细胞机械特性作为一种无标签(Label-free)的生物标记,正得到越来越多的关注.然而现有进行细胞机械特性测量的方法多以手工模式进行,耗时长、效率低下,无法满足生物学统计分析对大批量样品测试的要求.针对该问题,本文在原子力显微镜(Atomic force microscopy,AFM)基础上,建立了一套高速自动化的细胞机械特性测量系统.该系统利用图像处理方法来识别细胞,利用局部扫描来实现AFM针尖和细胞相对位置的精确标定,进而不需要AFM成像就能实现细胞机械特性的连续测定,配合上程序化控制的运动载物平台,可以高速自动化完成大范围区域内细胞机械特性的批量规模化测量.实验结果表明,该系统可以使得细胞机械特性的测量效率提高27倍,从而为Label-free生物标记的批量化测试提供了技术支撑.
Mechanical properties play an important role in regulating cellular activities and are critical for unlocking the mysteries of life. Atomic force microscopy (AFM) enables researchers to measure mechanical properties of single living cells under physiological conditions. Here, AFM was used to investigate the topography and mechanical properties of red blood cells (RBCs) and three types of aggressive cancer cells (Burkitt's lymphoma Raji, cutaneous lymphoma Hut, and chronic myeloid leukemia K562). The surface topography of the RBCs and the three cancer cells was mapped with a conventional AFM probe, while mechanical properties were investigated with a microsphere glued onto a tip-less cantilever. The diameters of RBCs are significantly smaller than those of the cancer cells, and mechanical measurements indicated that Young's modulus of RBCs is smaller than those of the cancer cells. Aggressive cancer cells have a lower Young's modulus than that of indolent cancer cells, which may improve our understanding of metastasis.
LI MiLIU LianQingXI NingWANG YueChaoDONG ZaiLiXIAO XiuBinZHANG WeiJing
Cell mechanics plays an important role in cellular physiological activities. Recent studies have shown that cellular mechanical properties are novel biomarkers for indicating the cell states. In this article, temperature-controllable atomic force microscopy(AFM) was applied to quantitatively investigate the effects of temperature and cellular interactions on the mechanics and morphology of human cancer cells. First, AFM indenting experiments were performed on six types of human cells to investigate the changes of cellular Young's modulus at different temperatures and the results showed that the mechanical responses to the changes of temperature were variable for different types of cancer cells. Second, AFM imaging experiments were performed to observe the morphological changes in living cells at different temperatures and the results showed the significant changes of cell morphology caused by the alterations of temperature. Finally, by co-culturing human cancer cells with human immune cells, the mechanical and morphological changes in cancer cells were investigated. The results showed that the co-culture of cancer cells and immune cells could cause the distinct mechanical changes in cancer cells, but no significant morphological differences were observed. The experimental results improved our understanding of the effects of temperature and cellular interactions on the mechanics and morphology of cancer cells.
LI MiLIU LianQingXI NingWANG YueChaoXIAO XiuBinZHANG WeiJing
Atomic force microscopy (AFM) was used to examine the morphology of live mammalian adherent and suspended cells. Time-lapse AFM was used to record the locomotion dynamics of MCF-7 and Neuro-2a cells. When a MCF-7 cell retracted, many small sawtooth-like filopodia formed and reorganized, and the thickness of cellular lamellipodium increased as the retraction progressed. In elongated Neuro-2a cells, the cytoskeleton reorganized from an irregular to a parallel, linear morphology. Suspended mammalian cells were immobilized by method combining polydimethylsiloxane-fabricated wells with poly-L-lysine electrostatic adsorption. In this way, the morphology of a single live lymphoma cell was imaged by AFM. The experimental results can improve our understanding of cell locomotion and may lead to improved immobilization strategies.
LI MiLIU LianQingXI NingWANG YueChaoDONG ZaiLiXIAO XiuBinZHANG WeiJing
The observation of friction anisotropy on graphene by friction measurement at atomic scale has been reported in this paper.Atomic-scale friction measurement revealed friction anisotropy with a periodicity of 60°,which is consistent with the hexagonal periodicity of the graphene.Both experiments and theory show that the value of the friction force is related to the graphene lattice orientation,and the friction force along armchair orientation is also larger than the one along zigzag orientation.These results will play a critical role in the use of graphene to manufacture nanoscale devices.
ZHANG YuLIU LianQingXI NingWANG YueChaoDONG ZaiLiWEJINYA Uchechukwu C
