Cartilage — the strong and flexible fibrous tissue that connects bones at joints, prevents the wearing of bones when they rub against one another, and acts as a shock absorber — can be damaged by injury, disease or hormonal changes. Repairing them has been a challenge in medical research.

Usually, doctors use hydrogels to replace damaged cartilage. Hydrogels are hydrophilic (water-loving) polymers that can swell in water and hold a large amount of water without losing their structure.

The commonly used hydrogels, made of polyacrylamide (PAM), lack the required mechanical strength and puncture resistance. Researchers at the departments of materials engineering, mechanical engineering and inorganic and physical chemistry in IISc have now developed hybrid hydrogels by combining PAM with either carbon nanotubes (CNTs) or titanium dioxide or both. They found that the most stable composite hydrogel (PAM+titanium dioxide+CNT) had remarkable self-healing ability, high mechanical strength, and compatibility with biological tissue. The researchers have also carried out computational studies to understand the binding features and structure of these hybrid hydrogels.

They have shown that the hydrogel modified by them is more hydrophilic than either PAM alone or in combination with just titanium dioxide or CNTs; this allows it to absorb more water and swell, which is important for biomedical applications. Its dense and compact structure helps it withstand degradation. The researchers also used a method called needle insertion to show that the hybrid hydrogel is puncture-resistant. “Such materials offer great promise for cartilage repair,” says a statement of IISc.