3D-Printed PLA/MgO/UCNPs composite scaffolds for immunomodulation and osteogenic bone repair

The persistent inflammatory microenvironment during bone defect repair can inhibit osteogenic differentiation, delay angiogenesis, and reduce the reparative efficacy of implanted materials. Therefore, developing biomaterials that combine immunomodulatory functions with bone-regenerative capacity is of great significance. In this study, composite scaffolds with anti-inflammatory and bone-repair-promoting properties were fabricated through surface functionalization and 3D printing. The structural and physicochemical properties of the scaffolds were systematically characterized by scanning electron microscopy (SEM), elemental mapping, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), contact angle measurement, and mechanical testing. Transmission electron microscopy and related analyses were further used to evaluate their microstructure and surface characteristics. The degradation behavior, pH variation, ion release profile, and antioxidant performance of the scaffolds under inflammatory conditions were then investigated to verify their ability to regulate the local microenvironment. In vitro, cytocompatibility was evaluated using CCK-8 assays, live/dead staining, and immunofluorescence staining. The effects of the scaffolds on macrophage polarization and inflammatory factor expression were further analyzed. Their osteogenic differentiation potential was assessed by alkaline phosphatase (ALP) staining, Alizarin Red staining, and osteogenesis-related gene expression analysis. In addition, Micro-CT, hematoxylin and eosin (HE) staining, and Masson's trichrome staining were performed in a bone defect animal model to evaluate bone regeneration and tissue repair. The results showed that the composite scaffolds effectively improved the inflammatory microenvironment in the defect region, promoted macrophage polarization toward an anti-inflammatory phenotype, enhanced cellular osteogenic activity and mineralization, and facilitated new bone formation and tissue reconstruction. This study provides a theoretical basis and experimental evidence for the design and application of bone repair materials under inflammatory conditions.