Electrodeformation, Electroporation, and Electrofusion of Giant Unilamellar Vesicles

Abstract

This chapter summarizes a spectrum of phenomena observed on model membranes exposed to electric fields. The considered model membrane system is giant unilamellar vesicles with sizes in the range of tens of microns. Because of their large size, the response of the membrane to electric fields can be directly visualized under the microscope. The membrane behavior is exemplified by several types of responses: First, the vesicles undergo morphological changes and adopt prolate, oblate, or spherocylindrical shapes. In general, the vesicle morphology depends on the conductivity conditions of the immersion and encapsulated solutions, and in the case of alternating fields – on the field frequency. Second, after switching the electric field off, these shapes can relax back to a sphere. The relaxation times depend on the initial membrane tension and on the reached transmembrane potential. Third, the vesicles can undergo topological changes such as formation of pores and, in the case of vesicles in contact, fusion. All these processes depend on the material characteristics of the membrane such as mechanical (bending rigidity and stretching elasticity), rheological (membrane shear surface viscosity), and electrical (capacitance) properties of the lipid bilayer. This chapter gives an overview of these properties and their dependence on the membrane phase state, and presents approaches for directly assessing them using giant unilamellar vesicles.