Medical Diagnostics at the Swipe of a Card

E-mail Melanie Martella

Sensors are increasingly being used in medical fields, whether to automate testing, monitor patients, or improve existing medical equipment. So, while it's no surprise to hear about new sensor use in medicine, some of those new developments are both extremely neat and extremely useful.

A prototype device developed recently could test for multiple disease markers simultaneously and give results in minutes. The research, headed by University of Utah scientists Marc Porter and Michael Granger was conducted at Iowa State University with John Norling, Rachel Millen, Heather Bullen and Mark Tondra, then with NVE Corp.

The system the researchers created combines a giant magnetoresistive (GMR) read head with a sample stick. Load the sample stick (currently made of Pyrex glass) with microscopic samples (blood, saliva, urine), run the stick through the sensors, and find out whether those samples contain any disease markers. According to Michael Granger, as quoted in "A Card-Swipe for Medical Tests", "You can envision this as a wellness check in which a patient sample—blood, urine, saliva—is spotted on a sample stick or card, scanned, and then the readout indicates your state of well-being. We have a great sensor able to look for many disease markers."

It turns out that GMR's ability to detect very low magnetic fields can also be used to do more than read back data from a computer hard drive. It can also detect the minute magnetic particles used to tag biological materials.

The researchers applied microscopic gold spots to the stick-gold has no magnetic signature-and then chemically bound biotin (Vitamin B7) to those spots. The result? No magnetic field to read. However, when magnetically tagged protein drops were placed on those spots, the protein bound to the biotin and the sensors could then detect the resulting tiny magnetic field. In fact, during testing of the prototype to divine just how small the gold spots could be, the researchers found that it could detect "as few as 800 microscopic particles that mimicked disease-related substances." (If you're interested in brushing up on your GMR knowledge, I refer you to "Low Magnetic Field Sensing with GMR Sensors Part I: The Theory of Solid-State Magnetic Sensing".)

The technology is great, but it's the scope of the applications that interests me more. What the researchers envision is a testing device affordable enough for small diagnostic labs and, maybe eventually, for pharmacies. It could be used for environmental monitoring, veterinary diagnostics, and for rapid homeland security-related testing. And the way it's designed, it should be very easy to use: just swipe the sample card through the reader and wait for the results.