Abstract：
Injectable in situ-forming scaffolds that induce both angiogenesis and osteogenesis have been proven to be promising for bone healing applications. Here, we report the synthesis of an injectable hydrogel containing cobalt-doped bioactive glass (BG)-loaded microspheres. Silk fibroin (SF)/gelatin microspheres containing BG particles were fabricated through microfluidics. The microspheres were mixed in an injectable alginate solution, which formed an in situ hydrogel by adding CaCl2. The hydrogel was evaluated for its physicochemical properties, in vitro interactions with osteoblast-like and endothelial cells, and bone healing potential in a rat model of calvarial defect. The microspheres were well-dispersed in the hydrogel and formed pores of >100 μm. The hydrogel displayed shear-thinning behavior and modulated the cobalt release so that the optimal cobalt concentration for angiogenic stimulation, cell proliferation, and deposition of mineralized matrix was only achieved by the scaffold that contained BG doped with 5% wt/wt cobalt (A-S-G5Co). In the scaffold containing higher cobalt content, a reduced biomimetic mineralization on the surface was observed. The gene expression study indicated an upregulation of the osteogenic genes of COL1A1, ALPL, OCN, and RUNX2 and angiogenic genes of HIF1A and VEGF at different time points in the cells cultured with the A-S-G5Co. Finally, the in vivo study demonstrated that A-S-G5Co significantly promoted both angiogenesis and osteogenesis and improved bone healing after 12 weeks of follow-up. These results show that incorporation of SF/gelatin microspheres containing cobalt-doped BG in an injectable in situ-forming scaffold can effectively enhance its bone healing potential through promotion of angiogenesis and osteogenesis.
摘要：
诱导血管生成和骨生成的可注射原位形成支架已被证明有希望用于骨愈合应用。这里,我们报道了含有钴掺杂生物活性玻璃（BG）微球的可注射水凝胶的合成。通过微流体制备含有BG颗粒的丝素蛋白(SF)/明胶微球。将微球混合在可注射的藻酸盐溶液中，通过添加CaCl2形成原位水凝胶。评价了水凝胶的物理化学性质,与成骨细胞样细胞和内皮细胞的体外相互作用，大鼠颅骨缺损模型的骨愈合潜力。微球充分分散在水凝胶中并形成>100μm的孔。水凝胶显示出剪切稀化行为并调节钴的释放，从而使血管生成刺激的最佳钴浓度，细胞增殖，和矿化基质的沉积仅通过包含掺杂有5％wt/wt钴的BG（A-S-G5Co）的支架实现。在含有较高钴含量的支架中，观察到表面上的仿生矿化减少。基因表达研究表明COL1A1，ALPL，OCN,在用A-S-G5Co培养的细胞中，不同时间点的HIF1A和VEGF的RUNX2和血管生成基因。最后,体内研究表明，A-S-G5Co在随访12周后可显著促进血管生成和成骨，并改善骨愈合。这些结果表明，在可注射的原位形成支架中掺入含有钴掺杂的BG的SF/明胶微球可以通过促进血管生成和成骨而有效地增强其骨愈合潜力。
