Differential effect of tantalum nanoparticles versus tantalum micron particles on immune regulation

The inflammatory microenvironment created by macrophages has been proven critical for bone regeneration. Both tantalum nanoparticles and micron particles have been applied to bone tissue engineering and have achieved good efficacy, but their effects on immune microenvironment remain unclear. Herein, we explored the different effects between nano- and micro-tantalum particles on the innate immunity of macrophages in vitro and in vivo. RAW 264.7 ​cells were co-cultured with nano- and micro-tantalum particles under inflammatory conditions to evaluate the effects on the morphology and behavior of macrophages. Air pouch model was used to evaluate the material-induced macrophage polarization in vivo. Compared to the tantalum micron particles (TaMPs), the morphology of macrophages was more similar to the M2 phenotype in co-culture with tantalum nanoparticles (TaNPs). At the same time, the TaNPs could also decrease the gene expression of interleukin-1β (IL-1β), tumor necrosis factor-α(TNF-α), inducible nitric oxide synthase (iNOS), and increase the expression of transforming growth factor-β1 (TGF-β1) and interleukin-10 (IL-10). Furthermore, the air pouch model showed more M2 macrophage infiltration under the intervention of TaNPs. Our findings demonstrated that TaNPs could significantly increase the polarization of M2 macrophages and decrease the macrophage polarization to the M1 phenotype under the inflammatory microenvironment, showing better immunomodulatory properties.