Cartilage plays a vital role in the knee, but unfortunately, once cartilage is damaged or worn out, it is difficult to repair and usually needs to be replaced. Now, researchers at Duke University have created a new hydrogel that is as strong as natural cartilage.
The knee is the main stress point of the human body, so the cartilage there must be strong enough to support the weight of the person, but soft enough to cushion the strong force of each step. But when these useful things are injured, or are worn out after decades of continuous use, they will not have a good effect. Sometimes, the only thing that can be done is total knee replacement, but these are never as good as before.
For a long time, people have been studying the potential of hydrogel as a substitute for cartilage. This is a type of multifunctional material, as the name suggests, a gel composed mainly of water. They are increasingly used in the medical field, such as helping wound healing, hemostasis, and even stimulating tissue regeneration.
Although it is expected to be a substitute for knee cartilage, most hydrogels are too fragile to support such a large weight. But now, researchers at Duke University claim to have created a new version of the material that has the mechanical properties of cartilage. The new hydrogel is composed of a network of several polymer chains woven together. One of the networks is composed of elastic strands, while the second network is more rigid and its strands are negatively charged. The third network contains cellulose fibers to reinforce the structure.
Together, these three networks give the hydrogel the ability to return to its original shape after being stretched or squeezed. Cellulose fibers are helpful for the first point because they can resist being pulled and prevent the material from tearing. At the same time, the rigid polymer network counteracts the squeezing force because the negatively charged strands repel each other.
"Only the combination of these three ingredients is both soft and rigid, so it is very strong." Yang Feichen, co-author of the study said. In the test, the team demonstrated the capabilities of the new hydrogel. A coin-sized hydrogel tray can withstand a 100-pound (45 kg) kettlebell weight without tearing or losing shape. It was stretched 100,000 times and found to be as strong as the porous titanium currently used for bone implants. This is even stronger than the team expected. Finally, it was rubbed with natural cartilage samples 1 million times, and it was found that its wear resistance is the same as the real thing, and it is 4 times higher than the existing synthetic cartilage.
The research team said that the new hydrogel showed promise as a replacement for damaged cartilage in the knee, but this clinical use will take a few years at the earliest. At the same time, the researchers plan to design an implant that can be tested on sheep.