Responsive Cysteine-Lighted Silver Nanoclusters Regulated by Highly Catalytic G-Quadruplex DNAzyme for Ultrasensitive Detection of Salmonella Typhimurium

Cysteine (Cys) can rapidly and sensitively react with 12 polycytosine-templated silver nanoclusters (polyC(12)-AgNCs) via the formation of Ag-S bond and enhance the fluorescence of polyC(12)-AgNCs. Herein, a smart and enzyme-free biosensing platform for ultrasensitive detection of Salmonella Typhimurium (S. Typhimurium) has been constructed by the ingenious coupling of Y-shaped G-quadruplex DNAzyme (GQH DNAzyme) with polyC(12)-AgNCs. It is worth mentioning that the self-assembly Y-shaped GQH DNAzyme has been utilized for the oxidation of Cys to control the fluorescence signal of polyC(12)-AgNCs. As expected, satisfactory analytical results toward S. Typhimurium were achieved with a good linear relationship in the range of 10 cfu center dot mL(-1) to 5.0 x 10(5) cfu center dot mL(-1) and an outstanding detection limit of 6.3 cfu center dot mL(-1). Emphatically, by replacing the corresponding aptamer for target recognition, this strategy can further extend for detection of various analytes. Thus, the fluorescence sensing strategy based on entropy-driven and self-assembly Y-shaped GQH DNAzyme indeed creates a versatile platform for S. Typhimurium analysis.