Reusable floating-electrode sensor for the quantitative electrophysiological monitoring of a nonadherent cell.

We report a reusable floating-electrode sensor based on aligned semiconducting single-walled carbon nanotubes for the quantitative monitoring of the electrophysiological responses from a nonadherent cell. This method allowed us to monitor and distinguish the real-time responses from normal and small-cell lung cancer (SCLC) cells to the addition of nicotine. The difference was attributed to the overexpressed nicotinic acetylcholine receptors (nAChRs) in the SCLC cells. The sensor was also utilized to monitor the effect of various drugs on the cells. The treatment with inhibitors such as genistin or daidzein was found to reduce Ca(2+) influx in SCLC cells. Moreover, tamoxifen, though known as the antiestrogen compound, was found to only partly block the binding of daidzein to nAChRs. Significantly, the activities of multiple individual cells could be measured repeatedly using a single sensor device, enabling statistically meaningful measurements without errors from the device-to-device variations of the sensor characteristics. This capability of the quantitative monitoring of nonadherent cells should be a major breakthrough for electrophysiology research and various biomedical applications such as drug screening and therapeutic monitoring.