Electroporative deformation of salt filled lipid vesicles

Kakorin S, Redeker E, Neumann E. Electroporative deformation of salt filled lipid vesicles. EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS. 1998;27(1):43-53.Membrane electroporation, vesicle shape deformation and aggregation of small, NaCl-filled lipid vesicles (of radius a = 50 nm) in DC electric fields was characterized using conductometric and turbidimetrical data, At pulse durations t(E) less than or equal to 55 +/- 5 ms the increase in the conductivity of the vesicle suspension is due to the field-induced efflux of electrolyte through membrane electropores. Membrane electroporation and Maxwell stress on the vesicle membrane lead to vesicle elongation concomitant with small volume reduction (up to 0.6% in an electric field of E = 1 MV m(-1)). At t(E) > 55 +/- 5 ms, further increases in the conductivity and the optical density suggest electroaggregation and electrofusion of vesicles. The conductivity changes after the electric pulse termination reflect salt ion efflux through slowly resealing electropores, The analysis of the volume reduction kinetics yields the bending rigidity kappa = (4.1 +/- 0.3) . 10(-20) J of the vesicle membrane, If the flow of Na+ and Cl(-)ions from the vesicle interior is treated in terms of Hagen-Poiseuille's equation, the number of permeable electropores is N = 39 per vesicle with mean pore radius r(p) = 0.85 +/- 0.05 nm at E = 1 MV m(-1) and t(E) less than or equal to 55 +/- 5 ms. The turbidimetric and conductometric data suggest that small lipid vesicles (a less than or equal to 50 nm) are not associated with extensive membrane thermal undulations or superstructures, In particular with respect to membrane curvature, the vesicle results are suggestive for the design and optimization of electroporative delivery of drugs and genes to cell tissue at small field strengths (less than or equal to 1 MV m(-1)) and large pulse durations (less than or equal to 100 ms)