"Inner swelling-outer restraint" strategy to fabricate poly (vinyl alcohol)/MoS-poly (vinyl alcohol)/sodium carboxymethyl cellulose Janus hydrogel for pressure-bearing cartilage replacement.

Due to the poor regeneration ability of cartilage tissue, the design and fabrication of permanent hydrogel cartilage scaffolds with mechanical properties matching is still an urgent challenge. In this study, we propose an "inner swelling-outer restraint" strategy to construct Janus hydrogel for pressure-bearing cartilage replacement, which is inspired by the "Lamina-splendens" structure of cartilage. As a proof of concept, the poly(vinyl alcohol)/carboxymethyl cellulose sodium (PVA/CMCNa) layer is designed to capture more fluid by introducing negatively charged aggregates, while the macromolecular conformation of the PVA/MoS layer can be densified through wet annealing, thereby increasing the liquid permeation resistance of the PVA/CMCNa layer. The Janus hydrogels exhibit an amazing liquid bearing capacity under pressure loads, enabling the hydrogels to withstand 30,000 cycles of repeated high-strength compressions without damaging the solid matrix. A robust interface forms between the two layers and the interfacial peeling force reaches 536 ± 39 N/m. The in vivo evaluation results demonstrate that the effect of Janus hydrogel on reducing the cartilage degeneration around the knee cartilage defect is similar to that of autogenous bone. The Janus hydrogel with asymmetric elastic modulus and swelling properties might provide valuable insights into the establishment of soft hydrogel pressure-bearing cartilage replacement.