat, U937, or excitable cells like chromaffin cells) and for a wide range of endpoints such as YO-PRO™-1 (YP) uptake, Ca 2+ transients, cell death, calcein efflux, nerve excitation, or phosphatidylserine externalization. Cancellation with nanosecond pulsed electric fields (nsPEF) was observed with both symmetric, where the front pulse is followed by a negative polarity pulse of the same duration and amplitude [1], [4], [10] and asymmetric, where the front pulse is followed by a negative polarity pulse of different duration and/or amplitude [10].…”

Paradoxical effects on voltage-gated Na+ conductance in adrenal chromaffin cells by twin vs single high intensity nanosecond electric pulses

“…This is analogous to the phenomenon of bipolar cancellation whereby the application of a second nanosecond pulse of opposite polarity can attenuate or abolish a cellular response (Ca 2+ transient, electronanoporation, fluorescent dye uptake, etc.) triggered by the corresponding unipolar pulse [25][26][27][28][29][30][31][32][33].…”

“…One plausible hypothesis is that twin NEPs produced a transient suppression of the number of active channels through perturbations of the lipid bilayer closely interacting with the channel protein. This suggestion is based on a number of indirect observations from our group and others: 1) theoretical molecular dynamics studies [34][35][36] demonstrated that high intensity NEPs are capable of triggering the formation of hydrophilic nanopores in the phospholipid bilayer that lower the energy barrier for ion conduction across the membrane; 2) single or multiple NEPs of various durations are known to cause important perturbations of the lipid bilayer, a process called electronanoporation, that allows the membrane to become permeable not only to ions [37,38] but in some cell types also to fluorescent organic molecules such as propidium iodide and YO-PRO-1 [25,26,29,33,[38][39][40][41][42]. Even though the application of up to ten 5 ns pulses does not lead to YO-PRO-1 uptake in chromaffin cells [23], a non-selective membrane conductance (I leak ) permeable to Na + could be elicited by a single 5 ns pulse in chromaffin cells clamped near the resting membrane potential (-70 mV) in these cells [5], which has also been detected for longer NEPs in GH3 and NG108 cells [7,8] and also in bovine chromaffin cells [8].…”

Probing Nanoelectroporation and Resealing of the Cell Membrane by the Entry of Ca2+ and Ba2+ Ions

“…Nowadays, electropermeabilization research has expanded to the nanosecond-range pulsed electric fields (nsPEFs), revealing new and different bioeffects. Specifically, nsPEFs are distinguished (1) by the ability to disrupt intracellular membranous structures, such as endoplasmic reticulum and mitochondria [6][7][8][9], (2) by the phenomenon of bipolar cancellation, which stands for the suppression of diverse bioeffects upon the nsPEF polarity reversal [10][11][12][13], and (3) by the predominant formation of smaller membrane defects, often referred to as "nanopores" or "nanoelectropores," although the exact nature of these defects remains uncertain [4,9,[14][15][16][17][18]. Nanopores may remain open for minutes, and demonstrate complex conductive properties unexpected from simple "holes" in a lipid bilayer, including inward rectification, current and voltage sensitivity, and ion selectivity [15,16].…”