High-Specificity and Sensitivity Imaging of Neutral Lipids Using Salt-Enhanced MALDI TIMS

Neutral lipids are vital to various cellular processes and disease pathologies. However, their characterization by matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) remains challenging due to poor ionization efficiency and difficulties distinguishing subtle structural differences among numerous isomeric and isobaric species. In this study, we enhanced neutral lipid detection by incorporating isotonic metal-cation washes into our MALDI IMS sample preparation workflow. Resulting salt adducts improved neutral lipid isobar and isomer separation by using trapped ion mobility spectrometry (TIMS). This approach increased both sensitivity and specificity for neutral lipid IMS experiments across multiple organ types, including murine brain, rabbit adrenal gland, human colon, and human kidney. Comparative analyses revealed that the most effective salt wash was tissue-dependent. However, the Na⁺ carbonate buffer solution (CBS) wash showed the greatest overall increase in neutral lipid detection. These findings provide a robust framework for mapping neutral lipids across multiple tissues and disease states and allow for the detailed characterization of neutral lipid isomers and isobars in complex biological tissues.