Mass spectrometry imaging of rat brain sections: nanomolar sensitivity with MALDI versus nanometer resolution by TOF–SIMS

Abstract

Mass spectrometry imaging is becoming a more and more widely used method for chemical mapping of organic and inorganic compounds from various surfaces, especially tissue sections. Two main different techniques are now available: matrix-assisted laser desorption/ionizaton, where the sample, preliminary coated by an organic matrix, is analyzed by a UV laser beam; and secondary ion mass spectrometry, for which the target is directly submitted to a focused ion beam. Both techniques revealed excellent performances for lipid mapping of tissue surfaces. This article will discuss similarities, differences, and specificities of ion images generated by these two techniques in terms of sample preparation, sensitivity, ultimate spatial resolution, and structural analysis.

Oxidative Lipidomics Coming of Age: Advances in Analysis of Oxidized Phospholipids in Physiology and Pathology

“…This fragmentation is favored compared with the loss of the ether-linked chain, and therefore plasmalogen PEs are also detected. An interesting application of this labeling approach is that isotope-labeled DMABA (D 0 , D 4 , D 6 , and D 10 ) can be used for differential isotope labeling of samples, allowing relative quantification of the PE profiles in different samples by precursor ion scanning for m/z 191.1, 195.1, 197.1, or 201.1, respectively. This has been used to demonstrate changes in profile of PEs extracted from RAW264.7 cells and subjected to oxidation with the radical initiator AAPH in vitro (153).…”

ToF-SIMS of tissues: “Lessons learned” from mice and women

“…A liquid metal ion gun was used to generate a pulsed 25 keV Bi 3 þ beam for spectra and image acquisition, whereas an electron impact gun was used to generate a 20 keV C 60 2þ beam for sputtering. Both beams are oriented at the sample at an angle of 45 . Primary ion currents were measured before each data set with a Faraday cup.…”

“…Other ToF-SIMS studies have also used this approach of using large area scans for studying other tissues. 15,[45][46][47] A comparison of the ToF-SIMS stitched image to an H&E stained serial tissue slice (nearby slice from same tissue block) shows that some histologic features can be correlated between the two images. As shown in Fig.…”

“…This has been demonstrated by other groups using MALDI and ToF-SIMS images. 45,48 The high spatial resolution of ToF-SIMS enables the ability to extract spectra from very specific regions within a tissue and then compare that data using PCA or other analytical methods. Spectra that are reconstructed from those regions can be used for comparison between tissue types or between the regions themselves.…”

Lipid mapping of colonic mucosa by cluster TOF-SIMS imaging and multivariate analysis in cftr knockout mice

“…This technology consists of the bombardment of the sample by a beam of mono-or polyatomic ions, which induces desorption/ ionization of secondary ions from the sample surface. Polyatomic ion beams have been used successfully in the analysis of organic surfaces with a resolution of some hundreds of nanometers (19)(20)(21)(22)(23)(24), which makes the technology particularly fi t for the analysis of tissue sections ( 19,22,(25)(26)(27)(28)(29)(30)(31)(32). Conversely, MALDI uses a matrix to allow soft desorption/ionization of intact compounds upon laser absorption; it is also adapted to imaging analysis but at a spatial resolution limited to ‫ف‬ 50 µm with the current stateof-the-art.…”