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Developed at Duke University in North Carolina, the hydrogel – a material made of water-absorbing polymers – can reportedly be pressed and pulled with more force than natural cartilage, and is three-times more resistant to wear and tear.
Knee pain often comes from the progressive wear and tear of cartilage known as osteoarthritis, which affects nearly one in six adults (867m people) worldwide. For people who want to avoid replacing the entire knee joint, the hydrogel could offer a long-lasting alternative.
Implants made of the material are currently being developed by North Carolina firm Sparta Biomedical, to be tested in sheep. Researchers aim to start clinical trials in humans next year.
“If everything goes according to plan, the clinical trial should start as soon as April 2023,” said chemistry professor Benjamin Wiley, who led the research with mechanical engineering and materials science professor Ken Gall.
To make the material, the Duke team took thin sheets of cellulose fibres and infused them with a water-soluble synthetic polymer called polyvinyl alcohol to form a gel.
The cellulose fibres act like the collagen fibres in natural cartilage, Wiley said, giving the gel strength when stretched. The polyvinyl alcohol helps it return to its original shape. With a 60% water content the resulting material is jelly-like, and supple yet strong.
Natural cartilage can withstand an intense 5,800-8,500 pounds per inch of tugging and compressing before reaching its breaking point. The lab-made version is the first hydrogel that can handle even more, the researchers said. It is 26% stronger than natural cartilage in tension – the equivalent of being able to suspend seven grand pianos from a key ring – and 66% stronger in compression – the equivalent of withstanding the weight of a parked car on the area of postage stamp.
“It’s really off the charts in terms of hydrogel strength,” Wiley said.
In the past, researchers attempting to create stronger hydrogels used a freeze-thaw process to produce crystals within the gel, which drive out water and help hold the polymer chains together. Instead of freezing and thawing the hydrogel, the researchers used a heat treatment called annealing to coax even more crystals to form within the polymer network.
By increasing the crystal content, the researchers were able to produce a gel that can withstand five-times as much stress from pulling and nearly twice as much compression relative to freeze-thaw methods.
Implants made of the artificial cartilage could be a “dramatic change” for people facing total knee replacement, Wiley said, particularly for younger patients who want to avoid major surgery for a device that will eventually need replacing.
The work was supported in part by Sparta Biomedical and by the Shared Materials Instrumentation Facility at Duke University. Wiley and Gall are shareholders in Sparta Biomedical.
The research was featured in Advanced Functional Materials.
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