Theory of electroporation

Abstract

Experiments conducted on artificial bilayers, suspensions of vesicles or cells, and tissues have demonstrated that a large, externally induced transmembrane potential (V m) causes an increase in the conductivity of the membrane by five to six orders of magnitude.1-3 This effect is generally attributed to the creation of pores, which are the aqueous pathways in the lipid bilayer of the membrane, and whose creation and subsequent growth are facilitated by large V m. This process, called electroporation, can be irreversible, leading to a mechanical rupture of the membrane,2,4 or reversible, in which case pores reseal and the same membrane can experience multiple episodes of the high conductivity state. 1,3 Electroporation occurs as an undesirable side effect following the delivery of defibrillation shocks to the heart5-10 and may be responsible for the late necrosis after accidental exposure to high voltage.11 On the other hand, the transient state of high membrane permeability has important practical applications, allowing the fusion of cells and the introduction of biologically active substances (drugs or genetic material) into cells.12-17 Because of great interest in this method, studies use a variety of experimental techniques to provide insight into the processes taking place during electroporation. These techniques include measuring the time course of transmembrane voltage1 or current though the membrane,3,18 monitoring uptake or leakage of fluorescent molecules,19-21 imaging the transmembrane potential, 8,10,22 measuring the tissue impedance,23,24 and observing pores with rapid-freezing electron microscopy.25 However, electroporation is difficult to observe directly because pores are very small (nanometers) and their creation and growth is very fast (microseconds), and many questions cannot be answered with available experimental techniques. Thus, there is a need to supplement experimental knowledge with a theoretical model. © 2009 Springer US.