Signal-on architecture for electrochemical aptasensors based on multiple ion channels

In this work, we described a signal-on architecture for electrochemical aptasensors that is applicable to a wide range of aptamers. Herein, we use thrombin as the model sensing target. The signal-on aptasensor is composed of multiple ion channels embedded within a polymeric membrane, with the antithrombin aptamers chemically modified onto the inner walls of each ion channel working as the sensing element. As the thrombin concentration increased, [Ru(NH₃)₆]³⁺, which was electrostatically absorbed onto the negatively charged phosphate backbones of aptamers beforehand, was displaced and pushed into the ion channels from the inner walls, leading to an increase in the current of redox cations at the working electrode surface. Compared with the traditional two-electrode design using a single ion channel sensing system, our ion channel sensing system is applied multiple times within an ordinary three-electrode system, providing such advantages as a high signal-to-noise ratio and suitability for a wide variety of redox species. The results indicate that multiple ion channel sensing provides improvements of orders of magnitude in signal sensitivity. In particular, this signal-on architecture avoids the problems of limited signal gain and "false positives". Moreover, the proposed aptasensor is simple, highly selective, stable, and applicable to real samples.