traffic lights. quantum dots injected under the skin of mice glow red, yellow and green.
researchers have found a way to make cancer cells advertise their location glowing bright red. By injecting so-called quantum dots in mice, a group of biomedical engineers gave the Prostate Tumors mouse equivalent of neon signs that could one day help diagnose and guide the surgeon's hands.
Quantum dots are tiny crystals made of nanoscale metals such as silver or gold or semiconductor. Because they are comparable to the diameter of the light wavelength, quantum dots interact with light in odd ways. Change the size of a quantum dot, and color changes. When light shines on a quantum dot, it will shine back, emitting brilliant light of its own.
In the online issue of July 18 Nature Biotechnology Shuming Nie of Emory University in Atlanta and colleagues describe a way to leverage the talents optical quantum dots. Researchers coated quantum dots of cadmium selenide with an antibody which binds to a protein found in the tumors of the prostate gland. When these points were injected into the tails of mice with prostate tumors, they accommodated in the cells of the cancerous prostate. When the mice were exposed to bright light, the points began to glow, indicating the site and size of the tumors with at least 1000 cells. This is the first time that quantum dots have sought target cells and revealed their location in a living animal.
Warren Chan of the University of Toronto is considering a future in which different colors of quantum dots correspond to different proteins and different types of tumors can be diagnosed by a color coding. It is possible because the quantum dots can shine in the entire range of visible light. "That's the thing that's great about quantum dots compared with dyes," says Chan.
The quantum dots also shine much brighter than fluorescent marker proteins commonly used in biomedical research. But Nie said that to be practical for use in humans, quantum dots must shine in the infrared, which penetrates tissue better than visible light. and both Chan and Nie caution as quantum dots have yet to be proven safe in living beings.
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