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22 February 2002 Superconducting quantum interference device detection of magnetically tagged micro-organisms
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Proceedings Volume 4576, Advanced Environmental Sensing Technology II; (2002)
Event: Environmental and Industrial Sensing, 2001, Boston, MA, United States
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.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Helene L. Grossman, SeungKyun Lee, Whittier R. Myers, Yann R. Chemla, Yan Poon, H. M. Cho, Robert McDermott, Raymond C. Stevens, Mark Alper, and John Clarke "Superconducting quantum interference device detection of magnetically tagged micro-organisms", Proc. SPIE 4576, Advanced Environmental Sensing Technology II, (22 February 2002);

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