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Electropermeabilization by uni- or bipolar nanosecond electric pulses: The impact of extracellular conductivity.

Authors
  • Gianulis, Elena C1
  • Casciola, Maura2
  • Xiao, Shu3
  • Pakhomova, Olga N2
  • Pakhomov, Andrei G2
  • 1 Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA. Electronic address: [email protected]
  • 2 Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA.
  • 3 Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA; Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23508, USA.
Type
Published Article
Journal
Bioelectrochemistry (Amsterdam, Netherlands)
Publication Date
Feb 01, 2018
Volume
119
Pages
10–19
Identifiers
DOI: 10.1016/j.bioelechem.2017.08.005
PMID: 28865240
Source
Medline
Keywords
License
Unknown

Abstract

Cellular effects caused by nanosecond electric pulses (nsEP) can be reduced by an electric field reversal, a phenomenon known as bipolar cancellation. The reason for this cancellation effect remains unknown. We hypothesized that assisted membrane discharge is the mechanism for bipolar cancellation. CHO-K1 cells bathed in high (16.1mS/cm; HCS) or low (1.8mS/cm; LCS) conductivity solutions were exposed to either one unipolar (300-ns) or two opposite polarity (300+300-ns; bipolar) nsEP (4-40kV/cm) with increasing interpulse intervals (0.1-50μs). Time-lapse YO-PRO-1 (YP) uptake revealed enhanced membrane permeabilization in LCS compared to HCS at all tested voltages. The time-dependence of bipolar cancellation was similar in both solutions, using either identical (22kV/cm) or isoeffective nsEP treatments (12 and 32kV/cm for LCS and HCS, respectively). However, cancellation was significantly stronger in LCS when the bipolar nsEP had no, or very short (<1μs), interpulse intervals. Finally, bipolar cancellation was still present with interpulse intervals as long as 50μs, beyond the time expected for membrane discharge. Our findings do not support assisted membrane discharge as the mechanism for bipolar cancellation. Instead they exemplify the sustained action of nsEP that can be reversed long after the initial stimulus.

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