Electrochemical sandwich aptasensor for the carcinoembryonic antigen using graphene quantum dots, gold nanoparticles and nitrogen doped graphene modified electrode and exploiting the peroxidase-mimicking activity of a G-quadruplex DNAzyme
A sandwich–type electrochemical aptasensor has been constructed and applied for sensitive and selective detection of the carcinoembryonic antigen (CEA). The surface of a glassy carbon electrode (GCE) was first modified with nitrogen–doped graphene and then gold nanoparticles and graphene quantum dots electrodeposited on it to obtain an architecture of type GQD/AuNP/NG/GCE. In the next step, the CEA-binding aptamer was immobilized on the modified GCE. Hemin intercalates in the amino-modified hemin aptamer to form a hemin–G–quadruplex (hemin–G4) DNAzyme. The amino modified CEA aptamer II is connected to hemin–G4 by glutaraldehyde (GA) as a linker to produce CEAaptamerII/GA/hemin–G4 (=ApII/GA/DNAzyme). Through a sandwich mode, the ApII/GA/DNAzyme bioconjugates are captured on the modified GCE. Subsequently, the hemin–G4 acts as peroxidase-mimicking DNAzyme and rapidly catalyzes the electroreduction of hydrogen peroxide. The quantitative determination of CEA was achieved by differential pulse voltammetry, best at a working potential of around −0.27 V vs. Ag/AgCl. Under optimized conditions, the assay has a linear response in the 10.0 fg mL−1 to 200.0 ng mL−1 CEA concentration range and a lower detection limit of 3.2 fg mL−1.
KeywordsBiomarker CEA Electroreduction Hydrogen peroxide Hemin–G–quadruplex ·
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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