Injectable mesoporous bioactive glass/sodium alginate hydrogel loaded with melatonin for intervertebral disc regeneration

Intervertebral disc degeneration (IDD) is a major contributing factor to both lower back and neck pain. As IDD progresses, the intervertebral disc (IVD) loses its ability to maintain its disc height when subjected to axial loading. This failure in the weight-bearing capacity of the IVD is a characteristic feature of degeneration. Natural polymer-based hydrogel, derived from biological polymers, possesses biocompatibility and is able to mimic the structure of extracellular matrix, enabling them to support cellular behavior. However, their mechanical performance is relatively poor, thus limiting their application in IVD regeneration. In this study, we developed an injectable composite hydrogel, namely, Mel-MBG/SA, which is similar to natural weight-bearing IVD. Mesoporous bioactive glasses not only enhance hydrogels, but also act as carriers for melatonin (Mel) to suppress inflammation during IDD. The Mel-MBG/SA hydrogel further provides a mixed system with sustained Mel release to alleviate IL-1β-induced oxidative stress and relieve inflammation associated with IDD pathology. Furthermore, our study shows that this delivery system can effectively suppress inflammation in the rat tail model, which is expected to further promote IVD regeneration. This approach presents a novel strategy for promoting tissue regeneration by effectively modulating the inflammatory environment while harnessing the mechanical properties of the material.