Mechanical properties of plasma membrane and nuclear envelope measured by scanning probe microscope

Atomic force microscopy has been used to visualize nano-scale structures of various cellular components and to characterize mechanical properties of biomolecules. In spite of its ability to measure non-fixed samples in liquid, the application of AFM for living cell manipulation has been hampered by the lack of knowledge of the mechanical properties of living cells. In this study, we successfully combine AFM imaging and force measurement to characterize the mechanical properties of the plasma membrane and the nuclear envelope of living HeLa cells in a culture medium. We examine cantilevers with different physical properties (spring constant, tip angle and length) to find out the one suitable for living cell imaging and manipulation. Our results of elasticity measurement revealed that both the plasma membrane and the nuclear envelope are soft enough to absorb a large deformation by the AFM probe. The penetrations of the plasma membrane and the nuclear envelope were possible when the probe indents the cell membranes far down close to a hard glass surface. These results provide useful information to the development of single-cell manipulation techniques.