摘要
We report a triplex signal amplification strategy for sensitive biosensing of cancer biomarker by taking advantage of hairpin-shaped oligonucleotide-functionalized gold nanorods (HO-GNRs), graphene and the avidin-biotin reation. The strategy expands electrochemical detection of carcinoembryonic antigen (CEA) by using an aptamer as biosensor's recognition element and HO-GNRs as signal enhancer. To construct this biosensor, the GNR was used as a carrier of horseradish peroxidase (HRP) and HO aptamer with a biotin at the 3′-end and a thiol at the 5′-end, which amplified the electrochemical response because of a large molar ratio of HRP to HO. In the presence of target CEA, the binding reactions of CEA with the loop portions of the HOs caused HOs’ loop-stem structure opened and exposed the biotins, and then HRP-GNRs-HO conjugates were captured on graphene and streptavidin modified electrodes via the reaction between the exposed biotins and preimmobilized streptavidins. The accumulation of HRP effectively catalyzed the hydrogen peroxide-mediated oxidation of o -phenylenediamine to generate an electrochemical reduction current for CEA detection. Under optimal conditions, the electrochemical biosensor exhibited a wide dynamic range of 5 pg mL −1 and 50 ng mL −1 toward CEA standards with a low detection limit of 1.5 pg mL −1 (signal-to-noise ratio of 3). The proposed biosensor accurately detected CEA concentration in 8 human serum samples from patients with lung diseases, showing excellent correlations with standard chemiluminescence immunoassay . Furthermore, these results of target DNA detection made it abundantly clear that the proposed strategy can also be extended for detection of other relative biomarkers using different functional DNA structures , which shows great prospects in single-nucleotide polymorphisms analysis, biomedical sensing and application for accurate clinical diseases diagnostic.
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