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Nano Lett. 2015 Sep 9;15(9):6239-46. doi: 10.1021/acs.nanolett.5b02837. Epub 2015 Aug 28.

Single-Digit Pathogen and Attomolar Detection with the Naked Eye Using Liposome-Amplified Plasmonic Immunoassay.

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Department of Bioproducts and Biosystems Engineering, University of Minnesota Twin Cities , St. Paul, Minnesota 55108-6005, United States.


We introduce an enzyme-free plasmonic immunoassay with a binary (all-or-none) response. The presence of a single pathogen in the sample results in a chemical cascade reaction leading to a large red to dark-blue colorimetric shift visible to the naked eye. The immediate and amplified response is initiated by a triggered breakdown of cysteine-loaded nanoliposomes and subsequent aggregation of plasmonic gold nanoparticles. Our approach enabled visual detection of a single-digit live pathogen of Salmonella, Listeria, and E. coli O157 in water and food samples. Furthermore, the assay allowed a naked-eye detection of target antibody concentrations as low as 6.7 attomolar (600 molecules in 150 μL); six orders of magnitude lower than conventional enzyme-linked immunosorbent assay (ELISA).


Plasmonic colorimetry; foodborne pathogens; gold nanoparticles; immunoassay; liposomes; signal amplification

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