Silk Fibroin/Polycaprolactone Coaxial Nanofibrous Scaffold Loaded with Kaempferol and Icariin: A Bioactive Macromolecular Platform for Bone Regeneration through Enhanced Antibacterial Activity and Osteoimmunomodulation

Abstract This study aims to fabricate a scaffold based on natural herbal active substances, achieving antibacterial, anti-inflammatory, and osteogenic activities by graded and sustained drug release, overcoming the high cost and instability of growth factors in conventional bone defect scaffolds. Coaxial electrospinning was employed to construct a scaffold with silk fibroin (SF)/polycaprolactone (PCL)/kaempferol (KAE) as the shell and icariin (ICA) as the core, preparing nanofibrous scaffolds (ICA@SF/PCL/KAE). Comprehensive characterizations confirmed the co-axial structure of the nanofibers and successful drug loading and favorable release profiles of KAE and ICA, as well as the significantly enhanced mechanical performance. The KAE-loaded scaffold exerted outstanding antibacterial activity, while all of the drug-containing scaffolds maintained excellent cytocompatibility. In LPS-induced inflammatory environments, macrophages co-cultured on KAE-containing scaffolds exhibited markedly reduced reactive oxygen species and nitric oxide production, along with a decreased M1 macrophage ratio and an increased M2 macrophage ratio. RT-PCR results demonstrated that KAE-loaded scaffolds downregulated pro-inflammatory gene expression and upregulated anti-inflammatory gene expression. In vitro osteogenic induction revealed that the incorporation of KAE and ICA, especially ICA, remarkably enhanced osteogenic activity of the nanofibrous scaffolds. Under inflammatory conditions, KAE-containing scaffolds exhibited superior regulation of the osteogenic immune microenvironment compared with ICA-containing scaffolds. Notably, the ICA@SF/PCL/KAE scaffold containing both components achieved the optimal performance in all of the above in vitro experiments. Finally, rat cranial defect experiments further verified the excellent osteogenic efficacy of ICA@SF/PCL/KAE in vivo. Collectively, the ICA@SF/PCL/KAE core–shell nanofibrous scaffold offers an innovative approach for clinical bone defect treatment and expands the application potential of natural herbal active substances.