Cell-transistor coupling: Investigation of potassium currents recorded with p- and n-channel FETs
Guenter Wrobel 1, Reinhard Seifert 1, Sven Ingebrandt 1, Joerg Enderlein 1, Holger Ecken 1, Arnd Baumann 1, U. Benjamin Kaupp 1 and Andreas Offenhäusser 1*
1 Forschungszentrum Jülich
* To whom correspondence should be addressed. E-mail: a.offenhaeusser{at}fz-juelich.de.
Submitted on July 20, 2004
Revised on August 17, 2004
Accepted on 1 August 2005
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Abstract |
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Microelectronic-based biosensors that allow non-invasive 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 non-metallized 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 electro-chemical processes at the cell-transistor interface are complex and that at least two different mechanisms contribute to the shape and amplitude of transistor signals.
Key Words:
EAG channels, field-effect transistor, ion-sensitivity, patch-clamp, point-contact model
