Electro-Deformation and Poration of Giant Vesicles Viewed with High Temporal Resolution.pdfVIP

Biophysical Journal Volume 88 February 2005 1143–1155 1143 Electro-Deformation and Poration of Giant Vesicles Viewed with High Temporal Resolution Karin A. Riske and Rumiana Dimova Max Planck Institute of Colloids and Interfaces, 14476 Golm, Germany ABSTRACT Fast digital imaging was used to study the deformation and poration of giant unilamellar vesicles subjected to electric pulses. For the ?rst time the dynamics of response and relaxation of the membrane at micron-scale level is revealed at a time resolution of 30 ms. Above a critical transmembrane potential the lipid bilayer ruptures. Formation of macropores (diameter ;2 mm) with pore lifetime of ;10 ms has been detected. The pore lifetime has been interpreted as interplay between the pore edge tension and the membrane viscosity. The reported data, covering six decades of time, show the following regimes in the relaxation dynamics of the membrane. Tensed vesicles ?rst relax to release the acquired stress due to stretching, ;100 ms. In the case of poration, membrane resealing occurs with a characteristic time of ;10 ms. Finally, for vesicles with excess area an additional slow regime was observed, ;1 s, which we associate with relaxation of membrane curvature. Dimensional analysis can reasonably well explain the corresponding characteristic timescales. Being performed on cell-sized giant unilamellar vesicles, this study brings insight to cell electroporation. The latter is widely used for gene transfection and drug transport across the membrane where processes occurring at different timescales may in?uence the ef?ciency. INTRODUCTION The interaction of electric ?elds with lipid membranes and cells has been extensively studied in the last decades (Neumann et al., 1989; Chang et al., 1992). The phenomenon of electroporation is of particular interest, because of its vast use in cell biology and biotechnology (Kinosita and Tsong, 1977; Chang et al., 1992; Zimmermann and Neil, 1996). Strong electric pulses of short dur