Paper-Supported Self-Powered System Based on a Glucose/O2 Biofuel Cell for Visual MicroRNA-21 Sensing.

The exploitation of self-powered devices that get rid of the power source restriction represents the development tendency of sensing systems. Herein, a paper-supported glucose/O2 biofuel cell (BFC)-based self-powered sensing platform for visual analysis was developed. The BFC device utilized gold nanoparticle-modified paper fibers as the electrode to wire glucose oxidase (GOx) and bilirubin oxidase for the fabrication of bioanodes and biocathodes. To implement an assay protocol, a target-responsive cargo release system based on mesoporous silica nanocarriers controlled by microRNA-21 (miRNA-21) was designed. During the BFC operation, undesired H2O2, the side product of glucose oxidation which would be deleterious for GOx, was generated, leading to inevitable degeneration of BFC performance. On the basis of the H2O2-mediated iodide oxidation reaction to form iodine that further modulated the starch chromogenic reaction, undesired H2O2 could be effectively removed, resulting in remarkably improved BFC performance as well as providing a means for visual signal readout. Thanks to the dual output signals (maximum power output density or length of blue bar), enhanced analysis reliability and sensitive detection of miRNA-21 over a range of 5 fM to 100 pM were achieved. Moreover, this study demonstrates a proof of concept in visualized BFC-based self-powered systems for sensing applications and provides a blueprint to advance future sensors and analysis devices powered by BFCs in a wide variety of in vitro applications.