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Non-Faradaic Current Suppression in DNA Based Electrochemical Assays with a Differential Potentiostat

preprint
submitted on 02.10.2019 and posted on 03.10.2019 by Mark D. Holtan, Subramaniam Somasundaram, Niamat Khuda, Christopher Easley
One of the key factors limiting sensitivity in many electrochemical assays is the non-faradaic or capacitive current. This is particularly true in modern assay systems based on DNA monolayers at gold electrode surfaces, which have shown great promise for bioanalysis in complex milieu such as whole blood or serum. While various changes in analytical parameters, redox reporter molecules, DNA structures, probe coverage, and electrode surface area have been shown useful, background reduction by hardware subtraction has not yet been explored for these assays. Here, we introduce new electrochemistry hardware that considerably suppresses non-faradaic currents through real-time analog subtraction during current-to-voltage conversion in the potentiostat. This differential potentiostat (DiffStat) configuration is shown to suppress or remove capacitance currents in chronoamperometry, cyclic voltammetry, and square-wave voltammetry measurements applied to nucleic acid hybridization assays at the electrode surface. The DiffStat makes larger electrodes and higher sensitivity settings accessible to the user, providing order-of-magnitude improvements in sensitivity, and it also significantly simplifies data processing to extract faradaic currents in square-wave voltammetry (SWV). Since two working electrodes are used for differential measurements, unique arrangements are introduced such as converting signal-OFF assays to signal-ON assays, or background drift correction in 50 % human serum. Overall, this new potentiostat design should be helpful not only in improving the sensitivity of most electrochemical assays, but it should also better support adaptation of assays to the point-of-care by circumventing complex data processing.

Funding

NIH R01 DK093810

NSF CBET-1403495

History

Email Address of Submitting Author

chris.easley@auburn.edu

Institution

Auburn University

Country

United States

ORCID For Submitting Author

0000-0002-2403-4147

Declaration of Conflict of Interest

The differential potentiostat and methodology presented in this article was included patent application filed in March of 2018.

Version Notes

Version 9.9, submitted for peer-review

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