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  • Quantum Dots Reveal Minute Details of Brain Chemistry
Oct 2003
HAYWARD, Calif., Oct. 20 --French researchers have used a new imaging tool, the size of individual molecules, to reveal more clearly than ever before the workings of the human nervous system -- including processes that may eventually provide clues to treating common neurological disorders.

In a study published in the Oct. 17 issue of the journal Science, the researchers reported they used quantum dots developed and manufactured by Hayward-based Quantum Dot Corp. (QDC) to track the movements of individual glycine receptor molecules in the membranes of living cells. The results mark the first time researchers have been able to track single-molecule properties in living cells for extended periods within a single experiment.

"This significant study again validates the importance of quantum dots for biomolecular imaging and drug development," said Carol Lou, president of QDC. "Our Qdot conjugates give researchers a powerful new tool in the quest to develop new drugs that can successfully treat human neurological disorders and other diseases."

Older imaging tools such as fluorescent dyes or polymer spheres are either too unstable or too big to effectively perform single-molecule tracking, the scientists wrote. QDC's quantum dot conjugates, by contrast, produced photo resolutions up to eight times more detailed than the older imaging tools. The quantum dot conjugates also proved to be "almost an order of magnitude" brighter than fluorescent dyes, and could be observed for as long as 40 minutes, compared to about 5 seconds for the dyes, the French scientists reported. Length of observation time is critical to studying cellular processes, which change rapidly over a span of several minutes.

Quantum dots are nanoscale crystals of semiconductor material that glow, or fluoresce, when excited by a light source such as a laser. They are used by life science researchers as tiny beacons or markers, allowing them to easily see individual genes, nucleic acids, proteins or small molecules. Quantum dot conjugates work by seeking out and bonding with target materials. Once bonded with a target, each individual quantum dot particle emits light. Depending on their size, they can glow in a variety of colors and are up to 1,000 times brighter than fluorescent dyes.

The study is one of several recent reports to validate the superior imaging qualities of quantum dots. Researchers at Cornell and QDC announced in May they had used quantum dot particles to see deeply into the tissues of living mice.

The new report, titled "Diffusion Dynamics of Glycine Receptors Revealed by Single-Quantum Dot Tracking," was jointly authored by Maxime Dahan, Sabine Levi, Camilla Luccardini, Philippe Rostaing, Beatrice Riveau and Antoine Triller. The work was performed at the Ecole Normale Superieure and the Universite Pierre et Marie Curie in Paris.

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The emission of light or other electromagnetic radiation of longer wavelengths by a substance as a result of the absorption of some other radiation of shorter wavelengths, provided the emission continues only as long as the stimulus producing it is maintained. In other words, fluorescence is the luminescence that persists for less than about 10-8 s after excitation.
quantum dots
Also known as QDs. Nanocrystals of semiconductor materials that fluoresce when excited by external light sources, primarily in narrow visible and near-infrared regions; they are commonly used as alternatives to organic dyes.  
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