The microcarrier system offers an attractive method for cellular amplification and phenotype enhancement in the field of bone tissue engineering. However, it remains a challenge to fabricate porous microcarriers with osteoinductive activity for speedy and high-quality osseointegration in regeneration of serious complication of bone fracture, like nonunion. Here, we present a facile method for the first time manufacture microcarriers with osteogenic effects and properties based on well controlled and long-term Sr²⁺ release. At first, strontium-substituted hydroxyapatite was prepared (Sr-HA) and a novel Sr-HA-graft-poly(γ-benzyl-l-glutamate) (Sr-HA-PBLG) nanocomposite was synthesized. Then, the microcarriers with highly interconnected macropores were fabricated by a double emulsion method, which allowed cells to adhere and proliferate and secrete extracellular matrix. Besides, the microcarriers with a relatively uniform diameter of 271.5 ± 45.0 μm are feasible for injection. The Sr-HA-PBLG microcarriers efficiently promoted osteogenic gene expression in vitro. With injection of the Sr-HA-PBLG microcarriers loading adipose derived stem cells (ADSCs) into the nonunion sites, bone regeneration was observed at 8 weeks after injection in a mice model.

中文翻译：

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Sr-HA-接枝-聚（γ-苄基-1-谷氨酸）纳米复合微载体：可控的Sr ²⁺释放，促进骨生成和骨不连修复

微载体系统为骨组织工程领域中的细胞扩增和表型增强提供了一种有吸引力的方法。然而，制造具有骨诱导活性的多孔微载体以在骨折的严重并发症（如骨不连）的再生中快速且高质量的骨整合仍然是一个挑战。在这里，我们提出了一种易于控制的方法，该方法首次基于可控的和长期的Sr ²⁺释放，具有成骨作用和特性的微载体的制造。起初，锶取代的羟基磷灰石制备的（Sr-HA）和一个新颖的Sr-HA-接枝-聚（γ苄基升合成了谷氨酸（Sr-HA-PBLG）纳米复合材料。然后，通过双重乳液法制备了具有高度相互连接的大孔的微载体，该微载体允许细胞粘附并增殖并分泌细胞外基质。此外，相对均匀的直径为271.5±45.0μm的微载体可用于注射。Sr-HA-PBLG微载体在体外有效促进成骨基因表达。通过注射Sr-HA-PBLG微载体，将脂肪来源的干细胞（ADSC）加载到骨不连部位，在小鼠模型中注射8周后观察到骨再生。