Quantum leap

Quantum dots - molecule-sized semiconductor materials embedded in polymer microbeads - have been proposed as a way to distinctly label specific DNA sequences or antibodies for multiplex, high throughput assays. But putting theory into practice has not been easy. Now a group at Indiana University reports that it may have solved some of the scale-up issues related to the technology. They also have demonstrated the use of the microbeads in a DNA hybridization assay and noted that such technology could be used to create 10,000-40,000 recognizable codes.

As published last week in Nature Biotechnology, the researchers developed a 1.2 µm diameter polymer microbead incorporating different sized quantum dots (cadmium selenide coated with zinc sulphide). Larger quantum dots (QDs) absorb and emit at a higher wavelength or spectrum, while the number of QDs in the microbead controls the emission intensity per spectrum. For example, one QD absorbing in the red spectrum will have a lower intensity than 10 red QDs encased in a microbead...