The electrical contact between mammalian cells and silicon chips was characterized. Cells were capacitively stimulated from a thin spot oxide on a specially designed silicon chip. The resulting membrane potential was imaged at optical resolution with a confocal microscope via voltage-sensitive fluorescence. The detection was accomplished in two ways: either the transfer function of a sinusoidal stimulation to the membrane potential was imaged in amplitude and phase with a software lock-in technique. Or the membrane potential transients in response to a rectangular stimulus were recorded with a time resolution of 0.2µs for each pixel. Both measurement methods could be fitted equally well by a spatially resolved planar core-coat conductor theory called the area contact model. The coupling was characterized for erythrocyte ghosts, HEK cells with different shape, confluent HEK cell layers, rat neurons, rat neurons on top of a glia cell layer and adsorbed giant vesicle membrane. Recorded images were corrected for the transfer functions of the stimulation chip and the photomultiplier. The shape of the cell defined the boundary conditions of the model. All features of the area contact model have been confirmed and fits on lock-in and transient measurements yielded equal parameter values of the model. Transients could also be fitted by the simpler point contact model with a spatially adapted time constant of junction voltage decay. The junction parameters of fused erythrocyte ghosts measured with transistors were confirmed for the junction of unfused erythrocyte ghosts. They showed a 13-fold reduced specific conductance in the junction cleft as compared to the bulk electrolyte. For mammalian cells grown on fibronectin and poly-lysine there is a 4-fold enhanced specific junction conductance. The measured junction time constant covers the range from 2µs to 5µs depending on cell size. The sustainable membrane potential can reach values of 600mV. With increased stimulation voltage, the cell membrane is electroporated. The voltage-sensitive fluorescence was shown to be linear with respect to the applied stimulation voltage. Furthermore it could be proved that the membrane of neurons can be stimulated capacitively through a glia cell layer. Confluent cell layers showed a slower junction time constant of up to 10µs.     «

The electrical contact between mammalian cells and silicon chips was characterized. Cells were capacitively stimulated from a thin spot oxide on a specially designed silicon chip. The resulting membrane potential was imaged at optical resolution with a confocal microscope via voltage-sensitive fluorescence. The detection was accomplished in two ways: either the transfer function of a sinusoidal stimulation to the membrane potential was imaged in amplitude and phase with a software lock-in techni...     »

Der elektrische Kontakt von Säugetierzellen zu einem isolierten Festkörper wurde charakterisiert. Die Zellen wurden kapazitiv stimuliert durch einen speziell angefertigten Siliziumchip mit sinus- oder rechteckförmiger Anregung. Die resultierende Membranspannung konnte mit spannungssensitiven Fluoreszenzfarbstoffen bildgebend mit hoher Ortsauflösung detektiert werden. Ein Kern-Mantel-Leiter Modell des Kontakts konnte die Messungen sehr genau beschreiben. Die kapazitiv angelegte Spannung der Kontaktmembran kann 600mV erreichen. Bei höheren Werten wird die Zelle zerstört. Abhängig von der Zellgröße klingt die Spannung mit einer Zeitkonstante von 2-5μs ab. Dies entspricht einer vierfach erhöhten Leitfähigkeit im Kontaktspalt. Konfluente Zellrasen zeigen Zeitkonstanten von 10μs.     «

Der elektrische Kontakt von Säugetierzellen zu einem isolierten Festkörper wurde charakterisiert. Die Zellen wurden kapazitiv stimuliert durch einen speziell angefertigten Siliziumchip mit sinus- oder rechteckförmiger Anregung. Die resultierende Membranspannung konnte mit spannungssensitiven Fluoreszenzfarbstoffen bildgebend mit hoher Ortsauflösung detektiert werden. Ein Kern-Mantel-Leiter Modell des Kontakts konnte die Messungen sehr genau beschreiben. Die kapazitiv angelegte Spannung der Konta...     »