Gold nanoparticles enhanced SERS aptasensor for the simultaneous detection of Salmonella typhimurium and Staphylococcus aureus.

Salmonella typhimurium and Staphylococcus aureus are most common causes of food-associated disease. A Raman based biosensor was developed for S. typhimurium and S. aureus detection simultaneously. The biosensor was based on nanoparticles enhanced Raman intensity and the specific recognition of aptamer. The Raman signal probe and the capture probe are built. Gold nanoparticles (GNPs) modified with Raman molecules (Mercaptobenzoic acid and 5,5'-Dithiobis(2-nitrobenzoic acid)) and aptamer are used as the signal probe for S. typhimurium and S. aureus, respectively. Fe3O4 magnetic gold nanoparticles (MGNPs) immobilized with both aptamer of S. typhimurium and S. aureus are used as the capture probe. When S. typhimurium and S. aureus are added in the reaction system, the capture probe will capture the target bacteria through the specific binding effect of aptamer. And then the signal probe will be connected to the bacteria also by the effect of aptamer to form the sandwich like detection structure. The Raman intensified spectrum was measured to quantify S. typhimurium and S. aureus. Under optimal conditions, the SERS intensity of MBA at 1582 cm(-1) are used to measure S. typhimurium (y=186.4762+704.8571x, R(2)=0.9921) and the SERS intensity of DNTB at 1333 cm(-1) are used to measure S. aureus (y=135.2381+211.4286x, R(2)=0.9946) in the range of 10(2)-10(7) cfu mL(-1). The LOD is 35 cfu mL(-1) for S. aureus and 15 cfu mL(-1) for S. typhimurium. This method is simple and rapid, results in high sensitivity and specificity, and can be used to detect actual samples.