Ventilation. When a new polymer absorbs infrared light ( left ), it discards ( right ), releasing any cargo inside.
N. Fomina et al, Macromolecules, 44 (2011); American Chemical Society
therapeutic drugs sometimes more damage they heal. One solution to this problem is to enclose medicines in a capsule, protecting the body and the body of them until they can be released at just the right spot. There are many ways to trigger this release, including changes in temperature, acidity and exposure to magnetic fields. But triggers can come with their own risk-burns, for example. Now, researchers in California have developed what could be the most benign trigger to date :. Shine the light in the near infrared (NIR) of the encapsulated drug
The idea of using light to release an encapsulated drug is not new. Researchers around the world have developed polymers and other materials begin to degrade when they absorb either ultraviolet (UV) or visible light. But fabrics also easily absorb UV and visible light, which means the drug release can be triggered near the skin, where the light can reach the capsule. NIR light largely passes through the tissues, so the researchers tried to use it as a trigger. But few compounds absorb NIR well and undergo chemical changes.
That changed last year when Adah Almutairi, a chemist at the University of California, San Diego, said she and her colleagues designed a polymer that decomposes when it absorbs the NIR light. Their NIR absorbing polymer used a group called commercially available o-nitrobenzyl (ONB). When they catch the light, the ONB groups fall the polymer, leading to its degradation. But ONB is only one NIR absorber so-so, and it could be toxic to cells when it is detached from the polymer.
So Almutairi and colleagues went back to the drawing board. On November 8 the number of macromolecules , they indicate the creation of a new material for capsules is even better. It consists of a long chain of small cyclic compounds containing said groups cresol in a chained polymer. Cresol contains reactive components that make it very unstable in its polymer form, a characteristic Almutairi and his colleagues use to their advantage. After the polymerization cresols, they cap each reactive component with a light absorbing compound Bhc called. When BHCS absorb NIR light, the reactive groups are exposed and to break the long polymer chains in two short. Bright light continues this additional ventilation, which could release drugs polymer locks. Moreover, Almutairi said Bhc is 10 times better absorb NIR than is ONB and is not toxic to cells.
Yue Zhao, a chemist at the University of Sherbrooke in Quebec, Canada, calls the new "special chemistry" approach and said he suspects other drug delivery experts will turn to the new made for their education. Almutairi says she and her colleagues plan to test whether the compound is useful for slow release of therapeutic proteins in the eye to treat macular degeneration.
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