Study On The Mechanical Properties Of Breast Cancer Cells

At present,the new incidence rate of breast cancer ranks the first among female malignant tumors,and it is urgent to develop new diagnosis and treatment methods.In vitro cell experiments are of vital importance in this procedure,where the physiological media are usually used to provide nutrition for cell and absorb the excretory product.However,few studies have been conducted on the effect of the experimental physiological media on the mechanical properties of breast cancer cells.Changes in the mechanical properties of the cells caused by the difference in the physiological media will inevitably affect the research and development of personalized therapy,targeted drug delivery and other diagnosis and treatment technologies.Therefore,in this thesis,atomic force microscopy was used to study the effects of different physiological media on the mechanical properties of breast cancer cells(MCF-7),providing the basis for the development of new techniques for the diagnosis and treatment of cancer based on the principle of mechanics.The effects of loading location on cell surface,loading rate of atomic force microscopy probe and indentation depth on the mechanical properties of breast cancer cells were studied with phosphate buffer solution as the experimental physiological medium.The results show that the loading location should be set at the center of the cell,which is basically the thickest position of the adherent cell.In this way,a relatively stable force-distance curve can be obtained and the influence of substrate effect can be reduced;when the experiments are conducted at the cell center,the indentation depth of 600 nm-1200 nm are suitable to decrease the experimental error caused by heat fluctuation or substrate effect;setting the loading rate between 0.5 μm/s-5 μm/s can achieve the goal of obtaining a relatively stable force-distance curve while decreasing the impact of the loading rate on the elastic response of cells.In order to study the effects of different physiological media on the mechanical behavior of breast cancer cells,DMEM culture medium,DMEM+10% fetal bovine serum(FBS)culture medium and phosphate buffer solution(PBS)were selected,which are commonly used in in vitro cell experiments.The mechanical properties of breast cancer cells in three physiological media were obtained by atomic force microscopy.The loading location was selected at the cell center with a loading force of 500 pN,and a loading rate of 3 μm/s.The experimental results show that the elastic modulus of breast cancer cells in phosphate buffer solution is the highest(2586.91 Pa),followed by DMEM medium(2106.86 Pa)and DMEM+10% fetal bovine serum medium(1586.52 Pa).The adhesion force between cell and the tip of atomic force microscopy probe in phosphate buffer solution(63.81 pN)and DMEM culture medium(66.09 pN)are similar,and it is the highest in DMEM+10% fetal bovine serum medium(121.97 pN).The difference of cell elastic modulus and the adhesion force between cell and the tip of atomic force microscope probe in different physiological media may be caused by the difference of acidity and alkalinity of physiological media and the presence of serum protein.In acidic physiological media,the elastic modulus of cells appears to be relatively large.In the physiological media containing serum protein,the interaction between the cell membrane and the tip of atomic force microscope probe is affected by the adsorption of serum protein on the tip surface.Thus the elastic modulus of the cell is relatively small compared with the intrinsic value of the cell,and the adhesion force between the cell membrane and the tip appears to be larger.