Impedance characterization and modelling of an improved patch clamp device

Abstract

The gold standard for studying the properties of ion channels is the patch clamp, a technique that measures pA currents passing through ion channels in an isolated patch of cell membrane. The authors sought to design an improved device for whole-cell patch clamp recordings using nanoscale pipettes which more readily form seals with the cell membrane and a movable metal electrode to decrease the access resistance, increase the signal bandwidth, and clear debris from the pipette tip. Electrical characterization of the instrument by impedance spectroscopy showed that advancing the metal electrode towards the pipette tip decreased the impedance distinctly in different frequency bands, the greatest decrease occurring between 1 and 100 kHz, and the smallest at 100 kHz. Finite element simulations of the electrode, incorporating the electrode/electrolyte interface, suggest that optimal signal transmission can be achieved with athick-walled pipette, nearly filled with alarge Ag/AgCl electrode, whose impedance can be reduced through surface modification.