Electrical impedance of living cells: a modified four electrode approach

A modified four-electrode chamber is used to perform both real-time and frequency-domain impedance measurements on living cells under physiological conditions. A large increase in measurement sensitivity is achieved by reducing the current shunt pathways when the cells are embedded in the pores of a polycarbonate sieve. A secondary advantage is realized in that the geometry of the cells under measurement is more precisely defined and known. The resistance of the leak pathway between the cell and the pore wall is 3-6.10/sup 7/ Omega . This value compares favorably with the 10/sup 9/- Omega seal achieved in patch clamp experiments. The low chamber-input impedance (25 Omega ) extends the upper frequency limit into the MHz range. The use of four electrodes with large surface areas reduces electrode polarization, permitting measurements into the sub-kHz range. An impedance model of the cell-filled sieve based on physical considerations is used to extract the cellular impedance over a wide frequency range.<>