| Pulsed electric fields on the order of 100 kilovolts per meter with durations from microseconds to milliseconds create conductive openings in the cytoplasmic membrane of biological cells, facilitating entry of normally excluded substances. A consensus view of the underlying mechanisms has not emerged, but long-pulse, low-field electroporation is a commercially successful technology widely deployed for the introduction of genetic material into cells, and for cell fusion. Bioelectromagnetic theory predicts that pulses with shorter durations and greater amplitudes can perturb the compartmentalized intracellular environment while causing little or no poration of the external membrane. Although considerable attention over many years has been devoted to the study of biological systems in electric fields, only recently has the advanced pulsed power technology required for generating ultra-short, high-field electric pulses been applied to testing this prediction. In this work we demonstrate that nanosecond, megavolt-per-meter pulses, nondestructively and in a dose-dependent manner, cause the release of calcium from intracellular stores, externalize the plasma membrane phospholipid phosphatidylserine, and induce apoptosis (programmed cell death) in Jurkat T lymphoblasts, without permeabilizing the cells. Another mammalian cell line, rat glioma C6, exhibits markedly less sensitivity to these pulse exposures, providing substantiating evidence for the hypothesis that selectivity in nanoelectropulse responses among cell types can be achieved with appropriate pulse regimens. The studies reported here confirm long-standing expectations regarding the intracellular effects of ultra-short, high-field electric pulses based on electrophysical models of membrane-bound biological systems, and point the way toward the experimentally driven development of more detailed and more accurate models. |
