Intracellular voltage transients of cultured cells are recorded by transistors and other planar electrodes as local extracellular voltages. The theoretical relation of extra- and intracellular voltage is investigated with a two-compartment circuit using the approximation of a fast, weak and small cell-silicon junction. It is shown that extracellular recording relies on the difference of specific ionic conductances in the attached and free region of the cell membrane. The result rationalizes various observations with neuron-transistors. It guides the optimization of extracellular recording and a development of cell-based chemical sensors.
Fig.1: Cell-silicon junction with two-compartment circuit (point-contact model). Cell membrane and silicon dioxide are marked as heavy lines. The actual distance of membrane and oxide is 10 - 100 nm, whereas the diameter of the junction is 10 - 100 µm. Attached and free membrane of the cell are described by a capacitance, by various (here two) specific ionic conductances which are driven by reversal voltages and which may be voltage-gated or ligand-gated. The oxide is described by a capacitance, the junction by a seal conductance (gJ). IINJ is the injection current through a pipette. The extracellular voltage VJ is recorded by a transistor in the silicon kept at a bias potential. The intracellular voltage VM may be monitored by a micropipette.
rss
Top
Print