The question how living biological cells adapt their local or global mechanical properties when they have to move or deform, is intriguing and a field of intensive study worldwide. One way to shed light on this issue is to study the incessant erratic motions of probe particles that are embedded in the cell’s cytoplasm. In cases where many such particles are spread over the cell, not only an average diffusivity of the particles (representing the global cellular state) can be measured, but also a statistical analysis can be applied. It then turns out that particles can undergo qualitatively and quantitatively very different motions. Since these different motions persist over timescales of at least a minute they can be further studied, to reveal intracellular mechanisms (like cytoskeleton remodeling) that are responsible for the dynamics of a cell.
Left: microscopy image of a Hmec-1 cell containing endogenous granules, visible as dark objects. Right: reconstruction in which each particle has been assigned a motion amplitude, represented via a color scale
Reference: "Mapping of spatiotemporal heterogeneous particle dynamics in living cells", M.H.G. Duits, Y. Li, S.A. Vanapalli, F. Mugele, Phys. Rev. E 79, 05191 (2009)