The spatial and temporal changes of the mechanical properties of living cells reflect complex underlying physiological processes. Following these changes should provide valuable insight into the biological importance of cellular mechanics and their regulation. The tip of an atomic force microscope (AFM) can be used to indent soft samples, and the force versus indentation measurement provides information about the local viscoelasticity. By collecting force-distance curves on a time scale where viscous contributions are small, the forces measured are dominated by the elastic properties of the sample. We have developed an experimental approach, using atomic force microscopy, called force integration to equal limits (FIEL) mapping, to produce robust, internally quantitative maps of relative elasticity. FIEL mapping has the advantage of essentially being independent of the tip-sample contact point and the cantilever spring constant. FIEL maps of living Madine-Darby canine kidney (MDCK) cells show that elasticity is uncoupled from topography and reveal a number of unexpected features. These results present a mode of high-resolution visualization in which the contrast is based on the mechanical properties of the sample.

Mechanical forces play a major role in the physiology of eukaryotic cells. Studies of the mechanical properties of cells are important for understanding their function in many physiological and pathological processes. Cytomechanics is an important factor in morphogenesis, in control of gene expression and protein synthesis and several other cellular processes especially in cellular division and proliferation. Progress has been made toward understanding the mechanics of cell division in a wide variety of organisms and cell types using several methods including molecular biology, light and electron microscopy, as well as various force transducers, methods including microneedles, laser and magnetic tweezers, and the atomic force microscope (AFM). Measurement of cellular viscoelasticity by such techniques can provide important functional information about the physiological role and mechanical properties of cellular components (in particular the cytoskeleton). Mitosis is a highly complex physiological and biochemical process. Although cellular structures and molecules involved in mitosis have been extensively characterized, the biomechanics of cell division remains poorly understood.