ARLINGTON, Va., Aug. 30, 2004 -- Quantum dots---tiny beads that glow in rainbow colors---can zero in with pinpoint accuracy on human prostate cancer.

The research by biomedical engineer Shuming Nie, Ph.D., and his colleagues at the Georgia Institute of Technology suggests a new way to detect and treat disease from the molecular level to that of the whole body.

Because of their size, quantum dots fall under the banner of nanotechnology. They are typically made from semiconductor crystals of cadmium selenide encased in a zinc sulfide shell as small as 1 nanometer (one-billionth of a meter). In ultraviolet light, each dot radiates a brilliant color.

Because exposure to cadmium could be hazardous, quantum dots have not found their way into clinical use, but have been used as markers to tag particles of interest in the laboratory.

Nie's group came up with a new design that protects the body from exposure to the cadmium by sealing quantum dots in a polymer capsule. The surface of each capsule can attach to different molecules. In this case, Nie's group attached monoclonal antibodies directed against prostate-specific surface antigen, which is found on prostate cancer cells.

The researchers injected these quantum dots into live mice that had human prostate cancers. The dots collected in the tumors in numbers large enough to be visible in ultraviolet light under a microscope.

Because the dots are so small, the can be used to locate individual molecules, making them extremely sensitive as detectors. Nie's group estimates that quantum dots could improve tumor imaging sensitivity tenfold with the ability to locate as few as 10 to 100 cancer cells.

The size of quantum dots also makes them potentially useful for delivering cancer-fighting drugs directly to the tumor site without affecting adjacent, healthy tissue. A major question standing in the way of developing quantum dots for medical purposes is how, or if, they are expelled from the body. These and other safety issues would have to be addressed before human testing could be considered.

Quantum dots have been used in the laboratory to detect breast cancer cells and to detect individual breast cancer cells that break away from the tumor site. They have also been useful as markers in other molecular and genetic research.

Nie received a Whitaker Foundation Biomedical Engineering Research Grant in 1991 for sensor research.

Contact:
Shuming Nie, Georgia Institute of Technology
Frank Blanchard, The Whitaker Foundation