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The tissue, which performs vital functions in many areas of the body but is difficult to replace, has “unparalleled strength” despite being 80% water, said the researchers at the University of Michigan in the US and Jiangnan University in China.
“We know that we consist mostly of water – all life does – and yet our bodies have a lot of structural stability,” said study lead Nicholas Kotov. “Understanding cartilage is understanding how life forms can combine properties that are sometimes unthinkable together.”
Synthetic materials have so far failed to match the tissue’s strength, the team said, despite many patients worldwide requiring replacements. Artificial replacements undergoing trials fail to combine the necessary strength with the high water content needed to transport nutrients for cells to survive, the engineers claimed.
The researchers looked to hydrogels – networks of long, flexible molecules which incorporate water – which can support the growth of chondrocyte cells necessary for natural cartilage build-up. However, hydrogels tear under a fraction of the strain that cartilage can handle, so the team turned to ultra-strong Kevlar for help.
The engineers combined a network of tough “aramid” fibres, best known for making bulletproof vests, with polyvinyl alcohol (PVA), which is commonly used in hydrogel cartilage replacements. The resulting material releases water under stress and recovers it later like a sponge, mirroring the natural tissue. The property is essential for undergoing repeated strain, such as running.
The synthetic cartilage could be a suitable replacement in areas such as the deeper parts of the knee, said Kotov, as it does not harm adjacent cells. The researcher also hopes to use different proportions of aramids and PVA to create other soft tissues which could work in other parts of the body.
“We have a lot of membranes in the body that require the same properties,” Kotov said. “I will talk to doctors about where the acute need is and where this intersection of the properties will allow us to make best headway and biggest impact."
The work appeared in Advanced Materials.
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