Ultrastructural modifications induced by "electroporation"

Despite the large bulk of literature on electroporation, there is a lack of knowledge about the cellular mechanism(s) and subcellular components controlling this phenomenon. In this chapter, we describe a number of ultrastructural alterations occurring in the tissues and in the cellular membranes after exposure to high voltage pulses. Specifically, experimental and ultrastructural data coming from literature body on transdermal drug delivery are briefly discussed. Moreover, alterations following the exposure of orthotopic melanomas and red blood cells to trains of biphasic pulses are reported. To look insight the intimate mechanism(s) controlling electroporation, several imaging techniques such as light and electron microscopy, electrochemical imaging, confocal microscopy have been employed. Freeze-fracture analysis allowed in more than one case to evidence alterations of cell membranes and defects in the dynamic assembly of lipids and proteins. Such modifications could be the hallmarks of a reduction of lipid-protein cohesion and of changes in lipid orientation inside cell membranes, as postulated in several mathematical models applied to electroporation.