An ultra-tough, creep-resistant, wear-resistant hydrogel for cartilage replacement

As a load-bearing tissue, natural cartilages possess a compressive stress above 50 MPa, a water content around 60%, and a friction coefficient (FC) less than 0.1, which remains difficult for synthetic materials to realize. Herein, a facile strategy was reported to achieve this goal. The hydrogel was obtained through a three-step strategy from polyvinyl alcohol (PVA), chitosan (CS), sodium carboxymethyl cellulose (CMC-Na), lecithin (LS), and deionized water. First, freezing–thawing the aqueous solution of PVA and CS three times generated the precursor gel. Second, immersing it in aqueous solution of CMC-Na to form multiple linkages (hydrogen bonds, ionic interactions, and crystallize domains). Third, it was coated with LS to form a lubrication layer. Due to the synergy of dynamic interactions, the compressive stress was 115 MPa, superior to most tough hydrogels. Owing to existence of LS, the FC was 0.03, better than the requirement for artificial cartilage. Remarkably, the FC remained stable within 50,000 wear cycles. On account of the reversible break/reformation of physical linkages, the creep recovery efficiency was 93%. The raw materials are all biocompatible and the fabrication process exclude the adoption of toxic additives. All of these features make it an ideal material for cartilage replacement.