Titanium Dioxide Particle Size Influences Macrophage Signal Switch Towards Osteogenesis In Vitro

OBJECTIVE: NPs) on macrophage internalisation and their downstream influence on regulating osteogenesis in vitro. DESIGN: MPs and NPs was collected and applied to human osteoblast (HOB) cells, with their functionality analysed at gene and protein expression levels, receptor activator of nuclear factor kappa-B ligand/osteoprotegerin (RANKL/OPG) ratio, and matrix mineralisation. RESULTS: NP CM group demonstrated enhanced osteogenic activity, evidenced by upregulation of RUNX2, increased alkaline phosphatase activity, collagen type I secretion, and extracellular matrix mineralisation, generating a lower RANKL/OPG ratio in HOB cells. Western blotting revealed elevated osteocalcin and BMP-7 levels in NP CM-treated cells. CONCLUSION: Titanium dioxide particle sizes are able to "switch" macrophage signalling toward either bone formation (nano) or bone resorption (micro) and may play a crucial role in osteo-immunomodulation.