A label-free electrochemical biosensor based on novel DNA nanotweezer coupled with G-quadruplex for sensitive DNA detection

In this work, a label-free electrochemical biosensor for DNA assay was constructed based on a novel structural DNA nanotweezer (DNT) coupled with split G-quadruplex. The novel DNT consists of a long single strand with two hairpin structures in the middle as a recognition element and two short single strands with split G-rich sequences at outsides as a signal reporter. The target triggered two hairpin structures hybridized with each other, it caused the DNT transformation from open to close. The closed DNT facilitated the split G-rich sequences combined together and provided electrochemical signals. Here, the hairpin structures were not only used for specific target identification but also avoided the false positive signals and improved the sensitivity. Additionally, the split G-rich sequences were put at outsides instead of insides, which significantly improved the signal-background ratio. Moreover, the construction of this biosensor was convenient and easy to control, which was beneficial to reduce the error generated by the operation process and improve stability and reproducibility. Under the optimal conditions, the proposed assay achieved a low detection limit (22 aM) and a wide linear range (1 fM to 1 nM) for circulating tumor DNA determination. This efficient and convenient DNT can be used as a template in electrochemical biosensors fabrication.

Automated summary

A label-free electrochemical biosensor for DNA assay was constructed using a novel structural DNA nanotweezer (DNT) coupled with split G-quadruplex. The biosensor showed high sensitivity, low detection limit, and ease of operation, contributing to improved stability and reproducibility in detecting circulating tumor DNA.