Fig. 1.

Architecture of E-AB sensors. A E-AB sensors generally comprise three elements: a blocking monolayer of short chain alkanethiols (SAM), target-binding nucleic acid aptamers, and a redox reporter (e.g., methylene blue) attached to the terminal end of the aptamer. B In the presence of target, aptamers undergo reversible binding-induced changes in conformation that alter the electron transfer rate (k_et) between the redox reporter and the electrode surface, with k_et1 <  < k_et2. C These changes in electron transfer can be monitored via changes in electrochemical currents, usually done via square wave voltammetry. D The relative change in peak currents can be monotonically correlated with target concentration in the sample via calibration curves that obey thermodynamic binding equilibria