Quenching of tungsten-based polyoxometalate nanoclusters on electrochemiluminescence emission of luminol loaded CeVO4/Au for immunoassay of protein

A quenching-typed electrochemiluminescence (ECL) immunosensing method was proposed for protein detection by the redox reaction of tungsten-based polyoxometalate nanoclusters (W-POM NCs) with free radical (O 2 •– ) as the intermediate of co-reactant H 2 O 2 . The immunosensor was constructed by co-immobilizing luminol loaded CeVO 4 /Au nanohybrids and capture antibody on an indium tin oxide electrode, which showed strong ECL emission in the presence of H 2 O 2 due to the catalysis of CeVO 4 /Au toward its electro-oxidation to produce O 2 •– via the reversible conversion between Ce 3+ and Ce 4+ . The W-POM NCs were encapsulated in the uniformly sized amino-silica nanosphere (SiO 2 ) to act as a label ( [email protected] 2 ) of the secondary antibody. Upon the sandwich-typed immunoreactions with the target, the W-POM NCs were introduced onto the immunosensor surface to reduce O 2 •– , and thus quenched the ECL emission of luminol-H 2 O 2 system. Using neuron-specific enolase (NSE) as a target, the proposed method showed a detection limit of 0.19 pg/mL and detectable range of 0.5 pg/mL to 18 ng/mL. The excellent performance of the proposed “ON-OFF” strategy demonstrated that the W-based quenching offers an effective tag for immunoassay of protein biomarkers.