Disease-Detecting Prototype Offers Rapid Results

NEWS TRENDS

With just a quick swipe, doctors may soon be able to test a patient for hundreds of diseases. University of Utah scientists have spent eight years developing a diagnostic prototype device, which is based on a giant magnetoresistance (GMR) platform.

Research scientist Michael Granger defines magnetoresistance (MR) as “the change in a material's resistance in the presence of an applied magnetic field.” Most conductive materials demonstrate a change around 1%, but Granger says that some multi­layered materials, composed of alternating magnetic and nonmagnetic layers, may demonstrate an MR effect near 80%. This is known as GMR, and it is the heart of the team's prototype bioassay reader.

The system works by applying a minute amount of sample, such as blood or saliva, to a test coupon. Granger says that the sample incubates “over spots coated with capture antibodies that bind specific markers of disease.” If the marker is present and captured on the test coupon's surface, a magnetic nanoparticle binds to the marker and serves as a label for subsequent readouts. From there, Granger says that the test coupon is rubbed across the GMR reader in a motion similar to a credit-card swipe. The GMR reader detects the presence of the magnetic nanoparticle label and provides the sample concentration of the marker. The results of the swipe are immediately available.

Granger says that the device can detect the presence of any disease markers for which an antibody has been developed. One example includes herpes. Obstetricians sometimes perform cesarean sections when they suspect maternal herpes but Granger says that his device could eliminate an unnecessary procedure by providing rapid results about a mother's health.

The GMR sensor technology is theoretically sensitive enough to detect markers at single-digit levels and could read out test coupons in less than 1 minute. According to Granger, the research team's current prototype of the device can detect 800 labels in 20 seconds.

The prototype is about the size of a desktop PC but, when developed commercially, it will look like a credit-card reader. Since GMR sensor platforms are currently used to read data on computer hard drives or listen to songs on portable music players, Granger says the device could be made small enough to use in a physician's office, pharmacy, or patient's home. Another benefit of the device is its cost. Small diagnostic labs would find it affordable because it is based on inexpensive hard-drive technology that is already available.

Granger's colleagues include Utah Science, Technology, and Research (USTAR) professor of chemistry, chemical engineering, and bioengineering Marc Porter, PhD, Iowa State University students John Nordling and Rachel Millen; postdoctoral research associates Heather Bullen and Toshiakzu Kawaguchi; and industrial collaborator Mark Tondra of NVE Corp. (Eden Prairie, MN).

The project has received funding from the National Science Foundation's XYZ-on-a-Chip initiative, the W. M. Keck foundation, and the Defense Advanced Research Projects Agency's BioMagnetICs program.

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