Dual-controlled release of Mg2+/Zn2+ cage system promotes osteointegration in interbody fusion

• The composite hydrogel with suitable physical and chemical properties was synthesized through electrostatic action. • The composite cage system ensured excellent compatibility and a continuous ion release process. • The synergistic effect of Mg 2+ and Zn 2+ promoted osteogenic ability and enhanced interbody fusion effect. Interbody fusion is a primary surgical procedure for conditions associated with intervertebral disc degeneration and nucleus pulposus herniation. However, osteointegration at the bone-implant interface is often hindered by the limited vascularization within the intervertebral space and the low biological activity of traditional cages. To address this limitation, we developed a composite cage system (Alg-Zn/Lap/Ta) by incorporating laponite (Lap) and alginate (Alg-Zn) with a tantalum (Ta) cage. The results of our experiments demonstrate that the Alg-Zn/Lap/Ta cage exhibits suitable physicochemical properties and excellent biocompatibility. In vitro, it effectively promoted the osteogenic differentiation of rabbit bone marrow mesenchymal stem cells (BMSCs) without showing any significant toxic effects on their adhesion and morphology. After implantation into the lumbar intervertebral space of rabbits, the composite cage significantly promoted new bone formation and achieved superior osteointegration at the interface. Therefore, this composite cage system, possessing excellent biocompatibility and a high capacity for osteointegration, represents a promising strategy for the treatment of spinal degenerative diseases.