Bipolar cancellation refers to a phenomenon when applying a second electric pulse reduces (“cancels”) cell membrane damage by a preceding electric pulse of the opposite polarity. Bipolar cancellation is a reason why bipolar nanosecond electric pulses (nsEP) cause weaker electroporation than just a single unipolar phase of the same pulse. This study was undertaken to explore the dependence of bipolar cancellation on nsEP parameters, with emphasis on the amplitude ratio of two opposite polarity phases of a bipolar pulse. Individual cells (CHO, U937, or adult mouse ventricular cardiomyocytes (VCM)) were exposed to either uni- or bipolar trapezoidal nsEP, or to nanosecond electric field oscillations (NEFO). The membrane injury was evaluated by time-lapse confocal imaging of the uptake of propidium (Pr) or YO-PRO-1 (YP) dyes and by phosphatidylserine (PS) externalization. Within studied limits, bipolar cancellation showed little or no dependence on the electric field intensity, pulse repetition rate, chosen endpoint, or cell type. However, cancellation could increase for larger pulse numbers and/or for longer pulses. The sole most critical parameter which determines bipolar cancellation was the phase ratio: maximum cancellation was observed with the 2nd phase of about 50% of the first one, whereas a larger 2nd phase could add a damaging effect of its own. “Swapping” the two phases, i.e., delivering the smaller phase before the larger one, reduced or eliminated cancellation. These findings are discussed in the context of hypothetical mechanisms of bipolar cancellation and electroporation by nsEP.

双极消除是指当施加第二电脉冲减少（“取消”）先前相反极性的电脉冲对细胞膜的损害时的现象。双极抵消是双极纳秒电脉冲（nsEP）导致电穿孔弱于同一脉冲的单个单极相的原因。进行这项研究以探索双极抵消对nsEP参数的依赖性，并着重于双极脉冲的两个相反极性相位的振幅比。将单个细胞（CHO，U937或成年小鼠心室心肌细胞（VCM））暴露于单极或双极梯形nsEP或纳秒电场振荡（NEFO）。通过延时共聚焦成像对丙啶（Pr）或YO-PRO-1（YP）染料的摄取以及磷脂酰丝氨酸（PS）的外在作用来评估膜损伤。在所研究的范围内，双极消除对电场强度，脉冲重复频率，选择的终点或细胞类型几乎没有依赖性。但是，对于较大的脉冲数和/或较长的脉冲，抵消可能会增加。决定双极性消除的唯一最关键的参数是相位比：第二相的最大消除约为第一相的50％，而较大的第二相可能会增加其自身的破坏作用。“交换”两个阶段，即在较大的阶段之前传递较小的阶段，减少或消除了抵消。