Rigger, P. (2011). Molecular mass imaging : technical and sample inherent aspects of imaging mass spectrometry [Diploma Thesis, Technische Universität Wien]. reposiTUm. http://hdl.handle.net/20.500.12708/160171
Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) arises as a very powerful method for investigating the distribution of molecules within biological samples. Unique for that method is its capability of visualizing the spatial distribution of hundreds of sometimes unknown compounds in a single measurement. The ability to obtain images from all analytes detected, from atomic to macromolecular ions, allows to determine the chemical organization within a sample and to correlate this with physical features. There is great potential in IMS applications especially in clinical fields, such as biomarker discovery. Examples demonstrating the localization of proteins in tumors have contributed to an increasing upsurge in the interest in IMS.<br />Sample preparation is a very important parameter that affects the type of information obtained. The matrix deposition on the samples is critical for producing reproducible analyte ion signals intensity. Here we report an automated method for matrix deposition, employing a chemical inkjet printer, to prevent sample-to-sample variation.<br />The chemical inkjet printer can also be used for automated sample preparation to identify sample inherent proteins after tryptic digestion. The most critical step here is keeping the analyte of interest localized although wetting a surface enhances analyte diffusion. Robotically spotting small volumes (repeatedly deposition of approx. 100 pL) of trypsin solution for further protease digestion provides access to protein fragments suitable for protein identification by peptide mass fingerprinting while retaining analyte localization.<br />The vast majority of the work so far has been performed on frozen tissue sections. Here I review technical and sample aspects as well as methodological approaches that arise at the implementation of MALDI-IMS for the analysis of human carcinoma cells lines A-498 (ATCC HTB-44) and Caki-1 (ATCC HTB 46) grown on calcium fluoride infrared-transparent slides.