Kinetics of the electroporative deformation of lipid vesicles and biological cells in an electric field

Abstract

AbstractThe 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 τ and 2τ, respectively. It is found that τ is proportional to E2·a9, 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 κ = 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 ≤ tE/ms ≤ 60, the number of water‐permeable electropores is found to be N=35±5 per vesicle of radius rp = 50 nm with mean pore radius rp=0.9±0.1 nm.The kinetic analysis developed here for vesicles is readily applied to cell membranes, aiming at physicalchemical guidelines to optimize the membrane electroporation techniques for the direct transfer of drugs and genes into tissue cells.