2 research outputs found
Oversampling To Improve Spatial Resolution for Liquid Extraction Mass Spectrometry Imaging
Liquid
extraction mass spectrometry imaging (MSI) experiments provide
users with direct analysis of biological surfaces with minimal sample
preparation. Until now, much of the effort to increase spatial resolution
for MSI with liquid extraction techniques has focused on reducing
the size of the sampling area. However, this can be experimentally
challenging. Here, we present oversampling as a simple alternative
to increase the spatial resolution using nanospray desorption electrospray
ionization (nano-DESI) MSI. By imaging partial rat spinal cord tissue
sections, two major concerns with oversampling are addressed: whether
endogenous molecules are significantly depleted from repeated sampling
events and whether analytes are redistributed as a result of oversampling.
In depth examination of ion images for representative analytes show
that depletion and redistribution do not affect analyte localization
in the tissue sample. Nano-DESI MSI experiments using three times
oversampling provided higher spatial resolution, allowing the observation
of features not visible with undersampling. Although proper care must
be taken to ensure that oversampling will work in specific applications,
we envision oversampling as a simple approach to increase image quality
for liquid extraction MSI techniques
Quantitative Mass Spectrometry Imaging of Prostaglandins as Silver Ion Adducts with Nanospray Desorption Electrospray Ionization
Prostaglandins
(PG) are an important class of lipid biomolecules
that are essential in many biological processes, including inflammation
and successful pregnancy. Despite a high bioactivity, physiological
concentrations are typically low, which makes direct mass spectrometric
analysis of endogenous PG species challenging. Consequently, there
have not been any studies investigating PG localization to specific
morphological regions in tissue sections using mass spectrometry imaging
(MSI) techniques. Herein, we show that silver ions, added to the solvent
used for nanospray desorption electrospray ionization (nano-DESI)
MSI, enhances the ionization of PGs and enables nano-DESI MSI
of several species in uterine tissue from day 4 pregnant mice. It
was found that detection of [PG + Ag]<sup>+</sup> ions increased the
sensitivity by ∼30 times, when compared to [PG – H]<sup>−</sup> ions. Further, the addition of isotopically labeled
internal standards enabled generation of quantitative ion images for
the detected PG species. Increased sensitivity and quantitative MSI
enabled the first proof-of-principle results detailing PG localization
in mouse uterus tissue sections. These results show that PG species
primarily localized to cellular regions of the luminal epithelium
and glandular epithelium in uterine tissue. Further, this study provides
a unique scaffold for future studies investigating the PG distribution
within biological tissue samples