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Cancer Research Quantum dots and nanoshells are driving development of novel analytical and therapeutic approaches for cancer
In the early 1980s, researchers at Bell Laboratories in the United States and at the Yoffe Institute in Russia made an unexpected observation: as semiconductor crystals grew ever smaller, their optical properties began to change in what, at the time, seemed a mysterious fashion. Depending on their size, the crystals fluoresced at different wavelengths even though the chemical composition of the crystals stayed the same. Eventually, the researchers came to understand that the unusual behavior of these “quantum dots” resulted from their nanoscale size, which changed the electronic properties of the semiconductor materials in a fundamental manner.
Fast forward to the mid-1990s, when researchers at Rice University made a similar discovery about another class of materials. Working with gold-coated silica nanoshells, Naomi Halas, professor of chemistry and electrical and computer engineering at Rice University in Houston, determined that by varying the thickness of the gold coating relative to the diameter of the silica core, it was possible to tune the optical behavior of the resulting nanoshells. But instead of emitting light of defined wavelength, i.e. color, as do quantum dots, the nanoshells absorbed or scattered light at well-defined frequencies. Two different materials, two different mechanisms explaining a color change, and both relying on fundamental differences in the way matter behaves at the nanoscale.
Today, those initial discoveries and the research they fostered have led to the devel development of new technologies that are changing the way that cancer researchers, among others, are observing the fundamental molecular events that occur in and around cells. Using nanoscale semiconductor quantum dots and gold nanoshells of various diameters, and thus different colors, biomedical researchers are able to tag multiple different biological molecules with brightly colored beacons that they can easily track in vivo using a variety of imaging technologies, such as fluorescence microscopy.
As an example of this type of approach, a team from Quantum Dot Corp., a company based in Hayward, CA, and Genentech, a pharmaceutical company in South San Francisco, CA, used quantum dots to simultaneously label and visualize Her-2 on the surface of live cancer cells and nuclear antigens inside the cell.1 More recently, investigators at Quantum Dot have used quantum dots that fluoresce at different colors to simultaneously label and track mammalian cells in culture using either standard fluorescence microscopy or a commercial cell sorter. To get the quantum dots into cells, the group used a ferrying peptide known as Pep- 1 to carry the quantum dots through the cell membrane. The researchers estimate that they can tag and image over 100 different cells simultaneously using this method.2
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Tags: cancer research | therapeutic approaches for cancer
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