Monday, September 21, 2009
Light Activated Mixing of Chemicals at Target Site
Filed under: Nanomedicine
Sometimes bringing separated ingredients of a chemical reaction to a disease is wiser than ferrying the reaction's final product. Pharmacokinetics is a finicky science. Drug molecules are often not very stable, or can get absorbed or cleared on the way to a distant site. Or the problem might be the drug's large molecular weight or ionization, preventing it from crossing physiologic boundaries. To address many of these issues, UC Berkeley researchers have developed tiny nylon microspheres laden with reactive chemicals, that can burst and mix only when a particular light source is applied.
They mix the chemical to be encapsulated with a small amount of carbon nanotubes and the precursors for making nylon, while continuously stirring. The stirring causes the nylon to form spheres that capture the nanotubes and the reactant. By varying the stir rate, the Berkeley chemists can vary the size of the resulting capsules from about 100 to 1,000 micrometers. When they aim a laser at a capsule, the carbon nanotubes absorb the light, heating up the liquid inside and causing it to expand until it explodes, releasing the contents. "The novelty is not the particle itself, but the fact that it can be addressed by a cheap laser," says Fréchet. This is possible because carbon nanotubes -- the blackest known substance -- absorb a broad spectrum of light very efficiently.
More from Technology Review...
Abstract in Journal of The American Chemical Society: Chemicals On Demand with Phototriggerable Microcapsules
Video below the fold showing microcapsules activated using a laser:
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