Determination of the invA gene of Salmonella using surface plasmon resonance along with streptavidin aptamer amplification

We have developed a sensitive method for the determination of Salmonella by integrating a streptavidinylated aptamer (SA-aptamer) as a signal amplification unit along with a modified asymmetric polymerase chain reaction (PCR) technique into the surface of an SPR sensor chip. The gold film of the sensor was first modified with a thiolated probe, and the target sequence and SA-aptamer were then induced to form a sandwich structure. If SA is added, the SA-aptamer forms a complex with SA which will amplify the signal. Under optimal conditions, this sensing scheme has a linear response in the 50 pM to 200 nM range, and the lower detection limit is 20 pM (for a synthetic target sequence). This strategy was successfully applied to the determination of Salmonella bacteria at levels as low as 60 CFU mL(-1). This biosensor is sensitive, selective and highly stable. These features make this strategy a promising and powerful screening tool to detect pathogens in food, and in clinical and environmental samples.