Kevlartilage – a material developed at the University of Michigan and Jiangnan University – can withstand just as much force as the cartilage in the human body while still being mostly water-based like real cartilage. The material is a Kevlar-based hydrogel that mimics the physical properties of cartilage.
“We know that we consist mostly of water – all life does – and yet our bodies have a lot of structural stability,” Nicholas Kotov, professor of engineering at the University of Michigan and leader of the study, said in a press release. “Understanding cartilage is understanding how life forms can combine properties that are sometimes unthinkable together.”
Other synthetic materials are undergoing clinical trials, but have not been able to match the strength of human cartilage while keeping the 80% water that is present in cartilage. Lack of water means that nutrients that cells need to grow will never be delivered.
Hydrogels, a material that has created robots and stopped bleeding, can be modified to support the growth of chondrocytes cells that help build natural cartilage. Since hydrogels are mostly water, they aren’t strong enough and tend to tear under strains that are much smaller than what cartilage typically goes through.
New Kevlar-based hydrogels are able to replicate both the strength and water consistency of cartilage by combining a network of tough nano fibers from Kevlar with polyvinyl alcohol (PVA), a material frequently used in hydrogel cartilage replacements.
Networks of proteins and biomolecules gain strength by resisting the flow of water in its chambers in natural cartilage. The water pressure reconfigures the network and allows it to deform without breaking. Water is released and the network can absorb more later later to recover. Because of that process, high impact joints like knees are able to withstand punishing forces.
Synthetic cartilage works using a similar process. It releases water under stress and absorbs it later under recovery. The aramid fibers found in Kevlar build the frame work of the synthetic cartilage while PVA traps water within the network when the material undergoes stretching and compression.
In different variations of the material, one with 92% water had comparable strength to cartilage while the 70% version had the resilience of rubber.
The researchers suggest that the Kevlar-based hydrogel materials could be a suitable implant for some situations like deep parts in the need. Aramid nano fibers and PVA are not harmful to surrounding cells and Kotov suggests that the material is not limited to just cartilage and could be used in other soft tissue situations.
“We have a lot of membranes in the body that require the same properties. I would like to evaluate the space,” 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 researchers are currently seeking patent protection and partners to begin to market the technology. The research was published in the journal Advanced Materials and was funded by the National Science Foundation and the Department of Defense.