Measurement Of Cell Mechanical Properties Based On Optical Tweezers

The mechanical properties of cells are important in the perception and external force transmission process of cell.Measuring the mechanical properties of cells can help dis-tinguish cells with identical appearance and changed structure,which is of great signifi-cance for disease diagnosis and drug development and has a broad application prospect.Aiming at the changes of the mechanical properties of blood cells under the background of different disease mechanisms,a method for measuring the shear modulus of cell mem-brane based on optical tweezers was studied by using the dual traps to manipulate the cells.The research content of this paper is as follows.The significance of measuring cellular mechanical properties and the research status at home and abroad are described.The different methods used in the study of cell me-chanics are introduced.The advantages and application background of these methods compared with optical tweezers are illustrated.The common microscopic methods for cell morphology measurement are enumerated,and the different types of digital holographic microscopy are compared.Off-axis digital holographic microscopy method is chosen in this paper,the reason is explained.The principle of measuring the mechanical properties of cells based on optical twee-zers is analyzed.The control principle of optical tweezers is expounded from the aspects of the mechanical analysis,the adjustment of key parameters of optical tweezers and the calibration method of optical trap stiffness.The wave dynamics theory of cell membrane is described,and the mechanical model of cell membrane is analyzed.The principle of shear modulus measurement for large cell deformation and off-axis digital holographic reconstruction for small cell deformation caused by weak tensile force are described re-spectively.A measuring method of shear modulus based on optical tweezers and cell extension ratio is proposed to measure the shear modulus of red blood cell.The red blood cells are modeled and simulated to observe the force distribution of blood cells under uniaxial ten-sile force,and an evaluation method for the validity of the measurement results is estab-lished.The effects of oxidative stress and extracellular calcium concentration on the elas-ticity of red blood cells are analyzed by measuring the shear modulus of blood cells treat-ed with H₂O₂ and Ca Cl₂ of different concentrations.The accuracy of the measurement re-sults is verified by comparing the results with the simulation results of the established blood cell mechanics model.The measurement method based on optical tweezers technology and off-axis digital holographic microscopy is proposed,the system structure is described.The adjustment method of fringes'visibility and the angle between object light and reference light are ex-plained.The position calibration method of optical trap is described.The system is used to measure the morphology of red blood cells and microspheres with different diameters.The accuracy of the system is verified by comparing the measured results of the microspheres with the scanning results of the electron microscope.Off-axis holographic microscopy is combined with optical tweezers technology to measure 3D morphological changes of red blood cell when the 2D shape variable is less than 200nm.The thickness of the red blood cells and the volume change are measured in the different level of oxidative stress state.The effect of oxidative stress on cell deforma-bility and volume under small deformation are analyzed.It is meaningful for accurate clinical detection of Parkinson's disease and has high academic value in basic biological research.