Glowing "Quantum Dots" May Speed Diagnosis, DNA Testing

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A new technology enables scientists to "see" the molecules they study with more ease and clarity than ever before. The technology--called quantum dots--may one day be used for speedy disease diagnosis, DNA testing, or analysis of biological samples.

Dr. Shuming Nie and coworkers at Indiana University adapted quantum dot technology to label proteins, genes, and other biological molecules. 1 Quantum dots are crystals made of semiconducting compounds and are so small (far less than a millionth of an inch in diameter) that they are referred to as "nanocrystals." Under ultraviolet light, each quantum dot radiates a brilliant color, depending on its size. For example, larger dots radiate red and smaller dots shine blue.

To use quantum dots as molecular labels, the researchers coax the nanocrystals into the pores of tiny, plastic beads that are tagged with a molecular probe--a protein or DNA sequence that binds strongly to the molecule of interest. After the probe binds to its molecular target in a cell or other biological sample, scientists can visualize the location or abundance of the molecule by lighting up the quantum dots with ultraviolet light.

By mixing quantum dots in different colors and intensities as an artist would mix paints, the scientists predict they can create 10,000 to 40,000 distinguishable quantum dot labels. With each label corresponding to a particular gene or protein, the researchers can detect tens of thousands of molecules all at once.

Quantum dots offer many technical advantages over traditional fluorescent dyes and newer DNA chip technologies, which are commonly used to detect and track biological molecules. They are brighter and easier to visualize than organic dyes. They are also more flexible and yield faster results than other current technologies, such as DNA chips.

In addition to their usefulness in identifying and tracking molecules in basic biomedical studies, quantum dots promise faster, more flexible, and less costly tests for on-the-spot clinical analyses such as screening for illegal drugs and diagnosing conditions ranging from HIV infection to allergies.


1 Han M, Gao X, Su JZ, Nie S. Quantum-dot-tagged microbeads for multiplexed optical coding of biomolecules. Nat. Biotechnol. 2001 Jul;19(7):631-5.

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