Combined atomic force microscopy and side-view optical imaging for mechanical studies of cells.

The mechanical rigidity of cells and adhesion forces between cells are important in various biological processes, including cell differentiation, proliferation and tissue organization. Atomic force microscopy has emerged as a powerful tool to quantify the mechanical properties of individual cells and adhesion forces between cells. Here we demonstrate an instrument that combines atomic force microscopy with a side-view fluorescent imaging path that enables direct imaging of cellular deformation and cytoskeletal rearrangements along the axis of loading. With this instrument, we directly observed cell shape under mechanical load, correlated changes in shape with force-induced ruptures and imaged formation of membrane tethers during cell-cell adhesion measurements. Additionally, we observed cytoskeletal reorganization and stress-fiber formation while measuring the contractile force of an individual cell. This instrument can be a useful tool for understanding the role of mechanics in biological processes.