Label-free SERS detection of Salmonella Typhimurium on DNA aptamer modified AgNR substrates

A straightforward label-free method based on aptamer binding and surface enhanced Raman spectroscopy (SERS) has been developed for the detection of Salmonella Typhimurium, an important foodborne pathogen which causes gastroenteritis in both humans and animals. Surface of the SERS-active silver nanorod array substrates was modified with anti-S. Typhimurium DNA aptamer and mercaptohexanol, and reacted with S. Typhimurium and S. Enteritidis, E. coli, and E. faecalis as negative control bacteria. Some noticeable spectral changes, including a significantly higher ratio of the 725 and 680 cm(-1) peak intensities (I-725/I-680) was found in the SERS spectra of S. Typhimurium compared to the negative and blank controls. Such spectral changes were confirmed by principle component analysis, and can potentially be used for specific detection of S. Typhimurium. Some limitations of this label-free SERS method with aptamers are also discussed.