Increasing attention has been paid on the application of biodegradable materials such as magnesium and its alloys in neuron repair. AZ91D magnesium alloy coated with carbon nanotubes (CNTs) and/or calcium phosphate (CaP)/chitosan (CS) was fabricated in this study. To evaluate the bioactivity of these AZ91D-based composites, the extracts were prepared by immersing samples in modified simulated body fluid (m-SBF) for 0, 2, 8, 16, 24, 34, 44, 60, or 90 days. Immunofluorescence staining for neuronal class III β-tubulin (TUJ1) revealed that both CNTs-CaP/CS-AZ91D and CaP/CS-AZ91D extracts promoted axon outgrowth of dorsal root ganglia (DRG) neurons, accompanied with increased expression of phosphorylated focal adhesion kinase (p-FAK) and growth associated protein-43 (GAP-43). Besides, the extracts increased the expression and the release of neurotrophic factors including nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). ERK signalling was activated in DRG neurons after treating with either CNTs-CaP/CS-AZ91D or CaP/CS-AZ91D extracts, and its inhibition with U0126 counteracted the beneficial effects of these extracts on DRG neuron. Overall, the extracts from these AZ91D-based composites might promote DRG neuron growth via activating ERK signalling pathway. Notably, CNTs-CaP/CS-AZ91D extracts showed a better promoting effect on neuron growth than CaP/CS-AZ91D. Assessment of ion elements showed that the addition of CNTs coating enhanced magnesium corrosion resistance and reduced the deposition of calcium and phosphorus on the surface of CaP/CS-AZ91D alloy. These findings demonstrate that CNTs-CaP/CS-AZ91D likely provide a more suitable environment for neuron growth, which suggests a potential implantable biomaterial for the treatment of nerve injury.

中文翻译：

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CNTs-CaP/壳聚糖包覆的AZ91D镁合金提取物通过激活ERK信号通路促进大鼠背根神经节神经元生长

镁及其合金等可生物降解材料在神经元修复中的应用越来越受到关注。本研究制备了涂有碳纳米管 (CNT) 和/或磷酸钙 (CaP)/壳聚糖 (CS) 的 AZ91D 镁合金。为了评估这些基于 AZ91D 的复合材料的生物活性，通过将样品浸泡在改良的模拟体液 (m-SBF) 中 0、2、8、16、24、34、44、60 或 90 天来制备提取物。神经元 III 类 β-微管蛋白 (TUJ1) 的免疫荧光染色显示，CNTs-CaP/CS-AZ91D 和 CaP/CS-AZ91D 提取物均促进背根神经节 (DRG) 神经元的轴突生长，并伴有磷酸化粘着斑激酶的表达增加(p-FAK) 和生长相关蛋白 43 (GAP-43)。除了，提取物增加了神经营养因子的表达和释放，包括神经生长因子 (NGF) 和脑源性神经营养因子 (BDNF)。在用 CNTs-CaP/CS-AZ91D 或 CaP/CS-AZ91D 提取物处理后，DRG 神经元中的 ERK 信号被激活，并且其对 U0126 的抑制抵消了这些提取物对 DRG 神经元的有益作用。总体而言，这些基于 AZ91D 的复合材料的提取物可能通过激活 ERK 信号通路促进 DRG 神经元生长。值得注意的是，CNTs-CaP/CS-AZ91D 提取物对神经元生长的促进作用比 CaP/CS-AZ91D 更好。离子元素评估表明，碳纳米管涂层的加入提高了镁的耐腐蚀性能，减少了钙磷在CaP/CS-AZ91D合金表面的沉积。