A straightforward label-free method based on aptamer binding and surface enhanced Raman specstroscopy (SERS) has been developed for the detection of Salmonella Typhimurium, an important foodborne pathogen that causes gastroenteritis in both humans and animals. Thiol-modified anti-S. Typhimurium DNA aptamer was anchored onto SERS-active silver nanorod array substrates through a self-assembling process, and a spacer molecule, mercaptohexanol, was used to block free adsorption sites on the substrate. Cultures of S. Typhimurium, S. Enteritidis, E. coli, and Enterococcus faecalis were allowed to incubate with the modified SERS substrate and then rinsed off. SERS spectra of S. Typhimurium showed significantly higher intensity ratios of the ?? = 725 and 680 cm-1 peaks (I725/I680) compared to the negative and blank controls. In contrast, when lysed bacterial cell components (supernatant, cell pellets, and mixture) were used, S. Typhimurium showed I725/I680 ratios significantly lower than the negative controls but higher than the blank controls. In both cases, S. Typhimurium can be distinguished from the other samples using principle component analysis. The observed spectral differences may be attributed to the conformational changes in the aptamer DNA when it binds to with its target bacteria, but further studies are needed to confirm this hypothesis.

Label-free SERS detection of <i>Salmonella</i> Typhimurium on aptamer modified AgNR substrates

248th National Meeting (2014)

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