Low frequency impedance spectroscopy of cell monolayers using the four-electrode method

Abstract

We have developed an impedance spectroscopy system for monitoring changes in extracellular conductivity and cell-to-cell coupling in cells cultured on microelectrode arrays (MEAs). Impedance spectra were measured at low frequencies (0.5-10kHz) using the four-electrode technique and standard electrophysiological instruments. A reduction in extracellular conductivity (using isotonic sucrose solution) was observed as an elevation of impedance at all measured frequencies. A reduction in cell coupling (using heptanol) was observed as an elevation of impedance at low frequencies (<100Hz) and small reductions or no change in impedance at higher frequencies. Monolayer confluency and cell adhesion to electrodes were major factors in the measurements. The effect of disrupting cell adhesion (using trypsin) was most apparent at frequencies below 1kHz. Impedance was dependent upon the spacing between stimulating electrodes. Impedance reduced with increasing spacing. Overall, using commercially available MEAs and the four-electrode method provides a fast and reliable way to measure cell monolayer impedances.