Electroporation for Electrochemotherapy and Gene Therapy

When a cell is exposed to an electric field, a transmembrane voltage is induced on the membrane. If this voltage exceeds a certain value, this leads to a significant increase of the electric conductivity and the permeability of the membrane. Typically, each increases by several orders of magnitude. Formation of a state of increased permeability of the membrane caused by an exposure to the electric field is called electroporation (also electropermeabilization). As the result of the increasedpermeability of themembrane,molecules that are otherwise deprived of transport mechanisms can be transported across the membrane. With appropriate duration and amplitude of the electric field, themembrane returns into its normal state after the end of the exposure to the electric field (reversible electroporation). However, if the exposure is too long or the amplitude of the electric field is too high, the membrane does not reseal after the end of the exposure, leading to cell death (irreversible electroporation). Reversible ‘‘electrical breakdown’’ of the membrane has first been reported by Stampfli in 1958, but for some time this report has been mostly unnoticed. Nearly a decade later, Sale