Near-infrared light and magnetic field dual-responsive 3D printed scaffolds for sequential treatment of infected bone defects

The treatment of infected bone defects remains a challenge due to the complex biological processes involved, including antibacterial, anti-inflammatory, angiogenesis and bone regeneration. Polyetherimide (PEI) has promising applications in orthopaedics, but its biological inertness limits its clinical efficacy. In this study, a smart near-infrared (NIR) light and magnetic field responsive 3D printed scaffold was developed by combining PEI and Fe₃O₄nanoparticles. Gelatin methacrylate hydrogel containing aloe-emodin (AE), a natural antimicrobial and antioxidant compound, was subsequently injected into the 3D printed scaffold to create the P-Fe₃O₄@GM-AE composite scaffold. This composite scaffold exhibited several key functionalities: Firstly, it effectively eliminated methicillin-resistant<i>Staphylococcus aureus</i>when exposed to NIR light, achieving an<i>in vivo</i>antimicrobial rate of 99.97 ± 0.1%. Secondly, it effectively removed reactive oxygen species and prevented the pro-inflammatory M1 polarization of macrophages in the infected bone defect microenvironment, creating favorable conditions for bone reconstruction. Moreover, during the reconstruction stage, the magnetic composite scaffold, when combined with a static magnetic field, promoted osteogenesis-angiogenesis coupling, thereby accelerating bone repair. Thus, this study provides new insights and methods for the sequential treatment of infected bone defects.