Microrheology of suspended cells using optical traps

Mammalian cells are highly complex, structured, active soft materials. The cytoskeleton is largely responsible for activity and mechanical response of whole cells. The cell nucleus typically occupies a substantial fraction of the cell volume and is itself an active material with a complex structure. We here report on measurements of viscoelastic properties as well as non-equilibrium fluctuations of both, suspended cells and isolated cell nuclei, using optical traps. Combining manipulation experiments with confocal microscopy, we also observe how drug interference affects mechanical response and activity.