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

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Author list: Pratiwi F.W., Rijiravanich P., Somasundrum M., Surareungchai W.

Publisher: Royal Society of Chemistry

Publication year: 2013

Journal: Analyst (0003-2654)

Volume number: 138

Issue number: 17

Start page: 5011

End page: 5018

Number of pages: 8

ISSN: 0003-2654

eISSN: 1364-5528

URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881181162&doi=10.1039%2fc3an00606a&partnerID=40&md5=23863af899ba4a6bfd58ec51c3093243

Languages: English-Great Britain (EN-GB)

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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 ฑ 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. ฉ The Royal Society of Chemistry.

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