A NIR assisted composite scaffold incorporating CuHP and melatonin for enhanced anti-infection and bone regeneration in an acute rat model of infected bone defect

Abstract

The clinical failure of infected bone repair is primarily due to the inability of conventional scaffolds to simultaneously eradicate resilient biofilms and orchestrate the subsequent bone regeneration within the hostile inflammatory microenvironment. In this study, we developed a NIR assisted composite scaffold based on a 3D printed polycaprolactone (PCL) framework coated with a gelatin methacryloyl (GelMA) hydrogel containing copper hydroxyphosphate (CuHP) and melatonin (MT). Under near-infrared (NIR) irradiation, the scaffold exhibited enhanced antibacterial activity against Staphylococcus aureus via photothermal effects. The presence of MT was associated with reduced local inflammation and increased M2 like macrophage markers in vivo, although direct immunomodulatory mechanisms were not proven. The scaffold supported osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) in vitro and promoted new bone formation in an acute rat model of infected femoral defect. This study presents a promising combination system.