Silver nanoparticle-assembled guided bone regeneration membranes showcase dual functions: Initial bacterial elimination and subsequent immune regulation

Silver nanoparticles (AgNPs) exhibit excellent antibacterial effects at higher concentrations, and exert proper immunoregulatory effects in bone regeneration at lower concentrations. An ideal guided bone regeneration (GBR) membrane should inhibit bacterial infection initially and regulate immune cells subsequently to achieve desired bone repair. In this study, the polycaprolactone (PCL) membranes were coated with AgNPs via triple layer-by-layer (LbL) self-assembly (hereafter referred as “PCL-3Ag”). The fabrication process successfully endowed the PCL-3Ag membranes with excellent antibacterial activities and anti-inflammatory effects due to the abundant release of Ag initially, and promoted lipopolysaccharide stimulated macrophages polarization to M2 phenotype due to the slower and steady release of Ag in the subsequent stage. The regulation of PCL-3Ag on macrophages promoted the osteogenic differentiation of rat bone mesenchymal stem cells in vitro. In vivo, superior bone regeneration with decreased number of CD86-positive cells and increased number of CD163-positive cells was observed in rat calvaria defects covered with PCL-3Ag membranes compared with defects covered with PCL membranes or uncovered defects. Overall, the LbL self-assembled antibacterial, anti-inflammatory, and immunoregulatory PCL-3Ag membrane presented here enhances tissue repair and shows excellent potential for application to bone tissue engineering.