Cell Swelling and Membrane Permeabilization after Nanoelectropulse Exposure

Abstract

Nanosecond, megavolt-per meter, pulsed electric field (nanoelectropulse) technology—a low-energy, nondestructive means for transiently electropermeabilizing biological cell membranes—is used in cancer therapy, genetic engineering, and cell biology. The effects of nanoelectropulses on the plasma membrane have been widely investigated. Opening of stable, long-lasting, lipid nanopores, selective uptake of fluorescence dyes, phosphatidylserine externalization, and cell volume change (swelling) due to water molecules uptake have been observed and reported. In particular, cell swelling has been recently introduced as a sensitive method for characterizing plasma membrane permeabilization. In this work, a systematic description and analysis of the cell swelling phenomenon is presented. Human Jurkat T lymphoblasts were exposed to 3 ns and 5 ns pulses from two different pulse generators, with different electrical characteristics. These pulse widths are much shorter than those reported previously. Different pulse counts (0, 1, 3, 5, 10, 20, 30, 50) and repetition rates (1 Hz or 1 kHz) were tested. In addition, to understand the types of pores formed by nanoelectropulses, swelling was induced in the presence of lanthanide ions (Gd3+ and La3+) and Hg2+, which are known to act on specific membrane channels. Mechanisms of nanoelectropulse-induced swelling will be discussed, and an empirical equation will be developed to describe the effects of different pulse parameters on cell membrane electropermeabilization.