DNA-Functionalized Porous Fe3O4 Nanoparticles for the Construction of Self-Powered miRNA Biosensor with Target Recycling Amplification.

Herein, we have developed an ultrasensitive self-powered biosensor for miRNA assay based on biofuel cells. The system is composed of indium tin oxide cathode and graphene oxide/gold nanoparticle/glucose oxidase anode. Redox probe of [Fe(CN)6]3- is entrapped inside porous Fe3O4 nanoparticles by DNA. However, in the presence of target miRNA, hybridization reaction occurs between miRNA and DNA, which initiates the release of [Fe(CN)6]3-. Moreover, duplex specific nuclease is further employed to trigger target recycling amplification. As a result, much more redox probes are released and the open circuit voltage is significantly increased. A "signal-on" self-powered biosensor for miRNA quantification is thus developed. The detection range is from 10 aM to 10 fM; meanwhile, the limit of detection is as low as 1.4 aM, which is superior to that in most reported methods. Therefore, the proposed biosensor is expected to be a powerful point-of-care tool for miRNA diagnostics, which may have wide applications in the future.