研究人员发明更好的人造软骨材料

A Duke research team has developed a better recipe for synthetic ¹ replacement ² cartilage（软骨） in joints ⁴. Combining two innovative ⁵ technologies they each helped develop, lead authors Farshid Guilak, a professor of orthopedic（整形外科的） surgery and biomedical engineering, and Xuanhe Zhao, assistant professor of mechanical engineering and materials science, found a way to create artificial replacement tissue that mimics ⁶ both the strength and suppleness ⁸ of native cartilage. Their results appear Dec. 17 in the journal Advanced Functional ⁹ Materials., ,Articular cartilage is the tissue on the ends of bones where they meet at joints in the body -- including in the knees, shoulders and hips ¹⁰. It can erode ¹¹ over time or be damaged by injury or overuse, causing pain and lack of mobility ¹². While replacing the tissue could bring relief to millions, replicating ¹³ the properties of native cartilage -- which is strong and load-bearing, yet smooth and cushiony（柔软的） -- has proven a challenge., ,In 2007 Guilak and his team developed a three-dimensional fabric ¹⁴ "scaffold" into which stem cells could be injected and successfully "grown" into articular cartilage tissue. Constructed of minuscule ¹⁵ woven fibers ¹⁶, each of the scaffold's seven layers is about as thick as a human hair. The finished product is about 1 millimeter thick., ,Since then, the challenge has been to develop the right medium to fill the empty spaces of the scaffold -- one that can sustain compressive loads, provide a lubricating surface and potentially support the growth of stem cells on the scaffold. Materials supple ⁷ enough to simulate native cartilage have been too squishy and fragile to grow in a joint ³ and withstand loading. "Think Jell-O," says Guilak. Stronger substances, on the other hand, haven't been smooth and flexible enough., ,That's where the partnership ¹⁷ with Zhao comes in., ,Zhao proposed a theory for the design of durable ¹⁸ hydrogels (water-based polymer gels) and in 2012 collaborated ¹⁹ with a team from Harvard University to develop an exceptionally strong yet pliable ²⁰ interpenetrating-network hydrogel., ,"It's extremely tough, flexible and formable, yet highly lubricating," Zhao says. "It has all the mechanical properties of native cartilage and can withstand wear and tear without fracturing.", ,He and Guilak began working together to integrate the hydrogel into the fabric of the 3-D woven scaffolds in a process Zhao compares to pouring concrete over a steel framework., ,In their experiments, the researchers compared the resulting composite material to other combinations of Guilak's scaffolding embedded ²¹ with previously ²² studied hydrogels. The tests showed that Zhao's invention was tougher than the competition with a lower coefficient of friction ²³. And though the resulting material did not quite meet the standards of natural cartilage, it easily outperformed all other known potential artificial replacements ²⁴ across the board, including the hydrogel and scaffolding by themselves., ,"From a mechanical standpoint, this technology remedies the issues that other types of synthetic cartilage have had," says Zhao, founder ²⁵ of Duke's Soft Active Materials (SAMs) Laboratory. "It's a very promising ²⁶ candidate for artificial cartilage in the future.", ,The team's next step will likely be to implant ²⁷ small patches of the synthetic cartilage in animal models, according to Guilak and Zhao.