Regensburg 2013 – scientific programme

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BP: Fachverband Biologische Physik

BP 24: Posters: Physics of Cells

BP 24.10: Poster

Wednesday, March 13, 2013, 17:30–19:30, Poster C

Measuring viscoelasticity in the extracellular space upon particle binding — •Felix Jünger and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

The cytoskeleton is a highly dynamic structure present in all cells, consisting of various kinds of filaments. It is responsible for movement, shape and division of cells as well as for particle uptake and transport processes inside the cell. Still, many principle questions remain open about the mechanics of particle uptake and the driving forces. What is the role of the membrane, the actin network, the myosin motors and the interplay among them?

Macrophages are essential components of the mammalian immune system, responsible for internalizing pathogens via phagocytosis. In our work we perform micro-rheological experiments on J774 mouse macrophages to investigate the viscous and elastic properties of the extracellular space prior to phagocytosis - parameters that the cell can actively control by reorganizing its actin cytoskeleton. We use photonic force microscopy (PFM) to analyse the temporal fluctuations of an optically trapped bead, which is approached to a cell membrane. The motion of the bead is tracked interferometrically in three dimensions with nanometer precision and on a microsecond time scale. The viscous modulus G″(ω), but also the elastic modulus G′(ω) can be obtained by analyzing the fluctuation data on a broad spectral bandwidth ω. We have measured several bead-cell arrangements and developed first simple theoretical models that help explain our experimental findings.