Multispatially Localized DNA Walker Coupling Covalent Organic Framework for Dual-Mode Detection of Nucleocapsid Protein Using the Walking-Recycling-Conversion Strategy

DNA walkers have emerged as a powerful tool in bioanalysis; however, many existing approaches are still restricted by low reaction kinetics and inaccurate single-mode detection. Herein, a fluorescence (FL) and electrochemical (EC) dual-mode biosensor was proposed based on a multispatially localized DNA walker (m-DNA walker) coupling covalent organic framework (COF) using the walking-recycling-conversion strategy. Specifically, the functionalized COF not only served as a three-dimensional nanocarrier but also acted as an effective quencher of the walking tracks. In the presence of the target, the activated m-DNA walker moved fast along the numerous quenching tracks, leading to the cleavage of Cy3-H1 and the recovery of the FL signal. To further improve the detection sensitivity, the Cy3-H1 fragments' recycling process was implemented with the generation of a large amount of S1 and S2, which caused the assembly of DNA-Fe