Abstract: Several essential metal ions participate in the control of numerous metabolic and signaling pathways, but their rich coordination chemistry and redox properties confer them a propensity to randomly coordinate and catalytically react inside the cell with protein sites other than those tailored for that purpose. Investigating metal homeostasis and its dysfunctions is crucial to better understand the cell functions and the influence on cellular pathology. The associated challenge to analytical chemistry techniques, consists in locating and quantifying these elements, mostly present at trace level, within the highly complex intracellular landscape. As such, cutting-edge technique providing quantitative imaging for detailed study of elemental homeostasis or the intracellular distribution of metal-based drugs at biologically relevant concentration in a label-free fashion is highly desirable.
The synchrotron X-ray fluorescence (XRF) nanoprobe as developed today provides the required sensitivity and spatial resolution for elucidating the 2-D and 3-D distribution and concentration of elements. particularly metals. inside entire cells at the organelle level.
The new state-of-the-art Nano-Imaging beamline ID16A-NI at ESRF offers unique capabilities for X-ray imaging at the nanoscale, delivering an extremely bright, nanofocused beam (> 5×1011ph/s at ∆λ/λ~10‑2) at high energies (~30 nm at 17 keV). X-ray tomography techniques offer the potential to image and quantify ‘thick’ cells and tissues in 3-D without excessive sample preparation. Recently, we reported the use of correlative synchrotron X-ray holographic and X-ray fluorescence nanotomography to quantify elemental 3-D distribution within fixed or freeze-dried single cells and also on frozen-hydrated cells. We will illustrate the capabilities of this technique to provide quantitative nanoscopic cryo-XRF of cells as diverse as cancer cells exposed to organometallic drugs, neurons, and cancer cells exposed to metal-based nanowires.