Colorimetric biosensor based on aptamer recognition-induced multi-DNA release and peroxidase-mimicking three-way junction DNA-Ag/PtNCs for the detection of Salmonella typhimurium.

Salmonella typhimurium, as a major foodborne pathogen, poses a serious threat to public health safety worldwide. Here, we present a colorimetric biosensor based on aptamer recognition-induced multi-DNA release and peroxidase-mimicking three-way junction DNA-silver/platinum bimetallic nanoclusters (3WJ/DNA-Ag/PtNCs) for the detection of S. typhimurium. In this method, S. typhimurium specifically binds to the aptamer and releases multiple cDNAs to form the three-way junction DNA structure and synthesize silver/platinum bimetallic nanoclusters, which induces signaling changes. Interestingly and importantly, the use of 3WJ/DNA as the template for synthesizing Ag/PtNCs gives the method an extremely low background signal. Under the optimal conditions, the constructed biosensor had a linear response range of 2.6 × 102 -2.6 × 106  CFU/mL and a detection limit of 2.6 × 102  CFU/mL for the detection of S. typhimurium. In addition, the proposed method can effectively detect S. typhimurium in milk.