Abstract

Mass Spectrometric Imaging and Tissuetyping for the Analysis of Proteins and Metabolites in Tissue

Sören-Oliver Deininger, MALDI Imaging Product Specialist, Bruker

MALDI (Matrix assisted laser desorption/ionization) mass spectrometry allows to do direct and label-free imaging of intact proteins, peptides, drugs and metabolites from tissue and other surfaces. The main application is the analysis of histological tissue sections. The technique has found particular interest in oncology and pathology research because it has the potential to map the heterogeneity in tumors. Other interesting applications have been shown in plant metabolism, neurosciences and others. One important requirement for all tissue based analysis is the corelation with microscopic analysis. This is possible by first measuring the MALDI imaging datasets followed by histological staining and the microsocpic analysis. Modern MALDI imaging software allows to correlate digital microscopic slides with the MALDI imaging information, so that molecular features can be analyzed in the detailed histological context. We will shows several examples where this combined information can be helpful. MALDI imaging is a label-free technique and allows to measure hundreds to thousands compounds simultaneously. It therefore allows to analyze tissue without prior knowledge of what compounds are to be expected and also allows the discovery of new biomarkers. Since many compounds are measured at once, one can interpret each mass spectrum as a mass spectrometric phenotype. This allows computational approaches such as spatial segmentation of tissue data based on spectral similartiy or the supervised molecular classification of tissue. In the past, MALDI imaging has been done on conventional MALDI instruments that were not specifically designed for this application. Recently, dedictaed instruments became available which lift speed of the analysis, throughput, reliability and robustness to new levels. This will open up the route to widespread use of this technique in the future.