Tungsten-based polyoxometalate nanoclusters with remarkable reactive oxygen species-scavenging activity efficiently quenched luminol-based electrochemiluminescence for sensitive detection of Her-2

This study aimed to develop a quenching-type electrochemiluminescence (ECL) immunosensor for human epidermal growth factor receptor (Her-2) detection. Firstly, Pd/NiFeOx nanoflowers decorated by in situ formation of gold nanoparticles (Au NPs) and 2D Ti₃C₂ MXene nanosheets were synthesized (AuPd/NiFeOx/Ti₃C₂) as carriers to load luminol and primary antibodies. Impressively, AuPd/NiFeOx/Ti₃C₂ with excellent peroxidase-like activity could accelerate the decomposition of the coreactant H₂O₂ generating more reactive oxygen species (ROSs) under the working potential from 0 to 0.8 V, resulting in highly efficient ECL emission at 435-nm wavelengths. The introduction of tungsten-based polyoxometalate nanoclusters (W-POM NCs) which exhibit remarkable ROSs-scavenging activity as secondary antibody labels could improve the sensitivity of immunosensors. The ZnO nanoflowers were employed to encapsulate minute-sized W-POM NCs, and polydopamine was self-polymerized on the surface of Zn(W-POM)O to anchor secondary antibodies. The mechanism of the quenching strategy was explored and it was found that W-POM NCs could consume ROSs by the redox reaction of W⁵⁺ resulting in W⁶⁺. The proposed ECL immunosensor displayed a wide linear response range of 0.1 pg·mL^-1 to 50 ng·mL^-1, and a low detection limit of 0.036 pg mL^-1 (S/N = 3). The recoveries ranged from 93.9 to 99.4%, and the relative standard deviation (RSD) was lower than 10%. This finding is promising for the design of detecting new protein biomarkers.