Oxygen-releasing biomaterials for bone tissue regeneration

Bone defects often exceed the body's innate self-healing capacity, inevitably disrupting local vascular networks and establishing a severe hypoxic microenvironment. This pathological hypoxia compromises cell survival, suppresses osteogenic differentiation, and ultimately dictates regenerative failure, representing a critical bottleneck in bone tissue engineering. Oxygen-releasing biomaterials (ORBs) have emerged as a transformative strategy to reprogram this hostile microenvironment into an oxygenous and pro-osteogenic niche. To advance this rapidly evolving field, this review provides a comprehensive and comparative analysis of state-of-the-art ORBs. We systematically establish an integrated framework categorizing these platforms-encompassing chemical oxygen-generating, physical oxygen-carrying, and bioenzyme-catalyzed systems, alongside emerging nanozyme- and photosynthesis-based strategies. Particular emphasis is placed on critically evaluating their distinct underlying mechanisms, intrinsic material features, and specific oxygen-release kinetics. Furthermore, we highlight the versatile applications of ORBs tailored to various complex bone defect scenarios. Finally, from a translationally oriented perspective, we discuss unresolved clinical challenges and outline future directions, aiming to provide rational guidance for the development of next-generation, biology-driven biomaterials for advanced bone regeneration.