Determination of DNA and Thrombin by an Electrochemical Sensor Employing Aggregation of Crosslinked Gold Nanoparticles and Aptamer Segments

Abstract

In this study, a novel and ultrasensitive biosensor strategy based on gold nanoparticles and aptamer segments was designed to detect two biomolecule targets: DNA and thrombin. Two DNA probes were designed that included aptamer segments and nucleic acids. The aptamer segments assembled into a G-quadruplex structure in the presence of thrombin, and the nucleic acids formed a double helix structure with the target DNA. The two gold nanoparticle-labeled DNA probes were effectively aggregated by specific recognition of the target molecules. Methylene blue, a redox-active indicator of single-stranded DNA, was incorporated in the unrecognized segment of the probe on the gold nanoparticle aggregation. Furthermore, the gold nanoparticle aggregation not only provided an excellent conductive matrix for methylene blue, but also abundantly enriched the methylene blue molecule. Using this method, DNA and thrombin were detected in low concentration ranges with both probes. These gold nanoparticle aggregation-based electrodes were independently characterized using cyclic voltammetry, electrochemical impedance measurements, and scanning electron microscopy. The peak currents had a linear relationship with DNA concentration from 2.0 fM to 2.0 pM and with thrombin concentration from 2.0 pM to 2.0 nM.

Keywords:

• Aptamer
• Electrochemistry
• Gold nanoparticle
• Methylene blue
• Sensor

Acknowledgments

This work was funded by the National Natural Science Foundation of China (Projects 21105062 and 21175091).