Single-molecule Force Microscopy: A Powerful Tool for Studying the Mechanical Properties of Cell Membranes

Background: Cell membrane is a physical barrier for cells, as well as an important structure with complex functions in cell activities. The cell membrane can not only receive external mechanical signal stimulation and make response (e.g. cell migration, differentiation, tumorigenesis, growth), but it can also spontaneously exert force on the environment to regulate cell activities (such as tissue repair, tumor metastasis, extracellular matrix regulation, etc.). Methods: This review provides the introduction of single-molecule force methods, as atomic force microscopy, optical tweezers, magnetic tweezers, micropipette adhesion assay, tension gauge tethers and traction force microscopy. Results: This review summarizes the principles, advantages and disadvantages of single-molecule force methods developed in recent years as well as their application in terms of force received and generated by cells. The study of cell mechanics enables us to understand the nature of mechanical signal transduction and the manifestation of the cell's own movement. Conclusion: The study of the mechanical properties of cell microenvironment leads to a gradual understanding of the important role of cell mechanics in development, physiology and pathology. Recently developed combined methods are beneficial to further study of cell mechanics. The optimization of these methods and the invention of new methods enable the continuing research on cell mechanics.