Enhancing Bone Repair Process: Application and Perspective on Photothermal Materials.

Repairing large bone defects remains a clinical challenge in orthopedics. Near-infrared (NIR) photothermal therapy (PTT) has recently expanded from high-temperature tumor ablation to the field of mild bone regeneration. Maintaining temperatures within a mild window of 40-42 °C accelerates bone healing by activating osteogenic signals, modulating the immune microenvironment, and providing antibacterial effects. It is important to note that the therapeutic efficacy is highly dependent on the precise control of both temperature and exposure duration: temperatures exceeding 42-43 °C can induce cell apoptosis, while temperatures above 45 °C typically cause necrosis. The reviewed studies employed controlled exposure times (typically 5-15 min per session) to maintain cell viability above 85%, with functional assessments confirming preserved osteogenic differentiation capacity of bone marrow-derived mesenchymal stem cells (BMSCs) and maintained macrophage plasticity after mild photothermal treatment. This performance depends on photothermal conversion materials. This paper reviews the applications of MXene, black phosphorus (BP), polydopamine/graphene oxide (PDA/GO), and metal-based nanomaterials in bone repair. We also analyze photothermal-based immune regulation, sequential repair strategies, and tumor theranostics. Finally, we discuss current challenges and future trends to guide the design of next-generation smart bone repair materials.