Label-free homogeneous electrochemical detection of MicroRNA based on target-induced anti-shielding against the catalytic activity of two-dimension nanozyme

In traditional homogeneous electrochemical sensing system, methylene blue was stricken with nonspecific intercalation and weak stability, inevitably distorting the diagnosis results. Given the unique catalytic activity of oxidase- and peroxidase-like nanozymes, it is interesting to develop a nanozyme-based homogeneous electrochemical biosensor. Whereas, the preparation of nanozymes with dual enzyme-like activities and two dimensional (2D) morphology is a great challenge. Herein, a soft template-directed wet chemical approach was proposed for preparation of 2D MnO2 nanoflakes, in which the morphology can be easily tuned by the template dosage. Interestingly, not only the oxidase-like activity was discovered, but 2D MnO2 nanoflakes also display a significant peroxidase-like activity. Noticeably, 2D MnO2 nanoflakes exhibit superior response to single stranded deoxyribonucleic acid (ssDNA) over double stranded DNA in the aspect of binding and catalytic activity, which triggers a highly sensitive homogeneous electrochemical detection of microRNA. This study about finding nanozymes with dual enzyme-like activities and ssDNA with inhibiting effect will set up a new avenue to extend the application range of nanozymes and throws a new light on the development of higher-performance electrochemical biosensors. •A nanozyme-based homogeneous electrochemical biosensor was designed for miRNA sensing.•The prepared MnO2 possessed dual enzyme-like activities and two dimensional shape.•They also displayed higher response to ssDNA than dsDNA in catalytic activity.•This biosensor realized label-free and enzyme-free detection of miRNA at ~ nM level.