Graded Modulation of Inflammation by Metal Ion-Coordinated Peptide-Based Hydrogel Chemical Regulators Promotes Tendon-Bone Junction Regeneration.

After rotator cuff injuries, uncontrolled inflammation hinders tendon-bone junction regeneration and induces scar formation in situ. Therefore, precisely controlling inflammation could be a solution to accelerate tendon-bone junction regeneration. In this study, we synthesized a peptide-metal ion complex hydrogel with thermosensitive capability that can be used as a hydrogel chemical regulator. By the coordination complex between Mg 2+ and BMP-12, the free and coordinated Mg 2+ can be programmability released from the hydrogel. The fast release of free Mg 2+ can prevent inflammation at the early stage of injuries, according to the results of RT-qPCR and immunofluorescence staining. Then, the coordinated Mg 2+ was slowly released from the hydrogel and provided an anti-inflammatory environment for tendon-bone junction regeneration in the long term. Finally, the hydrogel demonstrated enhanced therapeutic effects in a rat rotator cuff tear model. Overall, the Mg 2+ /BMP-12 peptide-metal ion complex-based hydrogel effectively addresses the regenerative requirements of the tendon-bone junction across various stages by graded modulating inflammation.