Diatom-Inspired Scaffold for Infected Bone Defect Therapy: Achieving Stable Photothermal Properties and Coordinated...

Bone defect therapy frequently encounters bacterial infections and chronic inflammation, which impair bone regeneration and threaten implant stability. Iron oxide nanoparticles have attracted attention due to cost-effectiveness, biocompatibility, and metabolic safety. However, iron oxide nanoparticles still struggle to balance low-temperature efficient antibacterial activity, effective immunomodulation, and bone regeneration. Therefore, inspired by diatoms, a multifunctional bone repair scaffold based on chitosan-hydroxyapatite (CH) is developed by integrating the multifunctional properties of copper-doped iron goethite (Fe(Cu)OOH) nanoparticles and a mesoporous SiO₂ protective layer (CH/FeCu@SiO₂). The "cytoskeleton" CH scaffold stabilizes the nanoparticles and supports tissue growth. The "chloroplast" Fe(Cu)OOH and the " frustule" SiO₂ layer synergistically capture near-infrared (NIR) light to generate localized mild hyperthermia (≈42 °C), with the release of Cu²⁺ to achieve antibacterial effects (>99%). In addition, Fe(Cu)OOH exhibits enzyme-like antioxidant activity, scavenging reactive oxygen species (ROS) (69.20%) and thereby promoting M2 macrophage polarization (1.64-fold), which protects stem cells and creates osteogenic immune microenvironment. Moreover, the mild hyperthermia and ion release upregulate the TGF-β signaling pathway and inhibit osteoclast differentiation, promoting vascularized bone regeneration and defect repair (1.3-fold). Overall, this biomimetic scaffold, enabling synergistic antibacterial, immunomodulatory, and osteogenic activities, offers a promising therapeutic strategy for infectious bone defects treatment.