An antifouling, robust and adhesive hydrogel for cartilage replacement

It remains challenging for traditional cartilage replacements to simultaneously have the antifouling ability, self-adhesion, and adequate mechanical properties in the physiological environment. Here we develop a tri-layer hydrogel to address this issue. The precursor hydrogel was prepared through a three-cycle freezing-thawing process involving a blend of poly vinyl alcohol, chitosan and deionized water, followed by 3 h immerse in 25 wt% aqueous solution of grape seed protein. The top layer was modified with methacryloyl chloride and polymerized with sulfobetaine methacrylate (SBMA). Meanwhile, the bottom layer was coated with the adhesive of gelatin and tannin. On account of the multiple linkages (crystalline domains, hydrogen bonds, and ionic interactions), the compressive stress remained 42 MPa and the swelling ratio was 0.1 g/g even after a week immersion in simulated synovial fluid. Because of the introduction of SBMA, the hydrogel could resist non-specific protein adsorption and the coefficient of friction was 0.023 in simulated synovial fluid. The amino acids and polyphenol groups could form noncovalent interactions with various substrates, resulting in excellent underwater adhesion capability. The synergy of biocompatible materials and environmentally friendly progress led to exceptional biocompatibility, having promising applications in cartilage replacement.