NANOTECHNOLOGY—TECHNOLOGY ON A MOLECULAR SCALE - Chemistry: Notable Research and Discoveries - page 60

work by entering the circulatory system—the patient receives an injec-
tion or swallows a pill in which the medicine eventually gets into the
bloodstream—and the blood carries it not only to the site of disease but
also to other tissues and organs as well.
Nanotechnology offers the promise of specific targeting in medi-
cine because its size is on the same scale as cells and proteins it needs
to find. Instead of flooding the body with medication, medical ap-
plications of nanotechnology zooms in on the problem areas. Nano-
technology seeks to hunt down the bad guys while leaving the peaceful
population alone.
Cancer is a particularly important disease to treat early, before the
disease invades too much tissue. Quantum dots may offer one impor-
tant method of detecting the disease in its early stages. Cancerous cells
often make certain proteins or other molecules that are attached to the
cell's membrane and help the cell to grow and divide. These proteins are
not found in healthy cells or are much rarer than in cancerous ones and,
therefore, can serve as miniature markers for the diseased cells. These
markers would make cancer cells easy to detect, but physicians do not
usually have an effective tool with which to see them.
Visualizing the markers is a good mission for nanotechnology since
quantum dots can be attached to molecules that bind to the markers.
Shuming Nie, a researcher at Georgia Institute of Technology, and
other scientists have developed quantum dots made of cadmium sel-
enide for this purpose. These quantum dots fluoresce—they emit light
when excited by electromagnetic radiation from the ultraviolet portion
of the spectrum, which is invisible radiation slightly beyond the violet
end—and the color of light depends on the size of the quantum dot.
Researchers can make a colorful array of dots by varying the size and
structure, then attach each one to a different molecule. When placed
in tissue samples, these dots bind to cancer cells. By shining a small,
safe amount of ultraviolet light on the sample, the dots—and the cancer
cells—stand out in full color.
Physicians are perfecting this technology in order to detect cancers
at the soonest possible moment. But nanotechnology may not only be
able to find cancer cells, it may also provide the means to attack and
destroy them.
Gold offers yet another example of a case where a small-scale ma-
terial has properties not shared by its bulkier form. Gold is an inert
metal (though a shiny and valuable one), but it makes quite a boisterous