Nanoparticle combines two kinds of quantum dots for color changing, molecule tagging

Columbus, OH--Engineers at Ohio State University have invented a new kind of light-emitting nanoparticle that can change colors to tag molecules in biomedical tests.

Mar 28th, 2011

Columbus, OH--Engineers at Ohio State University have invented a new kind of light-emitting nanoparticle that can change colors to tag molecules in biomedical testing.

Two different types of quantum dot (QD), one green-emitting and one red-emitting, are stuffed inside a "micelle," which is a nano-sized spherical container. The micelles have varying combinations of red and green QDs inside them.

Due to quantum-mechanical effects, QDs blink on and off in random sequences. When many QDs come together, however, their random blinking is less noticeable. So, large clusters of QDs appear to glow with a steady light.

This blinking has been a problem for researchers, because it breaks up the trajectory of a moving particle or tagged molecule that they are trying to follow. Yet blinking is also beneficial, because when QDs come together and the blinking disappears, researchers know for certain that tagged molecules have aggregated.

"Blinking is good and bad," explained Gang Ruan, one of the researchers. "But one day we realized that we could use the 'good' and avoid the 'bad' at the same time, by grouping a few QDs of different colors together inside a micelle."

Micelles of a feather flock together
In tests, he and fellow researcher Jessica Winter confirmed that the micelles appeared to glow steadily. Those stuffed with only red QDs glowed red, and those stuffed with green glowed green. But those he stuffed with red and green dots alternated from red to green to yellow.

"We can tailor these particles to tag particular molecules, and use the colors to track processes that we wouldn't otherwise be able to," he added. "Also, this work could be groundbreaking for the field of nanotechnology as a whole, because it solves two seemingly irreconcilable problems with using QDs."

Winter and Ruan said that the particles could also be used in microfluidics: researchers who are developing medical devices with fluid-separation channels could use QDs to follow the fluid's path.

Winter and Ruan want to explore what happens when QDs of a third color are added to the mix.

Ohio State University will look to license the technology for industry, and Winter and Ruan have created a website for the technologies they are developing: http://nanoforneuro.com.

Posted by John Wallace

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