Organic Electrochemical Transistor as an On-site Signal Amplifier for Electrochemical Aptamer-based Sensing

Abstract

Electrochemical aptamer-based (E-AB) sensors are typically deployed as individual, passive, surface-functionalized electrodes, but they exhibit limited sensitivity especially when the area of the electrode is reduced for miniaturization purposes. We demonstrated that organic electrochemical transistors (OECTs), electrolyte gated tran-istors with volumetric gating, can serve as on-site amplifiers to improve the sensitivity of single electrode-based E-AB sensors. By monolithically integrating an Au working/sensing electrode, on-chip Ag/AgCl reference electrode and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) counter electrode -- also serving as the OECT channel, we can simultaneously perform OECT testing and traditional electroanalytical measurement on E-AB sensors including cyclic voltammetry (CV) and square-wave voltammetry (SWV). This device can directly amplify the current from the E-AB sensor via the in-plane current modulation in the counter electrode/transistor channel. The integrated OECT-based E-AB sensor is able to sense transforming growth factor beta 1 (TGF-{beta}1) with 3 to 4 orders of magnitude enhancement of sensitivity compared to that in a single electrode-based E-AB sensor (292 {micro}A/dec vs. 85 nA/dec for OECT vs. single electrode SWV). This approach is believed to be universal, which can be applied to a wide range of tethered electrochemical reporter-based sensors to enhance sensitivity, aiding in sensor miniaturization and easing the burden on backend signal processing.