A generic and non-enzymatic electrochemical biosensor integrated molecular beacon-like catalyzed hairpin assembly circuit with MOF@Au@G-triplex/hemin nanozyme for ultrasensitive detection of miR-721

MicroRNAs (miRNAs) have been extensively studied as circulating biomarkers for early diagnosis and prognosis of many human diseases. However, it has been found challenging to accurately detect and quantify the trace amounts of miRNAs in biological samples. Herein, we propose a generic and non-enzymatic electrochemical strategy integrated molecular beacon-like catalyzed hairpin assembly (mCHA) circuit with MOF@Au@G-triplex/hemin nanozyme for ultrasensitive detection of miR-721 (a novel diagnostic biomarker of acute myocarditis). Nitro-functionalized MIL-101 functions as an ideal nanocatalyst and nanocarrier to facilitate efficient immobilization of G-triplex/hemin DNAzyme, to form signal probes. Tetrahedral nanostructured DNA probes self-assemble onto the Au nanoparticles/proton-functionalized graphitic carbon nitride nanosheets films, to fabricate a coordinated sensing interface. A mCHA circuit is designed to convert and amplify each target to DNA duplexes, which cause signal probes anchored on the sensing interface and produce an enhanced electrochemical signal. With the assistance of the mCHA circuit, double-amplified nanozymes and sensing interface for signal amplification, this biosensor had a low detection limit of 0.25 fM and high specificity. The proposed biosensor has been successfully used in miR-721 detection in real biological samples, which provided a promising potential method for acute myocarditis early diagnosis.