Water imaging in cells cryosections by electron energy loss spectroscopy

Abstract

Water is concerned in ionic flows regulation and in cellular volume regulation. Measurement of water content variations in the cell allows to study cellular life phenomena and especially pathologies related to ionic or water channels failing. Moreover the knowledge of water content can be coupled with elemental microanalysis by EDXS to express ionic concentrations in mmol/l. Hence it is an important task to measure water content at a subcellular level. In this way, different methods based on Xray microanalysis or using the STEM quantitative darkfield intensity on freeze-dried cryosections have been developed. Unfortunately methods based on X-ray microanalysis require an important electron dose which can induce a considerable mass loss in the electron beam sensitive hydrated specimen. Moreover all these methods estimate water content by using freeze-dried cryosections. Thereby they are indirect methods based on the assumption that no differential shrinkage occurs during freeze-drying. In this lecture, we will present a direct method of water mass measurement on hydrated cryosections by EELS.