Cholera toxin B (CTB) modified mesoporous silica nanoparticle supported lipid bilayers (CTB-protocells) are a promising, customizable approach for targeting therapeutic cargo to motoneurons. In the present study, the endocytic mechanism and intracellular fate of CTB-protocells in motoneurons were examined to provide information for the development of therapeutic application and cargo delivery. Pharmacological inhibitors elucidated CTB-protocells endocytosis to be dependent on the integrity of lipid rafts and macropinocytosis. Using immunofluorescence techniques, live confocal and transmission electron microscopy, CTB-protocells were primarily found in the cytosol, membrane lipid domains and Golgi. There was no difference in the amount of motoneuron activity dependent uptake of CTB-protocells in neuromuscular junctions, consistent with clathrin activation at the axon terminals during low frequency activity. In conclusion, CTB-protocells uptake is mediated principally by lipid rafts and macropinocytosis. Once internalized, CTB-protocells escape lysosomal degradation, and engage biological pathways that are not readily accessible by untargeted delivery methods.

霍乱毒素B（CTB）修饰的介孔二氧化硅纳米颗粒支持的脂质双层（CTB-protocells）是一种有前途的可定制方法，可将治疗性货物靶向运动神经元。在本研究中，检查了运动神经元中CTB原始细胞的内吞机制和细胞内命运，为治疗应用和货物运输的发展提供信息。药理学抑制剂阐明CTB-protocells的胞吞作用取决于脂质筏和巨胞饮作用的完整性。使用免疫荧光技术，共聚焦和透射电镜观察，CTB-原代细胞主要存在于细胞质，膜脂质结构域和高尔基体中。神经肌肉接头中依赖运动神经元活性的CTB-protocells摄取量没有差异，与低频活动期间轴突末端的网格蛋白激活相符。总之，CTB-原始细胞的摄取主要是由脂质筏和巨胞饮作用介导的。一旦内在化，CTB-protocells逃脱了溶酶体降解，并参与了非靶向递送方法不易接近的生物学途径。