The Construction And Application Of High-Throughput Magnetic Tweezer For Mechanical Phenotyping Of Cells

The mechanical phenotyping of cells is closely related to cell function.For instance,tumors cells show significantly different elasticity than normal cells during formation and metastasis,which demonstrates the potential of mechanical properties to be markers of cancer in clinical diagnosis.However,there exists dramatic variance among the mechanical phenotyping of individual cells even for the same cell type as a consequence of cell heterogeneity which causes uncertainty and unreliability in cell mechanics.To solve the problem,researchers have to conduct large numbers of measurements and obtain statistical results.Nowadays the instruments widely used in cell mechanics(e.g.atomic force microscopy)are still in lack of the ability of probing cells in high-throughput which lowers the efficiency of research and limits the potential clinical application.In this thesis,we first made improvement to the raw magnetic tweezer of our research group.The ameliorative instrument was able to generate the maximum force of?35p N over 1mm~2 area.Meanwhile,fluorescence imaging was embedded in the system to prevent the background interference from cells in imaging and locate the magnetic beads vertically with high precision.Besides,a novel data processing method based on noise convolution was put forward to derive the elasticity of cells.Further,we measured the elasticity of agarose,human breast cancer(MCF-7)cells and mouse fibroblast(NIH-3T3)cells.Data from hundreds of beads could be obtained in a single experiment which increased the efficiency and the results are in consistence with published data,indicating the validity and high-throughput property of the new magnetic tweezer.Finally,human colon cancer(HCT-116)cells in different initial seeding density were made use of to explore the change of cell mechanical phenotyping in epithelial-mesenchymal transition(EMT).The data indicated that epithelial HCT-116 cells in high seeding density tend to be softer the mesenchymal ones in low seeding density,which in our opinion tumor lead cells become harder in EMT and thus can squeeze through base membrane and helped other cells move into different tissues during metastasis.