PEDOT:PSS organic electrochemical transistors for electrical cell-substrate impedance sensing down to single cells

The adhesion of cells on organic electrochemical transistors (OECT) is investigated down to a single cell resolution using an impedimetric readout method of the transistors. For this purpose a fabrication protocol for micro-sized OECTs based on Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) was developed. OECTs with gate dimensions of 20 μm × 20 μm with cut-off frequencies up to 10 kHz at -3 dB were fabricated. Impedance spectra of the OECTs changed drastically when HEK 293 cells were adhered to the OECT gates. To confirm the single-cell sensitivity, individual cells were removed from the device surface with patch-clamp pipettes while impedance measurements were performed. In addition, the calcium chelator EGTA was used to demonstrate the reproducible activation and deactivation of tight gap junctions in Madin Darby Canine Kidney cells adhered on the OECT gates. We applied an analytical mathematical model combined with an electrically equivalent circuit model to describe the measured impedance spectra and to calculate the cell-related parameters of the adherent cells. The novel technique of impedimetric readout of OECTs for the detection of single cell adhesion offers various future applications.