Up to 400 times more sensitive than existing ELISA-based methods
Detecting any of seven cancers in their earliest stages may be feasible through the use of a new biomarker chip that was recently unveiled by scientists from Stanford University’s Center for Magnetic Nanotechnology. To give their biomarker chip increased sensitivity over fluorescent detection methods, the scientists use magnetic technologies to accomplish detection.
Reporting in Proceedings of the National Academy of Sciences (PNAS), lead scientist Shan X. Wang, Ph.D., director of the center and professor of materials science and electrical engineering, says the chip is able to detect very low levels of seven cancers. The biodetection chip is to be marketed by Silicon Valley startup MagArray Inc., of Sunnyvale, California. It detects multiple proteins in blood or DNA strands using magnetic technology similar to how a computer reads a hard drive. Developers say this chip could also be used to diagnose cardiovascular disease and monitor cancer therapy.
The device combines a sandwich antibody assay with 64 magnetic sensors called spin valves. Each valve is coated with a cancer-specific antibody—a molecule primed to attach to that cancer protein. When the chip is exposed to a patient’s blood, the tumor proteins bind to the antibodies. Next, a second batch of antibodies is added. These antibodies bind to both the cancer biomarkers and the magnetic nanoparticles. This changes the resistance on the sensor, so the concentration of nanoparticles on the sensor matches tumor antigens in the blood sample.
In a process that takes less than one hour, Wang says the signal is read by magnetizing the nanoparticles. “The resistance of the sensor changes [and] the more nanoparticles [there] are above each sensor, the more [the] resistance will change,” He explained.
Holding a blood sample and a model of an electron with a magnetic pole to indicate its “spin,” Stanford research scientist Shan Wang, Ph.D., illustrates two applications of his magnetic nanotechnology work: fighting cancer and advancing computing. Photo by Sebastian Osterfeld
The MagArray chip is an exciting breakthrough for several reasons. First, it offers much greater sensitivity than fluorescence-based biomarker tests. That’s because biological samples have some background fluorescence but are magnetically neutral, so “a magnetic field stands out like a flare in the night sky.”
In fact, Wang claims his chip is tens to hundreds of times more sensitive than fluorescent-based tests. In the article published in PNAS, he estimates that the MagArray chip detects levels of human chorionic gonadotropin—a pregnancy hormone and important tumor marker—at levels 400 times lower than what is required for detection by the Enzyme Linked ImmunoSorbent Assay (ELISA).
Second, the chip is based on robust technology widely used in consumer electronic products. It is expected to be both easy to manufacture and cost-effective to use in clinical applications. The instrument that reads the chip is smaller than optical systems used to read fluorescent signals. Wang expects the MagArray system will be less expensive and will sell for less than $10,000.
Wang’s biomarker chip represents one more example of how the intersection of traditional in vitro diagnostics (IVD) with other scientific disciplines is producing novel solutions for detecting cancer and other diseases. These innovations are likely to arm pathologists with highly sensitive tools for early detection of disease, thus giving them an opportunity to add significant value to the clinical care continuum. – P. Kirk
Magnetic nanotechnology holds promise in fighting cancer, advancing computing