A sandwich-type electrochemical biosensing platform for microRNA-21 detection using carbon sphere-MoS2 and catalyzed hairpin assembly for signal amplification

In this work, a sandwich-type electrochemical biosensing platform is developed based on carbon sphere-MoS2 (CS-MoS2) and target recycling amplification of catalyzed hairpin assembly (CHA) strategy for ultrasensitive determination of microRNA (miRNA). The CS-MoS2 is prepared and used as sensing substrate, which shows high specific surface area, enhanced stability and good dispersibility. The capture probe is first modified on Au nanoparticles/CS-MoS2 modified glassy carbon electrode through Au-S band, and hairpin DNA1 (H1) then reacts with it and unfolds its loop domain by hybridizing with target miRNA-21. The opened H1 subsequently assembles with biotin labeled hairpin DNA 2 (H2) to displace the target. The liberated miRNA-21 is free and backs to the original solution to proceed next circulation, resulting in the generation of large amounts of H1-H2 duplex. Massive signal indicators horseradish peroxidase are then immobilized on electrode, and catalyze hydrogenperoxide + hydroquinone (H2O2 + HQ) system to produce a strong electrochemical response. The proposed assay benefits from advantages of sandwich-type structure, favorable electrochemical properties of CS-MoS2 and CHA target recycling amplification strategy. Therefore, it exhibits a wide linear relation between 1 × 10−16 and 1 × 10−10 M with a low detection limit of 1.6 × 10−17 M for miRNA-21 detection.