Smart” Suture Aids Minimally Invasive Surgery

Based on new biodegradable plastics, a suture has been designed that can tie itself into a perfect knot or be taught to have one shape at one temperature and another shape at a different temperature. This advance could be particularly useful in minimally invasive surgery.

The biocompatible plastics were developed by two scientists, Robert Langer, professor of chemical and biomedical engineering at the Massachusetts Institute of Technology (Cambridge, MA, USA) and Andreas Lendlein, a researcher at the University of Technology (Aachen, Germany). To create the new material, they designed a biodegradable multiblockcopolymer in which block-building segments are linked together in linear chains. The polymer contains a hard segment and a "switching” segment, both with different thermal properties, so that the material forms a temporary shape at one temperature and a permanent shape at a higher temperature.

This "shape memory” makes the material ideal for use in sutures for minimally invasive surgery, where it is extremely difficult to knot a suture in a confined space. "We created a temporary shape in the form of an elongated fiber, which was then used to loosely tie a suture to close a wound on a rat,” explained Dr. Langer. After increasing the temperature, the suture material shrunk, creating a knot with just the right amount of tension on the surrounding tissue.

The polymer could also be first shaped as a string that, when heated, could change into a sheet to prevent adhesion between two internal tissues after an operation, or change into a screw for holding bones together, or a stent. "I think there could be many different applications,” said Dr. Langer.


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