Large unilamellar vesicles (LUV) from di-oleoylphosphatidylcholine (DOPC) are used as model systems to investigate mechanisms of electric field-induced membrane pore formation, as well as subsequent resealing processes. In a related project, the possible use of loaded vesicle systems is being explored to study fast mixing reactions, as the vesicles can be made to rupture in the microsecond time scale using a short, intense electric pulse. Using a membrane-bound potential sensitive dye, we have been able to map the electric potential profile across the vesicle membrane, and capture images of the formation and resealing of large membrane pores of the order of several micrometers. The pore distribution found at the membrane level is asymmetric and confirms our earlier hypothesis of a small number of large pores at the depolarized and a large number of small pores at the hyperpolarized regions of the vesicle membrane. A fast (within a few video frames) and a slower (seconds) resealing processes were identified based on rates of dye release measurements from loaded vesicles. In experiments designed to use vesicles as reaction vessels, we have confirmed (at video rates) content mixing between vesicles loaded with different dyes in response to an external applied electric field. An optical detection system using photomultipliers is being developed to enhance both the sensitivity and time resolution (into microseconds) of this method. - vesicles, LUV, electroporation, membrane pores, fast reactions
