title: Cell-transistor coupling: investigation of potassium currents recorded with p- and n-channel FETs.
abstract: Microelectronic-based biosensors that allow noninvasive measurement of cell activity are in the focus of current developments, however, the mechanisms underlying the cell-transistor coupling are not completely understood. In particular, characteristic properties of the extracellular voltage response such as the waveform and amplitude are not satisfactorily described by electrical circuit models. Here we examine the electrical coupling between a nonmetallized field-effect transistor (FET) and a cell line expressing a voltage-gated EAG K+ channel. The activation kinetics of this channel depends on the voltage pulse protocol and extracellular divalent cations. This feature allows testing, whether the extracellular voltage signal recorded with the FET faithfully tracks the current simultaneously recorded with the patch-clamp technique. We find that the FET signals contain different kinetic components that cannot be entirely explained by equivalent electrical-circuit models. Rather, we suggest that changes in ion concentration in the small cleft between cell and FET may change the surface potential of the FET. This study provides evidence that the electrochemical processes at the cell-transistor interface are complex and that at least two different mechanisms contribute to the shape and amplitude of transistor signals.
authors.affiliation: Institute of Thin Films and Interfaces (ISG2) and Center of Nanoelectronic Systems for Information Technology, Research Centre Jülich, D-52425 Jülich, Germany.
authors.forename: Günter
authors.initials: G
authors.lastname: Wrobel
authors.forename: Reinhard
authors.initials: R
authors.lastname: Seifert
authors.forename: Sven
authors.initials: S
authors.lastname: Ingebrandt
authors.forename: Jörg
authors.initials: J
authors.lastname: Enderlein
authors.forename: Holger
authors.initials: H
authors.lastname: Ecken
authors.forename: Arnd
authors.initials: A
authors.lastname: Baumann
authors.forename: U Benjamin
authors.initials: UB
authors.lastname: Kaupp
authors.forename: Andreas
authors.initials: A
authors.lastname: Offenhäusser
mesh_terms: D000200:Action Potentials; D001703:Biophysics / Q000295:instrumentation* / Q000379:methods*; D015374:Biosensing Techniques; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004581:Electronics; D004594:Electrophysiology / Q000379:methods*; D006801:Humans; D007477:Ions; D007700:Kinetics; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000737:chemistry; D008564:Membrane Potentials; D008853:Microscopy; D015233:Models, Statistical; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000737:chemistry*; D015221:Potassium Channels / Q000737:chemistry; D013997:Time Factors; D014173:Transistors, Electronic
chemical_list: D007477:Ions; D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D011188:Potassium