A newly developed method of detecting morphology and morphological changes of adherent mammalian cells cultured on thin film gold electrodes (electrical cell-substrate impedance sensing) has been used to measure the response of cells to external electrical stimuli. When sufficiently high ac voltage pulses were applied, the impedance of the cell layer changed reproducibly, indicating morphological changes in the cell layer, as no such impedance changes were seen with cell-free electrodes. The response increased with increasing voltage pulses and was distinct for different cell types. The threshold voltage across the cell layer causing an observable change was found to be of the order of 0.1 V, which is higher than that reported by others using dc fields. In certain cases, it was found that the impedance of the cell layer decreased upon pulsation and then started to recover, but decreased again before finally recovering. This suggests that two different events cause a drop in impedance of the cell layer when the adherent mammalian cells are transiently exposed to an external electrical field.
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