Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: 3/17/2008
Publication Date: 4/15/2008
Citation: Liu, Y., Chao, K., Kim, M.S., Nou, X. 2008. Rapid Screening and Species Identification of E. Coli, Listeria, and Salmonella by SERS Technique. Proceedings of SPIE. 6381:6381OU-1-6381OU-9. Interpretive Summary: Citrate-reduced silver colloids have been used extensively for surface-enhanced Raman scattering (SERS) research. To reveal consistent SERS bands from poor reproducibility of SERS signal of bacterial analyte, numerous spectra of mixing various batches of bacterial cultures with different colloidal batches were carefully examined. Characteristic bands at 712 and 390 cm-1, consistently appeared and had the strongest intensity, were identified. Two unique bands were then used to identify E. coli, L. monocytogenes, and S. typhimurium cultures with 100% success. The SERS technique for screening of the presence of bacteria presented in this paper is useful to food processing engineering, regulatory government agencies, and food processing industries.
Technical Abstract: Techniques for routine and rapid screening of the presence of foodborne bacteria are needed, and this study reports the feasibility of citrate-reduced silver colloidal SERS for identifying E. coli, Listeria, and Salmonella. Relative standard deviation (RSD) of SERS spectra from silver colloidal suspensions and ratios of P-O SERS peaks from small molecule (K3PO4) were used to assess the reproducibility, stability, and binding effectiveness of citrate-reduced silver colloids over batch and storage process. The results suggested the reproducibility of silver colloids over batch process and also stability and consistent binding effectiveness over 60-day storage period. Notably, although silver colloidal nanoparticles were stable for at least 90 days, their binding effectiveness began to decrease slightly after 60-day storage, with a binding reduction of about 12% at 90th day. Colloidal silver SERS, as demonstrated here, could be an important alternative technique in the rapid and simultaneous screening of the presence of three most outbreak bacteria due to the exclusive biomarkers, label-free and easy sampling attribute.