Sublimation of New Matrix
Candidates for High Spatial
Resolution Imaging Mass Spectrometry of Lipids: Enhanced Information
in Both Positive and Negative Polarities after 1,5-Diaminonapthalene
Deposition
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Abstract
Matrix sublimation has demonstrated to be a powerful
approach for
high-resolution matrix-assisted laser desorption ionization (MALDI)
imaging of lipids, providing very homogeneous solvent-free deposition.
This work presents a comprehensive study aiming to evaluate current
and novel matrix candidates for high spatial resolution MALDI imaging
mass spectrometry of lipids from tissue section after deposition by
sublimation. For this purpose, 12 matrices including 2,5-dihydroxybenzoic
acid (DHB), sinapinic acid (SA), α-cyano-4-hydroxycinnamic acid
(CHCA), 2,6-dihydroxyacetphenone (DHA), 2′,4′,6′-trihydroxyacetophenone
(THAP), 3-hydroxypicolinic acid (3-HPA), 1,8-bis(dimethylamino)naphthalene
(DMAN), 1,8,9-anthracentriol (DIT), 1,5-diaminonapthalene (DAN), <i>p</i>-nitroaniline (NIT), 9-aminoacridine (9-AA), and 2-mercaptobenzothiazole
(MBT) were investigated for lipid detection efficiency in both positive
and negative ionization modes, matrix interferences, and stability
under vacuum. For the most relevant matrices, ion maps of the different
lipid species were obtained from tissue sections at high spatial resolution
and the detected peaks were characterized by matrix-assisted laser
desorption ionization time-of-flight/time-of-flight (MALDI-TOF/TOF)
mass spectrometry. First proposed for imaging mass spectrometry (IMS)
after sublimation, DAN has demonstrated to be of high efficiency providing
rich lipid signatures in both positive and negative polarities with
high vacuum stability and sub-20 μm resolution capacity. Ion
images from adult mouse brain were generated with a 10 μm scanning
resolution. Furthermore, ion images from adult mouse brain and whole-body
fish tissue sections were also acquired in both polarity modes from
the same tissue section at 100 μm spatial resolution. Sublimation
of DAN represents an interesting approach to improve information with
respect to currently employed matrices providing a deeper analysis
of the lipidome by IMS