Enhancing resolution in DNA staining dye-based label-free visual fluorescence aptasensor: Strategy for eliminating non-specific binding-induced signal interference.

By optimizing the quenching capabilities of diverse two-dimensional (2D) nanomaterials such as graphene oxide (GO), TiC MXene, and MoS, we have pioneered a label-free fluorescence aptasensor with near-zero background signal, enabling highly sensitive detection of aflatoxin B1 (AFB1). This aptasensor was equipped with a newly synthesized dicationic fluorophore, VLM, which exhibited binding-induced turn-on fluorescence properties. Among the evaluated 2D nanosheets, MoS nanosheets were found to exhibit exceptional quenching efficiency for the background emission of the cDNA/VLM complex (cDNA was the complementary DNA of the aptamer), further enhancing the overall performance of our aptasensor. Upon exposure to AFB1, the aptamers underwent conformational switching and target binding, leading to the formation of aptamer/AFB1 complex. Additionally, the aptamers bound complementarily to cDNA, creating aptamer-cDNA duplexes that interacted with VLM, resulting in a robust fluorescence signal. Despite the presence of a weakly fluorescent cDNA/VLM background, this fluorescence could be effectively quenched by the addition of MoS nanosheets. Consequently, the label-free fluorescence aptasensor exhibited excellent linearity with AFB1 concentration within 2-3000 ng mL, achieving a limit of detection (LOD) of 0.006 ng mL. Remarkably, the visual fluorescence captured by a smartphone camera can be processed using extracted grayscale values, consistently revealing a linear relationship with the AFB1 concentration within 2-3000 ng mL, with a LOD of 0.197 ng mL. This aptasensor demonstrated exceptional sensitivity and a remarkably rapid sample-to-answer detection time of 74 min, showcasing its immense potential as a straightforward, sensitive, and visually intuitive method for rapid AFB1 detection with enhanced resolution.