Electrochemiluminescence behaviour of silver/silver orthophosphate/graphene oxide quenched by Pd@Au core-shell nanoflowers for ultrasensitive detection of insulin.

Herein, a highly efficient electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor was established for ultrasensitive insulin detection. Silver/silver orthophosphate/graphene oxide composites (Ag/Ag3PO4/GO) were prepared as sensing platform for capture-antibody (Ab1) incubation. Ag3PO4 is a novel ECL donor whose emission could be remarkably enhanced by the synergetic assistance of GO with Ag NPs. Notably, GO presented excellent electrical conductivity and ultrahigh specific surface area to improve the loading capacity Ab1 and Ag3PO4, and Ag NPs with fine biocompatibility and catalytic property could immobilize Ab1 via Ag–N bond and further hasten the electron transfer to catalyze the generation of SO4•− radicals for boosting the ECL emission of donor. To establish a new ECL-RET system, Pd@Au core-shell nanoflower was prepared as a suitable ECL acceptor which could immobilize the detection-antibody (Ab2). Due to the fine spectral overlap, Pd@Au nanoflower could significantly quench the ECL emission of Ag3PO4, causing distinct decreases in ECL intensity. The proposed ECL-RET immunosensor exhibited sensitive response to insulin in a linear range of 0.0001–80 ng/mL with a low detection limit of 0.02 pg/mL (S/N = 3), it not only provides a reliable tool for insulin detection in diagnostics of diabetes, but also lights up a new avenue for designing effective ECL-RET pairs in bioanalysis.