6th Annual Symposium
Physics of Cancer
September 7-9, 2015
|PoC - Physics of Cancer - Annual Symposium|
Adhesion strengths, shapes and the dynamics of red blood cell clusters at stasis and in microcapillary flow
Saarland University, Experimental Physics, 66123, Saarbruecken, Germany
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Cell migration and flow through the vascular network is mostly determined by bloods majority component, the red blood cells (RBC´s). RBC´s at stasis have the tendency to form large aggregates, the so called rouleaux. They are induced by the plasma proteins such as fibrinogen but can be reversibly broken up in the non-equilibrium situation of a shear flow. The addition of synthetic macromolecules such as dextran to a physiological solution containing RBC´s can mimic the formation of rouleaux.
We use single cell force spectroscopy to characterize typical adhesion energies, both for dextran and fibrinogen, and we use confocal microscopy and numerical simulations to study the topology of these aggregates as a function of the adhesion energy. Our in vitro, in vivo and numerical studies show that despite large shear rates, the presence of either fibrinogen or the synthetic polymer dextran leads to an enhanced formation of robust clusters of RBC´s in microcapillaries under flow conditions. However, the contribution of hydrodynamic interactions compared to the interactions induced by the presence of macromolecules in the cluster formation has not been established. Here we compare hydrodynamical cluster formation of RBC´s and cluster formation of RBC´s in the presence of macromolecules in microfluidic flow. The results reveal strong differences in the cluster morphology. The surface-to-surface distance between cells in the different solutions shows a bimodal distribution that can be reproduced with our numerical simulations by varying the bending rigidity of the cell membrane within the tabulated range reported in healthy physiological conditions.