Electrokinetic preconcentration and electrochemical detection of Escherichia coli at a microelectrode

In this paper, we describe a novel electroanalytical approach that utilizes preconcentration of Escherichia coli (E. coli) bacteria by electrokinetic phenomena (dielectrophoresis and electrothermal fluid flow), which are generated in an electrolyte solution by a high frequency alternating current (ac) waveform. The bacteria are decorated with silver nanoparticles, so it becomes possible to detect individual bacterial cells one by one, i.e., perform electrochemical counting, due to silver oxidation on a working microelectrode (UME) biased at an appropriate dc potential. We demonstrate that the developed methodology allows for detection of E. coli concentrations two orders of magnitude smaller than what one could detect based on the transfer of E. coli by diffusion only (Sepunaru et al., Biomater. Sci., 3 (2015) 816-820).