Application of conducting polymer electrodes in cell impedance sensing

Research in label free methods for biological analysis has brought interesting developments. Cell impedance spectroscopy has been one of the promising outcomes. It allows the measurement of cell proliferation and motility whereby it is possible to study wound healing and cell behavior in vitro. This thesis presents the progress towards an 8-well impedance measurement setup that uses conducting polymers as electrode material in cell impedance spectroscopy. A step by step fabrication of devices with PEDOT:PSS electrodes is described along with the hardware and software, developed and integrated, to perform impedance measurements of cell cultures. Electrochemical analysis was performed for PEDOT:PSS and Au electrodes to compare the two materials for use in cell impedance spectroscopy. PEDOT:PSS electrodes showed lower interfacial impedance and reach electrochemical equilibrium faster than Au electrodes. It was observed through electrochemical impedance analysis that the lower interfacial impedance is due to the low charge transfer resistance of PEDOT:PSS. MDCK cell proliferation experiments were performed using both types of electrode materials to provide a comparative study. The impedance measurement results showed differences between the two materials that led to a different kind of electrical model for the changes measured due to cell proliferation. Curve fitting results to the electrical model provided an understanding of the cell-substrate interactions and the capabilities of cell impedance spectroscopy. The application of cell impedance spectroscopy to human embryonic stem cells was also explored. The impedance changes of pluripotent stem cells during differentiation to trophoblasts were measured and analyzed. Analysis of changes to the phase values in the frequency spectrum show that by measuring the frequency where the phase is minimum, it is possible to distinguish between the two cell types. It provides a new method of using cell impedance spectroscopy to study stem cells behavior in real time and help researchers in the maintaining of stem cell cultures in the lab. Another new application of cell impedance spectroscopy to determine cell types based on the flexibility of the cytoskeleton was also explored. Some preliminary data is presented in the last chapter.