The electrochemical DNA (E-DNA) sensing platform is a sequence-specific DNA and RNA detection platform developed in response to the increasing demand for real time detection of pathogens. The first generation E-DNA sensors are composed of a self-assembled monolayer with redox label-modified stem-loop or linear DNA probes. The sensing mechanism is based on the change in the conformation and/or flexibility of the probes in the presence of the target. These changes affect the electron transfer efficiency between the redox label, methylene blue (MB), and the gold electrode surface. Despite being reagentless, reusable, and highly selective, both sensors are “signal-off” sensors. In this study, we exploit a recently developed electrocatalytic reaction between hexavalent chromium (Cr(VI)) and MB to convert these “signal-off” sensors into “signal-on” sensors. Our results suggest that the hybridization-induced probe rigidity confines the redox labels to the top of a dense duplex DNA film, thereby increases the accessibility of Cr(VI) to the redox labels. The reaction between Cr(VI) and MB is more efficient in the presence of the target DNA, resulting in a concomitant increase in the cathodic peak current and decrease in the anodic peak current when the sensor is interrogated using cyclic voltammetry. This detection strategy has demonstrated to be sensitive and more importantly, specific enough to be employed directly in complex samples such as serum and saliva.

Hexavalent chromium as an electrocatalyst in DNA sensing

251st National Meeting (2016)

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