Cell Mechanics in Engineering Mechanics

Cell Mechanics in Engineering Mechanics
Cell mechanics is not only a frontier field of biomechanics, but also an important part of tissue engineering. It involves the study of cell membrane, cytoskeleton deformation, elastic constant, viscoelasticity, adhesion and other mechanical properties under mechanical load. and the effects of mechanical factors on cell growth, development, maturation, proliferation, senescence and death and its mechanism. Cell mechanics focuses on all kinds of cells of the human body, especially those related to the blood circulatory system, human body support motor system, digestive system and so on.
In the study of cellular mechanics model, the cell is usually regarded as a rheological fluid surrounded by a membrane, and the thickness of the cell membrane is about 4-5 nm, which separates the interior of the cell from the environment. The cell membrane is a lipid bilayer composed of double-stranded lipids and proteins, which can be changed into various shapes at will, which is equivalent to two-dimensional fluid. The force and deformation of the cell membrane have a direct effect on the function and structure of the membrane. In addition, the connection between cells is also a connection device formed by the special biochemical process of the adjacent cell membrane. Inside the cell, there is an extremely complex network structure system of protein fibers-cytoskeleton, which includes microtubules, microfilaments and intermediate fibers, which makes cells have the ability to actively deform and resist passive deformation.
The key for a cell to receive mechanical stimulation lies in the integrity of the cell structure, especially the tension integrity of the cytoskeleton, which can realize the transmission and distribution of mechanical forces in the cell and finally show the mechanical signal at the effect point. Integrin is also one of the mechanical receptors on the cell surface, which can transfer external force to the channel of the cytoskeleton and mediate the adhesion between cells and extracellular matrix. Through the timely response of the integrin receptor on its surface, the cell selectively converts the mechanical signal to different structural components of the cell in the form of tension integration. After the cell is stimulated, it transforms the stimulus into a corresponding signal into the cell, causing a series of responses. In addition, the regulation of intracellular free calcium concentration is also a key link in mechanical signal transmission. The concentration change of calcium ion is mainly realized by the calcium channel on the membrane, in which the voltage-operated calcium channel is thought to directly induce mechanical signals to regulate the transmission of various extracellular signals to the cell, causing a cascade of intracellular signals, thereby regulating cell proliferation and differentiation.
As far as cell mechanics is concerned, the key to the research of cell mechanics is the mechanical loading mode of cells, so finding suitable cell loading methods, cell deformation and related biological measurement methods is the primary problem in the research of cell mechanics. Cell mechanics experiment is to simulate the biomechanical environment of cells under certain conditions. According to the different sources of the simulated force, it is usually divided into two categories: simulating the mechanical environment in vivo and simulating the mechanical environment in vitro.
The main experimental methods to simulate the mechanical environment in vivo are flow shear stress method, substrate stretching method, hydrostatic pressure method and circumferential stress method. The main experimental methods to simulate the mechanical environment in vitro are microgravity cell culture method, centrifugal force field method, gas pressure method, acoustic stimulation method and microbeam irradiation method. In addition, the main experimental methods to study the mechanical properties of single cell are microtubule sucking method, atomic force microscope cantilever stimulation method, magnetic bead twisting method and optical clamp method.