Shape reconstruction and height fluctuations of red blood cells using defocusing microscopy

TL;DR

This paper introduces a defocusing microscopy technique to quantitatively reconstruct the 3D structure and analyze the height fluctuations of red blood cell membranes, providing insights into their physical properties.

Contribution

The study presents a novel application of defocusing microscopy for detailed 3D reconstruction and membrane fluctuation analysis of red blood cells, including a method to extract physical parameters.

Findings

Reconstructed 3D profiles of RBC surfaces.

Measured membrane fluctuation spectra and derived physical parameters.

Analyzed radial variations of membrane properties.

Abstract

In this paper the bright-field defocusing microscopy (DM) technique is presented. DM is able to obtain quantitative information of each plane/surface of pure phase objects, as live unlabeled cells, and its application to red blood cells (RBCs) is demonstrated. Based on contrast, simple methods to obtain thickness profile and three dimensional (3D) total reconstruction of RBCs are proposed and the actual height profiles of upper and lower surface-membranes (lipid bilayer$/$cytoskeleton) of discocyte and stomatocyte red cells are presented as examples. In addition, using the mean square contrast fluctuation and modeling the RBC membranes fluctuations spectra as dependent of a bending modulus $(\kappa_c)$, a surface tension $(\sigma)$ and a confining potential $(\gamma)$ term, slowly varying quantities along the cell radius, a genetic algorithm (GA) is used and the radial height fluctuations of each surface-membrane are accessed, separately. The radial behaviors of $\kappa_c$, $\sigma$ and $\gamma$ are also obtained, allowing the discussion of physical aspects of the RBC membrane.