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More than two decades ago, scientists demonstrated that the self-assembly of nanoparticles – for use in fabricating miniaturized devices, for example – was possible if the nanoparticles could be labeled with a known number of DNA molecules.

Such a labeling technique would allow them to create well-defined nanocomposites simply by mixing DNA-tagged nanoparticles together. For this approach to work, scientists would need to precisely control the number of DNA molecules, or DNA valency, on the nanoparticle surface.

But the challenge to actually do that, in practice, went unmet for 25 years.

This week, the Department of Chemistry’s Yang Lab publishes research on the first sorting technology that distinguishes nanoparticles through the mechanism of Watson-Crick digital recognition, thus enabling a new range of molecule-like building blocks.

The lab accomplished this feat by exploiting DNA’s programming language—its ability to selectively associate with and recognize complementary sequences—through a process called DNA barcoding.

DNA barcoding functions much like the codes used by supermarket scanners to identify a product. In this case, researchers tapped into the short genetic sequences in DNA as a means of sorting the nanoparticles to which they are attached.

The technique allows for the assembly of complex static and dynamic structures with predictable valency-defined nanoparticles.

The paper, Sorting Nanoparticles by Valency with DNA Barcoding, was published this week in the Journal of the American Chemical Society (JACS).

Using valency-defined nanoparticles to do novel nanochemistry wasn’t specifically the Yang Lab’s idea. “It’s a concept that’s been floating around in the literature for a long time. But it hasn’t been demonstrated,” said Nyssa Emerson, a postdoctoral associate and first author on the research paper, and the scientist whom Professor of Chemistry Haw Yang credits with the persistence to solve the challenge.