A method for detecting cancer proteins uses the same electromagnetics that let computer hard drives read and write data. Stanford University researchers developing the method hope it will detect cancer in stages earlier than previously possible, when it's easier to treat. Magarray Inc, Sunnyvale, Calif., plan to commercialize the technology.

Cancer cells release small amounts of telltale proteins into the blood before they are visible in medical scans. These proteins are usually detected by tagging them with fluorescent labels. But while all biological samples have some background fluorescence, they have almost no magnetic background. Hence, magnetic protein detection could provide a clearer signal, says Stanford professor of materials science and electrical engineering Shan Wang.

His device takes advantage of grand magnetohyrodyanamics, a significant drop in electrical resistance in the presence of magnetic fields. The device is built on a silicon chip arrayed with 64 magnetic sensors or spin valves. Each valve is coated with a different antibody — a molecule primed to latch onto a particular cancer protein. Exposing the chip to blood serum lets proteins stick to the antibodies. Wang then adds a solution of magnetic nanoparticles, also attached to antibodies, that stick to the captured proteins. The magnetic field of the captured nanoparticles changes the resistance of the underlying spin valve, thereby revealing the concentration of cancer proteins in the serum. Tests of the prototype showed it two orders of magnitude more sensitive than a standard technique for detecting blood proteins. Detecting low levels of seven cancer markers in serum takes about 30 minutes.

Wang says magnetic scanners should be less expensive than standard biomarker scanners. The instrument that reads the output of Wang's chip is smaller than the optical devices that required to read fluorescent signals, and it will probably cost less than $10,000.