Au@Ag core-shell nanorods enhance surface-enhanced Raman scattering aptasensor for ultrasensitive detection of Salmonella Typhimurium

Salmonella Typhimurium is the prevalent pathogenic bacterium that causes foodborne-related diseases. Here, we developed a surface-enhanced Raman scattering (SERS) biosensor for S . Typhimurium detection. The biosensor was based on Au@Ag core-shell nanorods (Au@Ag NRs) to enhance Raman signal and aptamer-specific identification. 4-mercaptobenzoic acid (4-MBA) and aptamer-modified Au@Ag NRs were used as Raman signal probes. The aptamer adsorbed on the Au@Ag NRs surface when the reaction system was free of bacteria. Once S . Typhimurium was added, the aptamer then specifically identified and captured the cells. The decrease of free aptamers in solution restoring the SERS “hot spot” between the Au@Ag NRs and enhancing the 4-mercaptobenzoic acid (4-MBA) Raman signal. Quantitative analysis of S . Typhimurium was performed using Raman-enhanced spectroscopy. Under optimised conditions, the 4-MBA SERS intensity at 1072 cm −1 was used to determine S . Typhimurium in the range of 10 2 –10 7  CFU mL −1 (y = 1660.84x+2340.7, R 2  = 0.9912). The limit of detection was 64 CFU mL −1 . This method also has high specificity and is not interfered by the other five control bacteria to complete the detection of S . Typhimurium. The developed method is simple, rapid, sensitive and specificity, which can be used to detect actual samples. It can be potentially used for detecting bacteria.