A Robust Equivalent Circuit Model for DNA-Mediated Electrochemistry.

DNA-mediated electrochemistry is a powerful technique for biosensing and understanding fundamental charge transfer reactions in DNA. Electrochemical impedance spectroscopy (EIS) is a ubiquitous tool for following DNA/RNA hybridization and biosensing with DNA. Despite the broad applicability of these two electrochemical methods, EIS is underutilized in DNA-mediated electrochemistry. Here, we use EIS with equivalent-circuit modeling to develop a robust circuit that represents DNA-mediated electrochemistry with a covalently bound redox probe on chips bearing multiplexed electrodes. This model circuit consistently decomposed into contributions from the working-electrode double layer, the counter electrode interface, and the solution resistance. Subsequently, this model was used to discern rational, statistically significant changes in circuit parameters that occurred upon changing the buffer, reducing the redox probe, and in the absence of DNA. Using the multiplexed chip platform with the EIS model circuit, the influence of single base pair mismatches was investigated relative to fully well-matched controls. EIS analysis revealed that the inclusion of the single base pair mismatch modulates the electrical double-layer resistance between the DNA-modified electrodes. Overall, these results show that impedance-derived interfacial parameters are sensitive to DNA structure, redox state, and the solution environment, providing new insight into the mechanisms governing DNA-mediated electrochemistry.