MONITORING ELECTROPERMEABILIZATION IN THE PLASMA-MEMBRANE OF ADHERENTMAMMALIAN-CELLS

When an electrical potential of order one volt is induced across a cel l membrane for a fraction of a second, temporary breakdown of ordinary membrane functions may occur. One result of such a breakdown is that molecules normally excluded by the membrane can now enter the cells. T his phenomenon, generally referred to as electropermeabilization, is k nown as electroporation when actual pores form in the membrane. This p aper presents a unique approach to the measurement of pore formation a nd closure in anchored mammalian cells. The cells are cultured on smal l gold electrodes, and by constantly monitoring the impedance of the e lectrode with a low-amplitude AC signal, small changes in cell morphol ogy, cell motion, and membrane resistance can be detected. Because the active electrode is small, the application of a few volts across the cell-covered electrode causes pore formation in the cell membrane. In addition, the heat transfer is very efficient, and the cells can be po rated in their regular growth medium. By this method, the formation an d resealing of pores due to applied electric fields can be followed in real time for anchorage-dependent cells.