Sub-micron X-ray microspectroscopy for life and environmental nanotoxicology

Roughly 2000 products currently available on the market contain engineered nanomaterials (ENMS), and this number is increasing. The physical and chemical properties of ENMs differ from their bulk counterparts and their industrial applications range from electronics and optics to medicine and foods. Hence, understanding the fate, and physical and chemical modifications of ENMs in living organisms, to assess their positive or negative impacts, requires specialized analytical techniques. Since both chemical and physical factors must be considered for a better understanding of ENMs behaviour in complex matrices, these materials might be considered a new type of analyte. An ideal technique should offer the best balance between sensitivity, chemical specificity, and spatial resolution. In this sense, microspectroscopic techniques, as available at ESRF beamline ID21, are of special interest in life and environmental nanotoxicology.

Localization and speciation of elements at ID21 is done using micro-X-ray fluorescence (µXRF) and micro X-ray absorption spectroscopy (µ-XANES) in the tender X-ray domain (2-9.1 keV). The X-ray beam is focused using KB optics to a sub-micron spot (~500 nm), which then allows localization of trace elements at subcellular level. The beamline is equipped with a passively cooled cryogenic stage that allows the study of frozen hydrated specimens (cells and cryo-sectioned tissues) preventing elemental redistribution and minimizing radiation damage. The combination of µXRF and µXANES allows precise localization and speciation of biologically relevant (P, S, Cl, Ca, K) and widely used elements in nanotechnology (Cd, Ag, Ti, La, Ce) in complex samples.

This presentation will highlight research done at ID21 taking full advantage of the beamline capabilities to investigate the distribution and speciation of ENMs in complex environmental and biological samples (e.g. soils, tissues, and cells). In the context of EBS and ID21’s refurbishment project the main technical challenges and keystone developments to consider for the design of the new end-station will be discussed.