Chemical Imaging with an X-Ray Nano-Probe

X-ray chemical imaging holds the potential for fundamental breakthroughs in the understanding of biological systems because chemical interactions can be evidenced at the sub-cellular level. What is the distribution of trace metals in cells? Do some elements accumulate within sub-cellular organelles? What is the local chemistry of the elements in these organelles? These are some of the fundamental questions that can be addressed using synchrotron radiation X-ray micro- and nano-probes. Such direct detection of chemical elements in single cells, and their speciation analysis, is a challenging task that requires sophisticated analytical developments. Improvements to obtain submicron X-ray beam sizes with synchrotron sources have been made in the last few years allowing chemical imaging at high lateral resolution. SR-XRF (Synchrotron Radiation X-ray Fluorescence) provides chemical element imaging with less than 100 nm spatial resolution. Moreover, synchrotron radiation offers the unique capability of spatially resolved chemical speciation using micro-XAS (X-ray Absorption Spectroscopy). The potential of these methods for biomedical investigations will be illustrated with examples of application in the fields of cell physiology, toxicology, and pharmacology involving trace metals.