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4 March 2019 Evaluation of membrane potential changes induced by unipolar and bipolar nanosecond pulsed electric fields
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Abstract
Nanosecond pulsed electric field (nsPEF) exposure to cells causes a myriad of bioeffects with great potential to translate into beneficial technology. However, a general lack of fundamental knowledge of how the field is interacting with the cell limits the advancement of predictive models and maximal exploitation. Despite 30 years of research, this same dearth of mechanistic understanding remains for longer pulse exposures. Fundamental to determining what is occurring as these strong electric fields are applied to cells is measuring the induced change in membrane potential on the time scale of the exposure. Such measurements are critical to validating commonly used electric circuit-based continuum models for electroporation, but have remained elusive due to limits in signal-to-noise and fluorescent reporters. In a previous publication, we described a high-speed fluorescent imaging modality that combined a streak camera and a high power laser source termed a high speed streak camera microscope (SCM) to resolve membrane charging during a single nsPEF. In this paper, we use the SCM to quantify changes in membrane potential in CHO-K1 cells exposed to unipolar and bipolar 600ns PEF within the context of the recently discovered “bipolar cancellation” phenomenon. Immediately after a unipolar pulse exposure, we see a prolonged “depolarization” of the cell that is roughly 50-100mV in amplitude. Such a prolonged depolarization is not seen in bipolar exposures nor is it predicted by membrane charging models. We postulate that this lasting membrane depolarization, seen only in unipolar pulse exposure, is either the cause of later uptake of impermeable ions or signifies the acute (during the pulse) breakdown of the plasma membrane (nanoporation). The lack of lasting depolarization in bipolar pulse exposures may be fundamental to “bipolar cancellation” and explain why uptake of ions is substantially reduced as compared to unipolar pulse exposures.
© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Bennett L. Ibey, Joel N. Bixler, Caleb C. Roth, and Hope T. Beier "Evaluation of membrane potential changes induced by unipolar and bipolar nanosecond pulsed electric fields", Proc. SPIE 10889, High-Speed Biomedical Imaging and Spectroscopy IV, 1088913 (4 March 2019); https://doi.org/10.1117/12.2511189
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