Jin Sumin, Wijesekara Piyumi, Boyer Patrick D, Dahl Kris Noel, Islam Mohammad F
Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3815, USA.
J Mater Chem B. 2017 Aug 28;5(32):6657-6665. doi: 10.1039/c7tb00735c. Epub 2017 Jul 11.
Single-walled carbon nanotubes (SWCNTs) are increasingly being investigated for biomedical imaging, sensing, and drug delivery. Cell types, cellular entry mechanisms, and SWCNT lengths dictate SWCNT uptake, subsequent intracellular trafficking, and retention. Specialized immune cells known as macrophages are capable of two size-dependent entry mechanisms: endocytosis of small particles (diameter < 200 nm) and phagocytosis of large particles (diameter > 500 nm). In comparison, fibroblasts uptake particles predominantly through endocytosis. We report dependence of cellular processing including uptake, subcellular distribution, and retention on the SWCNT length and immune cell-specific processes. We chose SWCNTs of three different average lengths: 50 nm (ultrashort, US), 150 nm (short) and 500 nm (long) to encompass two different entry mechanisms, and noncovalently dispersed them in water, cell culture media, and phosphate buffer (pH 5) with bovine serum albumin, which maintains the SWCNT optical properties and promotes their cellular uptake. Using confocal Raman imaging and spectroscopy, we quantified cellular uptake, tracked the intracellular dispersion state (i.e., individualized versus bundled), and monitored recovery as a function of SWCNT lengths in macrophages. Cellular uptake of SWCNTs increases with decreasing SWCNT length. Interestingly, short-SWCNTs become highly bundled in concentrated phase dense regions of macrophages after uptake and most of these SWCNTs are retained for at least 24 h. On the other hand, both US- and long-SWCNTs remain largely individualized after uptake into macrophages and are lost over a similar elapsed time. After uptake into fibroblasts, however, short-SWCNTs remain individualized and are exocytosed over 24 h. We hypothesize that aggregation of SWCNTs within macrophages but not fibroblasts may facilitate the retention of SWCNTs within the former cell type. Furthermore, the differential length-dependent cellular processing suggests potential applications of macrophages as live cell carriers of SWCNTs into tumors and regions of inflammation for therapy and imaging.
单壁碳纳米管（SWCNTs）正越来越多地被用于生物医学成像、传感和药物递送研究。细胞类型、细胞进入机制以及SWCNT的长度决定了SWCNT的摄取、随后的细胞内运输以及滞留情况。被称为巨噬细胞的特殊免疫细胞能够通过两种大小依赖性进入机制摄取物质：小颗粒（直径<200 nm）的内吞作用和大颗粒（直径>500 nm）的吞噬作用。相比之下，成纤维细胞主要通过内吞作用摄取颗粒。我们报告了包括摄取、亚细胞分布和滞留在内的细胞处理过程对SWCNT长度以及免疫细胞特异性过程的依赖性。我们选择了三种不同平均长度的SWCNTs：50 nm（超短，US）、150 nm（短）和500 nm（长），以涵盖两种不同的进入机制，并将它们与牛血清白蛋白非共价分散在水、细胞培养基和磷酸盐缓冲液（pH 5）中，牛血清白蛋白可维持SWCNT的光学性质并促进其细胞摄取。使用共聚焦拉曼成像和光谱技术，我们量化了细胞摄取情况，追踪了细胞内的分散状态（即单个化与成束状态），并监测了巨噬细胞中SWCNT长度与恢复情况之间的关系。SWCNT的细胞摄取量随SWCNT长度的减小而增加。有趣的是，短SWCNTs在摄取后在巨噬细胞的浓缩相密集区域中高度成束，并且这些SWCNTs中的大多数至少保留24小时。另一方面，超短和长SWCNTs在被巨噬细胞摄取后在很大程度上仍保持单个化，并在相似的时间内消失。然而，在被成纤维细胞摄取后，短SWCNTs仍保持单个化，并在24小时内被胞吐。我们推测，SWCNTs在巨噬细胞而非成纤维细胞内聚集可能有助于它们在前者细胞类型中滞留。此外，不同长度依赖性的细胞处理过程表明巨噬细胞作为SWCNTs的活细胞载体在肿瘤和炎症区域进行治疗和成像方面具有潜在应用。
