The new technique uses a magnetic field to selectively separate tiny magnetic particles, representing a highly sensitive method for potentially diagnosing disease by testing samples from patients.
Gil Lee, a professor of chemical and biomedical engineering at Purdue, explained that 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.
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.
Lee said that 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.
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.
The technique works using an array of disks made of cobalt and coated with chromium to prevent corrosion. The disks are regularly, or periodically, spaced on the surface of the silicon chip.
Shang, co-founder of MagSense Life Sciences Inc. and a research scientist at the company, located at the Purdue Research Park said that a benefit of the non-linear magnetophoresis technique is that it can be used to simultaneously separate and identify pathogens with a sensitivity up to a million times higher than the "solid phase immunoassays" commonly used today for human diagnostics.
The company is developing a new method to produce the magnetic particles.
The 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.