Freeze-Thaw-Induced Hybrid Porous PVA/PEG Hydrogels with Dynamic Load-Dissipation Capability for Cartilage...

Osteoarthritis is the most prevalent age-related joint disease, yet the limited regenerative capacity of articular cartilage severely constrains spontaneous repair. Here, we present a freeze-thaw polyvinyl alcohol (PVA)/polyethylene glycol (PEG) hydrogel platform featuring a hybrid open-closed macroporous architecture that enables cartilage-mimetic load dissipation for artificial cartilage applications. The hybrid porous structure provides synergistic advantages, where closed pores enhance load-bearing stiffness while open pores facilitate energy dissipation. By systematically tuning polymer composition and processing conditions, clear structure-property relationships among porosity, water content, and mechanical performance are established. An optimized formulation (18 wt.% PVA, 85-124 kDa; 18 wt.% PEG; three freeze-thaw cycles) yields hydrogels with high water content (39.1 ± 7.8 wt.%), high compressive Young's modulus (3.60 ± 0.67 MPa), and excellent resilience under cyclic loading. Notably, under dynamic compression (2 m/s), a frequently overlooked yet physiologically relevant mechanical property of hydrogels, the materials exhibit nearly twofold enhancement in compressive modulus compared to static conditions, demonstrating pronounced strain-rate-dependent stiffening. Finite element analysis reveals efficient load redistribution across the interconnected porous network, providing mechanistic insight into the observed mechanical robustness. Compared with native cartilage and recently reported hydrogel systems, the developed hydrogels exhibit superior stiffness while maintaining mechanical and structural resilience. In vitro cytotoxicity and direct-contact assays confirm excellent cytocompatibility. These results establish a scalable and cost-effective design strategy for engineering mechanically robust, rate-adaptive hydrogels, advancing the development of next-generation artificial cartilage substitutes.