Large bone defects resulting from fractures and disease are a major clinical challenge, being often unable to heal spontaneously by the body's repair mechanisms. Lines of evidence have shown that hypoxia-induced overproduction of ROS in bone defect region has a major impact on delaying bone regeneration. However, replenishing excess oxygen in a short time cause high oxygen tension that affect the activity of osteoblast precursor cells. Therefore, reasonably restoring the hypoxic condition of bone microenvironment is essential for facilitating bone repair. Herein, we designed ROS scavenging and responsive prolonged oxygen-generating hydrogels (CPP-L/GelMA) as a “bone microenvironment regulative hydrogel” to reverse the hypoxic microenvironment in bone defects region. CPP-L/GelMA hydrogels comprises an antioxidant enzyme catalase (CAT) and ROS-responsive oxygen-releasing nanoparticles (PFC@PLGA/PPS) co-loaded liposome (CCP-L) and GelMA hydrogels. Under hypoxic condition, CPP-L/GelMA can release CAT for degrading hydrogen peroxide to generate oxygen and be triggered by superfluous ROS to continuously release the oxygen for more than 2 weeks. The prolonged oxygen enriched microenvironment generated by CPP-L/GelMA hydrogel significantly enhanced angiogenesis and osteogenesis while inhibited osteoclastogenesis. Finally, CPP-L/GelMA showed excellent bone regeneration effect in a mice skull defect model through the Nrf2-BMAL1-autophagy pathway. Hence, CPP-L/GelMA, as a bone microenvironment regulative hydrogel for bone tissue respiration, can effectively scavenge ROS and provide prolonged oxygen supply according to the demand in bone defect region, possessing of great clinical therapeutic potential.

骨折和疾病导致的大骨缺损是一项重大的临床挑战，通常无法通过身体的修复机制自发愈合。证据表明，骨缺损区域缺氧诱导的 ROS 过量产生对延迟骨再生有重大影响。然而，短时间内补充过量氧气会导致高氧分压，影响成骨前体细胞的活性。因此，合理恢复骨微环境的缺氧状态对于促进骨修复至关重要。在此，我们设计了 ROS 清除和响应性延长产氧水凝胶 (CPP-L/GelMA) 作为“骨微环境调节水凝胶”，以逆转骨缺损区域的缺氧微环境。CPP-L/GelMA 水凝胶包含抗氧化酶过氧化氢酶 (CAT) 和 ROS 响应性释氧纳米颗粒 (PFC@PLGA/PPS) 共载脂质体 (CCP-L) 和 GelMA 水凝胶。在缺氧条件下，CPP-L/GelMA可释放CAT降解过氧化氢产生氧气，并在过量ROS的作用下持续释放氧气2周以上。CPP-L/GelMA 水凝胶产生的长期富氧微环境显着增强了血管生成和成骨作用，同时抑制了破骨细胞生成。最后，CPP-L/GelMA通过Nrf2-BMAL1-自噬途径在小鼠颅骨缺损模型中显示出优异的骨再生效果。因此，CPP-L/GelMA 作为骨微环境调节骨组织呼吸水凝胶，