MALDI Imaging of Lipid Biochemistry in Tissues by Mass Spectrometry

Several significant reasons for the success of matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) applied to lipid imaging have emerged. The first is the high abundance of various lipids in biological tissues because these hydrophobic molecules constitute the external and internal defining membranes of each cell. The mass defect or fractional mass of the molecular ion species provides information about the elemental composition of the desorbed ion from the tissue. MALDI IMS depicts regional localization of specific lipids in many different types of tissues. The validity of these MALDI images, specifically the relationship between MALDI IMS ion intensity and the amount of the lipid actually present in the tissue, although visually intuitive, is in reality affected by a complex combination of ion chemistry, tissue structure, lipid location within the cells of the tissue, and water and salt content.