Vacuum promoted on-tissue derivatization strategy: Unravelling spatial distribution of glycerides on tissue

Matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) has shown its capability in visualizing the spatial distribution of various kinds of endogenous metabolites. Nevertheless, high quality mass imaging of low polar metabolites remains challenging. Herein, a platform for sensitive matrix-assisted laser desorption ionization-mass spectrometry imaging of cholesterol and glycerides has been proposed. In the platform, a vacuum promoted on-tissue derivatization strategy was proposed to constantly make the derivatization reaction proceed towards to the direction of products. Compared with traditional on-tissue derivatization procedure, the strategy improved the acquired intensity of derivatized glycerides about 50%. Additionally, the mass spectrometry image reflecting the signal ratio between 3 classes of glycerides was achieved to exploit the metabolic level of glycerides on tissue slice. Finally, the platform was applied to brain slices of Alzheimer's transgenic mice, type 2 diabetes mice and normal mice. Significant difference was found in mass spectrometry images reflecting the signal ratio of multiple endogenous metabolites. The work constructed a promising platform for mapping of glycerides in tissue by mass spectrometry imaging.