Research on nano mechanical properties and ultra-structure of yeast cells

Cellular mechanics is a hot field of biological mechanics and biological engineering. The development of the Nano-indentation technique provides a new way for examining the nano-mechanical characteristics of the yeast cells. The nano-indentation properties and the ultra-structure of yeast cells were examined by using the Tribo Indenter in nano-mechanical test Instrument. The largest indentation depth was much less than 10 percent of the diameter of yeast cells, which was measured by the atomic force microscope (AFM). The indentation pit was gradually deepened with the increase of applied loads. The variation amplitudes of nano-hardness and elastic modulus changed with the applied load. The hardness of M22-2 was greater than M22-2/h VDAC at first, whereas it was less than the later one with the increased indentation depth. When yeast cells were on monocrystalline silicon wafer, the elastic modulus of M22-2 was towards an approximate constant of about 0.3854GPa. The elastic modulus of M22-2 was less than that of M-3 at the beginning and was larger than that of M-3 when the indentation depth was larger than 237nm as the elastic modulus of M-3 decreased. The hardness of M22-2 was gradually decreased with the increased indentation depth. The hardness of M-3 was bigger than that of M22-2 at first, whereas was less than that of the latter with the increased indentation depth. The results show that VDAC played an important role on cell function and elasticity of the M22-2 yeast strain supplemented with a human VDAC1 gene better than VDAC1-deficient yeast strain, and also elasticity of the M22-2 yeast better than M-3 yeast strain. The elasticity of the yeast cells on monocrystalline silicon wafer and was better than that on cover glass. By repetitive tests and analyses, the mechanical properties of yeast cells and the load they can sustain were obtained. The experiment proved the feasibility of nano-mechanics property research of yeast cells with the aid of the Tribo Indenter. Nano-indentation technology not only provides useful information for cell physiology and pathology processes, but also brings a new method for the precise quantitative analysis of cell function which is helpful in the surface bionic engineering.