ON THE DYNAMICS OF THE ELECTRIC-FIELD-INDUCED BREAKDOWN IN LIPID-MEMBRANES

Electric field methods are powerful tools for cell characterization an d manipulation. Important biotechnological applications, e.g., electro fusion of cells or electroinjection of macromolecules into living cell s, rely on membrane breakdown, Despite the widespread use of these tec hniques, the process of membrane breakdown is poorly understood: a bet ter understanding can be expected to lead to higher efficiencies, The present study used planar lipid bilayers in order to limit the number of experimental parameters, Membrane rupture was induced by careful ap plication of short electric field pulses: measurement of the subsequen t increase in membrane conductivity with time permitted the underlying mechanism to be characterized, The initial process of pore formation starts a few mu s after the onset of the pulse, and the ensuing breakd own of the entire lipid membrane occurs within about a millisecond (po re widening velocity of a few cm/s). The kinetics of the pore-opening process could be influenced qualitatively by adding surfactants and li pid-attached macromolecules, respectively. Changing the effective mass per unit area of membrane, which could be brought about by using know n percentages of lipids with covalently bound, hydrophilic polymers, a llowed a model for the pore widening process to be quantitatively test ed.