Ratiometric Electrochemical Detection of MicroRNA Based on Construction of A Hierarchical C@SnS2 Nanoflower Sensing Interface

Building a precise, sensitive, and selective sensing platform is highly significant for microRNA (miRNA) detection. Herein, an innovative ratiometric electrochemical biosensor sensitized with carbon nanoparticles-functionalized SnS2 nanoflowers (C@SnS2 NFs) and enzyme-assisted target recycling was explored for analysis of miRNA-21. In this strategy, the application of hierarchical C@SnS2 NFs structure as electrode material not only enhanced the surface loading capability for subsequent reactions but also improved the interfacial electron transfer. After introducing enzyme-assisted target recycling, single-target miRNA-21 could initiate the cleavage of multiple capture DNA strands by duplex-specific nuclease (DSN), leading to numerous rest single-strand DNAs on the electrode. Two probes, methylene blue-labeled probe 1 (probe 1-MB) and ferrocene-labeled probe 2 (probe 2-Fc), could selectively and competitively hybridize with the capture DNA and the rest single-strand DNA, depending on the completeness of DNA hybridization. By measuring the peak current intensity ratio of Fc and MB, miRNA-21 was quantified in a wide concentration range from 1 fmol/L to 10 pmol/L, with a detection limit of 300 amol/L. Moreover, this sensing system showed good analytical performance in the presence of interfering sequences and complex matrices, illuminating excellent selectivity and practical application potential of the hierarchical C@SnS2 NF sensing interface.