Detection of bacteria in suspension using a superconducting Quantum interference device

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We demonstrate a technique for detecting magnetically-labeled Listeria monocytogenes and for measuring the binding rate between antibody-linked magnetic particles and bacteria. This assay, which is both sensitive and straightforward to perform, can quantify specific bacteria in a sample without the need to immobilize the bacteria or wash away unbound magnetic particles. In the measurement, we add 50 nm diameter superparamagnetic particles, coated with antibodies, to a liquid sample containing L. monocytogenes. We apply a pulsed magnetic field to align the magnetic dipole moments and use a high transition temperature Superconducting Quantum Interference Device (SQUID), an extremely sensitive detector of magnetic ... continued below

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31 pages

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Grossman, H.L.; Myers, W.R.; Vreeland, V.J.; Alper, J.D.; Bertozzi, C.R. & Clarke, J. June 9, 2003.

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We demonstrate a technique for detecting magnetically-labeled Listeria monocytogenes and for measuring the binding rate between antibody-linked magnetic particles and bacteria. This assay, which is both sensitive and straightforward to perform, can quantify specific bacteria in a sample without the need to immobilize the bacteria or wash away unbound magnetic particles. In the measurement, we add 50 nm diameter superparamagnetic particles, coated with antibodies, to a liquid sample containing L. monocytogenes. We apply a pulsed magnetic field to align the magnetic dipole moments and use a high transition temperature Superconducting Quantum Interference Device (SQUID), an extremely sensitive detector of magnetic flux, to measure the magnetic relaxation signal when the field is turned off. Unbound particles randomize direction by Brownian rotation too quickly to be detected. In contrast, particles bound to L. monocytogenes are effectively immobilized and relax in about 1 s by rotation of the internal dipole moment. This Neel relaxation process is detected by the SQUID. The measurements indicate a detection limit of (5.6 {+-} 1.1) x 10{sup 6} L. monocytogenes for a 20 {micro}L sample volume. If the sample volume were reduced to 1 nL, we estimate that the detection limit could be improved to 230 {+-} 40 L. monocytogenes cells. Time-resolved measurements yield the binding rate between the particles and bacteria.

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31 pages

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INIS; OSTI as DE00836039

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  • Journal Name: Proceedings of the National Academy of Sciences USA; Journal Volume: 101; Journal Issue: 1; Other Information: Submitted to the Proceedings of the National Academy of Sciences USA: Volume 101, No.1; Journal Publication Date: 01/06/2004

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  • Report No.: LBNL--53187
  • Grant Number: AC03-76SF00098
  • DOI: 10.1073/pnas.0307128101 | External Link
  • Office of Scientific & Technical Information Report Number: 836039
  • Archival Resource Key: ark:/67531/metadc783524

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  • June 9, 2003

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  • Dec. 3, 2015, 9:30 a.m.

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  • June 15, 2016, 1:05 p.m.

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Grossman, H.L.; Myers, W.R.; Vreeland, V.J.; Alper, J.D.; Bertozzi, C.R. & Clarke, J. Detection of bacteria in suspension using a superconducting Quantum interference device, article, June 9, 2003; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc783524/: accessed September 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.