Time-lapse monitoring of cell mechanical properties

Atomic force microscopy (AFM) is a highly sensitive non-invasive surface method able to provide insight into cells' mechanical parameters. Membrane and sub-membrane development, as well as internal cellular properties, can be monitored. The stiffness of cells is a fundamental phenomenon that reflects changes in cell physiology. More importantly, changes in cell mechanical properties are also often found to be closely associated with various disease conditions. Cell mechanics are mainly dependent on cytoskeletal architecture. The development of cryopreserved cells' mechanical properties (stiffness) after thawing was studied using AFM. Cell stiffness was mapped and thus monitored in time and space under nearly physiological conditions (i.e., in culture medium and at elevated temperature). In AFM force spectroscopy mode, cells are indented at many sites, and their complete elastic responses are recorded, enabling them to reconstruct a stiffness map. We measured the frozen cell surface stiffness immediately after thawing; they, when the dynamics of development of the cell stiffness were monitored in time up to 24 hours. Moreover, the AFM spectroscopy was combined with fluorescence-based staining of the cytoskeleton, thus enabling to directly correlate cytoskeleton development with stiffness mapping