On the dynamics of the electric field induced breakdown in lipid membranes

Electric fields deliver a unique tool for cell characterization or manipulation. Important biotechnological applications are e.g. electrofusion of cells or electroinjection of macromolecules into living cells. Despite the widespread use little is known about the underlying processes. From a better understanding higher efficiencies are expected. To limit the number of parameters the authors perform a study on planar lipid bilayers. Optical black lipid membranes were formed in the usual way. Rupture was induced by a careful application of short electric field pulses. The measurement of the subsequent increase in membrane conductivity with time allowed conclusions to be made on the underlying mechanism. The initial process of pore formation starts statistically distributed a few μsec after the onset of the pulse. The following rupture of the entire lipid membrane is a fast process with an opening velocity of a few cm/s. Decreasing the surface tension of the lipid film by adding surfactant molecules slowed down the rupture. Adsorption of macromolecules decreased the opening velocity. A quantitative measurement was possible by inserting specific amounts of lipids with covalently bound polymers