Doktoratskolleg MEIBio - Molecular and Elemental Imaging in Bioscience
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martina.marchetti-deschmann@tuwien.ac.at

PhD Fellow #8

Mass Spectrometry Imaging and Fluorescence Imaging of Polymer Surfaces after Contact with Biological Fluids

Faculty: Martina Marchetti-Deschmann

Dispersions of macromolecules in a solid polymer matrix are of particular interest. Not only that blends of conjugated polymers can enhance the performance of light emitting devices, transistors, lasers and other optical components it also plays a critical role for Biomedical engineering where the in vivo application of artificial devices is of importance. Biocompatibility and wear resistance are crucial parameter if polymers used as implants. High reactive hydroxyl radicals were identified to be the most important cause of in vivo polymer degradation which is critical in case of implants intended to be permanent, like joint replacements (1). In contrary, clinical research demands biodegradable material, as smaller grafts (e.g. vascular grafts) are associated with a high incidence of thrombosis if cellular ingrowth is not enhanced (2). Today optic instrumentation like infrared (FT-IR) and fluorescence microscopy are the methods of choice to get information on polymer changes and reactions at the interface of biology and the polymer. Biomolecule behaviour (lipid, protein, carbohydrate) and reactions induced by these analytes are of interest.

We already started to use MSI to visualize molecular distributions on graft explants (Figure 8).

  • Using mass spectrometry allows for the first time an unbiased access to molecular information for analytes distributed on a surface. No labelling is necessary to identify a species.
  • Additionally, mass spectrometry allows co-localization of many analytes and the read-out of relative intensities gives information on analyte clustering on surfaces.

Yet lateral resolution is limited for this approach and we therefore suggest a new approach to combine the molecular information with single molecule fluorescence imaging.

Fluorescence labelled molecules of interest - previously identified by MSI (e.g. GFP-labelled proteins, nitrobenzofurazan-labeled lipids), will be brought into contact with the porous polymer surface and diffusion processes into the material will be studied by single particle tracking. This approach is already available for small molecules (3) but was never attempted for macromolecules or biomolecules.

  • The expertise of G. Schütz will help to facilitate this approach which provides insight into dynamics of various surface induced processes. Finally molecular information from consecutive polymer slices will be gathered from the very same slice after fluorescence imaging.
  • The 2-dimensional information from mass spectrometry will be aligned with dynamic molecular information provided by single molecule imaging and combined to a 3D visualisation of proteins and lipids diffusion into implant material. This will be done with the expertise of R. Sablatnig.
  • To do multimodal imaging beyond using only two modalities, Raman spectroscopy will be applied. The expertise of B. Lendl will help to visualize spectral information at ultrahigh resolution. Although no molecular information will be available by this technique its lateral and depth resolutions (5 nm) are possibilities of interest to understand biological processes at nanostructured surfaces.

1. Carotenuto G, Di Palo M, Marino G, Ambrosio L, Nicolais L. 1997. Comparison between in vitro and in vivo UHMW-PE degradation. J Biomater Sci Polym Ed;8(6):481-91.
2. Sung H-J, Meredith C, Johnson C, Galis ZS. 2004. The effect of scaffold degradation rate on three-dimensional cell growth and angiogenesis. Biomaterials.25: 5735-5742
3. Zürner A, Kirstein J, Döblinger M, Bräuchle Ch, Bein Th. 2007. Visualizing single-molecule diffusion in mesoporous materials. Nature 450: 705-708

Collaborations:

  • Close collaborations with the Institute of Applied Synthetic Chemistry and the Institute of Materials Science and Technology (both TU Vienna) and AC2T are well documented.
  • International collaborations and knowledge exchange is documented for FOM AMOLF and Leiden University Medical Center (both NL).
  • Knowledge Exchange, samples and fundings will be provided by the Medical University of Vienna.
  • The development of methods and strategies to gather and combine molecular and spectroscopic information on biological processes at nanostructured surfaces will be done with G. Schütz, B. Lendl and R. Sablatnig (all TU Vienna).