title: Ion transport into cells exposed to monopolar and bipolar nanosecond pulses.
abstract: Experiments with CHO cells exposed to 60 and 300 ns pulsed electric fields with amplitudes in the range from several kV/cm to tens of kV/cm showed a decrease of the uptake of calcium ions by more than an order of magnitude when, immediately after a first pulse, a second one of opposite polarity was applied. This effect is assumed to be due to the reversal of the electrophoretic transport of ions through the electroporated membrane during the second phase of the bipolar pulse. This assumption, however, is only valid if electrophoresis is the dominant transport mechanism, rather than diffusion. Comparison of calculated calcium ion currents with experimental results showed that for nanosecond pulses, electrophoresis is at least as important as diffusion. By delaying the second pulse with respect to the first one, the effect of reverse electrophoresis is reduced. Consequently, separating nanosecond pulses of opposite polarity by up to approximately hundred microseconds allows us to vary the uptake of ions from very small values to those obtained with two pulses of the same polarity. The measured calcium ion uptake obtained with bipolar pulses also allowed us to determine the membrane pore recovery time. The calculated recovery time constants are on the order of 10 μs.
authors.affiliation: Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA. Electronic address: kschoenb@odu.edu.
authors.forename: Karl H
authors.initials: KH
authors.lastname: Schoenbach
authors.affiliation: Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA.
authors.forename: Andrei G
authors.initials: AG
authors.lastname: Pakhomov
authors.affiliation: Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA.
authors.forename: Iurii
authors.initials: I
authors.lastname: Semenov
authors.affiliation: 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.
authors.forename: Shu
authors.initials: S
authors.lastname: Xiao
authors.affiliation: Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA.
authors.forename: Olga N
authors.initials: ON
authors.lastname: Pakhomova
authors.affiliation: Bioeffects Division, 711th Human Performance Wing, Air Force Research Laboratory, Fort Sam Houston, San Antonio, TX 78234, USA.
authors.forename: Bennett L
authors.initials: BL
authors.lastname: Ibey
mesh_terms: D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D003412:Cricetulus; D004058:Diffusion; D004558:Electric Stimulation; D055664:Electrochemical Techniques / Q000379:methods*; D018274:Electroporation / Q000379:methods; D017136:Ion Transport; D008962:Models, Theoretical
chemical_list: D002118:Calcium
keywords: Diffusion; Electrophoresis; Electroporation; Nanosecond pulses; Pore recovery