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 molecu�lar 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.