Electrocatalytic excitation and Co-reaction acceleration synergistic amplification signal of hydrazide-conjugated carbon dots for an electrochemiluminescence immunoassay

Abstract

Biocompatible nitrogen-doped hydrazide-conjugated carbon dots (NHCDs) as an anodic luminophores with low excitation potential were equipped with an efficient multiple signal-amplification strategy for electrochemiluminescence (ECL) trace bioanalysis. To promote the ECL emission of NHCDs-H2O2 system, gold nanoparticles (Au NPs) functionalized tin oxide nanocrystals (Au@SnO2 NCs) were adopted to anchor large amount of NHCDs, the formed NHCDs-Au@SnO2 NCs could conjugate with detection antibody as the signal label. Moreover, 3,4,9,10-perylenetetracarboxylic acid (PTCA) molecules were immobilized on the flower-like microsphere (PTCA@ZnCo2O4/ZnO) nanocomposites to fabricate as an electro-active sensing substrate to incubate the capture antibody, which could efficiently accelerate the generation of reactive oxygen species (OH·/O2·-) through electrocatalytic excitation and co-reaction acceleration. Integrating with the sandwich-type sensing model, an ECL immunosensor was established to detect biomarkers of squamous cell carcinomas named cytokeratin 19 fragments (cyfra21–1). Combining with the synergistic signal-amplification induced by the Au@SnO2 NCs, PTCA, and ZnCo2O4/ZnO nanocomposites, the developed immunosensor performed detection range from 0.09 pg/mL to 100 ng/mL with a detection limit of 34.38 fg/mL. The results showcased the great potential of this sensing strategy for real sample analysis of biomarker with reliable stability, selectivity and repeatability.