Low circulating levels of insulin-like growth factor 1 (IGF-1) have been correlated with an increased risk for cardiovascular diseases in humans. In this work, an injectable alginate hydrogel containing silk fibroin (SF) microspheres with the capability to sustain the release of IGF-1 was prepared to induce myocardial repair after myocardial infarction (MI). First, IGF-1 was physically adsorbed onto SF microspheres prepared by the coaxial needle system, and these IGF-1-containing microspheres were subsequently encapsulated into sodium alginate solutions at different concentrations (1.0-2.5%). Finally, this solution was crosslinked with 0.68% calcium gluconate solution to prepare the composite injectable hydrogel. The composite hydrogel prepared using a sodium alginate solution at a concentration of 1.5% could promote proliferation of H9C2 cardiomyocytes and reduce the cellular apoptosis rate under hypoxic conditions. The enzyme-linked immunosorbent assay results indicated that SF microspheres as microcarriers could effectively enhance the sustained release of IGF-1 from the hydrogels, causing the composite hydrogel to possess a better sustained release ability than the system without the SF microspheres. Moreover, echocardiography, hematoxylin-eosin staining, and Masson trichrome staining results indicated that an intramyocardial injection of the composite hydrogel into the peripheral region of a MI rat model could reduce the infarct size and improve the cardiac function after 28 days. The applications of such a composite hydrogel may comprise a powerful platform in cardiac tissue engineering.

中文翻译：

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从基于丝素蛋白微球的可注射藻酸盐水凝胶中持续释放生物活性IGF-1，用于治疗心肌梗塞。

胰岛素样生长因子1（IGF-1）的低循环水平与人类心血管疾病的风险增加相关。在这项工作中，准备了一种可注射的藻酸水凝胶，其中含有能够维持IGF-1释放的丝素蛋白（SF）微球，可诱导心肌梗死（MI）后进行心肌修复。首先，将IGF-1物理吸附到同轴针系统制备的SF微球上，然后将这些包含IGF-1的微球以不同的浓度（1.0-2.5％）封装到藻酸钠溶液中。最后，将该溶液与0.68％的葡萄糖酸钙溶液交联以制备复合的可注射水凝胶。使用浓度为1.的藻酸钠溶液制备的复合水凝胶。5％可促进缺氧条件下H9C2心肌细胞的增殖并降低细胞凋亡率。酶联免疫吸附试验结果表明，SF微球作为微载体可以有效增强IGF-1从水凝胶中的缓释，从而使复合水凝胶具有比不使用SF微球的系统更好的缓释能力。此外，超声心动图，苏木精-伊红染色和Masson三色染色结果表明，心肌梗死后28天心肌内注射复合水凝胶可减少梗死面积并改善心功能。这种复合水凝胶的应用可包括心脏组织工程中的强大平台。