Seminars Archive

Synchrotron based imaging techniques for the study of bio-samples

Abstract
In almost all fields of science, and especially in the areas of bio-medecine, biology, bio-chemistry, or bio-environmental science, there is a growing need to explore the detailed structural, morphological, magnetic and chemical properties of heterogeneous matter with the best spatial, elemental and chemical sensitivity achievable. Researchers need to examine their sample on localized and specific area rather than observing average of large one. But they need as well to get the most complete characterization of their sample as possible, without destroying it and/or with as little degradation as possible. Ideally, this characterization should be realized on the same specimen, on the very same area, which has subsequently to be submitted successively and safely to different techniques.  Among the techniques which can respond to these demands, infrared micro-spectroscopy is an easy-to-use and non-destructive method, which has the ability to identify molecular constituents from vibrational spectrum. Combined with a synchrotron source, and thanks to the high brilliance and broadband nature of this latter which improve the spatial resolution, IR microscopy permits the chemical mapping of spatially resolved inhomogeneous, diluted or small samples. Moreover, IR microscopy can be easily combined with fluorescence microscopy. Primary (natural) and secondary fluorescence (fluorescent labels, low concentration) do not interfere with the IR imaging, allowing a clear sample visualization, marking specific region of interest and providing an accurate correlation between the infrared images, the light and fluorescent images of the structures present into the sample. Others techniques of high output are soft and hard x-ray microscopy. They offers large elemental, chemical and magnetic sensitivities, good spectral resolution and a myriad of permissible in situ sample conditions at, presently, sub micrometer spatial resolution (20-100 nm). X-rays high penetration power allows, under defined circumstances, non destructive imaging in 2D or 3D (tomography) of internal structures of an object, in its natural state and non-stained. X-ray microscopy has also many contrast mechanisms (absorption, phase contrast, fluorescence) that can be employed beyond simple structural imaging, such as chemical state imaging with x-ray absorption spectroscopy (EXAFS, XANES) or elemental specific imaging.  The purpose of this seminar is to provide an overview of ways in which synchrotron based imaging techniques can be correlated and combined to get the most complete characterization of bio-samples. Presented by the mean of examples, some future developments of the techniques to fulfill the correlation procedures and possible