Lipidomics can be considered as one of the important fields of metabolomics that provides a comprehensive structural and functional characterization of various lipids. DESI has been currently used as MSI technique for the analysis as well as the identification of lipids in the cell culture.
In this study, we aimed to investigate the distribution and the localisation of lipids among three different cell lines: two of the gut epithelial cell lines (Caco2 and HT29-MTX cells) and one of cancerous basophil cells RBL.
Cells were grown on cover slips and had the media removed for the MSI experiment by a wash in 150 mM ammonium acetate followed by drying step for 15-20 min. The cover slips were directly mounted onto microscope glass slides, using double sided tape and place onto the DESI stage, with no sample preparation. Data were acquired using a Prosolia DESI source which was mounted on a Waters Xevo G2-XS mass spectrometer.
Positive ion mode experiments, at 50 µm pixel size, generated strong signals directly from all three type of cell lines, identified to be mainly glycerophospholipids such as m/z 798.54 identified as PC (34:1), K+ as well as triglycerides. However, difference in the lipid intensity profiles can be observed between the cell lines. In particular lipids such as m/z 820.54 putatively identified as PC (36:4),K+ was more expressed in the Caco2 cell line whereas m/z 756.53 (PC(P-32:0), K+ was more intense in HT29-MTX cell line. Furthermore, an experiment at 20 µm pixel size showed individual agglomerate of cell with different distribution within the same sample cell line.
Negative mode experiments also showed a very rich level of molecular information for the metabolites and lipidic mass range with the strongest signal at m/z 281.25, putatively identified as oleic acid which was the most abundant in Caco2 cell line.