PUB - Publikationen an der Universität Bielefeld

The electric conductivity of a suspension of unilamellar lipid vesicles of phosphatidylcholine and phosphatidylglycerol. filled with electrolyte, increases after exposure to external field pulses. The electrolyte efflux through the electropores is described in terms of volume decrease under Maxwell stress at constant membrane surface area. Applying the Hagen-Poiseuille Ansatz, the exact analytical solution for the kinetics of the electromechanical vesicle deformation is obtained in terms of a LambertW function. The initial and final phases of the volume decrease can be approximated by exponential functions with the time constants tau and 2 tau, respectively. It is found that tau is proportional to E-2.a(9), describing the extreme sensitivity of the deformation to the vesicle radius a in electric field of strength E. The kinetic analysis yields the membrane bending rigidity kappa=3.0+/-0.3.10(-20) J, At the field strength E=1.0 MV m(-1) and in the range of pulse duration 5 less than or equal to t(E)/ms less than or equal to 60, the number of water-permeable electropores is found to be N=35+/-5 per vesicle of radius a=50 nm with mean parr radius r(p)=0.9+/-0.1 nm. The kinetic analysis developed here for vesicles is readily applied to cell membranes, aiming at physical-chemical guidelines to optimize the membrane electroporation techniques for the direct transfer of drugs and genes into tissue cells.