INM - Leibniz Institute for New Materials, 66123 Saarbrücken, Germany; Department of Pharmacy, Biopharmaceutics & Pharmaceutical Technology, Saarland University, 66123 Saarbrücken, Germany.
INM - Leibniz Institute for New Materials, 66123 Saarbrücken, Germany.
Int J Pharm. 2021 Mar 15;597:120238. doi: 10.1016/j.ijpharm.2021.120238. Epub 2021 Feb 2.
Human respiratory mucus lining the airway epithelium forms a challenging barrier to inhalation therapeutics. Therefore, structural elucidation of hydrated mucus is essential for an efficient drug delivery development. The structure of mucus has been primarily investigated by conventional electron microscopy techniques, which operate under vacuum conditions and require sample preparation steps that might alter the structure of mucus. In this study we investigated the impact of dehydration on mucus and analyzed the structure of mucus in its hydrated state. Cryo-scanning electron microscopy (Cryo-SEM) analysis of mucus showed, that during the process of sublimation, non-porous structure of mucus is transformed into a porous network. Similarly, images acquired by environmental scanning electron microscopy (ESEM), revealed a non-porous structure of hydrated mucus, while further observation at decreasing pressure demonstrated the strong influence of dehydration on mucus structure. We could successfully visualize the structural organization of the major gel forming mucin MUC5B in its hydrated state by employing stimulated emission depletion (STED) microscopy, which allowed resolving the nano-scale patterns of mucin macromolecules within the essentially pore-free mucus structure. The general structural organization of mucus components was addressed by confocal laser scanning microscopy (CLSM), which revealed the heterogeneous and composite structure of mucus. These results provide a novel view on the native structure of mucus and will affect drug delivery development.
人体呼吸道中的黏液衬里覆盖在气道上皮细胞表面，形成了一个具有挑战性的屏障，使吸入疗法难以发挥作用。因此，对水合黏液的结构进行阐明对于高效药物输送的发展至关重要。传统的电子显微镜技术主要用于研究黏液的结构，这些技术在真空条件下运行，并且需要进行样品制备步骤，这可能会改变黏液的结构。在本研究中，我们研究了脱水对黏液的影响，并分析了水合状态下黏液的结构。冷冻扫描电子显微镜（Cryo-SEM）分析显示，在升华过程中，黏液的无孔结构转变为多孔网络。类似地，环境扫描电子显微镜（ESEM）获得的图像显示了水合黏液的无孔结构，而在降低压力下的进一步观察表明，脱水对黏液结构有很强的影响。通过采用受激发射损耗（STED）显微镜，我们成功地可视化了水合状态下主要凝胶形成黏蛋白 MUC5B 的结构组织，这使得能够在基本上无孔的黏液结构内解析黏蛋白大分子的纳米级图案。通过共聚焦激光扫描显微镜（CLSM）解决了黏液成分的一般结构组织问题，揭示了黏液的异质和复合结构。这些结果为黏液的天然结构提供了新的视角，并将影响药物输送的发展。
