More rapid and efficient detection methods for foodborne pathogenic bacteria and toxins are needed to address the long assay time and limitations in multiplex capacity. Surface plasmon resonance imaging (SPRi) is an emerging optical technique, which allows for rapid and label-free screening of multiple targets simultaneously. We have evaluated the potential of SPRi in label-free detection of <i>Salmonella</i> isolates and Shiga-toxins (Stx1, Stx2) produced by <i>E. coli</i>. Corresponding antibodies were attached to the gold sensor surface through mercaptoundecanoic acid monolayer and carbodiimide crosslinking, and subsequently blocked with skim milk proteins. Target bacteria and toxins were detected based on SPR sensorgram analysis and difference images. Satisfactory ligand immobilization was achieved at higher antibody concentrations and neutral pH as opposed to acidic and alkali conditions. Polyclonal antibody was more efficiently immobilized compared to monoclonal antibody. Heat-lysed cells were found to generate higher SPR signals due to higher accessibility to the dielectric interface, but non-specific binding to the surface also increased. Nevertheless, blocking of the surface with skim milk solution was found to be effective against non-specific binding. In addition, glycine-HCl and NaOH were found suitable for removing protein and DNA residues from the cell debris. Overall, SPRi demonstrated potentials in sensing both whole pathogenic bacterial cells and their protein metabolites, which makes it a versatile tool in multiplex food safety detection.

Surface plasmon resonance imaging for label-free detection of foodborne pathogens and toxins

254th National Meeting (2017)

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