Tiny Crystals with Great Potential
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Fluorescent labeling has become a mainstay in today's biological experiments. Scientists use organic dyes to visualize specific proteins, DNA sequences, and cellular compartments. When subjected to light, these dyes fluoresce to form a "tag" that scientists can follow. Quantum Dot Corporation (QDC) is pioneering the use of quantum dots--tiny crystals only a few nanometers wide--as a revolutionary new type of biological tag. These nanocrystals have numerous advantages over conventional organic dyes. Quantum dots are well on the way to becoming a powerful new tool with both medical and biological applications. In April of 2001, Quantum Dot Corporation was named in the annual Red Herring "Ten to Watch", a list of the top ten startup companies with noteworthy up-and-coming technology. QDC's exciting advances promise to make a significant impact in the scientific world.
The New Idea
Paul Alivisatos and Shimon Weiss, researchers in the Materials Sciences Division of Lawrence Berkeley National Laboratory, were the key developers of QDC's nanocrystal fluorescent probe technology. Alivisatos had studied quantum dots since his work at Bell Laboratories in the 1980s. In the mid-1990s, Weiss suggested the use of quantum dots as biological probes, and a joint Berkeley Lab-UC Berkeley scientific team launched research and development efforts. This R&D took a running start--Alivisatos says the team "knew from almost the moment they started that the technology should be commercialized."
The concepts behind fluorescent labeling can help to illuminate the power of quantum dots. The ability of a molecule to absorb light is dependent upon how the electrons of its nucleus are situated. Quantum theory states that these electrons occupy a variety of "energy levels." When light hits a molecule, its electrons become "excited" and move to higher energy levels. The difference in energy between the normally occupied level and the excited level is equivalent to the energy of the incoming photon of light. When electrons are excited, molecules become relatively unstable. To return to a stable resting state, the electrons that were excited move back to their normal, lower-energy levels and emit fluorescent light during the reversion process.
Conventional organic dyes put these concepts into action. These dyes are used in biological assays to visualize cellular components of interest. When light is shined upon a cell, the organic dye visibly fluoresces as excited electrons return to their resting levels. These dyes come with their share of problems. To generate different colors of fluorescence, distinct types of dye molecules must be employed. Different light sources must be used to visualize these varying types of dyes, and the different colors tend to bleed together. Additionally, when subjected to light sources, fluorescent dyes are prone to photobleaching: fading with increased exposure to light.
The Quantum Dot Advantage
Instead of using organic dyes for fluorescent labeling, Quantum Dot Corporation promotes the use of quantum dots: nanometer-sized crystals made of semiconductor material. As Alivisatos states, these "small semiconductor crystals are very robust and photochemically stable." Unlike conventional dyes, quantum dots can emit multiple colors of light. Changing the size of the dot changes the color of fluorescence. A single, inexpensive light source is sufficient to visualize the multiple colors of quantum dots--a much simpler process than using a different laser to see each individual color of fluorescent dye. Since the dots do not bleed together, many colors can be used simultaneously. Quantum dots also make the visualization process easier with greatly lessened photobleaching. Using these dots allows for "multiplexed" assays: experiments in which many variables are simultaneously tested and analyzed. The ability to multiplex will increase efficiency and provide financial benefits.
From Concept to Startup
As Alivisatos and Weiss developed these nanocrystal probes, Silicon Valley entrepreneurs Joel Martin and Bala Manian were out on the hunt for new technologies with commercial potential. In the January/February 2000 edition of MIT's Technology Review, Martin says he was searching for "something that will be on the market in the next couple years...[that also] captures people's imagination". This description matched that of Berkeley Lab's quantum dot probes. Licensing negotiations began with the Lab's Technology Transfer Department and Quantum Dot Corporation was founded in November of 1998. As part of the licensing fees, the University of California was issued shares of QDC stock. In addition to the agreement with Berkeley Lab, Quantum Dot Corporation has licensed complimentary technology from MIT, University of Melbourne, and Indiana University.
Martin and Manian were by no means alone in recognizing the commercial potential of quantum dot probes. In the startup's first eight months, $7.5 million of venture capital had been raised. To date, over $37.5 million in financing has been accumulated from prestigious venture groups, including Versant Ventures, MPM Asset Management, and CMEA Ventures.
Nanocrystals in Action
Alivisatos acknowledges that the nanocrystal probe technology was "just in the stages of laboratory observation" before QDC was founded. Additional research and development efforts were needed to make the quantum dots commercially viable. Kenneth Barovsky, Quantum Dot Corporation's Vice President and Intellectual Property Counsel, characterizes the company's current status as "in the late R and early D phase of R&D". A commercial product is expected in the near future.
Biological applications stand as QDC's primary field of interest. Quantum dot probes have many powerful uses in the biomedicine and biotechnology arenas. The recent completion of the Human Genome Project has brought about a need to characterize large numbers of genes in a complex cellular environment. Quantum Dot Corporation hopes to incorporate nanoparticles into the diagnostic kits and analytical instruments of prominent biotech corporations. However, this nanocrystal technology also has great potential outside the field of biology, including possible uses in light-emitting diodes, optical fibers and transistors. All in all, Barovsky states that QDC aims "to become the premier company for the preparation, operation, development and chemistry of quantum dots".
As evidenced by the citing in Red Herring, Quantum Dot Corporation holds promise for a greatly successful future. Quantum dots are tiny in size, but they hold massive potential. We are sure to hear much more about this exciting technology in the years to come. |
