Knee cartilage performs an important role in our bodies, acting as both a barrier to protect our joints from harm and a soft cushion. This amazing biological substance has proved difficult to replace. However, a breakthrough from bio-engineers at Duke University is set to change that.
The team of researchers, led by Duke chemistry and materials scientists Ben Wiley and Ken Gall, believe they have finally developed a material which could be used as a replacement material after injuries or in old age.
Ben Wiley explains that the team goal was to “make the first hydrogel that has the mechanical properties of cartilage”. Like other hydrogels, the material breakthrough came from using new material water-absorbing polymers.
This new gel is mainly made from a single polymer whose spaghetti-like strands are intertwined with another less flexible and more basket-like polymer. The substance then uses a third cellulose fibre polymer to act like a mesh holding everything together.
When the material is then stretched the third polymer holds it together. When it is squeezed the first two restore the original shape because they pack a negative charge running through their length. This charge allows the two polymers to repel each other and stick to water.
Early tests look promising for the new tech with the material holding up under a 100,000 repeated pull test. Not only beating out existing hydrogels but performing as well as the existing porous titanium material used in bone implants.
Knee replacements vs hydrogels
The breakthrough could benefit hundreds of thousands of people a year. In the UK alone there are 115,000 knee replacements.
Typically surgery is invasive and lasts only a few decades before the knee must be replaced again. However, the idea behind using hydrogel is that it would just replace the worn-out cartilage rather than being forced to remove and replace the whole joint.
The next step will require a three-year wait until the material can be used in humans so widespread human adoption of this type of technology is still some way off. In the meantime, the team will now be testing the toxicity of the gel in lab-grown cells and then move on to trialling the technique on sheep.
The hope is that the material will go on one day restore joints without long recovery times or replacements.
Published as A Synthetic Hydrogel Composite with the Mechanical Behavior and Durability of Cartilage in Advanced Functional Materials, June 26, 2020. DOI: 10.1002/adfm.202003451