Cell membrane permeabilization and death caused by subnanosecond electric pulses

Subnanosecond electric pulses (200 ps) at an electric field intensity of 25 kV/cm induce the death of B16 skin melanoma cells. We have observed 20% cell death after the exposure to 1.8 million pulses. The cytotoxic effect is due to the electric field effect coupled with temperature rise. A higher number of pulses, 2.4 million, causes 90% cell death, which is largely due to hyperthermia. When exposed to a much lower number of pulses (2000 pulses), NG108 cells exhibit an increase in membrane conductance, which allows a leakage current to flow from the extracellular medium to the interior of the cell. Such an increase of rectified current is likely due to pores of nanometer size being formed in the cell membrane. The pore formation is a nonthermal process, as the temperature rise due to the pulsing is negligible. The pores are not associated with cell death, as the number of pulses is much less than that required for cell killing.