Student Summer Scholars


Sensing of Single Bacteria Using Blocking Electrochemical Collisions and the Dependence of Current Transients on Supporting Electrolyte Concentration

First Advisor

Scott Thorgaard


electrochemistry, bacteria sensing, bioanalysis, microelectrodes, single entity electrochemistry, blocking collisions



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Analytical methods using electrochemical collisions can enable determinations of nano- and micro-sized bioanalyes with greater speed than traditional microbiological techniques and can also provide characterization at the single entity level. We have extended the application of blocking electrochemical collisions to several previously untested bacteria species to better understand how bacteria characteristics influence current transients produced during experiments. In blocking collision experiments, decreases in the current (either “step” or “blip” shaped) at an ultramicroelectrode (UME) were observed when bacteria collided with it in solution. These current transients occur because the bacteria act to block diffusive flux of a redox molecule to the UME. Bacteria arrived at the UME by electrophoretic migration due to the negative charge on their cell walls. The shapes of current transients in the experiment depended on the identity of bacteria species as well as the solution electrolyte concentration. At low electrolyte concentrations (0.1 mM), blip-shaped transients were more abundant for some bacteria species. At higher electrolyte concentrations (5 mM), only step-shaped transients observed. These results suggest that analysis of such collision transient shapes could provide a route to selective determinations of bacteria in liquid samples. Information obtained from simultaneous fluorescence microscopy of the experiments implied that the mechanism of the blip-shaped transients involves reversal of the bacteria cell wall charge.