Electrochemiluminescence quenching of luminol by CuS in situ grown on reduced graphene oxide for detection of N-terminal pro-brain natriuretic peptide

Abstract

A novel electrochemiluminescence (ECL) signal-off strategy based on CuS in situ grown on reduced graphene oxide (CuS-rGO) quenching luminol/H₂O₂ system was firstly proposed. Luminol was grafted on the surface of Au@Fe₃O₄-Cu₃(PO₄)₂ nanoflowers (Luminol-Au@Fe₃O₄-Cu₃(PO₄)₂) which exhibited excellent catalytic effect towards the reduction of H₂O₂ to enhance the ECL intensity of luminol. Cu₃(PO₄)₂ nanoflowers showed large surface area which can immobilize more Fe₃O₄ and Au nanoparticles. The quenching mechanism of CuS-rGO was due to ECL resonance energy transfer (RET). The spectral overlap between fluorescence spectrum of Luminol-Au@Fe₃O₄-Cu₃(PO₄)₂ and UV-vis absorption spectrum of CuS-rGO revealed that resonance energy transfer was possible. Au nanoparticles were immobilized on the surface of CuS-rGO to capture secondary antibodies. After a sandwich-type immunoreaction, a remarkable decrease of ECL signal was observed. Under the optimal conditions, the immunosensor showed excellent performance for N-terminal pro-brain natriuretic peptide (NT-proBNP) detection with a wide detection range from 0.5 pg mL^-1 to 20 ng mL^-1 and a low detection limit of 0.12 pg mL^-1 (S/N = 3). The prepared NT-proBNP immunosensor displayed high sensitivity, excellent stability and good specificity.

Keywords: CuS in situ grown on reduced graphene oxide; Fe(3)O(4)-Cu(3)(PO(4))(2) nanoflowers; Luminol; Quench.