Sodium butyrate-modified sulfonated polyetheretherketone modulates macrophage behavior and shows enhanced antibacterial and osteogenic functions during implant-associated infections

Abstract

Prevention of implant-associated infections and insufficient bone tissue integration is critical to exploit the immunomodulatory properties and antibacterial effects of implant materials, which have attracted considerable attention. Modulation of the functions of immune cells in different environments is crucial for managing infection and inferior bone integration via immunomodulation. In this work, sodium butyrate, a fermentation product of gut microbiota, was loaded onto 3D porous sulfonated polyetheretherketone (SP) to modulate the immune responses of cells in different environments. Evaluation of in vitro antibacterial effects showed that sodium butyrate-loaded SP exhibited superior antibacterial activity, especially in the samples containing high concentrations of sodium butyrate. Under bacterial stimulation, the phagocytic activity of macrophages increased with an increase in the sodium butyrate concentration via the production of reactive oxygen species (ROS), which favoured bactericidal activity in the implant-associated infection stage. For bacterial elimination, sodium butyrate-containing SP could polarize macrophages to the M2 phenotype and subsequently stimulate anti-inflammatory cytokine secretion, which is considered beneficial for bone regeneration in the tissue repair stage. In vitro osteogenesis was evaluated and the results demonstrated that treatment with sodium butyrate-containing SP increased the expression of osteogenic genes and proteins. An in vivo rat osteomyelitis model was used to evaluate the protective effect of the SP-loaded with sodium butyrate on bone destruction and osteolysis under infection conditions. To study osteogenesis in vivo, a rat femoral model without infection was used. The results indicated that the SP-B2 group exhibited superior anti-infection capacity and induced new bone formation around the implant in vivo. Treatment with sodium butyrate-containing porous SP modulated the macrophage response under different stimuli, thereby serving as a new approach for the design of smart implant materials with superior antibacterial and bone repair properties.