The U.S. Department of Agriculture (USDA) is exploring a detection technology called Surface-Enhancing Raman Scattering (SERS) for new applications in foodborne pathogen detection. USDA scientist Bosoon Park, an agricultural engineer with USDA’s Agricultural Research Service (ARS), is leading exploratory studies of this analytical technique’s potential, where even the smallest quantity of Salmonella can be detected for quick, easy and reliable detection of Salmonella and other foodborne pathogens.
To conduct a SERS assay, a specimen is placed on a surface which has been enhanced so that it is not smooth. For example, Park’s team enhanced the surface of stainless steel plates by coating them with tiny spheres made up of a biopolymer encapsulated with nanoparticles of silver.
Rough surfaces, and colloidal metals such as silver, can enhance the scattering of light that occurs when a specimen is placed on this “nanosubstrate,” and scanned with the Raman spectrometer’s laser beam. The scattered light that comes back to the spectroscope forms a distinct spectral pattern known as a Raman spectral signature, or Raman scattered signal.
The research team demonstrated for the first time that SERS can distinguish two Salmonella serotypes (Enteritidis and Typhimurium) in mixed concentrations. Park notes that with further research, SERS may prove to be the optimum choice in detection of very small quantities of bacteria in complex matrices such as food or beverage samples. The researchers intend to prove that all molecules, such as those that make up Salmonella, have their own distinctive Raman spectral signature.
Park says SERS has the potential to be used at public health laboratories around the nation to rapidly distinguish salmonella or other pathogens culpable for outbreaks of foodborne illness.
Research collaborators on the project include team members from the USDA ARS Richard B. Russell Research Center in Athens; the University of Georgia-Athens; and South Korea’s Animal, Plant, and Fisheries Quarantine and Inspection Agency.
Photo by Jerry Heitschmidt – Agricultural engineer Bosoon Park (right) and postdoctoral research associate Jaya Sundaram examine a hyperspectral microscope image of an experimental substrate developed for SERS food-safety analyses