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Nanotech News


August 14, 2006

Mixing Nanostructures Yields New Approach to Rapid Bioassays

Using silica beads with nanoscale pores as a carrier for two other nanoscale materials, researchers at the Emory-Georgia Tech Nanotechnology Center for Personalized and Predictive Oncology, one of eight Centers for Cancer Nanotechnology funded by the National Cancer Institute, have created a powerful new tool for conducting rapid, high-throughput assays of biological function. These assays could speed the detection of cancer and the development of new antitumor agents. The results of this work appear in the journal Analytical Chemistry.

Shuming Nie, Ph.D., principal investigator of the Emory-Georgia Institute of Technology CCNE, and his colleagues created their new multifunctional device using semiconductor quantum dots and iron oxide nanocrystals. The investigators embedded, or doped, the nanoparticles into the nanoscale pores in 4-micron-diameter silica beads, and then coated the microbeads with a biocompatible polymer. This polymer coating helps the microbeads dissolve in water and provides a chemically reactive surface onto which the investigators plan to attach targeting molecules.

The investigators determined that each microbead has approximately 1 million pores into which they can dope quantum dots and magnetic iron oxide beads. They also found that quantum dots fill approximately 300,000 to 400,000 of these pores, far in excess of the number needed to make the microbeads visible. As a result, the researchers note, it is possible to dope the microbeads with multiple quantum dots, each shining with a different color, and use the microbeads in multiplexed assays.

To confirm that they can use the iron oxide nanoparticles as a handle for purifying molecules attached to the microbeads, the investigators mixed microbeads doped with a red quantum dot and iron oxide nanocrystals with a second set of microbeads doped solely with green quantum dots. Exposing this mixture to a magnetic field for five minutes allowed the investigators to completely separate the two sets of microbeads. If the microbeads had contained a targeting molecule, this separation would have also purified the biomolecule or cell recognized by that targeting molecule.

This work, which was supported in part by the National Cancer Institute’s Alliance for Nanotechnology in Cancer, is detailed in a paper titled, “Mesoporous silica beads embedded with semiconductor quantum dots and iron oxide nanocrystals: dual-function microcarriers for optical encoding and magnetic separation.” This paper was published online in advance of print publication. An abstract is available at the journal’s website.
View abstract.