Electrical detection and characterization of bacterial adhesion using electrochemical impedance spectroscopy-based flow chamber

In the present work, we report on the electrochemical detection and characterization of bacterial adhesion onto a semiconducting indium tin oxide (ITO) plate using an electrochemical impedance spectroscopy (EIS)-based flow chamber. We used two different bacterial strains (Pseudomonas stutzeri (PS) and Staphylococcus epidermidis (SE)) so that their adhesion behavior and charge transporting property could be compared. The electrical detection was achieved by monitoring the impedance variations in the low frequency range during the adhesion process of both bacterial strains. The electrical characterization was achieved by measuring the impedance over a large frequency range before and after 2 hr of adhesion. The electrical properties of the electrode/bacteria/electrolyte interfaces were explained in terms of resistances and capacitances of an equivalent circuit whose frequency-dependant impedance was fitted to the measured data curves. The magnitude of the impedance was found to decay exponentially as the number of adhering cells increased during the deposition time for both bacterial cells. The adhesion of PS bacteria was detected electrically before SE bacteria. Also, the impedance fitting results revealed that PS bacterial cell allow more charge transfer to the electrode than SE bacterial cell, and therefore it donates more charges and adheres faster and more firmly to ITO surface. (C) 2008 Elsevier B.V. All rights reserved.