When Caltech researcher Paul Rothemund wove DNA molecules into miniature smiley faces, snowflakes and stars in 2006, it heralded an era of “DNA origami.” Now, a decade later, scientists have taken this art to another level by re-creating a miniaturized version of Vincent van Gogh’s masterpiece “Starry Night” using folded DNA molecules.
The researchers say that the monochrome painting — a dime’s width across — is a proof-of-concept that the extremely precise technique can be used to build nanoscale chip-based devices like computer circuits, conductive carbon nanotubes, and for extremely efficient targeted drug delivery.
In order to reproduce the painting, the researchers used a technique first described by Rothemund and colleagues at IBM in 2009. The first step of the process involves folding DNA strands to create the desired shape, with short “staple strands” being used to literally staple the molecules. Then this pattern, which, at this stage, is floating in a saline solution, is poured into patches on a chip whose shapes match the DNA origami’s.
The folded DNA now acts as scaffolding onto which researchers then install fluorescent molecules inside microscopic light sources called photonic crystal cavities (PCC) — much like putting light bulbs into lamps.
“Think of it a bit like the pegboards people use to organize tools in their garages, only in this case, the pegboard assembles itself from DNA strands and the tools likewise find their own positions,” Rothemund, who co-authored a paper describing the work, said in a statement. “It all happens in a test tube without human intervention, which is important because all of the parts are too small to manipulate efficiently, and we want to make billions of devices.”
Depending on the exact size and spacing of the PCCs, a particular wavelength of light reflects off the edge of the cavity — in this case, a deep shade of red.
“A fluorescent molecule tuned to the same color as a PCC actually glows more brightly inside the cavity, but the strength of this coupling effect depends strongly on the molecule's position within the cavity. A few tens of nanometers is the difference between the molecule glowing brightly, or not at all,” Ashwin Gopinath, a senior postdoctoral scholar in bioengineering at Caltech, said in the statement.
The next step would be to refine the technique further by improving the molecules' life span — currently just 45 seconds — and to make them emit a "pure" shade of red rather than the many shades they currently emit. Once this is done, the technique can be used for optical and quantum computing at the nanoscale.