Etching of Ag nanoparticles triggered bidirectional regulation for electrochemiluminescence ratiometric immunoassay

A highly efficient ratiometric electrochemiluminescence (ECL) immunoassay was explored by bidirectionally regulating the ECL intensity of two luminophors. The immunoassay was conducted in a split-type mode consisting of an ECL detection procedure and a sandwich immunoreaction. The ECL detection was executed using a dual-disk glassy carbon electrode modified with two potential-resolved luminophors (g-C₃N₄-Ag and Ru-MOF-Ag nanocomposites), and the sandwich immunoreaction using glucose oxidase (GOx)-modified SiO₂ nanospheres as labels was carried out in a 96-well plate. The Ag nanoparticles (NPs) acted as bifunctional units both for triggering the resonance energy transfer (RET) with g-C₃N₄ and for accelerating the electron transfer rate of the Ru-MOF-Ag ECL reaction. When the H₂O₂ catalyzed by GOx in the 96-well plate was transferred to the dual-disk glass carbon electrode, the doped Ag NPs in the two luminophors could be etched, thus destroying the RET between C₃N₄ and the accelerated reaction to Ru-MOF, resulting in an opposite trend in the ECL signal outputted from the dual disks. Using the ratio of the two signals for quantification, the constructed immunosensor for a model target, i.e. myoglobin, exhibited a low detection limit of 4.7 × 10^-14 g/mL. The ingenious combination of ECL ratiometry, bifunctional Ag NPs, and a split-type strategy effectively reduces environmental and human errors, offering a more precise and sensitive analysis for complex samples.