Interrogation of Electrochemical Aptamer-Based Sensors via Peak-to-Peak Separation in Cyclic Voltammetry Improves the Temporal Stability and Batch-to-Batch Variability in Biological Fluids

Electrochemical, aptamer-based (E-AB) sensors support continuous, realtime measurements of specific molecular targets in complex fluids such as undiluted serum. They achieve these measurements by using redox-reporter-modified, electrode-attached aptamers that undergo target binding-induced conformational changes which, in turn, change electron transfer between the reporter and the sensor surface. Traditionally, E-AB sensors are interrogated via pulse voltammetry to monitor binding-induced changes in transfer kinetics. While these pulse techniques are sensitive to changes in electron transfer, they also respond to progressive changes in the sensor surface driven by biofouling or monolayer desorption and, consequently, present a significant drift. Moreover, we have empirically observed that differential voltage pulsing can accelerate monolayer desorption from the sensor surface, presumably via field-induced actuation of aptamers. Here, in contrast, we demonstrate the potential advantages of employing cyclic voltammetry to measure electron-transfer changes directly. In our approach, the target concentration is reported via changes in the peak-to-peak separation, Delta E-P, of cyclic voltammograms. Because the magnitude of Delta E-P is insensitive to variations in the number of aptamer probes on the electrode, Delta E-P interrogated E-AB sensors are resistant to drift and show decreased batch-to-batch and day-to-day variability in sensor performance. Moreover, Delta E-P-based measurements can also be performed in a few hundred milliseconds and are, thus, competitive with other subsecond interrogation strategies such as chronoamperometry but with the added benefit of retaining sensor capacitance information that can report on monolayer stability over time.

Automated summary

This study demonstrates the potential advantages of using cyclic voltammetry to directly measure electron-transfer changes, reporting target concentration through changes in the peak-to-peak separation, ΔE-P, of cyclic voltammograms. Sensors interrogated with ΔE-P are resistant to drift, showing decreased variability in performance between batches and days. Additionally, ΔE-P-based measurements can be performed quickly and are competitive with other subsecond interrogation strategies.