Extracellular resistance in cell adhesion measured with a transistor probe

The electrical resistance in the narrow space between a cell and a solid substrate is unknown. It may differ from the resistance of the bulk electrolyte due to electrical interactions of the surfaces involved. Here we present an approach to measure the extracellular resistance in the region of adhesion using transistor recording. We studied the adhesion of erythrocytes which were attached with polylysine to oxidized silicon. The cell membrane followed the surface profile of the chip at a distance of 10 nm as measured by fluorescence interference contrast microscopy. Ac voltages of various frequencies were applied to the bath and the local voltage beneath a cell was recorded by a transistor. On the basis of a representative electrical circuit we determined a sheet resistance of 280 Omega n. Multiplication with the distance lead to a specific resistance of 280 Omega cm, far above the specific resistance 74 Omega cm of the bulk electrolyte.