Masahiro Tsuchiya

The number distribution of complex shear modulus of single cells measured by atomic force microscopy

The viscoelastic properties of a large number of mouse fibroblast NIH3T3 cells (n approximately 130) were investigated by combining atomic force microscopy (AFM) with a microarray technique. In the experiments, the cells were arranged and cultured in the wells of a microarray substrate, and a force modulation mode experiment was used to measure the complex shear modulus, G*, of individual cells in a frequency range 0.5-200Hz. The frequency dependence of G* of the cells exhibited a power-law behavior and similar frequency dependencies have been observed in several cell types cultured on flat substrates. This indicated that the NIH3T3 cells cultured in the wells of a microarray have analogous structural organization to those cells cultured on flat substrates. The number distribution of both the storage and loss moduli of G* fitted well to a log-normal distribution function, whereas the power-law exponent estimated by a power-law structural damping model showed a normal distribution function. These results showed that combining AFM with a microarray technique was a suitable approach for investigating the statistics of rheological properties of living cells without the requirement of cell surface modification.

High-throughput measurements of cell mechanics using atomic force microscopy with micro-patterned substrates

Cell mechanics is strongly related to various cell functions such as migration and proliferation. Since the mechanical properties of cells exhibited a large cell-to-cell variation, statistical evaluation of cell mechanics is crucial for understanding cell behavior. In this study, we investigated the deviation of cell complex shear modulus storage modulus, which was measured by atomic force microscopy (AFM) with micro-patterned substrates. The result showed that the cell number more than 50 was required to obtain the converged deviation in the case of NIH3T3 cells cultured in isolated substrates.

Development of an atomic force microscope for measuring mechanical properties of cell population

Biomechanical properties of cells have been identified as an important factor in various biological processes. As cells migrate collectively, they interact mechanically with their surrounding cells. Thus, it is crucial to quantify mechanical properties of cell population in a large scale from intra-to inter-cellular regions. To measure the stiffness of confluent cells in a large scale, we developed an atomic force microscope (AFM), with a wide-range scanner, equipped with a non-inverted (up-light) optical microscope. A liquid-immersion objective lens was employed to focus the laser light and collect the reflected light from a cantilever for optical lever unit. The AFM allowed us to map the height and the Youngs modulus of confluent epithelial cells (n ~ 200) in a range of about 300 μm × 300 μm.