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Issue 17, 2013
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Electrochemical immunoassay for Salmonella Typhimurium based on magnetically collected Ag-enhanced DNA biobarcode labels

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Abstract

We describe a sensitive electrochemical immunoassay for Salmonella enterica serovar Typhimurium, a common foodborne pathogen which can cause infection at extremely small doses. The assay is based on the recognition of DNA biobarcode labels by differential pulse anodic stripping voltammetry (DPASV), following Ag enhancement. The biobarcodes consist of latex spheres (mean diameter 506 nm ± 22 nm) modified by ferromagnetic Fe3O4 particles. Each biobarcode is loaded by adsorption with approx. 27 molecules of mouse monoclonal antibody against S. Typhimurium and 3.5 × 105 molecules of 12 mer ssDNA. The assay is performed by adding the biobarcode, S. Typhimurium cells, and biotin-conjugated rabbit polyclonal antibody against Salmonella into well plates. After antigen–antibody binding, magnetic collection enables the excess polyclonal antibody to be washed off. Exposure to avidin-coated screen printed electrodes, and formation of the avidin–biotin bond, then enables the excess biobarcode to be removed. The biobarcode remaining on the electrode is quantified by DPASV measurement of Ag+ ions following catalytic Ag deposition. The assay showed a negligible response to 107 CFU mL−1E. coli and had a limit of detection of 12 CFU mL−1 in buffer, and 13 to 26 CFU mL−1 for heat-killed and whole cell S. Typhimurium in plain milk, green bean sprouts and raw eggs. To the best of our knowledge, this is the lowest reported limit of detection for Salmonella by an electrochemical immunoassay not requiring sample pre-enrichment.

Graphical abstract: Electrochemical immunoassay for Salmonella Typhimurium based on magnetically collected Ag-enhanced DNA biobarcode labels

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Publication details

The article was received on 28 Mar 2013, accepted on 23 Jun 2013 and first published on 24 Jun 2013


Article type: Paper
DOI: 10.1039/C3AN00606A
Citation: Analyst, 2013,138, 5011-5018

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    Electrochemical immunoassay for Salmonella Typhimurium based on magnetically collected Ag-enhanced DNA biobarcode labels

    F. W. Pratiwi, P. Rijiravanich, M. Somasundrum and W. Surareungchai, Analyst, 2013, 138, 5011
    DOI: 10.1039/C3AN00606A

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