Analysis of the effects of an orifice plate on the membrane potential in electroporation and electrofusion of cells

This paper presents a numerical analysis of the membrane voltage induced on biological cells, under the influence of an externally applied field in such processes as electroporation or electrofusion. We focus on the configurations in which an insulator plate with an orifice is used and study the cases of (a) a cell placed on the orifice or (b) two cells in contact at the orifice, when a stepwise voltage is applied across the plate. Formulation based on the boundary element method is made assuming that a biological membrane is an infinitesimally thin insulator. Results of the calculation show that, due to the field constriction created by the orifice plate, almost all the externally applied voltage is imposed on the membrane at the orifice, and the membrane voltage outside the orifice is virtually zero; field tailoring with the use of the orifice plate enables control over the magnitude and localization of the membrane voltage. It is also shown that we can induce breakdown exclusively around the contact point of a pair of cells for high-yield electrofusion with such a geometry