The thin, slippery layer of cartilage in the knee between the bones is magical stuff: strong enough to withstand the weight of a person, but soft and supple enough to cushion the joint against impact, over decades of repeated use.
The material may seem like a distant Jell-O cousin - which it is - but it is incredibly strong.
Its developers say that it is the first hydrogel - materials made of water-absorbing polymers - able to withstand tugging and heavy loads as well as human cartilage, without wearing out over time.
Led by Duke chemistry and materials scientists Ben Wiley and Ken Gall, the research could one day offer a replacement for damaged cartilage to people with knee disorders and an alternative to the 600,000 knee replacement surgeries performed each year in the United States.
A smooth rubbery tissue that covers the ends of the bones and allows them to glide smoothly against each other, cartilage helps to absorb an enormous amount of force at each step - typically between two and three times your body mass.
Cartilage also has limited ability to self-heal and repair.
Artificial cartilage can help in patients who want to avoid or postpone a knee replacement that may last only 20 years.
Since the 1970s hydrogels have been explored for use as a cartilage replacement and are used in soft contact lenses and disposable diapers.
Researchers are attracted to these materials for their slippery, shock-absorbing properties and for not harming nearby cells.
"We set out to make the first hydrogel that has the cartilage's mechanical properties," said Wiley, a Duke chemistry professor.
The cellulose fibers resist pulling when the gel is stretched, and help hold the material together.
When the researchers compared the resulting material to other hydrogels, under both squishing and stretching, theirs was the only one that was as strong as cartilage.
The team subjected it to 100,000 cycles of repeat pulling in one experiment, and the material held up just as much as porous titanium used for bone implants, "which exceeded our initial expectations," said co-author William Koshut, a PhD student at the Gall laboratory.
They rubbed the new material a million times against natural cartilage, too.
It would take at least another three years to move the material from the lab to the clinic, Wiley said.
The team says the research could eventually offer new options for people with knee pain, and get them back to doing the things they love without the long recovery times and the limited lifespan associated with cartilage repair or knee replacement operation.Read the original article "The First Cartilage-Mimicking Gel That's Strong To Knees from the Lab" at https://today.duke.edu/2020/06/lab-first-cartilage-mimicking-gel-strong-enough-knees