Biofunctional supramolecular injectable hydrogel with spongy-like metal-organic coordination for effective repair of critical-sized calvarial defects.

In clinical settings, regenerating critical-sized calvarial bone defects presents substantial problems owing to the intricacy of surgical methods, restricted bone growth medications, and a scarcity of commercial bone grafts. To treat this life-threatening issue, improved biofunctional grafts capable of properly healing critical-sized bone defects are required. In this study, we effectively created anti-fracture hydrogel systems using spongy-like metal-organic (magnesium-phosphate) coordinated chitosan-modified injectable hydrogels (CPMg) loaded with a bioinspired neobavaisoflavone (NBF) component. The CPMg-NBF hydrogels showed outstanding anti-fracture capabilities during compression testing and retained exceptional mechanical stability even after 28 d of immersion in phosphate-buffered saline. They also demonstrated prolonged and stable release profiles of Mg2+ and NBF. Importantly, CPMg-NBF hydrogels revealed robust biphasic mineralization and were non-toxic to MC3T3-E1 cells. To better understand the underlying mechanism of Mg2+ and NBF component, as well as their synergistic effect on osteogenesis, we investigated the expression of key osteogenic proteins in the p38 MAPK and NOTCH pathways. Our results showed that CPMg-NBF hydrogels greatly increased the expression of osteogenic proteins (Runx2, OCN, OPN, BMPS and ALP). In vivo experiments showed that the implantation of CPMg-NBF hydrogels resulted in a significant increase in new bone growth within critical-sized calvarial defects. Based on these findings, we expect that the CPMg-NBF supramolecular hydrogel has tremendous promise for use as a therapeutic biomaterial for treating critical-sized calvarial defects.