Crustacean Shell with Polyester Is Suitable for Nerve Repair

photo: chitosan and polyester fibers

Closeup of chitosan and polyester
fibers woven at the nanometer
scale; © University of Washington

In the clothing industry it is common to mix natural and synthetic fibers. Take cotton and add polyester to make clothing that is soft, breathable and wrinkle free.

Now researchers at the University of Washington (UW) are using the same principle for biomedical applications.

They created a new hybrid fiber which combines the biologically favorable qualities of the natural material chitosan with the mechanical strength of the synthetic polymer.

"The new material showed promise for nerve guides but would also work well for wound dressings, heart grafts, tendons, ligament, cartilage, muscle repair and other biomedical applications”, Miqin Zhang, a UW professor of material science and engineering said.

Today's commercial nerve guides are made from collagen, a structural protein derived from animal cells. But collagen is expensive, the protein tends to trigger an immune response and the material is weak in wet environments, such as those inside the body.

Zhang and colleagues developed an alternative. The first component of their material, polycaprolactone, is a strong, flexible, biodegradable polyester commonly used in sutures. It is not suitable on its own for use as a nerve guide because water-based cells don't like to grow on the polyester's water-repelling surface.

The second component, chitosan, is biodegradable and biocompatible, meaning that it won't trigger an immune response. Chitosan has a rough surface similar to the surfaces found inside the body that cells can attach to. The problem is chitosan swells in water, making it weak in wet environments.

Researchers combined the fibers at the nanometer scale by first using a technique called electrospinning to draw the materials into nanometer-scale fibers, and then weaving the fibers together. The resulting material has a texture similar to that of the nanosized fibers of the connective tissue which surrounds human cells.; Source: University of Washington