Dual-mode corroborative detection of miRNA-21 based on catalytic hairpin assembly reaction and oxygen reduction reaction combined strategy for the signal amplification

Here, we first combined the catalytic hairpin assembly (CHA) reaction and oxygen reduction reaction (ORR) to amplify the electrochemical signal for the determination of miRNA-21. In the presence of target microRNA-21, C-Ag + -C structure probe formed by hairpin DNA1 (H1) and Ag + could be opened and catalytic hairpin assembly reaction could be carried out. Then the capture probe (C1) modified Fe 3 O 4 @PDA@AuNPs could immobilize all the H1 and the typical oxygen reduction reaction AuNPs could be electrodeposited in situ in the I-T test. Besides, the released Ag + in the solution could be also detected by fluorescence and colorimetry with the assistance of CdSe QDs. The fluorescence intensity and emission wavelength of CdSe QDs could be changed by the Ag + , which could reflect the concentration of miRNA-21. As a result, the limit of detection (LOD) was 323 aM. Besides, the constructed biosensor exhibited its good performance in the real samples demonstrating its practical application potential. This rarely dual-mode detection strategy makes the miRNA-21 detection results more accurate and reliable. • A novel catalytic hairpin assembly reaction was designed to detect miRNA-21 • Catalytic hairpin assembly reaction and oxygen reduction reaction was firstly combined to amplify the electrochemical signal • Dual-mode detection strategy was designed to detect miRNA-21 sensitively • A detection limit of 323 aM was obtained with excellent selectivity and reproducibility.