Time-of-flight secondary ion mass spectrometry investigation of the influence of ambient air exposure on the migration of brain lipids in a matrix commonly used in matrix assisted laser desorption ionization mass spectrometry imaging.

This article focuses on investigating how exposure to ambient laboratory environmental conditions affects the migration and integration of analytes, specifically lipids, into an α-Cyano-4-hydroxycinnamic acid (CHCA) matrix layer applied to mouse brain tissue for matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Using time-of-flight secondary ion mass spectrometry (ToF-SIMS) with vacuum transfer to prevent contamination, the study found that lipid redistribution within the matrix is influenced by relative humidity, with minimal migration below 50% humidity and significant changes occurring above this threshold. Different lipids and brain tissue types exhibited distinct migration behaviors, and prolonged exposure to high humidity led to lateral migration of lipids and salts into surrounding embedding material, as well as diffusion of the matrix into the tissue, which can affect image reproducibility and accuracy. The findings highlight the importance of controlling environmental factors such as humidity and storage time during sample preparation to optimize MALDI-MSI and matrix-enhanced SIMS imaging results.