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10 April 2014 11:44 am ,
Vol. 344 ,
Balkan endemic kidney disease surfaced in the 1950s and for decades defied attempts to finger the cause. It occurred...
The Pyrenean ibex, an impressive mountain goat that lived in the central Pyrenees in Spain, went extinct in 2000. But a...
Tight budgets are forcing NASA to consider turning off one or more planetary science projects that have completed their...
Ebola is not a stranger to West Africa—an outbreak in the 1990s killed chimpanzees and sickened one researcher. But the...
In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...
Tropical disease experts tried and failed before to eradicate yaws, a rare disfiguring disease of poor countries. Now,...
Since 2002, researchers have reported that agricultural communities in the hot and humid Pacific Coast of Central...
- 10 April 2014 11:44 am , Vol. 344 , #6180
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29 April 2002 (All day)
Surgeons may soon seal hard-to-reach wounds with the aid of novel shape-shifting threads that know how to tie themselves and never need to be removed. The new "smart" biodegradable plastic fiber can knot itself when heated to a few degrees above body temperature. The researchers say the same material could be made to last much longer and one day be used for self-repairing medical devices and shrink otherwise bulky implants--such as screws that hold bones together.
A growing class of materials possess "shape memory"--they hold one form at a certain temperature and transform into another shape when heated. Until now, no such plastics had been used in medical devices, nor had any proved to be biodegradable. The new material, described online 25 April in Science by synthetic chemist Andreas Lendlein of mnemoScience GmbH in Aachen, Germany, and biomedical engineer Robert Langer of the Massachusetts Institute of Technology, is composed of two polymers, each already used separately in clinical applications such as drug delivery.
When combined, the two polymers react to temperature. The higher temperature shape is the plastic's "permanent" form, which it assumes after it's heated. After it cools, the plastic can be stretched or scrunched into temporary forms up to four times larger or smaller than the permanent form. To make the sutures, the researchers took a fiber of their shape-shifting material and, after warming it for a few minutes, cooled it down and stretched it. They used the thread to loosely stitch a wound on a rat. When heated to 40°C, the suture tightened with just the right amount of tension, avoiding damage to the surrounding tissue.
Medical devices that can fit through tiny holes in the body and expand into designed shapes on demand would be invaluable, says laparoscopic surgeon Frederick Finelli at George Washington University Medical Center in Washington, D.C. But he cautions that surgeons might feel uncomfortable not having direct control over shape-changing implants. "If the size is predetermined and you have it in and you heat it up and then it turns out it's too small, what do you do then? These are the things surgeons worry about."