Conductometric and electrooptic relaxation spectrometry of lipid vesicle electroporation at high fields

Abstract

Electrooptic and conductometric relaxation spectrometry of lipid unilamellar vesicles (Avanti 20) of radius a ¼ 90 nm, filled with 0.2 M NaCl electrolyte, suspended in low conductive 0.33 M sucrose and 0.2 mM NaCl solution of vesicle number density r v % 2.4 Â 10 15 L À1 and exposed to a rectangular electric field pulse (up to E ¼ 7.5 MV m À1 , pulse duration t E ¼ 10 ms) has been used to quantify the structural changes involved in membrane electroporation (ME) and rapid membrane transport, sometimes also called electropermeation (MP), as well as extent and rate of shape deformations. The data are consistent with the formation of ionconductive membrane pores contributing to conductance not only via the ionic vesicle interior but also by releasing intravesicular electrolyte through the pores during the electric pulse, dominantly by interactive electrodiffusion. The surface area fraction f p and the conductivity l p of the membrane pores increase with increasing field strength, 0 E/MV m À1 7.5, in the ranges 0 f p 1.4 Â 10 À2 and 0 l p /S m À1 2.7 Â 10 À3 , respectively. The data analysis suggests that electrostatic interactions between the ions and the low dielectric pore wall are the origin of the very small values of the Nernst distribution coefficient, e.g. g g ¼ 6.6 Â 10 À4 at E ¼ 7.5 MVm À1 . The pore conductivity l p and g g are non-linear functions of the applied electric field, yielding a field-independent pore transport length l p ¼ 0.56 nm. In summary, the new analytical proposal establishes quantitative relationships between structural electroporation quantities and characteristic parameters of the small ion transport or electropermeation.

Lipid membranes in external electric fields: Kinetics of large pore formation causing rupture

“…In the latter case, the membrane tension (the driving force for the opening) relaxes as the pore widens, and so vesicles can close due to the finite edge energy. A larger number of experiments have been devoted to characterize electroporation of vesicles [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79]. In particular, application of mechanical stress using micropipettes combined with electric field pulses allows to point out the balance between both type of forces [80,81].…”

Interaction of Silica Nanoparticles with Phospholipid Membranes

“…12 In addition, it has been found that resealing after electroporation of a lipid membrane takes milliseconds to seconds. 13,14 Thus, if a single particle is able to disrupt a membrane, 100% leakage can be expected if the concentration of the particles is close to one particle per vesicle or more. Conversely, if leakage below 100% is found and the particle concentration is well above one particle per vesicle, then more than one particle is needed to disrupt the vesicle membrane.…”

Giant vesicles in electric fields

“…13,14 A few other experiments have been performed but mainly with small vesicles, which are hundreds of nanometres in size. 45,51,52 Poration of small vesicles induced by DC pulses has attracted stronger interest. [52][53][54][55] Because of the small size of the vesicles, direct observation of the deformation and poration is not feasible.…”