Toehold-regulated Competitive Assembly to Accelerate Kinetics of Graphene Oxide-based Biosensors
With effective adsorption and quench efficiency, graphene oxide (GO) can be utilized for biomolecules sensing, such as nucleic acid or protein detection. In theses assays, fluorephore-labeled nucleic acid (reporter) is usually absored by GO first, and followed by adding the target molecules to bind the reporter, thus restoring the fluorescence signal. However, this kinetic of fluorescence recovery is usually very slow because the target is probably absorbed by GO and comprimise the binding of the target and the repoerter. Herein, we proposed a toehold-regulated strand displacement strategy to accelerate the kinetic of GO-based biosensing. In this strategy, the toehold of duplex mediated a competitive assembly of the target, the reporter and GO by eliminating the absorption of the target and facilitating the binding of the target and the reporter. While the duplex with toehold of target-blocker DNA or reporter-blocker DNA formed, the rigid structure of duplex will weaken the absorption of the target by GO and enhance the recognition of reporter to the target. This strategy achieved up to 2.6-fold enhancement of fluorescence signal restoration for nucleic acids detection, while 3.2-fold enhancement of fluorescence signal restoration for thrombin detection. It is also demonstrated that this strategy can be used for determination of DNA and thrombin in diluted serum with excellent specificity.