Microtech2010 2010

Towards an asynchronous magnetic bead rotation method for immunological assays

A. Hecht, P. Kinnunen, B. McNaughton, R. Kopelman
University of Michigan, US

Keywords: paramagnetic particles, biodetection, rotation


Much attention has been focused on using magnetic particles for biodetection applications on chip. Most of these applications involve using the magnetic particles either for translational motion in a magnetic field, or as labels for magnetoresistive sensing. Here we present an application using paramagnetic particles as the basis for rotational motion in a magnetic field, correlating the rate of rotation of a magnetic cluster with the concentration of a sample target analyte. In a rotating magnetic field, paramagnetic particles rotate out of synch with the field. Rotation that is asynchronous depends on the volume, drag and total magnetic moment of the particle, which is ideal for biosensing applications. These principles have been previously applied with ferromagnetic particles for viscosity sensing, pH sensing, and single bacterial cell detection. The principle of using asynchronous magnetic rotation for biodetection is illustrated in Figure 1, using paramagnetically labeled biotin and streptavidin particles to mimic an antibody-antigen system. The rate of rotation of the particle cluster increases with particle concentration over 2 orders of magnitude, demonstrating the potential for using this system as a biosensor.
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