A high strength, low friction, and biocompatible hydrogel from PVA, chitosan and sodium alginate for articular cartilage

Developing articular cartilage substitutes required a combination of high compressive strength , excellent biocompatibility and low friction. Despite great success in tough hydrogels, this combination was hardly realized. Herein, a high strength, low friction, and biocompatible hydrogel was obtained by freezing-thawing polyvinyl alcohol and chitosan aqueous solutions three times, followed with soaking in sodium alginate aqueous solution. Owing to the synergy of crystalline domains, hydrogen bonds , and ionic interactions, the obtained hydrogel exhibited high strength (maximum compressive strength = 141 MPa). Because of the reversible linkages, the gel was also creep-resistant (recovery efficiency = 93%). Benefitted from the negative carboxyl groups from sodium alginate, the water lubrication layer between the gel and the opposing surface was thickened greatly, resulting in a low coefficient of friction (0.044). The biocompatible materials and green progress led to excellent cell compatibility. All these merits made it an ideal substitute for articular cartilage.