Scanning X-ray nano-diffraction on eukaryotic cells

X-rays provide an ideal probe for studying structures at the nano-scale and are routinely employed for investigating the structure and the composition of biological systems, making use of the variety of different techniques. By raster scanning the sample with a small beam, structural information obtained from individual scattering patterns in reciprocal space can be combined with positional information in real space. In this work, scanning X-ray diffraction using a nano-focused beam was applied to samples of biological cells in order to probe the structure of cytoskeletal bundles and networks of keratin intermediate filaments. Cellular samples were prepared using different methods, starting from well-established freeze-dried samples and going on to fixed-hydrated and finally living cells. In this context, the development of X-ray compatible microfluidic devices allowing for measurements on living cellular samples was an important aspect. Comparing the scattering signal from freeze-dried, fixed-hydrated and living cells, differences between the sample types at length scales of several tens of nanometers were determined. The successful application to hydrated and living cells further demonstrates the potential for structural analysis at hardly accessible length scales in native samples.