I’m just back from Shanghai, where I attended the 2nd DNA nanotechnology workshop, a very exciting meeting at which we also celebrated the prestigious Albert Einstein professorship of the Chinese Academy of Sciences being awarded to Ned Seeman, often called ‘the father of DNA nanotechnology’. The story goes that as a young crystallographer, worried about getting tenure, he went to the campus bar to have a few beers and mull things over. Seeman found inspiration in the Escher woodcut Depth to make crystals using DNA, so as to avoid the guessing game (and potentially praying) that everyone who ever tried to crystallize anything is only too familiar with. The rest, as they say, is DNA nanotechnology.
The idea of hybridization — mixing two separate DNA strands to make a double helix — was reported in 1956 by Alex Rich, in a paper that incidentally very nearly fitted into a single column (half a page) of the journal! The beauty of the assembly lies in the precisely controlled positioning it enables at the nanoscale, and by carefully designing strands you can fold them up into increasingly complex designer structures (origami).
The meeting — whose theme was “From structure to function” — undeniably showed that DNA nanotechnology now branches out in many directions. We saw a wide variety of DNA items, triangle, cube, tetrahedron, octahedron, and even curved architectures; used for example to position other species (from gold nanoparticles to proteins); or manipulated to form nanomechanical devices such as tweezers, chopsticks-renamed-pliers, or walkers. These behaviours can in turn be used for example for guest recognition, detection, or to construct logic gates; make up DNAzymes (single-stranded DNA sequences that act as enzymes). It would be impossible to try and discuss here all the elegant structures and systems presented at the workshop, but I would like to mention an unusual one. Fritz Simmel from Munich looked into autonomous behaviours, and coupled DNA tweezers with oscillating systems. You will find more details at PNAS, 108, E784-E793 (2011) but essentially, they used transcription and RNA degradation reactions to induce, under the right conditions, the periodic opening and closing of DNA tweezers, making for a synthetic transcriptional clock.
There was also quite a lot of talk of cell studies — which perhaps shouldn’t be surprising as we are, after all, discussing DNA here. When it comes to therapeutic applications though, as William Shih mentioned, it is great to have new drugs but the hurdle we need to get passed is their delivery — how to get them in the cells? And so he’s exploring how the shape, size and function of DNA items affects the rate at which they are internalized.
The wide variety of DNA assemblies presented leaves no doubt that the field will only continue to get more exciting, and I look forward to seeing these developments and further branching out. I have to say as well that, for me, all of this made all the more exciting by being hosted at the Shanghai synchrotron facility!
Anne Pichon (Associate Editor, Nature Chemistry)