[Pharmwaste] Sending drugs to specific spots in a tiny cage - drug delivery using nanotechnology

Tenace, Laurie Laurie.Tenace at dep.state.fl.us
Fri Nov 6 10:32:12 EST 2009

Targeted drug delivery can help eliminate unmetabolized drugs from being
flushed from our bodies. On the other hand, unforeseen consequences of
nanotechnology may be the next thing we are all scrambling to control. 

Sending Drugs to Specific Spots in a Tiny Cage

Published: November 2, 2009 
For years, biomedical engineers have been trying to develop ways to deliver
tiny amounts of a drug to a specific target - anticancer compounds directly
to tumors, for example. Much of the work involves microscale capsules or
other hollow structures with openings that can be controlled from outside the

One of the latest research efforts comes from the laboratory of Younan Xia at
Washington University in St. Louis. His idea? Put the drugs inside tiny cages
and use light to unseal them and let the drugs out.

These "nanocages" are cubes of gold, with sides about 50-billionths of a
meter long and holes at each corner. They are easily made, using silver
particles as a mold, and then coated with strands of a smart polymer. The
polymer strands are normally extended and bushy and cover the holes in the
cube. But when heated the strands collapse, leaving the holes open and
allowing the drug inside to escape.

How does the polymer becoming heated? By heating the nanocage with
near-infrared light. Near-infrared wavelengths are not greatly absorbed by
body tissues, so light from a near-infrared laser could penetrate a couple of
inches inside the body, but they are absorbed by gold.

Dr. Xia, who describes the work in a paper in Nature Materials written with
Mustafa S. Yavuz, Yiyun Cheng, Jingyi Chen and others, said that by altering
the composition of the polymers, they could be made to collapse, say, at a
couple of degrees above normal body temperature.

The nanocages can also be made to bind with tumors. Once injected, they would
find their way to the tumors and sit, inert, until exposed to near-infrared
light. The holes would then open and the drug would be released. By changing
the power intensity of the laser, it should also be possible to adjust the
rate of release.

Laurie Tenace
Environmental Specialist
Waste Reduction Section
Florida Department of Environmental Protection
2600 Blair Stone Rd., MS 4555
Tallahassee FL 32399-2400
P: 850.245.8759
F: 850.245.8811
Laurie.Tenace at dep.state.fl.us 

Mercury: http://www.dep.state.fl.us/waste/categories/mercury/default.htm 

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