New non-toxic hydrogel binds defected bones strongly

Researchers have developed a new kind of tough, non-toxic hydrogel that bonds spontaneously and strongly to defected bones, an advance that may have potential use in the treatments of joint injuries.
When soft supporting human tissues - including cartilage and ligaments, which are joined firmly to bones - are damaged, they cannot spontaneously repair inside the body, researchers said.
The use of artificial supporting tissues has the potential to significantly ameliorate damage to soft tissues. Progress has till now been hampered by the lack of materials that are strong, yet soft and pliant, for adhering to bone, they said.
Researchers from Hokkaido University in Japan had previously developed a tough, high-strength network gel, called double-network gel (DN gel), that exhibited excellent performance such as low wear and inductive function for cartilage regeneration.

However, as the gel's main component is water, it was difficult for it to bond with other surfaces - a major stumbling block in its practical application.
The new gel, however, overcomes this problem. Researchers successfully added hydroxyapatite (HAp), the major inorganic component of bone, to the surface of DN gel by dipping it in calcium solution and phosphate solution.

The HAp-coated DN gel (HAp/DN gel) was then transplanted into a defected bone in a rabbit.
Four weeks later, researchers observed that the gel had bonded to the bone very strongly, while the non-coated gel had not bonded at all.

Electron-microscopic analysis showed that the newly formed bone component in the defected area had penetrated into the gel surface, and fused to it seamlessly, researchers said.
Tough, nontoxic hydrogel that adheres strongly to bone is a major advance in the treatment of joint and soft tissue injuries. The results are also promising for the potential application of tough hydrogel materials as cartilages, they said.
"The bonding between HAp/DN gel and bone mimics physiological bonding seen with cartilage, ligament and tendon, causing less stress to the body," said Jian Ping Gong from Hokkaido University.
"We expect that the gel could be used to firmly attach artificial ligament or tendon to bone," said Gong.

The findings were published in the journal Advanced Materials.