Quantum dots light up cancer cells in mice.

By tagging living cells with nanometer-size semiconductor crystals known as quantum dots, researchers recently opened a new way of viewing the cell's machinery (SN: 2/15/03, p. 107). With the goal of developing more-sensitive screens for detecting cancer, scientists have now used quantum dots to track down and light up cancer cells in mice.

Typically made with elements such as cadmium, quantum dots are toxic, making them questionable for use in animals. So biomedical engineer Shuming Nie of the Georgia Institute of Technologic in Atlanta and his colleagues coated the quantum dots with a protective polymer that lets the nanoparticles' fluorescence shine through. To the coating, the researchers then affixed antibodies that seek out prostate cancer cells. All dressed up, each quantum-dot particle measured 20 nanometers to 30 nm in diameter.

Once injected into the bloodstream of mice bearing prostate tumors, the quantum dots homed in on the tumors. When the researchers viewed the mice under a mercury lamp, the tumors lit up through the skin. Nie's team details the technique in the August Nature Biotechnology.

Compared with conventional fluorescent labels, which are typically made of organic molecules and come in only a few colors, quantum dots are brighter, and stabler, and can be tuned to emit a variety of wavelengths simply by varying the size of the particle. By using different-colored quantum dots, researchers might track down a variety of proteins and genes associated with disease. How, or even whether, the body would clear itself of the nanoparticles is among the questions that will need answers before the technology can be used in people.--A.G.