In-situ single cell mechanical characterization of W303 Yeast cells inside Environmental-SEM

We present the Environmental-SEM (ESEM)-Nanomanipulator system for in-situ measurement of mechanical properties of the Yeast cells (W303 strain). This enhanced ESEM system comprises of a standard ESEM instrument as a nano imaging tool, a cooling stage as a cellular biology's humidity controller and 7 D.O.F. linear actuators as nanomanipulator/effector. Two types of experiments have been conducted, i.e. mechanical properties of individual yeast cells and forces on cell-substrate area. Different kinds of spring constants (0.02 N/m, 0.09 N/m and 0.7 N/m) and tip's shapes (sharp, flat and needle-like) of the cantilevers have been used during the experiments. From the analysis, the compressed forces needed to penetrate the cell wall of the yeast cells using sharp and flat tips (0.02 N/m for both) are in the range of 87-278 nN and 57-207 nN respectively. Locality mechanical measurement has been performed using needle-like tip (0.09 N/m) on single-cell and mother-daughter cells where the elastic properties of the cells are in the range of 1.32-3.95 MPa. In addition to the above data, we have also investigated forces on cell-substrate area which can be divided into noncontact and contact forces. Under noncontact forces, average electrostatic forces between Au tip-Al substrate and tip-cell surfaces are measured to be 16 ± 2 nN and 5 ± 2 nN respectively. While under contact forces, two types of surface adhesions are measured which are cantilever's tip-wet surface adhesion and cell-surface adhesion where the release forces for each adhesion are 1107 ± 129 nN and 26578 nN respectively.