In this work, a rapid method for foodborne pathogen extraction and concentration using magnetic nanoparticles (MNPs) was integrated with a gold nanoparticle (GNP) colorimetric DNA biosensor for fast and accessible detection of target bacteria. Experiments for both extraction and detection were conducted first using pure cultures without interfering food matrix components and followed by testing in food matrices commonly associated foodborne outbreaks. Magnetic concentration was tested with three bacterial species: Listeria spp., Escherichia coli O157, and Staphylococcus aureus. Then, a colorimetric GNP biosensor was developed and tested for E. coli O157. Glycan-coated MNPs are ideal for foodborne pathogen concentration due to their low cost, simple storage conditions, and bacteria binding capabilities. Meanwhile, GNPs visibly change color upon aggregation, which allows for easy use in colorimetric biosensors without the need for expensive analytical equipment. Results from this study indicate concentration of bacteria to up to 60 times its initial concentration in buffer solution and 11 times in select food matrices. In addition, the colorimetric biosensor was capable of differentiating between target and non-target DNA from pure cultures at concentrations as low as 2.5 ng/ÎơL. Finally, the integrated extraction and detection assay was capable of detecting E. coli O157 from contaminated flour. This assay shows immense promise for rapid foodborne pathogen detection, and evidence-based recommendations for continued optimization have also been identified.
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