Investigation on fluorescence enhancement of DNA tetrahedral structures modified DNA-silver nanoclusters for biosensing

DNA-templated silver nanoclusters (DNA-AgNCs) exhibit infinite application foreground for biosensing due to their fluorescence enhancement properties induced by G-quadruplex (G4). Albeit advanced, their synergistic effects of G4 topologies, and spatial proximity between G4 and DNA-AgNCs remain unclear, which will influence the design of DNA-AgNCs based biosensors and their performance. Herein, the fluorescence enhancement of DNA-AgNCs initiated by three distinct G4 topologies (parallel antiparallel, hybrid) and their distance-dependent behaviors were systematically investigated, using a DNA tetrahedron as a mechanically rigid scaffold to precisely regulate the distance between DNA-AgNCs and G4. We found that parallel G4 structures significantly boosted the fluorescence intensity of DNA-AgNCs, and their closer proximity resulted in elevated fluorescence, which were ascribed to a denser surrounding electron environment that facilitates electron transfer to nearby AgNCs, achieving fluorescence enhancement. Consequently, after encoding a specific aptamer into the reconfigurable edge of the DNA tetrahedron, a novel biosensor was fabricated as a proof-of-concept for rapid detection of aflatoxin B1 with a detection limit of 0.068 ng/mL. Our strategy offered some new insights for rational bioassay design and its performance improvement.