Stanford University researchers developing a new magnetic protein detection system that uses the same magnetic phenomenon (giant magnetoresistance) that lets computer hard drives read and write data, and is two orders of magnitude more sensitive than the standard technique for detecting blood proteins.

The device is built on a silicon chip arrayed with 64 magnetic sensors called spin valves. Each valve is coated with a different kind of antibody, a molecule primed to latch on to a particular cancer protein. When the chip is exposed to blood serum, the target proteins stick to the antibodies. A solution of magnetic nanoparticles, also attached to antibodies, is then added, that stick to the captured proteins. The magnetic field of the captured nanoparticles measurably changes the resistance of the underlying spin valve, allowing for determining the concentration of cancer proteins in the serum.