A novel fluorescent platform of DNA-stabilized silver nanoclusters based on exonuclease III amplification-assisted detection of Salmonella Typhimurium

A novel fluorescent platform of DNA-stabilized silver nanoclusters (DNA-AgNCs) has been developed based on exonuclease III (Exo III) amplification-assisted for simple and sensitive detection of Salmonella Typhimurium ( S. Typhimurium). The platform was designed by using magnetic beads, aptamer, its complementary DNA , hairpin probe (HP), Exo III, AgNO 3 , and NaBH 4 . The functionalized HP contained a cytosine-rich oligonucleotide loop (C-rich loop), which served as an effective template for the chemical reduction of Ag + with NaBH 4 to synthesize DNA-AgNCs. In the presence of S. Typhimurium, the C-rich loop was converted into an open form of ssDNA by the recycle digestion of Exo III, leading to a corresponding decrease in fluorescence intensity . Based on the fluorescence changes of the formed DNA-AgNCs, the sensitive detection of S. Typhimurium was achieved. Under the optimal conditions, a wide linear relationship was observed in the concentration of S. Typhimurium ranging from 4.6 × 10 2 to 4.6 × 10 7  cfu mL −1 with the limit of detection (LOD) being 82 cfu mL −1 . The method showed good selectivity for detecting S. Typhimurium. In addition, the platform could be used for the detection of S. Typhimurium in milk samples. The LOD reached 6.6 × 10 2  cfu mL −1 with a good linear range, indicating that the method had excellent practicability in complex food samples.