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Proceedings Paper

Superconducting quantum interference device detection of magnetically tagged micro-organisms
Author(s): Helene L. Grossman; SeungKyun Lee; Whittier R. Myers; Yann R. Chemla; Yan Poon; H. M. Cho; Robert McDermott; Raymond C. Stevens; Mark Alper; John Clarke
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Paper Abstract

A fast and versatile technique has been developed for detecting small quantities of specific microorganisms or molecules with high specificity. The target analytes are bound to a substrate and placed in the measurement cell of a microscope based on a high-transition temperature Superconducting Quantum Interference Device (SQUID). A solution containing nanometer-size magnetite particles, coated with antibodies specific to the target, is added. The particles, which bind to the target via the antibody- antigen interaction, are superparamagnetic with a Neel relaxation time of ~1s. A pulsed magnetic field aligns the dipole moments, and the SQUID measures the magnetic relaxation signal when the field is turned off. Unbound magnetic particles relax rapidly (~15microsecond(s) ) by Brownian rotation and are not detected. On the other hand, particles bound to targets cannot rotate and instead relax slowly by the Neel mechanism. As a result, only bound particles contribute to the signal, allowing for quantification of the number of targets present without the need for a wash step. The current system can detect as few as 2000 magnetic particles. This technique could be used to detect a wide range of bacteria, viruses, and molecules, with potential applications in the food industry, clinical settings, or research laboratories.

Paper Details

Date Published: 22 February 2002
PDF: 4 pages
Proc. SPIE 4576, Advanced Environmental Sensing Technology II, (22 February 2002); doi: 10.1117/12.456943
Show Author Affiliations
Helene L. Grossman, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
SeungKyun Lee, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
Whittier R. Myers, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
Yann R. Chemla, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
Yan Poon, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
H. M. Cho, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
Robert McDermott, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
Raymond C. Stevens, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
Mark Alper, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)
John Clarke, Univ. of California/Berkeley and Lawrence Berkeley National Lab. (United States)


Published in SPIE Proceedings Vol. 4576:
Advanced Environmental Sensing Technology II
Tuan Vo-Dinh; Stephanus Buettgenbach, Editor(s)

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