OPTICAL DETECTION OF FOOD SAFETY AND FOOD DEFENSE HAZARDS
Location: Quality and Safety Assessment Research Unit
Title: Surface enhanced raman spectroscopy technique in rapid detection of live and dead salmonella cells
Submitted to: American Chemistry Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: December 17, 2010
Publication Date: March 25, 2011
Citation: Sundaram, J., Park, B., Zhao, Y., Hinton Jr, A., Windham, W.R., Yoon, S.C., Lawrence, K.C. 2011. Surface enhanced raman spectroscopy technique in rapid detection of live and dead salmonella cells [abstract]. American Chemistry Society Abstracts. 24th ACS National Meeting March 26-31, 2011, Anaheim, CA.
Interpretive Summary: Conventional microbiological methods need more time from days to week to get the result. Though this method is very accurate, rapid detection of pathogens is very much in need nowadays. Many researches proved that Surface Enhanced Raman Spectroscopy (SERS) can detect the pathogen rapidly and accurately. In this study a silver metal surface was used. Nano silver rods were deposited on a thin titanium coating over the glass plates. This was used as a metal substrate for SERS. Salmonella typhimurium, a common food pathogen, was selected for this study and they were prepared in different forms such as live, dead, freeze-dried live and freeze dried dead cells. Principle Component Analysis (PCA) was performed to differentiate the live and dead cells.
Many research proved that Surface Enhanced Raman Spectroscopy (SERS) can detect pathogens rapidly and accurately. In this study, a silver metal substrate was used for the selected common food pathogen Salmonella typhimurium bacteria. Nano silver rods were deposited on a thin titanium coating over the glass plates. Bacteria cells were prepared in the forms of live, dead, freeze dried dead and live cells. These cells were loaded on the metal substrate and spectra were recorded using confocal Raman microscope. The cells were exposed to a laser diode at 785 nm excitation and object 50x was used to focus the laser light on the sample. Raman shifts were obtained from 200 to 2400 cm-1. Spectral signatures of the dead and live cells were compared to differentiate them. Also freeze-dried live cells were compared with the dried cells. These spectral signatures showed the structural changes in bacteria cell components. The results showed that it could be possible to differentiate the live and dead bacteria cells using SERS.