Purpose: The purpose of this study is to demonstrate the performance of a direct pathogen measurement system using a nanotechnology-based immunoassay coupled with Surface enhanced Raman scattering (SERS) detection methodology. The system has been designed not only to reduce the time of detection as wells as to minimize the risk of pathogen exposure to the user running the system and the surrounding environment.
Methods: The surface of 60nm colloidal gold nanoparticleis coated with a Raman activere reporter molecule (SERS-Tag). The SERS-Tag is then conjugated to pathogen specific antibodies while magnetic microparticles are coupled with complementary antibodies to the same pathogen target. The target pathogen is immunologically bound by both the SERS-Tag nanoparticle and the magnetic particle. Aggregates form a large magnetic pellet that can be pulled to the side of a culture vessel where the pellet is interrogated with a laser at defined wavelength.
Results: Pathogen specific SERS nanoparticles and pathogen specific magnetic particles were directly added to the selective media. These conditions did not interfere with the growth kinetics of the target pathogen. Direct measurement of the resulting Raman spectral signal corresponded to the amount of pathogen present in the sample. The limit of detection was 1 CFU per food sample. Analytical sensitivity was typically 105CFU/mL.
Significance: The results obtained in this study support that SERS nanotechnology-based immunoassay coupled with real-time measurement during enrichment is a powerful method for rapid detection of foodborne pathogen.