Hydrogenated TiO2 Nanotubes Regulate Osseointegration by Influencing Macrophage Polarization in the Osteogenic Environment

Abstract

The immunomodulatory role of monocytes is essential for tissue healing and can influence the osseointegration of implanted materials. Properties such as the surface structure, hydrophilicity, and roughness of the implanted materials can modulate monocyte–macrophage function. In this study, we characterized material-hydrogenated TiO2 nanotubes (H-TNT) with superhydrophilic surfaces to investigate the effect of H-TNT on macrophage polarization and osseointegration. H-TNT were prepared by anodic oxidation and hydrogenation and used in the experimental group, while TNT and smooth pure Ti were employed in the control groups. RAW264.7 cells were selected to observe the immunomodulatory effect of these samples. The cell morphology was observed via scanning electron microscopy, and cytokine expression was detected using an enzyme-linked immunosorbent assay and immunofluorescence staining. After 24 hr of cultivation, the macrophage-conditioned medium was collected and used for indirect coculture with MC3T3-E1 cells. The morphology of MC3T3-E1 cells was observed using fluorescence staining. Cell adhesion and proliferation were measured using the Cell Counting Kit-8 assay. Alkaline phosphatase activity measurement, alizarin red staining, calcium quantification, and reverse transcription polymerase chain reaction were performed to assess the osteogenic differentiation of MC3T3-E1 cells. The results showed that H-TNT promoted the M2-type polarization of macrophages, which in turn influenced the adhesion, proliferation, and osteogenic differentiation of MC3T3-E1 cells. These materials can serve as useful candidates for bone implants because they activate macrophages to produce a favorable osteoimmunomodulatory microenvironment.