Researchers from the University of Washington have developed a new hybrid material that may end up serving as a scaffold for regenerative nerve repairs. The material combines the benefits of chitosan, a chemical found in the shells of crab and shrimp, with industrial polyester. Investigators believe that ability of the material to be shaped into tiny tubes that are strong, do not trigger an immune response, and work well in the moist environment of the body, will set the material apart.
From the University of Washington:
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 found in the shells of crustaceans. It’s cheap, readily available, 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 that surrrounds human cells.
The two materials are different and are difficult to blend, but proper mixing is crucial because imperfectly blended fibers have weak points.
Zhang [Miqin Zhang, UW professor of material science and engineering] and colleagues built prototype nerve guides measuring 1.5 millimeters (0.06 inches) in diameter, and between five and 15 centimeters (two to six inches) long. They tested a guide made from the chitosan-polyester blend against another biomaterial under study, polylacticcoglycolic acid, and a commercially available collagen guide.
Of the three materials, the chitosan-polyester weave showed the most consistent performance for strength, flexibility and resistance to compression under both dry and wet conditions. Under wet conditions, which the researchers say best mimics those in the body, the chitosan-polyester blend required twice as much force to push the tube halfway shut as the other biomaterial, and eight times as much force as the collagen tube.
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, Zhang said.
Press release: Crustacean shell with polyester creates mixed-fiber material for nerve repair
Image: Upper panel shows a closeup of chitosan and polyester fibers woven at the nanometer scale. The middle panel shows a nerve cell growing on the resulting mesh, which has a texture similar to the body’s fibrous connective tissue. The lower panel shows a cross-section of the synthetic nerve guide. Arrows point to nerve cells that have attached to the inner and outer surfaces of the tube.