Figure 2.

The hyaluronic acid hydrogel was cross-linked with MnCO and BMP-2, while the hydrogel was modified internally to be ROS sensitive. The hydrogel with the judgement-response feature was injected into the bone defect area of rats, and the hydrogel degraded after reacting with ROS, releasing the internal MnCO and BMP-2. MnCO can be degraded to Mn²⁺ and CO in the defect area, promoting macrophages to differentiate to M2 type and also causing M2 type macrophages to secrete anti-inflammatory factors VEGF and BMP-2, contributing to vascular regeneration and osteogenesis. The release of BMP-2 recruits local BMSCs, enhances their differentiation to osteoblasts and increases osteogenesis.