SKM 2023 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 35: Statistical Physics of Biological Systems I (joint session BP/DY)

DY 35.7: Vortrag

Donnerstag, 30. März 2023, 11:30–11:45, TOE 317

Physical mechanism of erythrocytes sedimentation rate — •Alexis Darras, Thomas John, Lars Kaestner, and Christian Wagner — Experimental Physics, Saarland University; D-66123 Saarbrücken, Germany

Red blood cells (or erythrocytes) sedimentation rate (ESR) is a physical parameter of blood which is often checked in medical diagnosis. It is indeed well known that in case of inflammation, the increase in fibrinogen and other proteins induces a higher ESR.

Until recently, researchers thought that the increase of fibrinogen accelerates the ESR by creating bigger aggregates of red blood cells (RBC). Fibrinogen is indeed an aggregation agent of RBCs, and bigger aggregates tend to sediment faster in Stokes regime. However, modeling the ESR measurements with this hypothesis is challenging and often requires physical assumptions specific to this system.

Besides, modern colloidal science has shown that attractive particles, in suspensions with a high volume fraction, form percolating aggregates, as wide as the container. The sedimentation of those colloids then follows a so-called "colloidal gel collapse" regime, governed by the geometry of the percolating aggregate acting as a porous material. In this talk, we show that RBCs actually follow the same behavior. We also demonstrate that a porous-material model naturally leads to an efficient description the RBC sedimentation, which also provides a long-sought dependency of the ESR as a function of the initial RBC volume fraction (i.e. the hematocrit).