Regensburg 2025 – scientific programme

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BP: Fachverband Biologische Physik

BP 17: Poster Session II

BP 17.16: Poster

Tuesday, March 18, 2025, 18:00–20:30, P4

Red Blood Cells under brightfield microscopy
— •Aaron Kreis, Sarah Tabea Hermes, Thomas John, and Christian Wagner — Experimental Physics, University Saarland

The observation of red blood cells under a conventional light microscope is a common practice in research and medicine. In many cases, the particular cell shape is the object of interest, see [1]. Red blood cells are composed mostly of hemoglobin, which shows its maximum absorption at ∼ 420 nm. Nevertheless, the cells are mostly observed under white or red light. Furthermore, the refractive index of the cytosol is greater than that of water and refraction occurs. The combination of refraction and absorption leads to very different microscopy images at different focal points. We have quantified this using calculations by ray tracing and we can explain the observed microscopy images, including the white ’halos’ due to refraction at various focal positions. Diffraction isn’t a major contribution in observed cell shapes. We demonstrate that the use of blue light results in a significantly better image contrast of the cell shapes without artifacts, compared to the usual observation with white light.

[1] Yoon at. al., Flickering Analysis of Erythrocyte Mechanical Properties, Biophysical Journal 97, 1606, (2009)

Keywords: Red Blood Cells; Brightfield Microscopy; Imaging