Near‐Infrared Light‐Responsive Cu₂MoS₄@GelMA Hydrogel with Photothermal Therapy, Antibacterial Effect and Bone Immunomodulation for Accelerating Infection Elimination and Fracture Healing

Managing fracture infections is a significant challenge in trauma orthopedics, given the limited self-healing capacity of fractures and the difficulty in eradicating infections. In this study, Cu₂MoS₄ nanoparticles (CMSs) with are prepared enzyme-like activity and both pH and near-infrared (NIR) light responsiveness. These CMSs are combined with methacrylated gelatin (GelMA) to synthesize CMSs hydrogels (CMSs@Gel) with antimicrobial and bone tissue repair-promoting capabilities. In vitro and in vivo experiments, the CMSs@Gel demonstrated good biocompatibility; peroxidase-like (POD), oxidase-like (OXD), and catalase-like (CAT) activities; excellent photothermal conversion efficiency; and immunomodulatory capacity. Furthermore, the CMSs@Gel exhibited slow degradation, enabling it to exert different pH-responsive enzyme activities and modulate the production of reactive oxygen species (ROS) and the polarization of macrophages throughout the treatment process. Notably, these effects are significantly enhanced under near-infrared (NIR) light. Additionally, under NIR irradiation, the CMSs@Gel maintained the fracture environment at a mild temperature (40-42 °C), promoting osteogenesis and angiogenesis. In summary, the CMSs@Gel enhances bactericidal activity during fracture infection and effectively promotes fracture healing after infection control, providing long-term therapeutic effects. This study offers a robust theoretical basis for the staged and long-term treatment of fracture infections in the future.