Strong Gel for Artificial Cartilage

Researchers at the National Institute of Standards and Technology (NIST) are studying an unusually pliant yet strong synthetic cartilage replacement in hopes of providing people with arthritis an alternative to total joint replacement. Scientists created a gel that, while having the pliancy of gelatin, won’t break apart even when deformed more than 1,000 percent. By using NIST’s neutron research facility to show how the molecules in the gel sustain such large deformations, the research team hopes to make it easier to design materials with even better mechanical properties.

Known as double-network hydrogels, the incredible strength of these new materials was a happy surprise when first discovered by researchers at Hokkaido University in Japan in 2003. Most conventionally prepared hydrogels—materials that are 80 to 90 percent water held in a polymer network—easily break apart like a gelatin. The Japanese team discovered that the addition of a second polymer to the gel made it so tough that it rivaled cartilage. A combination of a brittle hydrogel and a soft polymer solution led to a surprisingly tough material.

Work using NIST’s neutron scattering techniques is exploring the structure of the gel to discover the molecular-level toughening mechanism found in this unique hydrogel. Establishing the details of the molecular structure will allow for more precise design of the next generation of hydrogels to be tough and rigid at the same time. Real cartilage goes through a process of constant daily destruction and regeneration under everyday stresses; the researchers hope a good synthetic cartilage could endure year after year under the rigors of the body before needing to be replaced.

To learn more about cartilage engineering, read about the work being done by Arthritis Foundation-funded scientists Jennifer H. Elisseeff, PhD, and Farshid Guilak, PhD.

Wu WL, Tirumala VR, Tominaga T, et al. A molecular model for toughening in double-network hydrogels. Presented at the March Meeting of the American Physical Society, March 11, 2008, New Orleans, La.

This article was adapted from a press release issued by National Institute of Standards and Technology.

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