4 years ago

Triple-Helix Molecular Switch Electrochemical Ratiometric Biosensor for Ultrasensitive Detection of Nucleic Acids

Triple-Helix Molecular Switch Electrochemical Ratiometric Biosensor for Ultrasensitive Detection of Nucleic Acids
Xiaoxia Yan, Zhenzhen Li, Jinhua Chen, Xiaohua Zhang, Jiawan Zhou, Yunqing Liu, Erhu Xiong
Biomolecular receptors such as nucleic acids that switch between two or more conformations upon binding to a specific target can be used to build specific and sensitive biosensors. In this work, based on the electrochemical dual-signaling ratiometric strategy and triple-helix molecular switch, we developed a selective, reusable, and simple electrochemical DNA (E-DNA) biosensor for target DNA (T-DNA) detection. A hairpin DNA capture probe labeled with methylene blue (MB-DNA) self-assembles on the surface of a gold electrode (GE) through Au–S bond, and then a single-strand DNA modified with two ferrocenes (Fc-DNA) on each end to enhance the oxidation signal hybridizes with the MB-DNA to form a triple-helix conformation. When T-DNA exists, the Fc-DNA hybridizes with T-DNA disassembling the triple-helix stem and allowing the MB-DNA to revert to its hairpin structure. Hence, the Fc tags diffuse away from the GE surface while the MB tags remain affixed close to it, resulting in a decrease in the peak current of Fc (IFc) and an increase in that of MB (IMB). The linear relationship between the value of IMB/IFc and the T-DNA concentration is observed from 0.5 to 80 pM, and the limit of detection is as low as 0.12 pM. The developed E-DNA biosensor may have great potential in the electrochemical detection of a wide range of analytes and be a biosensing platform for early clinical diagnosis and biomedical research.

Publisher URL: http://dx.doi.org/10.1021/acs.analchem.7b01251

DOI: 10.1021/acs.analchem.7b01251

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