Combination of Ternary Electrochemiluminescence System of BNQDs/AgMOG-K2S2O8 and Electrochemiluminescence Resonance Energy Transfer Strategy for Ultrasensitive Immunoassay of Amyloid-ß Protein.

In this work, based on boron nitride quantum dots (BNQDs) as energy donors and MnO2@MWCNTs-COOH as energy receptors, we designed an efficient electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor for the detection of amyloid-ß (Aß42) protein, a biomarker of Alzheimer's disease (AD). First, the signal amplification of a ternary ECL system composed of BNQDs (as the ECL emitter), K2S2O8 (as the coreactant), and silver metal-organic gels (AgMOG, as the coreaction accelerator) was realized, and PDDA as stabilizer was added, a strong and stable initial ECL signal was obtained. AgMOG could not only support a large amount of BNQDs and Aß42 capture antibody (Ab1) through Ag-N bond but also exhibit excellent ECL catalytic performance and enhance the luminescent intensity of BNQDs@PDDA-K2S2O8 system. In addition, due to the broad absorption spectrum of MnO2@MWCNTs-COOH and the extensive overlap with the ECL emission spectrum of BNQDs, the quenching probe Ab2-MnO2@MWCNTs-COOH could be introduced into the ternary system through a sandwich immune response. On this basis, the signal on-off ECL immunosensor was constructed to achieve the ultrasensitive detection of Aß42 through signal transformation. Under the optimal conditions, the prepared ECL biosensor manifested a wide linear range (10 fg/mL-100 ng/mL) with a detection limit of 2.89 fg/mL and showed excellent stability, selectivity, and repeatability, which provided an effective strategy for the ultrasensitive detection of biomarkers in clinical analysis.

Electrochemical Biosensing Platform Based on Toehold-Mediated Strand Displacement Reaction and DSN Enzyme-Assisted Amplification for Two-Target Detection.

Simultaneous detection of multiple targets is of great significance for accurate disease diagnosis. Herein, based on duplex-specific nuclease (DSN) assisted signal amplification and the toehold-mediated strand displacement reaction (TSDR), we constructed an electrochemical biosensor with high sensitivity and high specificity for dual-target detection. MiRNA-141 and miRNA-133a were used as the targets, and ferrocene (Fc) and methylene blue (MB) with significant peak potential differentiation were used as the electrochemical signal probes. The elaborately designed hairpin probe H1, which was fixed on the electrode surface, could be hybridized with the target miRNA-141 to perform signal amplification by the DSN-assisted enzyme cleavage cycle; thus, miRNA-141 could be detected by Fc signal changes at 0.41 V. The hairpin H1 can also combine with the MB-labeled signal probe (SP) output from miRNA-133a-induced TSDR, and the detection of miRNA-133a can be realized according to the response signal generated by MB at -0.26 V. The two sensing lines are independent of each other, and there is no mutual interference in the detection process. Therefore, two independent detection lines could be connected in series, and the simultaneous detection of two targets can be achieved on a single electrode. This novel detection strategy provides a new way to simultaneously detect different biomarkers.