New system would use rotating magnetic field to detect...( WEST LAFAYETTE Ind. - Researchers at...)

WEST LAFAYETTE, Ind. - Researchers at Purdue and Duke universities have developed a technique that uses a magnetic field to selectively separate tiny magnetic particles, representing a highly sensitive method for potentially diagnosing disease by testing samples from patients.

Because different pathogens could be attracted to specific-size magnetic particles and the new technique can selectively separate particles by size, the method could be used to diagnose the presence of many diseases in a single sample, said Gil Lee, a professor of chemical and biomedical engineering at Purdue.

The micron-size magnetic particles have been coated with antibodies that attract certain pathogens and are then mixed with blood samples from patients. A critical piece of the technology is a microchip containing an array of metal disks as wide as 5 microns, or millionths of a meter. The magnetic particles are dispersed in a liquid placed in a container housing the chip. The container is surrounded by three electromagnets energized in sequence to produce a rotating magnetic field.

As the magnetic field rotates, the particles move from one disk to another until they are separated from the rest of the sample. Rotating the magnetic field at specific speeds separates only particles of certain sizes, meaning pathogens attached to those particles would be separated from the sample by varying the rotation speed, Lee said.

In recent experiments, samples containing magnetic particles attached to yeast were placed inside the rotating magnetic field and separated from the rest of the samples. Findings are detailed in a research paper appearing online this month in Lab on a Chip magazine and in the December print edition of the publication. The paper was written by assistant professor Benjamin Yellen, graduate students Randall Erb and H. Son, and undergraduate student R. Hewlin Jr., all from Duke University's Department of Mechanical Engineering and Materials
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