University of Waterloo researchers have developed a sea cucumber-inspired gel that could one day help repair damaged tendons and other soft tissues without leaving permanent material behind. The design borrows from the sea cucumber’s ability to change the stiffness of its body.The water-rich material, known as a hydrogel, acts as a temporary support structure that lets new tissue grow as the material gradually breaks down. Like the animal that inspired it, the gel can be made softer or stiffer, potentially letting it support the healing of different tissues throughout the body.Matching stiffness to tissueThat tunability matters because soft tissues have different mechanical needs. “Soft tissues don’t all require the same scaffold,” said Dr. Yimin Wu, a mechanical engineering professor at Waterloo who spearheaded the study. A scaffold for delicate brain tissue, he explained, must behave differently from one that repairs a hard tendon.To make the gel, researchers first freeze the material to form its internal structure. They then soak it in specially prepared salt solutions that adjust its stiffness, making it softer or firmer depending on the tissue it must support.Promising results in ratsAfter nearly four years of research, the international team tested the gel in a preclinical study involving rats. Rats with damaged tendons treated with the gel showed improved healing compared with those repaired with stitches alone.The gel helped support the growth of new, more organized tissue. As the tendons healed, it gradually broke down and was absorbed by the body over about eight weeks.Dr. Youchao Teng, who led the project under Wu’s supervision, said the team was extremely encouraged. The treated tendon regenerated with more organized new tissue and function comparable to a healthy tendon, he said.Next steps beyond tendonsThe ability to customize the gel could eventually make it useful for repairing muscles, cartilage, skin and even delicate tissues in the brain and other organs. Further research is needed to determine whether it can safely and effectively support healing in those parts of the body. The researchers describe the results as promising but preclinical, meaning that human benefit is not yet established.Wu and Teng have applied for two patents related to their work and formed a company to try to commercialize it. Next steps include testing on larger animals and, eventually, clinical trials.The project involved collaboration with Dr. Song Li at the University of California, Los Angeles, and Dr. Badri Narayanan at the University of Louisville. The team also included Waterloo engineering professors Dr. Zhao Pan and Michael K.C. Tham, plus members at facilities and universities in the United States, Taiwan, China and Canada.The paper, “Bioinspired Hydrogels with Broadly Programmable Mechanics for Soft-Tissue Interfaces,” was recently published in Advanced Functional Materials.