Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful tool that enables the simultaneous detection and identification of biomolecules in analytes. MALDI-imaging mass spectrometry (MALDI-IMS) is a two-dimensional MALDI-MS technique used to visualize the spatial distribution of biomolecules without extraction, purification, separation, or labeling of biological samples. This technique can reveal the distribution of hundreds of ion signals in a single measurement and also helps in understanding the cellular profile of the biological system. MALDI-IMS has already revealed the characteristic distribution of several kinds of lipids in various tissues. The versatility of MALDI-IMS has opened a new frontier in several fields, especially in lipidomics.
Fig1. The protocol workflow of MALDI-Imaging lipidomics (Noh SA.; et al, 2019)
TOF is the most widely-used technology. TOF analyzers allow the separation of ionized accelerated molecules according to their mass-to-charge ratio (m/z). TOF-MS offers suitable performance for MALDI-IMS, namely a good transmission ratio (50–100%), sensitivity, and repetition rate. However, TOF-MS lacks the capability to perform effective tandem MS analyses for identification. This disadvantage of TOF-MS has been addressed with the introduction of hybrid analyzers pairing various technologies with TOF: a quadrupole mass analyzer and TOF, a quadrupole ion trap and TOF, an ion mobility spectrometer and TOF, and tandem TOF mass spectrometers. These combination systems have revolutionized the application of TOF-MS to structural analysis with tandem MS analyses.
MALDI-IMS is currently one of the only methodologies enabling simultaneous visualization of lipids. Visualization of various types of lipids, such as phospholipids, neutral lipids, glycolipids, and fatty acids has been reported.
Noh SA.; et al. Alterations in Lipid Profile of the Aging Kidney Identified by MALDI Imaging Mass Spectrometry. J Proteome Res. 2019, 5;18(7):2803-2812.