A new form of hydrogel promises to go where other forms haven’t by mimicking the near-magical qualities of cartilage.

Researchers at Duke University believe they have made a significant breakthrough by producing a hydrogel which can replace cartilage. It is the first time a man-made gel has shown any potential of matching the strong, but soft, qualities of the real thing [1].

Longevity.Technology: Knee surgery is expensive, invasive and has an enormous impact on a person’s quality of life. In this new hydrogel, scientists potentially have something they have wanted for years: a substance that can replace cartilage and circumvent the dreaded knee replacement.

Human cartilage is magic; it is hard enough to sustain decades of heavy wear and tear, yet soft and subtle enough to allow your knees to move. Until now, those are qualities most hydrogels, which are made from water-absorbing polymers, have been unable to mimic.

Now, however, the team of researchers from Duke believe they’ve done it. Resembling jelly, this material is 60% water but has incredible strength qualities. A small disc can withstand the weight of a 100-pound kettlebell without losing shape or being damaged.

Researchers, led by Ben Wiley and Ken Gall, have hailed it as the first hydrogel capable of enduring all the tugging and heavy loads human cartilage must undergo, with the added benefit that it will not wear out over time.

With thousands of knee surgeries taking place every year, this research represents a potentially huge cost saving for healthcare systems, but more importantly, stable knees = ability to exercise = increased healthspan and morbidity deferral.

Cartilage replacement
Scientists have been looking into the potential of hydrogels to replace cartilage for decades. Every step we take puts a strain of roughly double our body weight through our knees. Cartilage will withstand a huge amount of pressure over the years but it has limited ability to heal and repair. Wear and tear over the years is difficult to treat which leaves many patients with no option other than a knee replacement which may last for only 10-15 years.

Hydrogels have many of the properties scientists are looking for. They are soft, slippery and shock absorbent and do not harm nearby cells. However, until this new breakthrough from Duke University, they have been too weak.

Their new hydrogel comprises two intertwined polymer networks; one network is a grouping of stretchy strands similar to spaghetti, while the other one is more rigid. These are bolstered with a network of cellulose fibres which give the gel its shock-absorbing qualities.

When it is stretched, the cellulose fibres pull back and keep the material together, and when it is squeezed the negative charges along the rigid polymer chains repel each other and stick to water, springing it back into its original shape.

Experiments showed that their hydrogel was the only one as strong as cartilage in both stretching and squashing situations. In one example it underwent 100,000 cycles of repeated pulling, but held up equally well as the porous titanium implants used in bone implants.

The results exceeded even their own expectations and the team believes it could have enormous potential for knee patients.

[1] https://www.sciencedaily.com/releases/2020/06/200626114755.htm
[2] CITATION: “A Synthetic Hydrogel Composite with the Mechanical Behavior and Durability of Cartilage,” Feichen Yang, Jiacheng Zhao, William J. Koshut, John Watt, Jonathan Riboh, Ken Gall, Benjamin J. Wiley. Advanced Functional Materials, June 26, 2020. DOI:  10.1002/adfm.202003451
Main image credit: Feichen Yang c/o Duke Today