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UCD Bionanoscience Research Group
Principal Investigator: Prof. Gil U. Lee
Research strands:
Early detection of infectious diseases could greatly enhance the quality of medical care and limit the spread of emerging diseases. Thus, there is a need for rapid, sensitive, and inexpensive point-of-care sensors that are capable of identifying multiple pathogens in complex samples such as blood.

Superparamagnetic microparticles have made it possible to rapidly and efficiently separate cells from complex mixtures such as fermentation broths and culture media without complicated equipment. In this technique, the magnetic particles are coated with antibodies that react with the cell-line of interest. After a short reaction, a simple permanent magnet can be used to separate the superparamagnetic particles and specific cell type of interest. Magnetic separation is exceptionally efficient because most biological materials are not susceptible to magnetic fields and the fluidized beds of microparticles have a very high reaction rate. This research group has developed novel techniques for sensing and separating pathogens bound to superparamagnetic microparticles. Early work at the Naval Research Laboratory focused on using magnetic particles to detect pathogens bound to a surface and using force to enhance the specificity of the specific molecular interaction. Techniques were developed to detect the magnetic particles through force, optical, and magnetic field sensing.

More recently, this group has focused on identifying magnetic particle pathogen complexes through magnetophoretic separation. Magnetophoresis is a separation process in which both hydrodynamic and magnetic fields are used to separate a magnetic microparticle from an aqueous solution. We have demonstrated magnetophoretic sensing is capable of detecting type 2 Dengue virus at a concentration < 103 virus per ml in serum, which in principle could allow this deadly disease to be accurately diagnosed when symptoms first become evident.

A new mode of magnetophoresis has also been described that is capable of separating micron-sized superparamagnetic beads from complex mixtures with high sensitivity to their size and magnetic moment. This separation technique employs a translating periodic potential energy landscape to transport magnetic beads horizontally across a substrate. The potential energy landscape is created by superimposing an external, rotating magnetic field on top of the local fixed magnetic field distribution near a periodic arrangement of micro-magnets. At low driving frequencies of the external field rotation, the beads become locked into the potential energy landscape and move at the same velocity as the traveling magnetic field wave. At frequencies above a critical threshold, defined by the bead.s hydrodynamic drag and magnetic moment, the motion of a specific population of magnetic beads becomes uncoupled from the potential energy landscape and its magnetophoretic mobility is dramatically reduced. By exploiting this frequency dependence, highly efficient separation of magnetic beads has been achieved based on fractional differences in bead diameter and/or their specific attachment to two microorganisms, i.e. B. globigii and S cerevisiae.