Imaging of whole zebra fish (Danio rerio) by desorption electrospray ionization mass spectrometry.

Abstract

To demonstrate the potential use of zebra fish (Danio rerio) as a model vertebrate organism by producing two-dimensional ion images of the whole zebra fish, and being able to distinguish particular areas of interest such as the brain, spinal cord, and stomach region using a desorption electrospray ionization (DESI) ion source coupled to a linear ion trap. Imaging experiments are performed on 45 µm sagittal slices of zebra fish (Danio rerio), which are thaw-mounted onto microscope glass slides. The slides are then analyzed using a solvent of acetonitrile/dimethylformamide (50:50) (ACN/DMF), with a solvent flow rate of 1.5 μL/min; data are acquired in negative ion mode. Raw mass spectrum data files are converted into a readable file for Biomap. The images produced are then analyzed for ion distributions. We are able to create clear, distinct, chemical intensity images of the brain, spinal cord, and stomach based on lipid content as well as bile salt. The identities of these compounds were confirmed by tandem mass spectrometric (MS/MS) experiments and comparisons with literature. Imaging of whole zebra fish is possible using ambient ionization techniques such as DESI. Analyses are fast and reliable. For most of the compounds observed, the identification by MS/MS can be performed directly from the fish tissue sample.