A ternary quenching electrochemiluminescence insulin immunosensor based on Mn²⁺ released from MnO₂@Carbon core-shell...

This work reported a ternary quenching strategy based on electrochemiluminescence resonance energy transfer (ECL-RET) between luminol/H₂O₂ system and MnO₂ capped carbon nanospheres (MnO₂@C) and Mn²⁺ released from the reduction of MnO₂ and ascorbic acid (AA) consumed superoxide radical (O₂^•-) for detection of insulin. To improve the ECL behavior of luminol, AuPdPt hybrid nanoparticles decorated MoS₂ nanosheet-coated TiO₂ nanobelt (AuPdPt-MoS₂@TiO₂) were applied to combine with luminol and primary antibodies via covalent linkage which exhibited perfectly catalysis for the electroreduction of H₂O₂. In order to sensitively detect insulin, labels MnO₂@C were used to anchor secondary antibodies via electrostatic interaction and inhibit the ECL intensity of luminol. The perfect overlap of the ECL spectrum of luminol with the absorption spectrum of MnO₂ allowed the ECL-RET to decrease ECL signals of luminol. Specifically, AA was introduced not only to inhibit the ECL of luminol, but also to reduce MnO₂ producing Mn²⁺ which can be reacted with O₂^•- to further quench the ECL reaction between luminol and H₂O₂. On the basis of the dual quenching effect of luminol, the sandwich immunosensor was prepared to determine insulin with wide linear range from 0.5 pg mL^-1 to 60 ng mL^-1 and a low detection limit of 0.13 pg mL^-1 (S/N = 3).