Cartilage-Adaptive Hydrogels via the Synergy Strategy of Protein Templating and Mechanical Training.

Cartilage, as a load-bearing tissue with high-water content, exhibits excellent elasticity and high strength. However, it is still a grand challenge to develop cartilage-adaptive biomaterials for replacement or regeneration of damaged cartilage tissue. Herein, protein templating and mechanical training is integrated to fabricate crystal-mediated oriented chitosan nanofibrillar hydrogels (O-CN gels) with similar mechanical properties and water content of cartilage. The O-CN gels with an ≈74 wt% water content exhibit high tensile strength (≈15.4 MPa) and Young's modulus (≈24.1 MPa), as well as excellent biocompatibility, antiswelling properties, and antibacterial capabilities. When implanted in the box defect of rat's tails, the O-CN gels seal the cartilage (annulus fibrosus) defect, maintain the intervertebral disc height and finally prevent the nucleus herniation. This synergy strategy of protein templating and mechanical training opens up a new possibility to design highly mechanical hydrogels, especially for the replacement and regeneration of load-bearing tissues.