Nanotechnology might be key to better detection of cancer's early stages

• If you are among the third of the population who will someday develop cancer, your body will contain warning signs well before your doctor is able to diagnose the disease.
• The problem is that the changes that mark the early stages of cancer are remarkably complex---and often slight, even on a molecular level.
• But James Heath, a physical chemist at the California Institute of Technology, believes that nanotechnology could finally provide the solution to this molecu­lar riddle.
• Heath is betting that banks of ultrasmall silicon wires, each made to detect a specific cancer-related protein, could pick up even the most subtle changes in our body chemistry.
• The nanosensors that Heath and his Caltech coworkers are developing will simultaneously look for hundreds or even thousands of different biomolecules in, say, a drop of blood.
• Blood tests exist for a few cancers, such as prostate and ovarian cancers, but their performance is woeful; not only are they slow and costly, but they're notoriously unreliable.
• Heath's ambition is to construct devices that can not only make multiple measurements at once, from a drop of blood or a few cells taken from a particular tissue, but also detect extremely small quantities of biomolecules.
• "We have identified 300 [cancer marker] genes that are uniquely expressed in the prostate," says Hood, "and we predict that about 62 of these may be secreted into the blood.
• A Fluid Situation What exactly would a nanosensor to detect such proteins look like?
• Charging this electrode alters the conductivity of the nanowire, turning it "on" and "off"---all familiar stuff to any electrical engineer.
• Heath then transforms his nanowire transistors into tiny biosensors.
• Say, for instance, that one nanowire is to act as a sensor for a particular protein.
• The researchers coat the surface of the wire with antibodies that will stick to the target protein but not to other molecules.