PEDOT:PSS Electropolymerization Protocol for Microelectrodes Enabling Low-Cost Impedance-Based Cellular Assays

Electric cell-substrate impedance sensing (ECIS) is a label-free method for in vitro cell analysis in different research fields such as virology, cancer research, and stem cell research. In the ECIS configuration, the working electrode (WE) is typically much smaller than the counter electrode, thus the measured impedance between both is mainly dominated by the impedance of the WE. However, if the impedance of the WE is too high, it is challenging to detect small changes in impedance caused by cells attached to the electrode surface. In this study, we present an easily reproducible and cost-effective method to lower the impedance of commercial ECIS electrodes, and by this increase the cell contribution in adhesion assays. Hereby we deposit a thin layer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) only onto the gold electrodes by electropolymerization and study the layer characteristics in detail. We compare cell-free and cell-covered impedance spectra of gold and PEDOT:PSS electrodes recorded with a low-cost potentiostat and analyze the ECIS spectra of two different cell lines in detail.