Pure Zwitterionic Hydrogels with High Entanglement Reinforcement for Biomedical Applications

Pure zwitterionic hydrogels have attracted great interest in the biomedical field but are not widely used due to their weak mechanical properties. It has proven challenging to achieve an optimal balance between the antifouling ability and the mechanical properties of existing zwitterionic hydrogel enhancement methods. Consequently, pure zwitterionic hydrogel materials that exhibit high strength and resistance to fatigue were developed in this study. A prepolymerized poly(sulfobetaine methacrylate) (PSBMA) solution with an average number of 56 chain entanglements was first prepared, and then, chemical cross-linking was introduced to produce a pure semi-interpenetrating network (semi-IPN) PSBMA hydrogel. The resulting high-density entanglement-reinforced pure zwitterionic hydrogel resisted at least 98% compression and achieved a compressive strength of 26.2 MPa, an elongation at break of 667%, and no fatigue damage after 600,000 compression cycles. The formation of long-chain sulfobetaine polymer chain entanglements and the energy dissipation mechanism were revealed by molecular dynamics simulations. This high-strength, high-toughness, and high-elasticity pure zwitterionic hydrogel is also highly biocompatible, lubricating, contamination-resistant, transparent, and oxygen-permeable and has been shown to have considerable potential for biomedical applications, including articular cartilage, advanced contact lenses, and tissue scaffolds.