Originally Published MPMN July 2009
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Electrospun Fibers Can Eliminate Toxins, Mimic Natural Tissues
Researchers at Massachusetts Institute of Technology (MIT; Cambridge, MA; www.mit.edu) are exploring new ways to create, enhance, and employ electrospun fibers for medical device applications. Using a variety of natural and synthetic polymers, the researchers have used electrospinning processes to form fibers continuously and achieved diameters ranging from 0.1 to 1 µm.
“Besides having very small fiber diameters, materials formed from these fibers have a very high specific surface area, very small distances between fibers, and are self-supporting,” says Gregory Rutledge, professor in MIT’s department of chemical engineering. These properties, he says, translate into potential for high chemical and biological activity.
Taking advantage of such properties, Rutledge and his team are experimenting with enhancing the fibers for drug-delivery and tissue-engineering applications. One method that is used for modifying the fibers is to incorporate a bactericide or chemically reactive compound into a solution with the polymer so that it is reactive to a certain chemical toxin when the fiber is spun. Rutledge’s team can also functionalize the fibers after they are formed using a cross-linking agent to bond the bactericide or chemically reactive group to the surface of the fiber. “Either way, the reactive groups are expressed in high concentration on the surface of the fibers, and because of the high specific surface area of the fabric itself, their availability to eliminate toxins or bacteria is better than most competing materials,” comments Rutledge.
It is also possible to form fibers with complex geometries to modulate a drug-release profile. “The fibers in the extracellular matrix (ECM) of many natural tissues are actually collagen nanofibers secreted by the cells themselves,” he explains. “It seems natural that a good synthetic tissue scaffold should mimic the ECM as closely as possible, and thus be comprised of biocompatible nanofibers; electrospinning is a way to produce such nanofibers.”
Using synthetic polymers, such as polyglycolic acid and polylactic acid, naturally occurring polymers, and blends of these materials, the research team has employed electrospinning techniques to form scaffolds for tissue engineering and semipermeable conduits used to guide the regeneration and repair of severed nerves. They have also created membranes for tendon wraps that hold severed tendons in place for photochemical tissue bonding. Tendons repaired in this manner have demonstrated better healing than those held together using sutures, according to Rutledge. Electrospun fabrics could also be used as ultrafiltration materials because they have the potential to exclude undesirable agents, such as bacteria and cells, while permitting diffusion of nutrients and biological products, he explains. “As components for medical devices, [the fabrics] allow one to think about designs that were not practical before.”
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