Bi-enzyme synergetic catalysis to in situ generate coreactant of peroxydisulfate solution for ultrasensitive electrochemiluminescence immunoassay

A novel electrochemiluminescence (ECL) immunosensor for ultrasensitive detection of alpha-1-fetoprotein (AFP) was designed based on the in situ bi-enzymatic reaction to generate coreactant of peroxydisulfate for signal amplification. In this work. AuNPs were electrodeposited on the glassy carbon electrode (GCE) surface, which promoted the electron transfer. Then, L-cysteine and another layer of AuNPs were, respectively assembled onto the modified electrode surface, which formed the multilayer films for amplifying the ECL signal of peroxydisulfate and immobilizing antibody. At last, glucose oxidase (GOD) and horseradish peroxidase (HRP) were employed to block the nonspecific binding sites. When proper amounts of glucose were added in the detection solution, GOD catalyzed the oxidation of glucose to generate H2O2, which could be further catalyzed by HRP to generate O-2 for the signal amplification. The linear range for AFP detection was 0.001-100 ng mL(-1), with a low detection limit of 3.3 x 10(-4) ng mL(-1). The novel strategy has the advantages of simplicity, sensitivity, good selectivity and reproducibility which might hold a new promise for highly sensitive bioassays applied in clinical detection. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.