Translational hydrogel platform for durable sealing and mechanical restoration of annular defects

Conventional discectomy surgery for treating intervertebral disc (IVD) herniation remains limited in addressing post-surgery annulus fibrosus (AF) injury, resulting in high reoccurrence rate. However, repair of AF defects following discectomy remains challenging due to the complex biomechanics and anatomy of the IVD, as well as the mechanical limitations of biomaterials, which often fails to provide sufficient mechanical integration, durable tissue adhesion, and long-term biocompatibility. To address these unmet clinical challenges, we developed an adhesive hydrogel scaffold (AHS) composed of a chitosan-based fibrous hydrogels mechanical patch (FH_CS, as structural support) and an alginate-catechol adhesive interface (OAD-P, as interfacial adhesive) for sealing the defect AF and preventing IVD re-herniation. FH_CS exhibited strong mechanical properties (fracture strength: 46.54 ± 3.68 MPa, Young's modulus: 9.68 ± 4.17 MPa), which matched the mechanical properties of natural AF. OAD-P held strong adhesion to FH_CS (shear strength: 90.1 ± 14.9 kPa) and to AF tissues (shear strength: 81.6 ± 39.9 kPa). The AHS effectively sealed the AF defect in the box defect model on rat caudal IVD, maintained the structural integrity of the defective IVD, and reduced nociceptive behavior and downregulated nociception markers, indicating its efficiency in alleviating low back pain. In the in vivo porcine lumbar spine model, the scaffold demonstrated seamless integration with AF tissue and prevented nucleus pulposus extrusion under mechanical loading. Our findings reveal the therapeutic effect and translational potential of the adhesive hydrogel scaffold for functional annular repair following discectomy.