Berlin 2018 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 17: Cell Mechanics I

BP 17.10: Vortrag

Mittwoch, 14. März 2018, 12:30–12:45, H 1058

Measurement and simulation of light scattering by deformed red blood cells (RBCs) in flow cytometry — •Jonas Gienger, Hermann Groß, Markus Bär, Volker Ost, and Jörg Neukammer — Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2–12, 10587 Berlin, Germany

Light scattering of single cells is widely applied for flow cytometric differentiation of cells. We developed a dedicated flow cytometer to simultaneously observe forward light scatter (FSC) of RBCs for orthogonal incident wave vectors k₁^→ ⊥ k₂^→. Bimodal distributions are observed in two-dimensional dot plots of FSC(k₁^→) vs. FSC(k₂^→) of typically 7.5×10⁴ RBCs, which is a result of the RBCs’ random orientation around the direction of flow, their distribution of size and optical properties.

Simulations of the light scattering by single RBCs were performed using the discrete dipole approximation (DDA). Using the axisymmetric equilibrium shape of healthy RBCs employed in most light scattering simulation studies to date, the experimentally observed bimodality cannot be reproduced. This is because this model does not account for the significant elongation due to hydrodynamic forces in the flow cytometer, involving extensional flow and Poiseuille flow at speeds of up to 5 m/s in channels of a few 100 µm width. Thus we propose a simple ad hoc model for elongated RBC shapes, which reproduces the bimodal 2D-distributions qualitatively. However, to quantitatively analyze the data and retrieve elastic parameters from such high-throughput optical measurements a detailed modeling of RBC deformation in the given flow conditions seems necessary.