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We introduce a novel technique of impedimetric sensing of cellular adhesion, which might have the potential to supplement the well-known technique of Electrical Cell-substrate Impedance Sensing (ECIS) in cell culture assays. In contrast to the already commercialized ECIS method, we are using ion-sensitive field-effect transistor (ISFET) devices. The standard gold microelectrode size in ECIS is in the range of 100-250 μm in diameter. Reason for this limitation is that when downscaling the sensing electrodes, their effective impedance governed by the metal-liquid interface impedance is becoming very large and hence the currents to be measured are becoming very small reaching the limit of standard instrumentation. This is the main reason why typical assays with ECIS are focusing on applications like cell-cell junctions in confluent cultures. Single cell resolution is barely reachable with these systems. Here we use impedance spectroscopy with ISFET devices having gate dimensions of only 16 × 2 μm(2), which is enabling a real single cell resolution. We introduce an electrically equivalent circuit model, explain the measured effects upon single cell detachment, and present different cellular detachment scenarios. Our approach might supplement the field of ECIS with an alternative tool opening up a route for novel cell-substrate impedance sensing assays with so far unreachable lateral resolution.

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The microelectrode array (MEA) was used to evaluate the cardioprotective effects of adenosine triphosphate sensitive potassium (K(ATP)) channel activation using potassium channel openers (KCOs) on HL-1 cardiomyocytes subjected to acute chemically induced metabolic inhibition. Beat frequency and extracellular action potential (exAP) amplitude were measured in the presence of metabolic inhibitors (sodium azide (NaN(3)) or 2-deoxyglucose (2-DG)) or KCOs (pinacidil (PIN, a cyanoguanidine derivative, activates sarcolemmal K(ATP) channels) or SDZ PCO400 (SDZ, a benzopyran derivative, activates mitochondrial K(ATP) channels)). The protective effects of these KCOs on metabolically inhibited HL-1 cells were subsequently investigated. Signal shapes indicated that NaN(3) and 2-DG reduced the rate of the sodium (Na(+)) influx signal as reflected by a reduction in beat frequency. PIN and SDZ appeared to reduce both rate of depolarization and extent of the Na(+) influx signals. Pre-treating cardiomyocytes with PIN (0.1 mM), but not SDZ, prevented the reduction of beat frequency associated with NaN(3)- or 2-DG-induced metabolic inhibition. The exAP amplitude was not affected by either KCO. The cardioprotective effect of PIN relative to SDZ may be due to the opening of different K(ATP) channels. This metabolic inhibition model on the MEA may provide a stable platform for the study of cardiac pathophysiology in the future.

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In this study we describe how we were able to use an equivalent‐electrical circuit for the cell–transistor contact to optimize a future chip design for better performance in cell–substrate adhesion experiments. From our simulations we found that higher capacitances of the source and drain contact lines are able to shift the cell adhesion effects to more moderate frequencies in the range of up to 200 kHz. For larger cell–substrate adhesion effects, the transconductance value of the FET devices needs to be increased as well. We used these simulation results to design a new generation of FET devices. These devices were successfully fabricated in our clean room facilities. In electronic cell–substrate adhesion experiments this new generation of devices showed superior performance compared to an earlier version. Most importantly, our new devices have now an almost flat topology enabling future single‐cell migration experiments. HEK293 cells adhered with a flat morphology to a newly fabricated FET sensor device (scale bar 50 µm)