The development of tumor is closely related to extracellular matrix, which changes the biomechanical behavior of cells.Research have prepared polyacrylamide hydrogel substrates of differing stiffness according to the hardness values of breast tissue under normal and tumor physiological conditions. Then AFM was used to measure the mechanical properties of breast cells with different degrees of malignancy grown on different stiffness substrates. To explore the reasons for the changes in the young’s modulus of three breast cells, the distribution of cellular actin filaments were observed with a confocal microscope. These results showed that when the substrate hardened, the viscoelasticity of benign breast cells increased significantly, and the other two cancer cells also changed to some extent. We also found that the harder the substrate, the more conducive to the spreading behavior of cells, and the weaker response of malignant cells to substrates.
Ovarian cancer has become one of the most common malignant tumors threatening female genital health. Recently, biomechanical properties of single cell have been reported as a potential index for early cancer detection. In this study, the viscoelastic properties of ovarian cancer cells were determined using stress-relaxation approach by atomic force microscopy (AFM). Individual force-time curves were recorded at maximum loads of 0.5, 1 and 2 nN, and the stressrelaxation time was 2 s for all the stress-relaxation measurements. A theoretical method of stress relaxation was proposed and the viscoelasticity of the cells was obtained according to a linear solid model. The results showed that the values of average viscosity of ovarian cancer cells were respectively 54.0±6.5 Pa-s, 100.5±13.2 Pa-s and 113.6±13.2 Pa-s using the three different loading forces from 0.5 nN to 2 nN. Furthermore, the values of average elasticity modulus were respectively 657.0±69.9 Pa, 730.9±67.0 Pa, 895.0±71.3 Pa. In conclusion, the viscoelasticity properties of the cells increased as the loading force increased from 0.5 nN to 2 nN. Our study indicates that the viscoelasticity of the ovarian cancer cells can be acquired by stress-relaxation approach and the loading force is an important factor that can affect the cellular viscoelasticity. It will shed new light on cancer early detection based on cellular viscoelasticity index at single cell level.
In this study, HOSEpiC ovarian cell was cultured on hydrogel substrates with three different Young moduli of 3, 19 and 35 kPa. Atomic force microscopy was used to measure the elasticity of cells on three different stiffness substrates. Furthermore, the distribution of actin filaments in HOSEpiC cell was observed by confocal imaging. From the measurements of atomic force microscopy, we found that substrate stiffness would cause changes of cellular elasticity. The largest one was on the substrate of 35 kPa, followed by the 19 kPa and cells on 3 kPa was the smallest. Besides, from the confocal imaging, it could be observed that the distribution of actin filaments in the cells was different on the three substrates. All these results showed that the elasticity of the cells was lower on the substrates with smaller stiffness, which indicated that cells appeared softer when the stiffness of substrate decreased.
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.
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