Physical Chemistry, Institute of Chemistry, University of Potsdam, 14476, Potsdam, Germany.
Technical University of Applied Sciences Wildau, Hochschulring 1, 15745, Wildau, Germany.
Sci Rep. 2019 Jul 19;9(1):10504. doi: 10.1038/s41598-019-46732-5.
Quantum dots increasingly gain popularity for in vivo applications. However, their delivery and accumulation into cells can be challenging and there is still lack of detailed information. Thereby, the application of advanced fluorescence techniques can expand the portfolio of useful parameters for a more comprehensive evaluation. Here, we encapsulated hydrophilic quantum dots into liposomes for studying cellular uptake of these so-called lipodots into living cells. First, we investigated photophysical properties of free quantum dots and lipodots observing changes in the fluorescence decay time and translational diffusion behaviour. In comparison to empty liposomes, lipodots exhibited an altered zeta potential, whereas their hydrodynamic size did not change. Fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS), both combined with two-photon excitation (2P), were used to investigate the interaction behaviour of lipodots with an insect epithelial tissue. In contrast to the application of free quantum dots, their successful delivery into the cytosol of salivary gland duct cells could be observed when applying lipodots. Lipodots with different lipid compositions and surface charges did not result in considerable differences in the intracellular labelling pattern, luminescence decay time and diffusion behaviour. However, quantum dot degradation after intracellular accumulation could be assumed from reduced luminescence decay times and blue-shifted luminescence signals. In addition to single diffusing quantum dots, possible intracellular clustering of quantum dots could be assumed from increased diffusion times. Thus, by using a simple and manageable liposome carrier system, 2P-FLIM and 2P-FCS recording protocols could be tested, which are promising for investigating the fate of quantum dots during cellular interaction.
量子点在体内应用中越来越受欢迎。然而，它们进入细胞的传递和积累可能具有挑战性，并且仍然缺乏详细信息。因此，先进荧光技术的应用可以扩展有用参数的组合，以进行更全面的评估。在这里，我们将亲水性量子点封装在脂质体中，用于研究这些所谓的脂质体进入活细胞的细胞摄取。首先，我们研究了游离量子点和脂质体的光物理性质，观察荧光衰减时间和平移扩散行为的变化。与空脂质体相比，脂质体表现出改变的 ζ 电位，而其水动力尺寸没有变化。荧光寿命成像显微镜 (FLIM) 和荧光相关光谱 (FCS) 都结合双光子激发 (2P) 用于研究脂质体与昆虫上皮组织的相互作用行为。与游离量子点的应用相反，当应用脂质体时，可以观察到它们成功地递送到唾液腺导管细胞的细胞质中。具有不同脂质组成和表面电荷的脂质体不会导致细胞内标记模式、荧光衰减时间和扩散行为有显著差异。然而，从荧光衰减时间的减少和荧光信号的蓝移可以推测出量子点在细胞内积累后的降解。除了单个扩散的量子点之外，还可以从扩散时间的增加来推测量子点在细胞内的聚集。因此，通过使用简单且易于管理的脂质体载体系统，可以测试 2P-FLIM 和 2P-FCS 记录方案，这些方案对于研究量子点在细胞相互作用过程中的命运具有很大的应用潜力。
