An Ultrasensitive Method Using Polymerase Chain Reaction-Dynamic Light Scattering for Detection of Salmonella in Milk

The development of rapid and effective detection of pathogens is necessary to prevent bacterial infection. Herein, we constructed a novel polymerase chain reaction-dynamic light scattering (PCR-DLS) sensing assay for detecting Salmonella sensitively. First, the invA gene specific for Salmonella was designed with upstream and downstream primers containing oxyethylene glycol bridge blockers which could hybridize with DNA-functionalized gold nanoparticle probes (probes-AuNPs). And the probes were hybridized complementary to the trailing end of the primers, which resulted in the aggregation of AuNPs and the change of particle diameter that could be measured by DLS. The results show that the PCR-DLS assay could improve the detection sensitivity and the limit of detection (LOD) was as low as 4.0 CFU/mL in pure culture and 1.8 × 10 2 CFU/mL in the spiked skim milk samples, which the detection time was less than 2 h. In conclusion, this work provides a promising strategy for developing the DLS technique of detecting foodborne pathogens.