Nanosized concave pits/convex dots microarray for immunomodulatory osteogenesis and angiogenesis

The immunomodulatory capability of biomaterials is of paramount importance for successful materials-mediated bone regeneration. Specifically, the design of surface nano-topography can be leveraged to instruct immune reactions, yet the understanding of such “nano-morphology effect” is still very limited. Herein, highly ordered nano-concave pits (denoted as NCPit) and nano-convex dots (denoted as NCDot) microarrays with two different sizes were successfully constructed on 316LSS surface via anodization and subsequently immersion-coating treatment, respectively. We, for the first time, comparatively investigated the interactions of NCPit and NCDot microarrays with RAW264.7 macrophages and their immunomodulatory impacts on osteogenesis and angiogenesis of human bone mesenchymal stem cells (hBMSCs) and human umbilical vein endothelial (HUVECs). NCDot microarrays induced macrophages towards M2 polarization with the higher expression level of anti-inflammatory markers (IL-10 and CD 206) and the lower level of pro-inflammatory markers (TNF-α, IL-1β, IL-6 and CD 86) than those of the corresponding NCPit microarrays. During the process, the expressions of osteogenesis-related genes (Runx2, OPN and OCN) of hBMSCs, and angiogenesis-related genes (eNOS, HIF-1α, KDR and VEGF) of HUVECs were significantly upregulated by NCDot microarray-modulating immune microenvironment of macrophages, and finally stimulated osteogenesis and angiogenesis. Thus, the prepared NCDot arrays were able to significantly promote osteo-/angiogenic activity by generating a more proper immune microenvironment than NCPit arrays, offering the substantial evidence for designing immunomodulatory biomaterials with specific microstructure and optimal bioactivity. Keywords: Macrophage, Inflammatory response, Osteogenesis, Angiogenesis, Surface nano-morphology