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

Abstract

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, AgNO3, and NaBH4. 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 NaBH4 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 × 102 to 4.6 × 107 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 × 102 cfu mL−1 with a good linear range, indicating that the method had excellent practicability in complex food samples.