Anti-Swelling and Thermally-Actuated Adhesive Dual-Network Hydrogel for Annulus Fibrosus Repair With Self-Healing Capability

To prevent nucleus pulposus reherniation following annulus fibrosus (AF) rupture, effective defect sealing is imperative post-discectomy. Ideal repair materials require excellent cytocompatibility, tailored adhesion, and long-term stability. Herein, a double-network hydrogel (PNG) featuring a dense hydrogen-bonded network is engineered by integrating gelatin with poly(acrylic acid-co-N-acryloyl glycinamide) via a pH-controllable crosslinking strategy. PNG exhibits exceptional dimensional stability (swelling ratio <1%) and temperature-responsive adhesion. Molecular dynamics simulations elucidate the adhesion-swelling equilibrium, identifying acrylic acid as the optimal comonomer for robust hydrogen-bonding. The hydrogel demonstrates a smart adhesive transition, achieving robust bonding strength of 274.4 kPa at physiological temperature (40°C), significantly superior to its state at room temperature (152.6 kPa), thus facilitating intraoperative handling. This provides robust interfacial adhesion sufficient to secure the defect site and withstand physiological conditions, ensuring reliable tissue-material integration. In a rat AF defect model, PNG effectively seals the defect, restores mechanical integrity, and promotes the regeneration of extracellular matrix components (COL1, COL2, and ACAN). This multifunctional hydrogel achieves a delicate adhesion-swelling balance, providing a novel biomimetic scaffold strategy to prevent postoperative reherniation and guide functional tissue regeneration.