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Ion microscopy

Leader : Jean-Luc Guerquin-Kern

 

This platform is based on a new generation of micro-probe that uses secondary ion mass spectrometry (SIMS): a powerful method for both quantifying and imaging the atomic composition of surfaces. In this technique, the surface to be tested is bombarded with a highly collimated beam of primary ions (Cs+ or O-); the secondary ions emitted from the surface of the sample then are analysed with a mass spectrometer to determine the elemental or isotopic composition of the surface. This technique is particularly suitable for biological, pharmacological or trace element studies, permitting analysis at subcellular level of the distribution of molecules either containing specific exogenous atoms (I, Fe or Pt, for example) or labelled with any isotope (e.g. 2H, 13C or 15N).

fig1: The NanoSIMS 50 micro-probefig1: The NanoSIMS 50 micro-probe

The facilities are located on the Orsay site of the Institut Curie. They include a Cameca NanoSIMS 50 ion probe (Fig.1), as well as all the specific equipment necessary for preparing biological samples by cryofixation, freeze-drying, ultramicrotomy, etc. for element analysis.

Established in 2001 as a pilot centre for dynamic SIMS imaging, the platform is open to the scientific community to develop new applications in biology and pharmacology on a collaborative basis with the platform staff. The platform also offers training in how to use low-temperature (-190oC) techniques (cryo-techniques) to prepare biological samples for analytical imaging.

The service collaborates in various national and international projects along three main axes of research:

  • Pharmacology, especially the targeting of exogenous molecules for diagnostic or therapeutic purposes.
  • Element analyses, specifically subcellular mapping of chemical elements (such as Fe, As, etc.), the presence of which is associated with certain pathologies.
  • Isotope analysis, which makes the most of SIMS as the only technique that can differentiate between isotopes of the same chemical element (Fig.2). Isotope analysis makes it possible to study intracellular and intercellular metabolic pathways by the use of stable isotope-labelled molecules.

 

fig 2: SIMS images of thyroid follicles from newborn rat after administration of a solution containing 129I to mimic accidental contamination with radioactivity (as after the Chernobyl accident, for example). The elements analysed were 31P (m=31), 32S (m=32), 127I (m=127) and 129I (m=129), as indicated (the ionised forms of these elements, produced by ion bombardment of the sample surface, are actually detected). The grey scale images show simultaneous analyses of the three elements on a single section (white indicates a high concentration of the element, black, a low concentration or absence of the element). The colour scale from 0-50%, gives information about the abundance of the 129I isotope in this tissue relative to the total 127I and 129I. Field area: 50 µm X 50 µm. Section thickness, 0.4 µm. (This work was carried out in collaboration with the Laboratory of Biophysics of the Faculty of Medicine at the University Paris VII).fig 2: SIMS images of thyroid follicles from newborn rat after administration of a solution containing 129I to mimic accidental contamination with radioactivity (as after the Chernobyl accident, for example). The elements analysed were 31P (m=31), 32S (m=32), 127I (m=127) and 129I (m=129), as indicated (the ionised forms of these elements, produced by ion bombardment of the sample surface, are actually detected). The grey scale images show simultaneous analyses of the three elements on a single section (white indicates a high concentration of the element, black, a low concentration or absence of the element). The colour scale from 0-50%, gives information about the abundance of the 129I isotope in this tissue relative to the total 127I and 129I. Field area: 50 µm X 50 µm. Section thickness, 0.4 µm. (This work was carried out in collaboration with the Laboratory of Biophysics of the Faculty of Medicine at the University Paris VII).