Two X-ray methods combine to map molarity of cellular substructures in a freeze-dried sample
Two X-ray methods combine to map molarity of cellular substructures in a freeze-dried sample lead image
As microscopy increasingly gives way to nanoscopy, quantitative biology can more precisely describe processes, like tissue inflammation, by using subcellular details of the cells involved. X-ray nanotomography, which uses synchrotron radiation, is especially promising because it nondestructively captures cross-sections through samples. Through reconstruction, this creates virtual 3-D spatial models with nanometer resolution.
A technique that combined X-ray phase nanotomagraphy with X-ray fluorescence microscopy, described in Applied Physics Letters, provided a map of the nanomolarity of elements inside subcellular components of freeze-dried human phagocytic cells. While X-ray fluorescence measurements have been combined with highly resolved spatial information provided, for instance, by AFM imaging, these kinds of approaches were typically only used qualitatively in a way that did not directly merge the two types of data.
“Our work makes elemental mapping for biological studies truly quantitative, and therefore more reliable and useful,” said corresponding author Chiara Gramaccioni. “We extracted the necessary morphological information from the X-ray phase nanotomography to inject it in the X-ray fluorescence data and obtain quantitative maps of the nanomolarity of elements inside subcellular compartments.”
While AFM measurements are limited to surface topographies, their relatively simpler acquisition process provided the authors with morphological information to verify the nanotomography’s results. At this point, their final molarity map is a proof of principle for performing the technique on freeze-dried cells. The authors are ultimately interested in quantitatively studying the role of lactoferrin in the inflammatory process. “From a methodological point of view, we work on moving on to frozen hydrated cells and on pushing the spatial resolution further,” Gramaccioni said. “The next step is to apply the methodology on frozen-hydrated cells to preserve better the structure and chemistry.”
Source: “Nanoscale quantification of intracellular element concentration by X-ray fluorescence microscopy combined with X-ray phase contrast nanotomography,” by Chiara Gramaccioni, Yang Yang, Alessandra Procopio, Alexandra Pacureanu, Sylvain Bohic, Emil Malucelli, Stefano Iotti, Giovanna Farruggia, Inna Bukreeva, Andrea Notargiacomo, Michela Fratini, Piera Valenti, Luigi Rosa, Francesca Berlutti, Peter Cloetens, and Stefano Lagomarsino, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5008834 .
