Regensburg 2022 – scientific programme

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BP: Fachverband Biologische Physik

BP 9: Bioimaging

BP 9.8: Talk

Tuesday, September 6, 2022, 11:30–11:45, H16

Thermal fluctuations of the trapped bead as the complementary tool to the microscopy for investigation of a phagocytosis. — •Tetiana Udod and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

Phagocytosis, the uptake of particle by cells, is typically investigated in vivo by different microscopy technics, such as Brightfield, DIC, or Fluorescence microscopy. But even with highest possible resolution we can*t observe receptor binding or derive binding strengths to the cell membrane during binding and uptake. In addition to continuously recording 3D stacks of J774 macrophages cells by DIC microscopy, we record the thermal fluctuations of beads during the engulfment process. We measure the bead*s position in 3D with nanometer precision at MHz rates with back focal plane interferometry. Running both methods in parallel we can correlate the bead position relative to the cell to record changes in binding parameters like stiffnesses or, viscous drags derived from position fluctuations. Furthermore, remaining measurement ambiguities are resolved by Brownian Dynamic simulations.

To better understand such processes we use a combination of experiments with Photonic Force Microscopy, Brownian Dynamic simulation and analytical theory.