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Efficient Separation and Sensitive Detection of Listeria monocytogenes Using an Impedance Immunosensor Based on Magnetic Nanoparticles, a Microfluidic Chip, and an Interdigitated Microelectrode

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Abstract:

Listeria monocytogenes continues to be a major foodborne pathogen that causes food poisoning, and sometimes death, among immunosuppressed people and abortion among pregnant women. In this study, magnetic nanoparticles with a diameter of 30 nm were functionalized with anti–L. monocytogenes antibodies via biotin-streptavidin bonds to become immunomagnetic nanoparticles (IMNPs) to capture L. monocytogenes in a sample during a 2-h immunoreaction. A magnetic separator was used to collect and hold the IMNPs–L. monocytogenes complex while the supernatants were removed. After the washing step, the nanoparticle–L. monocytogenes complex was separated from the sample and injected into a microfluidic chip. The impedance change caused by L. monocytogenes was measured by an impedance analyzer through the interdigitated microelectrode in the microfluidic chip. For L. monocytogenes in phosphate-buffered saline solution, up to 75% of the cells in the sample could be separated, and as few as three to five cells in the microfluidic chip could be detected, which is equivalent to 103 CFU/ml of cells in the original sample. The detection of L. monocytogenes was not interfered with by other major foodborne bacteria, including E. coli O157:H7, E. coli K-12, L. innocua, Salmonella Typhimurium, and Staphylococcus aureus. A linear correlation (R 2 = 0.86) was found between the impedance change and the number of L. monocytogenes in a range of 103 to 107 CFU/ml. Equivalent circuit analysis indicated that the impedance change was mainly due to the decrease in medium resistance when the IMNPs–L. monocytogenes complexes existed in mannitol solution. Finally, the immunosensor was evaluated with food sample tests; the results showed that, without preenrichment and labeling, 104 and 105 CFU/ml L. monocytogenes in lettuce, milk, and ground beef samples could be detected in 3 h.

Document Type: Research Article

DOI: http://dx.doi.org/10.4315/0362-028X.JFP-11-516

Affiliations: 1: Cell and Molecular Biology Program, University of Arkansas, Fayetteville, Arkansas 72701, USA, Center for Energy Research, Nazarbayev University, Astana 010000, Kazakhstan 2: Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA 3: Cell and Molecular Biology Program, Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, USA 4: Cell and Molecular Biology Program, Department of Poultry Science, University of Arkansas, Fayetteville, Arkansas 72701, USA 5: Department of Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA 6: Cell and Molecular Biology Program, Department of Biological and Agricultural Engineering, Department of Poultry Science, University of Arkansas, Fayetteville, Arkansas 72701, USA. yanbinli@uark.edu

Publication date: November 1, 2012

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    The Journal of Food Protection (JFP) is a refereed monthly publication. Each issue contains scientific research and authoritative review articles reporting on a variety of topics in food science pertaining to food safety and quality. The Journal is internationally recognized as the leading publication in the field of food microbiology with a readership exceeding 11,000 scientists from 70 countries. The Journal of Food Protection is indexed in Index Medicus, Current Contents, BIOSIS, PubMed, Medline, and many others.

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