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Covalent Hemin/G4 complex-linked sandwich bioassay on magnetic beads for femtomolar HER-2/neu detection in human serum via direct electrocatalytic reduction of oxygen

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Liquid biopsy assays for tumour biomarkers circulating in blood are perspective non-invasive tools for cancer diagnosis and treatment monitoring. Here, we suggest a simple, 1 h long electrochemical DNAzyme-linked aptamer- and immuno-sandwich magnetic assay for analysis of serum HER-2/neu protein overexpressed in several aggressive cancers. In the assay, we used a covalent hemin-guanine quadruplex (G4) complex as a novel O2-dependent electrocatalytic label that allowed 10 fM (aptamer-aptamer) and 1 fM (aptamer-antibody) detection of HER-2/neu in human serum. The O2 reactivity of the aptamer-conjugated label was detected at high-surface-area graphite electrodes displaying a high efficiency of O2 reduction electro-catalyzed by this DNAzyme. In contrast to the recognised H2O2 reactivity, the O2 reactivity of the covalent hemin/G4 complex depended only on ambient O2 present in solutions, and did not require adding such traditional reagents as hemin and H2O2, and solution de-aeration. Human serum albumin, urokinase plasminogen activator and thrombin did not interfere, and the assay was used for analysis of basal serum levels of HER-2/neu. Due to the simplicity and low cost, sandwich assays exploiting O2-linked electrocatalysis by the covalent hemin-G4 complexes represent a more advanced electrochemical ELISA platform for ultrasensitive and fast detection of low concentrations of proteins in complex biological matrices.

Original languageEnglish
Article number340049
JournalAnalytica Chimica Acta
Number of pages7
Publication statusPublished - Aug 2022

Bibliographical note

Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.

    Research areas

  • Antibody, Aptamer, Covalent Hemin/G4 complex, DNAzyme, Electrochemical sandwich assay, HER-2/neu, Magnetic beads, O electrocatalysis, Limit of Detection, Oxygen, Hydrogen Peroxide/chemistry, Humans, Hemin/chemistry, DNA, Catalytic/chemistry, Magnetic Phenomena, Biosensing Techniques, Biological Assay, G-Quadruplexes, Aptamers, Nucleotide/chemistry

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