Bipolar nanosecond electric pulses are less efficient at electropermeabilization and killing cells than monopolar pulses

• Published in: Biochemical and biophysical research communications 2014-01, Vol.443 (2), p.568-573
• Main Authors: Ibey, Bennett L., Ullery, Jody C., Pakhomova, Olga N., Roth, Caleb C., Semenov, Iurii, Beier, Hope T., Tarango, Melissa, Xiao, Shu, Schoenbach, Karl H., Pakhomov, Andrei G.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - radiation effects; Bipolar; Calcium; Cell Membrane Permeability - physiology; Cell Membrane Permeability - radiation effects; CHO; CHO Cells; Cricetinae; Cricetulus; Dose-Response Relationship, Radiation; Electric Stimulation - methods; Electromagnetic Fields; Electroporation - methods; FM1-43; Humans; Jurkat Cells; Monopolar; Nanosecond electric pulse; Radiation Dosage
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2013.12.004

•Bipolar nanosecond pulses are less effective at plasma membrane permeabilization.•Bipolar nanosecond pulses are much less effective at killing cells.•Cell electropermeabilization is not solely dependent on peak electric field. Multiple studies have shown that bipolar (BP) electric pulses in the microsecond range are more effective at permeabilizing cells while maintaining similar cell survival rates as compared to monopolar (MP) pulse equivalents. In this paper, we investigated whether the same advantage existed for BP nanosecond-pulsed electric fields (nsPEF) as compared to MP nsPEF. To study permeabilization effectiveness, MP or BP pulses were delivered to single Chinese hamster ovary (CHO) cells and the response of three dyes, Calcium Green-1, propidium iodide (PI), and FM1-43, was measured by confocal microscopy. Results show that BP pulses were less effective at increasing intracellular calcium concentration or PI uptake and cause less membrane reorganization (FM1-43) than MP pulses. Twenty-four hour survival was measured in three cell lines (Jurkat, U937, CHO) and over ten times more BP pulses were required to induce death as compared to MP pulses of similar magnitude and duration. Flow cytometry analysis of CHO cells after exposure (at 15min) revealed that to achieve positive FITC-Annexin V and PI expression, ten times more BP pulses were required than MP pulses. Overall, unlike longer pulse exposures, BP nsPEF exposures proved far less effective at both membrane permeabilization and cell killing than MP nsPEF.