Low-dose, high-throughput scanning small-angle X-ray scattering of adherent mouse embryonic fibroblasts

by Chiara Cassini
Doctoral thesis
Date of Examination:2021-03-26
Date of issue:2022-02-24
Advisor:Prof. Dr. Sarah Köster
Referee:Prof. Dr. Sarah Köster
Referee:Prof. Dr. Tim Salditt
Referee:Prof. Dr. Alexander Egner
Referee:Prof. Dr. Timo Betz
Referee:Prof. Dr. Stefan Klumpp
Referee:Prof. Dr. Simone Techert
Persistent Address: http://dx.doi.org/10.53846/goediss-459

 

 

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Description:Low-dose, high-throughput scanning small-angle X-ray scattering of adherent mouse embryonic fibroblasts

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Abstract

English

Biological cells are highly variable: differences in e. g. gene expression emerge even among monoclonal cells in the same culture dish. The characterization of a highly variable statistical population calls for high-throughput experimental methods, that is, a large number of members of the population needs to be assessed in order to discern individual properties from properties of the population as a whole. When studying cells it is thus desirable to combine large field-of-view images with high spatial resolution, so that subcellular details can be captured. Large field-of-view small-angle X-ray scattering (SAXS) scans provide moderate-resolution dark-field contrast images of the whole scanned area, as well as structural information stemming from the nanometer-sized structures probed at each scanning position. Thus, both the high-throughput and the high-resolution requirements are met. In this work, we transfer this high-throughput scanning SAXS approach, that has been demonstrated on cardiac tissue, to the single cell level. In order to speed up the acquisition process, short exposure times are employed, with potentially negative consequences on the signal quality but positive consequences on radiation damage. This way, in a single experiment, we manage to image an unprecedented number of cells, in the order of hundreds instead of tens. The large amount of data thus produced is efficiently dealt with thanks to a semi-automated segmentation procedure, that enables the quantitative comparison of different cell lines. Such comparison is illustrated both on a cellular level, by examining the scattering properties of cells as a whole, and on a subcellular level, by analyzing individual scattering patterns that reveal properties of the local position of the cell that was irradiated to obtain them. Finally, a system closer to physiological conditions is investigated thanks to a wet sample chamber that allows for measuring fixed-hydrated rather than freeze-dried cells. Our contributions at multiple stages of the experimental process, from the sample preparation and sample chamber design to the data analysis strategies, push scanning SAXS of biological cells towards a low-dose, high-throughput technique that lends itself to being routinely used for structural characterization and comparison of biological cell lines.
Keywords: scanning SAXS; biological cells; high throughput; radiation damage; image segmentation
 
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