Dual “on-off” signal conversion strategy based on surface plasmon coupling and resonance energy transfer for visual electrochemiluminescence ratiometric analysis of MiRNA-141

An electrochemiluminescence (ECL) biosensor with a pair of new ECL emitters and a novel sensing mechanism was designed for the high-sensitivity detection of microRNA-141 (miRNA-141). Sulfur-doped boron nitrogen quantum dots (S-BN QDs) were initially employed to modify the cathode of the bipolar electrode (BPE), while the anode reservoir was [Ir(dfppy)₂(bpy)]PF₆/TPrA system. The next step involved attaching H1-bound ultra-small WO_3-x nanodots (WO_3-x NDs) to the S-BN QDs-modified BPE cathode via DNA hybridization. A strong surface plasmon coupling (SPC) effect was observed between S-BN QDs and WO_3-x NDs, which allowed for the enhancement of the red and visible ECL emission from S-BN QDs. After target-induced cyclic amplification to produce abundant Zn²⁺ and Au NPs-DNA3-Au NPs (Au NPs-S3-Au NPs), Zn²⁺ could cleave DNA at a nucleotide sequence-specific recognition site to release the WO_3-x NDs, resulting in the first diminution of cathode ECL signal and the first enhancement of anode ECL signal. Moreover, the ECL signal at cathode decreased for the second time and the emission of [Ir(dfppy)₂(bpy)]PF₆ was continuously enhanced after the introduction of Au nanoparticles-S3-Au nanoparticles on the cathode surface. Our sensing mode with a dual “on-off” signal conversion strategy shows a good detection capability for miRNAs ranging from 10⁻¹⁷ to 10⁻¹⁰ M, with a limit of detection (LOD) as low as 10⁻¹⁷ M, which has great application potential in biomedical research and clinical diagnosis.