Bipolar Cancellation of Cell Membrane Electroporation by Nanosecond Pulsed Electric Field

At present, some of the most promising techniques for cell ablation, stimulation, and excitation are based on utilizing nanosecond pulsed electric field (nsPEF). NsPEF can activate or inhibit voltage-gated ion channels, cause cytoskeleton rearrangements, osmotic stress, cell swelling and blebbing, and apoptotic or necrotic cell death without appreciable heating. NsPEF is distinguished by a negligible formation of harmful electrochemical byproducts at the electrode-tissue interface and can even be delivered by antennas without a contact. Another unique feature of nsPEF (may include the lower µs range) is a phenomenon of bipolar cancellation, which stands for suppression of nsPEF effects by switching the stimulus polarity. Our team was the first to discover that the electric field reversal weakens nsPEF effects. The goal of this study was to investigate how the bipolar cancellation efficiency (ratio of cell responses to unipolar and bipolar nsPEF stimulations) depends on nsPEF parameters: pulse duration, electric strength field, pulse number, frequency, the ratio of the first and second nsPEF phases, and the angle between the electric field vectors given by each phase. Experiments consisted of the cell membrane electroporation by applying nsPEF through needle electrodes to a monolayer of BPAE cells. Electroporation in exposed cell monolayers was quantified by fluorescence imaging with YO-PRO-1 dye. We found that the efficiency of bipolar cancellation for 600ns bipolar nsPEF reached maximum values from 5 to 6 when the amplitude of nsPEF second phase equals 50-75% of the first one. An increase in the number of pulses (from 5 to 15) didn\u27t affect cancellation with 50% bipolar nsPEF. However, bipolar nsPEF with a shorter duration (down to 300ns) and higher frequency (up to 833kHz) were more efficient at cancellation. The angle between the electric field vectors of two nsPEF delivered one after another determined whether the effect is canceled (with the vectors pointing in the opposite directions) or enhanced (when the vectors pointed in the same direction). These results are essential to improve the efficiency of remote stimulation protocols by nsPEF