Bursting Instability of Charged Multicomponent Vesicles Subjected to Electric Pulses

Abstract

Strong electric pulses applied to neutral phosphatidylcholine (PC) giant vesicles induce the formation of pores, which typically reseal within milliseconds [1]. Here, we study the response of vesicles containing PC and negatively charged phospatidylglycerol (PG) to such pulses. Vesicles composed of 1:1 PG:PC in buffered solution of Hepes and EDTA exhibit the same behavior as observed with PC, namely, the electroporated membrane reseals. Surprisingly, when the medium is changed to a non-buffered solution with or without salt, the vesicles burst and disintegrate to tubular structures after the pulse is applied. Vesicle bursting is abolished when EDTA is present, and recovered with further addition of CaCl2. This suggests that the presence of small amounts (impurities) of multivalent cations (possibly calcium) in the salt and non-buffered solutions is the reason for the membrane instability upon pulse application in the absence of EDTA. In a similar fashion, such impurities were found to induce changes in the thermal behavior of dimyristoyl phosphatidylglycerol [2].In this work, we use fast digital camera and confocal microscopy to observe the dynamics of vesicle rupture and the membrane reorganization after the applied pulse. The nature of this structural rearrangement is poorly understood. Vesicles made of lipid extract from human plasma membranes behave in the same fashion. Thus, the reported bilayer reorganization may also occur to a certain degree in the membrane of electroporated cells. Studying the electric-pulse response and reorganization of charged model membranes in different medium conditions is a significant and necessary step towards understanding the long pore lifetime in electroporated cells, which allows the transport of drug and DNA molecules.1. Riske, K.A., and R. Dimova. 2005. Biophys. J. 88:1143-1155.2. Riske, K.A., H.-G. Dobereiner, and M.T. Lamy-Freund. 2003. J. Phys. Chem. B 107:5391-5392.