Gene Delivery by Electroporation In Vitro: Mechanisms

Abstract

Cell membranes can be transiently permeabilized by application of electric pulses. This process, called electropermeabilization or electroporation, allows hydrophilic molecules, such as anticancer drugs and nucleic acids, to enter into targeted cells and tissues. The knowledge of the processes involved in membrane permeabilization and in gene transfer is mandatory for this promising method to be efficiently and safely used. The behavior of the membranes and the cells both while the electric field is on and after its application has therefore to be addressed. The description of the full mechanisms takes benefit from studies performed on different biological models (lipid vesicles, cells in 2D and 3D culture) and from different microscopy tools that allow to visualize the processes. Single-cell imaging experiments revealed that the uptake of molecules (antitumor drugs, nucleic acids) takes place in well-defined membrane regions and depends on their chemical and physical properties (size, charge). Small molecules can freely cross the electropermeabilized membrane and have a free access to the cytoplasm. Heavier molecules, such as plasmid DNA, face physical barriers (plasma membrane, cytoplasm crowding, nuclear envelope) which engender a complex mechanism of transfer. Gene electrotransfer indeed involves different steps, occurring over relatively large time scales. As will be presented in this chapter, these steps include the initial interaction with the electropermeabilized membrane, the crossing of the membrane, the transport within the cell toward the nuclei, and finally gene expression.