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DBL%20Hendrix%20small.png College chemistry, 1983

Derek Lowe The 2002 Model

Dbl%20new%20portrait%20B%26W.png After 10 years of blogging. . .

Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases. To contact Derek email him directly: Twitter: Dereklowe

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« Right Where You Want Them | Main | To What End? »

September 9, 2009

"Scratch and Sniff" Turns Into "Zap and React"

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Posted by Derek

Here's an odd idea that might turn into something useful. A group at Berkeley (spanning both the chemistry and physics departments of Cal-Berkeley and the Lawrence labs) have reported a method for encapsulating organic molecules and releasing them inside a reaction when needed.

What they do is form microcapsules, small polymer spheres, from branched acid chlorides and amines. That technology is already known, but in this case they're also incorporating carbon nanotubes inside the capsules, as shown in the photo. If you do this from a solution of some reagent of interest, you now have it, the solvent, and the carbon nanotubes wrapped up in small polymer beads.
And if you irradiate these things, the carbon nanotubes heat up rapidly, causing the microcapsules to break open. There's the control mechanism. They've demonstrated this for reactions such as the "click" triazole formation and for olefin metathesis. You can follow the reaction progress, and it goes stepwise, further every time you hit the solution with a near-IR laser, and stopping until you do it again and release more coupling partner.

The limits of this system, so far, are (1) that the microcapsules aren't compatible with the full range of organic solvents, (2) that heat-sensitive reagents probably won't do very well in a system that require local heating to burst the capsules, and (3) that you eventually have to clean out (presumably by some sort of filtration) the capsule and nanotube residue after things have burst. But some of these can be addressed in further rounds of improvements.

For example, there must be different sorts of polymers that can form these beads, for one thing. And if it's possible to encapsulate things on the surface of a larger sheet of solid material, you could just dip that in and pull it back out when you're through, which should cut down on the capsule residue. (That would also allow you to quantitate how much reagent you've released, by following the surface area of the sheet that you've irradiated with the laser). What would really make this something to see would be if a way could be found to release different sorts of capsules at different wavelengths, selectively. . .

Comments (3) + TrackBacks (0) | Category: Chemical News


1. Brian on September 9, 2009 9:46 AM writes...

If you had your capsules on the surface of a sheet, you wouldn't even need to muck around with different wavelengths. You'd just put each product in a separate physical area, and choose where to aim the laser.

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2. Zach on September 9, 2009 11:36 AM writes...

Well, there's no reason you have to use tubes -- you could get local heating with something like a CdSe nanoparticle, which can be tuned to all sorts of wavelengths. You can also do Au/silica nanoshells, if you want to stick with tunable IR. If you're wedded to the idea of tubes, of course, there are ways to embed magnetic materials in them that will heat up with RF, so you don't even need a laser. Don't know how tunable that can get, though...

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3. crucide on September 9, 2009 11:20 PM writes...

Isn't it very much not unlike your previous post? Way cool. Insanely clever. But how do you get it to do something practically useful? At cost?

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