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.