Nanosecond pulsed electric field (nsPEF) application effects on human cells: intracellular membrane disruption and apoptosis induction

Abstract

Summary form only given. Pulse power technology using high intensity (up to 300 kV/cm) nanosecond pulsed electric fields (nsPEF) has been applied for bacterial decontamination, but until now effects on human cells have not been investigated. To analyze the effects of nsPEF on human cells and solid tumors, we have utilized several methods [electron and fluorescence microscopy; flow cytometry; biochemical (enzymes), molecular (DNA), and cell morphologic assays; and real time fluorescence microscopy to analyze cellular events milliseconds after pulsing]. We provide biological proof for the hypothesis that as the pulse duration is decreased, there is a lower incidence of electric field interactions that modify the plasma membrane and a higher incidence of interactions that modify intracellular structures. Unlike electroporation, nsPEF target intracellular structures without damage to the plasma membrane. The nsPEF effects are pulse duration/electric field intensity-dependent and energy density- or temperature-independent. Low intensity electric fields appear to enhance cell function. Here we focus on high electric fields that induce programmed cell death or apoptosis in cells and tumors in mice. Mitochondria, and probably nucleus/DNA and membrane pump mechanisms, are intracellular targets that contribute to cell death. Because human disease almost always reveals an aberrant component of apoptosis, the ability to modulate apoptosis provides new applications for nanosecond pulse technology that will join other therapies to modulate apoptosis that will appear in clinical practice over the next several years. Use of nsPEF technology on human cells significantly extends the boundaries defined by electroporation. In addition to therapeutic application, we also are developing this technology for application as a basic science tool to selectively target intracellular structures by tuning the pulses based on electric field intensity, pulse duration, frequency distribution, and pulse train length.