4 research outputs found
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
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
Silver-Assisted Laser Desorption Ionization For High Spatial Resolution Imaging Mass Spectrometry of Olefins from Thin Tissue Sections
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
Histology-Driven Data Mining of Lipid Signatures from Multiple Imaging Mass Spectrometry Analyses: Application to Human Colorectal Cancer Liver Metastasis Biopsies
Imaging mass spectrometry (IMS) represents an innovative
tool in
the cancer research pipeline, which is increasingly being used in
clinical and pharmaceutical applications. The unique properties of
the technique, especially the amount of data generated, make the handling
of data from multiple IMS acquisitions challenging. This work presents
a histology-driven IMS approach aiming to identify discriminant lipid
signatures from the simultaneous mining of IMS data sets from multiple
samples. The feasibility of the developed workflow is evaluated on
a set of three human colorectal cancer liver metastasis (CRCLM) tissue
sections. Lipid IMS on tissue sections was performed using MALDI-TOF/TOF
MS in both negative and positive ionization modes after 1,5-diaminonaphthalene
matrix deposition by sublimation. The combination of both positive
and negative acquisition results was performed during data mining
to simplify the process and interrogate a larger lipidome into a single
analysis. To reduce the complexity of the IMS data sets, a sub data
set was generated by randomly selecting a fixed number of spectra
from a histologically defined region of interest, resulting in a 10-fold
data reduction. Principal component analysis confirmed that the molecular
selectivity of the regions of interest is maintained after data reduction.
Partial least-squares and heat map analyses demonstrated a selective
signature of the CRCLM, revealing lipids that are significantly up-
and down-regulated in the tumor region. This comprehensive approach
is thus of interest for defining disease signatures directly from
IMS data sets by the use of combinatory data mining, opening novel
routes of investigation for addressing the demands of the clinical
setting
New Microfluidic-Based Sampling Procedure for Overcoming the Hematocrit Problem Associated with Dried Blood Spot Analysis
Hematocrit (Hct) is one of the most
critical issues associated
with the bioanalytical methods used for dried blood spot (DBS) sample
analysis. Because Hct determines the viscosity of blood, it may affect
the spreading of blood onto the filter paper. Hence, accurate quantitative
data can only be obtained if the size of the paper filter extracted
contains a fixed blood volume. We describe for the first time a microfluidic-based
sampling procedure to enable accurate blood volume collection on commercially
available DBS cards. The system allows the collection of a controlled
volume of blood (e.g., 5 or 10 μL) within several seconds. Reproducibility
of the sampling volume was examined in vivo on capillary blood by
quantifying caffeine and paraxanthine on 5 different extracted DBS
spots at two different time points and in vitro with a test compound,
Mavoglurant, on 10 different spots at two Hct levels. Entire spots
were extracted. In addition, the accuracy and precision (<i>n</i> = 3) data for the Mavoglurant quantitation in blood with Hct levels
between 26% and 62% were evaluated. The interspot precision data were
below 9.0%, which was equivalent to that of a manually spotted volume
with a pipet. No Hct effect was observed in the quantitative results
obtained for Hct levels from 26% to 62%. These data indicate that
our microfluidic-based sampling procedure is accurate and precise
and that the analysis of Mavoglurant is not affected by the Hct values.
This provides a simple procedure for DBS sampling with a fixed volume
of capillary blood, which could eliminate the recurrent Hct issue
linked to DBS sample analysis