The cell membrane is composed of phospholipids, glycolipids, cholesterol and proteins that are dynamic and heterogeneous distributed in the bilayer structure and many researches have showed that the plasma membrane in eukaryotic cells contains microdomains termed “lipid raft” in which cholesterol, sphingolipids and specific membrane proteins are enriched. Cholesterol extraction induced lipid raft disruption is one of the most widely used methods for lipid raft research and MβCD is a type of solvent to extract the cholesterol from cell membranes. In this study, the effect of MβCD treatment on the membrane nanostructure in MCF-7 living cells was investigated by atomic force microscopy. Different concentrations of MβCD were selected to deplete cholesterol for 30 min and the viability of cells was tested by MTT assay to obtain the optimal concentration. Then the nanostructure of the cell membrane was detected. The results show that an appropriate concentration of MβCD can induce the alteration of cell membranes nanostructure and the roughness of membrane surface decreases significantly. This may indicate that microdomains of the cell membrane disappear and the cell membrane appears more smoothly. Cholesterol can affect nanostructure and inhomogeneity of the plasma membrane in living cells.
Estrogen plays an important role in the development and progression of breast cancer, and it promotes proliferation, invasion and metastasis of breast cancer cells. In this paper, we investigated the effect of estrogen on the elasticity of breast cancer cells. 17β-estradiol, one of the most active estrogens in the human body was applied to MCF-7 living cells and the elasticity of breast cancer cells was measured by atomic force microscopy. The force spectroscopy was performed on the center of the cell and the Hertz model was used to calculate the elasticity modulus. Furthermore, the confocal fluorescence imaging was taken to observe the effect of 17β-estradiol on the actin distribution in the cells. The results show that the elasticity of the cells decreases rapidly after the addition of 17β-estradiol, which indicates that the cells appear softer for 17β-estradiol’s treatment. From the confocal imaging, it can be observed that the actin filament rearranged for 17β-estradiol’s treatment, which may lead to the alteration of the cell elasticity. Our findings may deepen our understanding on the rapid effect of 17β-estradiol to MCF-7 cells.
Biomechanics of cell plays an important role in the behavior and development of diseases, which has a profound influence on the health, structural integrity, and function of cells. In this study, we proposed a method to assess the biomechanical properties in single breast cancer cell line MCF-7 by combining structured illumination microscopy (SIM) with atomic force microscopy (AFM). High resolution optical image of actin in MCF-7 cell and its elastography were obtained. The result shows that the quantitative resolution was improved by SIM, with 490 nm of conventional fluorescence image and 285 nm of reconstructed SIM image, which could give a precise location for AFM measurement. The elasticity of actin is about in the range of 10~1000 kPa. The proposed methods will be helpful in the understanding and clinical diagnosis of diseases at single cell level.
Cell mitosis plays a crucial role in cell life activity, which is one of the important phases in cell division cycle. During the mitosis, the cytoskeleton micro-structure of the cell changed and the biomechanical properties of the cell may vary depending upon different mitosis stages. In this study, the elasticity property of HeLa cells during mitosis was monitored by atomic force microscopy. Also, the actin filaments in different mitosis stages of the cells were observed by confocal imaging. Our results show that the cell in anaphase is stiffer than that in metaphase and telophase. Furthermore, lots of actin filaments gathered in cells’ center area in anaphase, which contributes to the rigidity of the cell in this phase. Our findings demonstrate that the nano-biomechanics of living cells could provide a new index for characterizing cell physiological states.
Mechanical properties of living cells play an important role in understanding various cells’ function and state. Therefore cell biomechanics is expected to become a useful tool for cancer diagnosis. In this study, atomic force microscopy (AFM) using a square pyramid probe was performed to investigate cancerous (MCF-7) and benign (MCF-10A) human breast epithelial cells. The new QITM mode was used to acquire high-resolution topographic images and elasticity of living cells. Furthermore, individual force curves were recorded at maximum loads of 0.2, 0.5 and 1 nN, and the dependence of cell’s elasticity with loading force was discussed. It was showed that the cancerous cells exhibited smaller elasticity modulus in comparison to non-cancerous counterparts. The elasticity modulus increased as the loading force increased from 0.2 nN to 1 nN. This observation indicates that loading force affects the cell’s apparent elasticity and it is important to choose the appropriate force applied to cells in order to distinguish normal and cancer cells. The results reveal that the mechanical properties of living cells measured by atomic force microscopy may be a useful indicator of cell type and disease.
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