Four versus two-electrode measurement strategies for cell growing and differentiation monitoring using electrical impedance spectroscopy.

The aim of this work is to provide optimization tools for cell and tissue engineering processes through continuous monitoring of cell cultures. Structural cell properties can be obtained from non-destructive electrical measurements by using electrical impedance spectroscopy (EIS). EIS measurements on monolayer animal cell cultures are usually performed using a two-electrode strategy. Because of this, the measurement is very sensitive to the electrode covering ratio and to the degree of adherence of cells. Of course, these parameters give useful information but can mask the behaviour of the cell layer above the electrodes. In a previous work, preliminary measurements with commercial microelectrode structures were performed with simulated grow processes using the settlement of cell suspensions with two and four microelectrode strategies to validate the technique. In this work, real cell growths of Vero cells are described and the resulting EIS biomass density estimators are compared to cell counts. The four-electrode impedance spectra are fitted to the Cole-Cole impedance model and the time course of their parameters are extracted and studied.