MALDI imaging mass spectrometry: applications, limitations and potential

Abstract

Matrix assisted laser desorption/ionization (MALDI) tissue imaging mass spectrometry (IMS), introduced in 1997 and exemplified by the work of Caprioli (Caprioli et al., 1997), Stoeckli (Stoeckli et al., 2001) and Chaurand (Chaurand et al., 2002; Chaurand et al., 1999), is a blooming field among the numerous applications of mass spectrometry for protein identification and analysis. IMS is a powerful technique that combines the multichannel (m/z) measurement capability of a mass spectrometer with a surface sampling process that allows probing and analyzing of the spatial arrangement of a wide range of molecules including proteins, peptides – both endogenous or enzymatically produced – lipids, drugs and metabolites, directly from thin slices of tissue (for a review, see Seeley and Caprioli, 2011). Specific information on the relative abundance and spatial distribution of target molecules is maintained, providing the opportunity to correlate ion-specific images with histological features observed by light microscopy. IMS is increasingly recognized as a powerful approach in clinical proteomics, particularly in cancer research (McDonnell et al., 2010). The technology holds a high potential for the discovery of new tissue biomarker candidates, for classification of tumors, early diagnosis or prognosis but also for elucidating pathogenesis pathways and for therapy monitoring (Seeley and Caprioli, 2011).