Bioinspired polymer-incorporating self-lubricating and antifouling hydrogels

Healthy articular cartilage exhibits a very low coefficient of friction (CoF ≈ 0.002-0.02) due to hydration lubrication at the slip plane, involving phospholipids bound to macromolecules in the cartilage matrix. Hydrogels that mimic this hydrated phosphorylcholine layer could replicate cartilage lubrication for biomedical devices. In this study, we synthesized a poly(2‑methacryloyloxyethyl phosphorylcholine‑co‑N‑isopropylacrylamide) (PMPC‑co‑PNIPAM, PMN) random copolymer containing highly hydrated lubricious MPC moieties. Incorporation of trace amounts of PMN into various hydrogels substantially reduces sliding friction, yielding extremely low CoF against hydrophilic stainless steel, hydrophobic polyethylene, and soft poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels. The PMN‑containing hydrogels are biocompatible and exhibit strong antifouling properties, with CoF an order of magnitude lower than those of commercial lubricated catheters, suggesting a potential basis for further exploration as coatings for stents or catheters. These materials achieve outstanding lubricity on both hydrophilic and hydrophobic surfaces, offering new opportunities for biomedical applications. STATEMENT OF SIGNIFICANCE: This study introduces a bioinspired polymer-incorporating hydrogel that achieves ultra-low friction (coefficient of friction, CoF<0.01) on both hydrophilic and hydrophobic surfaces, overcoming a key limitation of lipid-based lubricating hydrogels. The phosphorylcholine‑based copolymer forms stable microreservoirs within poly(2-hydroxyethyl methacrylate) hydrogels, enabling self-lubrication, wear resistance, and efficient antifouling properties against cells and bacteria. The hydrogel is biocompatible and retains lubricity after drying-rehydration. When coated on commercial catheters, it reduces friction 20‑fold compared to existing lubricated devices. This work offers a versatile, durable, and translational platform for biomedical implants and devices requiring boundary lubrication on diverse material surfaces.