Cell spheroids are three-dimensional in vitro models that, compared with conventional two-dimensional cultures, more accurately reproduce the physiological properties of multicellular tissues. In this paper, we present a label-free method for evaluating cell spheroids using electrical impedance spectroscopy (EIS) with microelectrode arrays. A thin-film microelectrode array was fabricated on a glass substrate and integrated with a polydimethylsiloxane chamber to enable stable placement of spheroids on the electrodes. Impedance was measured over a frequency range of 1 kHz to 5 MHz using an alternating current voltage of 0.1 V. HEK293T spheroids exhibited impedance values that differed by approximately one order of magnitude from those of the culture medium. Equivalent circuit analysis allowed estimation of extracellular and intracellular resistances. Impedance also increased with spheroid size, reflecting differences in the number of cells contained within the spheroids. Cancer cell spheroids (DLD-1 and HepG2) showed electrical characteristics distinct from those of HEK293T spheroids, indicating sensitivity to cell type. Surfactant-induced membrane disruption resulted in a decrease in membrane capacitance, corresponding to loss of cell viability. These results demonstrate that EIS enables noninvasive, quantitative evaluation of cell spheroids, with potential applications in drug screening and biomedical diagnostics.

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