Doktoratskolleg MEIBio - Molecular and Elemental Imaging in Bioscience
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herbert.hutter(a)tuwien.ac.at

PhD Fellow #6

Secondary Ion Mass Sepctrometry (SIMS) analysis of bioorganic samples.

Faculty: Herbert Hutter

SIMS in combination with a time-of-flight mass analyser (TOF-SIMS) provides elemental (1) AND organic (2-4) imaging capacities. Due to the main goal of this proposal, the combination of different techniques to pave the way for new multimodal imaging techniques, both capabilities will be used. Therefore this PhD thesis intends to assess all possibilities of multimodal imaging (optical, molecular and elemental) which is only possible in an intensive cooperation within the partners of the faculty. Within this planned cooperation with well-established bioanalysis groups at the VUT we will develop advanced SIMS measurement methods for biological samples.

It is the aim to quantify trace and major element distributions in bioorganic samples of many kinds. TOF-SIMS is a very powerful method, but it is characterized by strong matrix effects especially in biological tissue. The most abundant elements are the matrix for SIMS-measurements. However trace elements have a linear signal-to-concentration ratio up to about one percent, and then we are confronted with a nonlinear sensitivity of major components. Knowing the main element distribution and concentrations by a combined approach of LA-ICP-MS and XRF measurements, apparent concentration mappings of trace elements can be corrected to "real" concentration distributions.

Additionally it is in the scope of this PhD thesis to interpret significant signals in TOF-SIMS spectra correctly and to correlate those to molecular structures of organic substances. TOF-SIMS is not a soft ionization technique. The identification of organic molecules is in the most cases only possible by a correct interpretation and assignment of small fragments generated during the ionization process (fingerprint spectra). In the usual case of unknown composition and the absence of "pure" reference samples an undoubtedly distribution of organic and bioorganic molecules in real world sample is not possible. Implementing a soft ionization techniques as MALDI in combination with collsion induced dissociation processes (G. Allmaier) offers not only the possibility to measure the mass of the intact molecule, but also the expected fragments. With this help TOF-SIMS mass spectra are interpretable. This allows the identification of organic and bioorganic molecules in TOF-SIMS images of bioorganic samples.

Lateral structured standard are necessary for development of advanced measurement techniques to assess resolution capabilities for this imaging technique. The planned AFM setup of B. Lendl is a method with comparable and even better lateral resolution as TOF-SIMS (below 100) nm. Complementary measurements will allow us a better interpretation of high lateral resolved images.

1. Krecar, Dragan; Zwanziger, Juergen; Vassileva, Vassilka; Danninger, Herbert; Hutter, Herbert. 2005. 2D and 3D SIMS investigations on sintered steels, Appl Surf Sci 252(1): 282-285.
2. Passarelli, Melissa K.; Winograd, Nicholas, Lipid imaging with time-of-flight secondary ion mass spectrometry (ToF-SIMS) 2011. Biochim Biophys Acta, Molecular and Cell Biology of Lipids 1811(11): 976-990.
3. Biological tissue imaging with time-of-flight secondary ion mass spectrometry and cluster ion sources. 2005. Brunelle, Alain; Touboul, David; Laprevote, Olivier, J Mass Spec 40(8), 985-999.
4. 3D subcellular SIMS imaging in cryogenically prepared single cells. 2004. Chandra, Subhash, Appl Surf Sci, 231-232, 467-469.

Collaborations:

 

  • In the neighboring laboratory of the TOF-SIMS the new XPS was installed during the last months. We have a long cooperation with Wolfgang Werner (TU Vienna, E134). The XPS will support the results with element mappings and with valuable information about the chemical bonding.
  • The NANOSIMS of Michael Wagner (University of Vienna) is able to detect trace elements with a detection power and high lateral resolution.
  • For further development of the instrument and for 3D-data evaluation and visualization we have an intense cooperation with IONTOF.
  • For quantification of trace elements an intense cooperation with LA-ICPMS, A. Limbeck (TU Vienna) is essential. This will combine the detection power, standard free quantification approaches and the lateral resolution of the methods. For quantitative distributions of the major elements reliable XRF, Ch. Streli (TU Vienna) measurements are useful.
  • The molecular structure of detected molecules will be gained by combining the more destructive method of TOF-SIMS with MALDI MS (G. Allmaier, M. Marchetti-Deschmann, both TU Vienna).
  • Optic spectroscopy will be implemented by B. Lendl (TU Vienna).