Combination of Ternary Electrochemiluminescence System of BNQDs/AgMOG-K2S2O8 and Electrochemiluminescence Resonance Energy Transfer Strategy for Ultrasensitive Immunoassay of Amyloid-β 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-β (Aβ42) 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 Aβ42 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 Aβ42 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.