Nanomechanical sub-surface mapping of living biological cells by force microscopy
Nanomechanical sub-surface mapping of living biological cells by force microscopy
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DOI：
10.1039/c9nr03497h
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发表时间：
2019-07-21
期刊：
影响因子：
6.7
通讯作者：
Dietz, Christian
中科院分区：
文献类型：
--
作者：
Stuehn, Lukas;Fritschen, Anna;Dietz, Christian
原子力显微镜允许在各种相关环境中以最高的空间精度对多种类型的材料进行纳米机械表面表征。近年来，研究人员已经改进了这种方法来分析体外活生物材料。因此，原子力显微镜已成为（在许多情况下）非破坏性的，高分辨率的细胞成像和可视化的动态机械过程的基本工具。映射力与距离曲线和软样品的局部评估允许操作员“看到”样品表面下方并捕获局部机械性能。在这项工作中，我们将联合收割机原子力显微镜与荧光显微镜相结合，研究培养基中的癌性乳腺上皮细胞。以前所未有的空间分辨率，我们提供断层图像的局部弹性融合层的细胞。对于这些特定的样品，观察到与平均弹性性质相比，位于细胞膜正下方的弹性模量更高的层。引人注目的是，该层似乎在机械性能最弱的样品表面的独特位置处被穿孔，其中明显的特征是可见的，允许尖端最远地进入细胞的体积中。我们将这一层解释为细胞膜，其由细胞骨架的组分机械支撑，细胞骨架的组分填充有整合膜蛋白的位点。这些蛋白质充当压头的断裂点，从而解释了这些位置处的机械弱点。相比之下，细胞的最高机械强度被发现在细胞核心的位置处，如通过染色实验的荧光显微镜图像交叉检查的，特别是在核仁位点处，因为累积弹性模量在那里包括细胞骨架特征和细胞的紧密包装的核糖体DNA。
Atomic force microscopy allows for the nanomechanical surface characterization of a multitude of types of materials with highest spatial precision in various relevant environments. In recent years, researchers have refined this methodology to analyze living biological materials in vitro. The atomic force microscope thus has become an essential instrument for the (in many cases) non-destructive, high-resolution imaging of cells and visualization of their dynamic mechanical processes. Mapping force versus distance curves and the local evaluation of soft samples allow the operator to "see" beneath the sample surface and to capture the local mechanical properties. In this work, we combine atomic force microscopy with fluorescence microscopy to investigate cancerous epithelial breast cells in culture medium. With unprecedented spatial resolution, we provide tomographic images for the local elasticity of confluent layers of cells. For these particular samples, a layer of higher elastic modulus located directly beneath the cell membrane in comparison with the average elastic properties was observed. Strikingly, this layer appears to be perforated at unique locations of the sample surface of weakest mechanical properties where distinct features were visible permitting the tip to indent farthest into the cell's volume. We interpret this layer as the cell membrane mechanically supported by the components of the cytoskeleton that is populated with sites of integral membrane proteins. These proteins act as breaking points for the indenter thus explaining the mechanical weakness at these locations. In contrast, the highest mechanical strength of the cell was found at locations of the cell cores as cross-checked by fluorescence microscopy images of staining experiments, in particular at nucleoli sites as the cumulative elastic modulus there comprises cytoskeletal features and the tight packing ribosomal DNA of the cell.