Mike Ramsey talked about nanopores and nanochannels. Making these nano-analytical devices looks easy in his movies, but nanofabrication is no mean feat. Getting lithography to behave at the 100 nm level with enough reproducibility to do their experiments was very impressive. They used a channel that step-tapered. A single DNA molecule was threaded into that channel with an electric field. Then they looked at the apparent length in different channel widths. A reasonable person might run a bunch of DNA molecules through a bunch of different-width channels, but then you run into statistical averaging problems. Use the same molecule over and over and the physics pop out more simply. In narrower channels, the DNA must be straighter – no wiggling. That means it looks longer. The mathematical relationship between confinement and apparent length then pops out at a single-molecule level. They are also doing moderate vacuum (instead of very high vacuum) mass spectrometry. You know, because everyone wants a little MS on their bench. I know I do.
David Zhang talked about ultra-specific DNA probes. It’s a competition assay, not very sensitive, but coupled to PCR it allows for super bright, super simple single-nucleotide-mutation detection. Shana Kelly talked about some of the limitations in analyzing rare molecules in serum with back-of-the-envelope calculations to describe just how hard that is. They have some great high surface area nanodevices that help. Kevin Plaxo talked about electrochemical readout of DNA-DNA reactions which I think should definitely be coupled to the Zhang probes (and probably already are). Electrochemistry is super reliable in commercial products, so coupling it to these new bioassays is very smart. I love that they have a biochip that takes whole blood and looks for drugs in that blood-flow in real time. And they use a laminar flow system to keep the electrode from getting all saturated with cell debris which I think is brilliant.
I say a great talk about about releasable nano-DNA-icosahedra that encapsulate dextran FITC. I only caught the end of Peng Yin’s talk, but his ideas are all over the poster sessions including one on (if I understood correctly) inorganic nanoparticles from a DNA scaffold.
There was a nice talk by Hareem Maune on self assembling DNA origami-like structures on surfaces other than mica. I was interested to hear that the old stand-by APTES is a problem (amino propyl triethoxy silane). which I have used to functionalize glass before They prefer an imidazole silane which evidently chelates metals and pulls DNA onto the surface by bridging di-cations.
The last few talks included Nicholas Kotov talking about self-assembly of inorganic particles. One particularly interesting phenomenon generated monodisperse particles from polydisperse muilding blocks. It reminded me of the old fable of the big rocks and the sand. If you put big rocks into a jug first, you can pour in the sand on top. But if you put the sand at the bottom, you can not fit all the large rocks in on top of it. This is the same thing. Big particles come together and then build smaller particles into the cracks. The system maximizes surface interactions while minimizing surface charge and the whole thing finds a nice energy minimum with very uniform products.
Anders Okholm and Chun Geng talked about DNA containers from different perspectives. The former used origami cages while the latter used DNA crystals. Both got lively questions.