The effect of Bonalive® bioactive glass on macrophage immune cell recruitment in response to S. aureus

Abstract

Bioactive glass is used in orthopedic implants for its regenerative and antibacterial properties, but its effects on immune cell behaviour are not fully understood. In this study, the influence of Bonalive® bioactive glass on macrophage responses to Staphylococcus aureus (S. aureus) was examined. THP-1-derived macrophages were exposed to small (S), medium (M), and large (L) bioactive glass granules under three different culture conditions: direct contact, pre-incubated (with medium) material, and conditioned medium. pH measurements of culture medium showed only modest changes after 24-hour incubation with bioactive glass. Macrophage polarization after bioactive glass exposure measured by the expression of M0 (CD14) or M1 (CD64 and CD86) surface marker showed no clear polarization. Chemokine secretion and transwell migration were measured after 24 hours after bacterial stimulation with S. aureus. Medium-sized granules led to the strongest chemokine release in response to S aureus and immune cell recruitment, particularly when cells were in direct contact with the material. Conditioned medium alone showed less migration, suggesting that physical interaction plays a key role. While no distinct M1 or M2 phenotype was observed in this model, functional responses were clearly influenced by granule size and culture conditions. These findings indicate that macrophage behaviour can be shaped by the physical properties of bioactive glass. Granule size may therefore be used to tune immune responses in biomaterial design, helping to balance antibacterial activity with tissue regeneration.