Characterization of Pressure Transients Generated by Nanosecond Electrical Pulse (nsEP) Exposure

Abstract

The mechanism(s) responsible for the breakdown (nanoporation) of cell plasma membranes after nanosecond pulse (nsEP) exposure remains poorly understood. Current theories focus exclusively on the electrical field, citing electrostriction, water dipole alignment and/or electrodeformation as the primary mechanisms for pore formation. However, the delivery of a high-voltage nsEP to cells by tungsten electrodes creates a multitude of biophysical phenomena, including electrohydraulic cavitation, electrochemical interactions, thermoelastic expansion, and others. To date, very limited research has investigated non-electric phenomena occurring during nsEP exposures and their potential effect on cell nanoporation. Of primary interest is the production of acoustic shock waves during nsEP exposure, as it is known that acoustic shock waves can cause membrane poration (sonoporation). Based on these observations, our group characterized the acoustic pressure transients generated by nsEP and determined if such transients played any role in nanoporation. In this paper, we show that nsEP exposures, equivalent to those used in cellular studies, are capable of generating high-frequency (2.5 MHz), high-intensity (>13 kPa) pressure transients. Using confocal microscopy to measure cell uptake of YO-PRO®-1 (indicator of nanoporation of the plasma membrane) and changing the electrode geometry, we determined that acoustic waves alone are not responsible for poration of the membrane.

Calcium-independent disruption of microtubule dynamics by nanosecond pulsed electric fields in U87 human glioblastoma cells

“…Microtubules also have mechanical properties and can be disrupted by ultrasound and shockwaves606162. Given that nsPEFs have recently been shown to generate mechanical pressure waves63, it is possible that this component of the stimulus might also disrupt microtubules in exposed cells. Future experiments should therefore endeavour to distinguish the relative roles of electrical and mechanical stimuli in the observed microtubule depolymerisation associated with nsPEF exposure.…”

Cellular response to high pulse repetition rate nanosecond pulses varies with fluorescent marker identity

“…Recent experiments have underscored the potential of mechanical stimuli to induce nanoporation-like effects [24]. The activation of stress-induced channels of the plasma membrane may provide a link between the two theories, and a new generation of mechanical spectroscopies with high spatial resolution could allow us to image these effects for the first time [25,26].…”

High frequency application of nanosecond pulsed electric fields alters cellular membrane disruption and fluorescent dye uptake

“…While we used two known channel blockers in association with YO-PRO-1, there is a significant amount of work to be done to elucidate the roles that protein channels play. Recent research has also shown that mechanical stress may induce some or all of the biophysical effects associated with nanoporation [8][9][10] . The improvement of mechanical spectroscopies 11,12 in recent years should prove useful in the investigation of this mechanism.…”