Research On Rapid 3D Traction Force Microscope Technology And Its Application In Cell Mechanics

Cells transfer the force generated by the cytoskeleton onto the extracellular matrix(ECM)through transmembrane proteins such as focal adhesions,changing the ECM;cells sense the mechanical force of the ECM through force-sensitive proteins,convert-ing mechanical signals to biochemical signals and then transmitting it to the nucleus.The nucleus regulates the expression of related proteins to change cell behaviors and functions.This series of processes is called force transduction.The mechanical force between cells and the ECM is crucial to many physiological processes,such as can-cer metastasis,cell apoptosis and stem cell differentiation.An in-depth understanding of the mechanical force between cells and the ECM,and the effect of the extra stim-uli on cell activity may offer ways toward understanding how the ECM regulates cell behaviors and functions,as well as gaining insight into disease diagnose and disease treatment.The main content of this paper:(1)Developing a rapid 3D traction force micro-scope method based on mono-layer fluorescent beads,realizing the rapid quantification of the 3D force between cells and the ECM with high temporal and spatial resolution.The method used mono-layer fluorescent beads to track the 3D deformation of the sub-strate caused by cells,greatly shortening the sampling time of the volumetric images and effectively reducing the phototoxicity.Additionally,the method introduced the inverse compositional Gauss-Newton algorithm combined with second-order shape function to the digital volume correlation,improving the calculation accuracy and precision,as well as calculation speed.Using the method,this paper studied the 3D interaction between a single cell and the extracellular matrix during cell migration,verifying the reliability of the rapid 3D traction force microscope.(2)Revealing the 3D interaction between a cancer cell and the ECM during mitosis:both the in-plane and the out-of-plane trac-tion force dropped sharply as the cell enters mitosis and stabilized at tens of Pa during mitosis till the daughter cells began to re-spread and migrate.Additionally,the author studied the mechanical effects of paclitaxel and nocodazole on a mitotic cancer cell.Results showed that low concentrations of paclitaxel and nocodazole had no significant effect on cell division and traction force.However,although cells were unable to di-vide under high concentrations of paclitaxel and nocodazole,their traction forces were significantly different.Both the in-plane and the out-of-plane traction forces exerted by cells treated with high concentrations of paclitaxel were much larger than those with high concentrations of nocodazole.Furthermore,this paper revealed the mechanical mechanism that the structure of the spindle results in the increase of the 3D traction force caused by paclitaxel during cell mitosis.(3)Revealing the force between the cells and the ECM during osmotic shock.Results showed that the osmotic shock caused a sig-nificant change in the traction force.And the traction force decreased as cell swelling,but increased as cell shrinking.Furthermore,the author unveiled that the change of the cell membrane tension caused by osmotic shock was the reason for the traction force change.(4)Based on the microcantilever sensors,the author investigated the effect of hypertonic and hypotonic solutions on the physiological activities of cells by measuring the real-time deflection of the micro-cantilever tip.Furthermore,the author uncovered the mechanical mechanism for the deflection of microcantilever caused by hypertonic and hypotonic solutions.Besides,the deflection of the microcantilever reflected the real-time osmotic pressure of the solution,which provided an effective and fast method for real-time monitoring of osmotic pressure.