Silver-Assisted
Laser Desorption Ionization For High
Spatial Resolution Imaging Mass Spectrometry of Olefins from Thin
Tissue Sections
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Abstract
Silver
has been demonstrated to be a powerful cationization agent
in mass spectrometry (MS) for various olefinic species such as cholesterol
and fatty acids. This work explores the utility of metallic silver
sputtering on tissue sections for high resolution imaging mass spectrometry
(IMS) of olefins by laser desorption ionization (LDI). For this purpose,
sputtered silver coating thickness was optimized on an assorted selection
of mouse and rat tissues including brain, kidney, liver, and testis.
For mouse brain tissue section, the thickness was adjusted to 23 ±
2 nm of silver to prevent ion suppression effects associated with
a higher cholesterol and lipid content. On all other tissues, a thickness
of at 16 ± 2 nm provided the best desorption/ionization efficiency.
Characterization of the species by MS/MS showed a wide variety of
olefinic compounds allowing the IMS of different lipid classes including
cholesterol, arachidonic acid, docosahexaenoic acid, and triacylglyceride
52:3. A range of spatial resolutions for IMS were investigated from
150 μm down to the high resolution cellular range at 5 μm.
The applicability of direct on-tissue silver sputtering to LDI-IMS
of cholesterol and other olefinic compounds presents a novel approach
to improve the amount of information that can be obtained from tissue
sections. This IMS strategy is thus of interest for providing new
biological insights on the role of cholesterol and other olefins in
physiological pathways or disease