Hannes Landmann博士，Sartorius Lab Instruments(德国哥廷根)

Kristin Menzel博士、科学作家(德国哥廷根)

1908年，Paul Ehrlich受到“Zauberkugel”概念的启发，在理论上描述了将毒性药物组装到所谓的“纳米载体”上。¹ 如今，纳米载体已在现代​医学和生物技术领域有多种应用。这些特殊纳米材料的一项关键应用就是药物定向输送，它们可发挥药物活性成分转运模块 (即：纳米颗粒、囊泡或胶束) 的作用。^2,3,4,5人们推测这种方式与传统给药方法相比对人体更为有效，且毒性更低。⁶除了药物输送外，过去数十年间还发展出其他一些应用纳米载体的领域，例如利用金属纳米颗粒进行磁共振成像或干细胞基因治疗，^7,8 或者利用量子点进行光学成像。⁹

纳米载体可以按照其初始材料 (即；金属、脂质、聚合物和蛋白) 以及制成后的构成 (即：囊泡、颗粒和胶束) 进行分类。一般而言，水性介质中纳米颗粒混悬液或囊泡分散液的制备包括三个步骤：a) 纳米载体组装 (例如通过注射、薄膜水化或反相蒸发)、b) 纯化 (例如：色谱、透析或超滤) 和 c) 浓缩 (如超滤或蒸发)。

这份短篇综述举例介绍了近期关于纳米载体制备的一些文献。重点介绍了浓缩和纯化步骤，该步骤使用不同孔径 (相应的截留分子量 (MWCO)) 的Sartorius Vivaspin^® 或Vivaflow^® 设备通过超滤完成。Vivaspin^® 系列产品的体积范围是从0.5 mL至20 mL，而Vivaflow^® 系统则涵盖了从0.05升到5升的范围。因此，Sartorius能够处理的样本体积、膜材料和MWCO范围，可满足不同预期用途的需求。这方面的挑战包括合成后的缓冲液更换、脱盐和清洗^10,11、去除溶解的化合物^12,13,14 或聚集物。¹⁵

纯化过程十分重要，通过纯化可以达到等渗状态，以便在体内应用时避免发生聚集或凝聚，还可去除毒性药物、配体或其他可能引起副作用的物质。浓缩步骤的重要意义在于调节药物中活性成分的含量，以便达到预期的治疗或诊断效果。

纯化时，通过分子排阻色谱 (SEC) 将游离物质 (起始材料) 与预期得到的纳米载体分离，这不可避免地导致产物稀释，并且需要后续的浓缩步骤。相比之下，透析过滤纯化时不会导致显著的稀释，但如果需要较高的纳米载体浓度，仍需要使用浓缩步骤。两种分离方法均需要大量昂贵且耗时的手工操作。通过Vivaspin^® 离心或者使用Vivaflow^® 系统的蠕动泵进行超滤可克服这一缺点。该技术成本较低，操作迅速，人工操作极少。值得一提的是，纯化和浓缩步骤可同时进行。¹⁶

纳米载体纯化后，通常需要测定载药量 (偶联或包囊效率)。偶联或包囊效率是描述和鉴定纳米载体的一个参考值。其他重要性质包括ζ电位和粒径分布，后者可通过光子相关光谱 (PCS)、高分辨率传递电子显微镜 (HRTEM) 成像或动态光散射 (DLS) 测定。在进行这些不同的鉴定前，需要成功地对混悬液或分散液进行纯化和浓缩。

下表为您概括列出了使用超滤步骤对各种纳米载体进行纯化和浓缩的文献。该表还可指导您使用多大的MWCO。

表1汇总了使用Sartorius Vivaspin^® 或Vivaflow^® 进行纳米载体超滤的应用示例：

SD = 粒径分布

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