Modulating, instead of suppressing, foreign body responses for biomaterials design

Microporous structures on mineralized collagen mediate osteogenesis by modulating the osteo-immune response of macrophages

It is a new hot pot in tissue engineering and regenerative medicine to study the effects of physicochemical properties of implanted biomaterials on regulating macrophage polarization to promote bone regeneration. In this study, we designed and fabricated mineralized collagen (MC) with different microporous structures via in vitro biomimetic mineralization method. The microporous structures, mechanical properties, shore hardness and water contact angle measurements were tested. Live/dead cell staining, CCK-8 assay, phalloidine staining, staining of focal adhesions were used to detect cell behavior. ELISA, qRT-PCR, ALP, and alizarin red staining (ARS) were performed to appraise osteogenic differentiation and investigated macrophage response and their subsequent effects on the osteogenic differentiation. The results showed that RAW264.7 and MC3T3-E1 cells were able to survive on the MC. MC with the microporous structure of approximately 84 μm and 70%–80% porosity could promote M2 macrophage polarization and increase the expression level of TGF-β and VEGF. Moreover, the gene expression of the osteogenic markers ALP, COL-1, and OCN increased. Therefore, MC with different microporous structures mediated osteoimmunomodulation in bone regeneration. These data will provide a new idea of biomaterials inducing bone repair and direct the optimal design of novel immune biomaterials, development, and rational usage.

Fabrication and Hemocompatibility Evaluation of a Robust Honeycomb Nanostructure on Medical Pure Titanium Surface

Thrombosis induced by blood-contacting medical devices is still a major clinical problem, resulting in some serious complications such as infarction, irreversible tissue damage, and even death. Therefore, seeking an effective and safe surface modification approach to improve the hemocompatibility of the material is still urgent. In this research, a novel and facile approach was proposed to fabricate a robust honeycomb nanostructure on medical pure titanium surface by two-step anodic oxidation, which effectively enhanced the physicochemical performance and hemocompatibility of the material. Especially, the honeycomb nanostructure that underwent annealing treatment at 500 °C (HN-Ti-500 °C) presented significant performance to suppress the coagulation cascade in the in vitro tests, the reason mainly ascribed to an overall repulsive interaction between the protein molecule related to thrombosis and material surface based on an extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory analysis. Furthermore, a vessel stent fabricated by HN-Ti-500 °C was implanted into the left carotid artery of rabbits for 1 month. The antithrombotic mechanism and biocompatibility of the modified surface were further verified. The results presented that no thrombus generated and adhered onto the inner surface of the modified stent, and no obvious disorder hyperplasia and inflammation were observed in the intima tissue of the vessel at the implantation site, which indicated that the modified surface could effectively decrease the risk of in-stent restenosis and thrombosis. This work offers a promising strategy for surface modification of blood-contacting medical titanium material to address the clinical complications associated with restenosis and thrombosis.