MALDI Imaging of Lipid Molecules in Mouse Brain

The CC or hippocampus of mice was embedded in an M1 medium and snap-frozen in liquid nitrogen. Serial sectioning of frozen tissues with 10 μm thickness was collected by cryostat microtome (Leica Microsystems) and thaw-mounted onto indium tin oxide-coated glass slides. Then, 1 mg/mL O-P, N-C/G matrix was employed to spray the above tissue slices in indium tin oxide with a 0.2 mm nozzle airbrush (NEW-LP, China) and completely dried in a vacuum drier for MALDI imaging analysis. All MALDI-TOF MSI data in the positive-ion mode were obtained with an Ultraflextreme mass spectrometer (Bruker Daltonics, America). The MS calibration was performed with the CHCA matrix, and the m/z range was changed between 500 to 1000. To acquire the higher levels of ionization, the spatial resolution of MALDI MSI was set as 50 μm, and the laser intensity was 70%. The ion images based on lipid molecules were visualized and screened by using SCiLS Lab 2020a software. The structural identification of lipids was conducted by using MetaboScape software (Bruker Daltonica, version 2022b).