Extracellular resistance in cell adhesion measured with a transistor probe

The electrical resistance in the narrow space between a cell and a solid su bstrate is unknown. It may differ from the resistance of the bulk electroly te due to electrical interactions of the surfaces involved. Here we present an approach to measure the extracellular resistance in the region of adhes ion using transistor recording. We studied the adhesion of erythrocytes whi ch were attached with polylysine to oxidized silicon. The cell membrane fol lowed the surface profile of the chip at a distance of 10 nm as measured by fluorescence interference contrast microscopy. Ac voltages of various freq uencies were applied to the bath and the local voltage beneath a cell was r ecorded by a transistor. On the basis of a representative electrical circui t 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 speci fic resistance 74 Omega cm of the bulk electrolyte.