Sensitive colorimetric detection of Salmonella enteric serovar typhimurium based on a gold nanoparticle conjugated bifunctional oligonucleotide probe and aptamer

A rapid, specific and visible detection method for Salmonella enteric serovar typhimurium (S. typhimurium) was developed based on a gold nanoparticle (AuNP) conjugated bifunctional oligonucleotide probe and aptamer. AuNPs were conjugated with bifunctional oligonucleotide probes and aptamer, then the target bacteria S. typhimurium cells were incubated with the conjugated AuNP. Since the aptamer had a higher affinity and specificity on binding with the cells and its configurations was therefore changed, AuNPs particles were released. These AuNPs particles would aggregate with NaCl and the color of the solution would turn blue from red. Under the optimal conditions, the correlation between the concentration of S. typhimurium and the intensity of the signals was observed to be linear within the range of 1.0 × 10¹∼1.0 × 10⁶ cfu/ml (R² = 0.9952), and the detection limit of the proposed method was observed to be 10 cfu/ml. This developed method offers the potential for rapid, sensitive, and visible detection of S. typhimurium in milk and shrimp samples. PRACTICAL APPLICATIONS: The developed method in this study can be used for the detection of S. typhimurium in food samples such as milk and shrimp. Furthermore, the developed method can be easily modified for the simultaneous detection of S. typhimurium and other bacteria.