Intense, nanosecond-duration electric pulses (nsEP) have been introduced as a novel modality to alter cellular function,
with a mechanism of action qualitatively different from micro- and millisecond duration pulses used in electroporation.
In this study, we determined the thresholds for plasma membrane injury (within 15 minutes) and cell death (at 24 hours)
for 4 different cell types (CHO-K1, HeLa, Jurkat and U937). Plasma membrane injury was measured by flow cytometry
using two fluorescent dyes, namely Annexin V-FITC, which binds to phosphatidylserine (PS) upon its externalization
(subtle membrane injury), and propidium iodide (PI), which is typically impermeable to the cell, but enters when large
pores are formed in the plasma membrane. In all cell types, 10-ns pulses caused phosphatidylserine (PS) externalization
at low doses (<150kV/cm and 100 pulses for each cell type) and no PI uptake. Jurkat and U937 cell lines showed
substantial cell death without uptake of PI (15 minutes post exposure) suggesting either delayed permeabilization due to
swelling, or damage to intracellular components. In CHO-K1 and HeLa cell lines, PI uptake occurred at low doses
relative to that necessary to cause cell death suggesting a necrotic death similar to longer pulse exposures. These findings
suggest that nanosecond pulses may be beneficial in applications that require selective elimination of specific cell types.