Key Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
J Am Chem Soc. 2015 Jan 14;137(1):436-44. doi: 10.1021/ja511273c. Epub 2015 Jan 6.
The crowded intracellular environment influences the diffusion-mediated cellular processes, such as metabolism, signaling, and transport. The hindered diffusion of macromolecules in heterogeneous cytoplasm has been studied over years, but the detailed diffusion distribution and its origin still remain unclear. Here, we introduce a novel method to map rapidly the diffusion distribution in single cells based on single-particle tracking (SPT) of quantum dots (QDs). The diffusion map reveals the heterogeneous intracellular environment and, more importantly, an unreported compartmentalization of QD diffusions in cytoplasm. Simultaneous observations of QD motion and green fluorescent protein-tagged endoplasmic reticulum (ER) dynamics provide direct evidence that the compartmentalization results from micron-scale domains defined by ER tubules, and ER cisternae form perinuclear areas that restrict QDs to enter. The same phenomenon was observed using fluorescein isothiocyanate-dextrans, further confirming the compartmentalized diffusion. These results shed new light on the diffusive movements of macromolecules in the cell, and the mapping of intracellular diffusion distribution may be used to develop strategies for nanoparticle-based drug deliveries and therapeutics.
拥挤的细胞内环境会影响代谢、信号转导和运输等扩散介导的细胞过程。多年来，人们一直在研究大分子在异质细胞质中的受限扩散，但详细的扩散分布及其来源仍不清楚。在这里，我们介绍了一种新的方法，可以基于量子点（QD）的单粒子跟踪（SPT）快速绘制单细胞中的扩散分布。扩散图谱揭示了异质的细胞内环境，更重要的是，揭示了细胞质中 QD 扩散的一种未被报道的分隔化现象。QD 运动和绿色荧光蛋白标记的内质网（ER）动力学的同步观察提供了直接证据，表明这种分隔化是由 ER 小管定义的微米级区域导致的，ER 潴泡在内核周围区域形成，限制 QD 进入。使用异硫氰酸荧光素标记的葡聚糖进一步证实了扩散的分隔化。这些结果为细胞内大分子的扩散运动提供了新的视角，细胞内扩散分布的绘图可能被用于开发基于纳米颗粒的药物输送和治疗策略。
