Obtaining high-quality matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) images and the reproducibility of the technique depend strongly on the sample preparation protocol. The most crucial part is the application of the MALDI matrix, which often relies on expensive spraying or sublimation coaters. In this work, we present a new dual-polarity matrix for MALDI mass spectrometry imaging (MSI): Basic Blue 7 (BB7), which belongs to the group of triarylmethane dyes. Thanks to its good solubility in water, this matrix allows a quick and simple sample preparation protocol without the need for sophisticated spraying or sublimation instrumentation: dipping the glass with tissue into the dye solution. This technique closely resembles the staining methods employed in classical histopathology. The technique is demonstrated on MSI of lipids in mouse brain sections in positive and negative ion modes using a subatmospheric pressure MALDI source coupled with an orbital trap mass spectrometer. The results are compared with traditional matrices, such as 2,5-dihydroxybenzoic acid (DHB) and 1,5-diaminonaphthalene (DAN). BB7 excels, especially in negative ion mode, offering low background signals and high signal intensities of many lipid classes. Furthermore, the stained tissue can simply be inspected visually and allows basic histopathology annotation prior to MSI. Here, we demonstrate that staining offers excellent image quality, reproducible sample preparation, and the potential for automation and utilization for high spatial resolution MSI.

• MeSH
• Staining and Labeling * MeSH
• Coloring Agents * chemistry   MeSH
• Lipids analysis   MeSH
• Brain Chemistry MeSH
• Brain metabolism   MeSH
• Mice MeSH
• Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization * methods   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Coloring Agents * MeSH
• Lipids MeSH

Cancer cells depend on nucleotides for proliferation. Inhibition of nucleotide metabolism by antimetabolites is a well-established anticancer therapy. However, resistance and toxicity to antimetabolite treatments reduce their effectiveness. Here, we focus on the pyrimidine de novo synthesis pathway, which is crucial for cancer cell proliferation, yet its pharmacological targeting in cancer has been without much clinical success so far. Hence, it is important to understand how cancer cells cope with the insufficiency of this pathway. Here, we describe a procedure to prepare subcutaneous tumor model deficient in de novo pyrimidine synthesis. For examination of metabolic responses to de novo synthesis blockade in tumors, we propose application of MALDI imaging that allows spatially resolved examination of metabolic responses to de novo synthesis blockade in tumors.

• Keywords
• CRISPR/Cas9, Cancer, MALDI, Metabolism, Nucleotides, Pyrimidines,
• MeSH
• Humans MeSH
• Neoplasms * metabolism   MeSH
• Nucleotides MeSH
• Spatial Analysis MeSH
• Pyrimidines MeSH
• Clustered Regularly Interspaced Short Palindromic Repeats * MeSH
• Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Nucleotides MeSH
• Pyrimidines MeSH

Pathological pain subtypes can be classified as either neuropathic pain, caused by a somatosensory nervous system lesion or disease, or nociplastic pain, which develops without evidence of somatosensory system damage. Since there is no gold standard for the diagnosis of pathological pain subtypes, the proper classification of individual patients is currently an unmet challenge for clinicians. While the determination of specific biomarkers for each condition by current biochemical techniques is a complex task, the use of multimolecular techniques, such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), combined with artificial intelligence allows specific fingerprints for pathological pain-subtypes to be obtained, which may be useful for diagnosis. We analyzed whether the information provided by the mass spectra of serum samples of four experimental models of neuropathic and nociplastic pain combined with their functional pain outcomes could enable pathological pain subtype classification by artificial neural networks. As a result, a simple and innovative clinical decision support method has been developed that combines MALDI-TOF MS serum spectra and pain evaluation with its subsequent data analysis by artificial neural networks and allows the identification and classification of pathological pain subtypes in experimental models with a high level of specificity.

• Keywords
• MALDI-TOF MS, artificial intelligence, diagnostics, fibromyalgia, mass spectrometry, neuropathic pain,
• MeSH
• Pain diagnosis   MeSH
• Humans MeSH
• Neural Networks, Computer * MeSH
• Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization methods   MeSH
• Artificial Intelligence * MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Intact (whole) cell matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) is an established method for biotyping in clinical microbiology as well as for revealing phenotypic shifts in cultured eukaryotic cells. Intact cell MALDI-TOF MS has recently been introduced as a quality control tool for long-term cultures of pluripotent stem cells. Despite the potential this method holds for revealing minute changes in cells, there is still a need for improving the ionization efficiency or peak reproducibility. Here we report for the first time that supplementation by fine particles of black phosphorus to the standard MALDI matrices, such as sinapinic and α-cyano-4-hydroxycinnamic acids enhance intensities of mass spectra of particular amino acids and peptides, presumably by interactions with aromatic groups within the molecules. In addition, the particles of black phosphorus induce the formation of small and regularly dispersed crystals of sinapinic acid and α-cyano-4-hydroxycinnamic acid with the analyte on a steel MALDI target plate. Patterns of mass spectra recorded from intact cells using black phosphorus-enriched matrix were more reproducible and contained peaks of higher intensities when compared to matrix without black phosphorus supplementation. In summary, enrichment of common organic matrices by black phosphorus can improve discrimination data analysis by enhancing peak intensity and reproducibility of mass spectra acquired from intact cells.

• MeSH
• Amino Acids analysis   chemistry   MeSH
• Cell Culture Techniques methods   MeSH
• Cell Line MeSH
• Phosphorus chemistry   MeSH
• Humans MeSH
• Human Embryonic Stem Cells MeSH
• Peptides analysis   chemistry   MeSH
• Reproducibility of Results MeSH
• Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization methods   standards   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Amino Acids MeSH
• Phosphorus MeSH
• Peptides MeSH

Amorphous chalcogenide thin films are widely studied due to their enhanced properties and extensive applications. Here, we have studied amorphous Ga-Sb-Se chalcogenide thin films prepared by magnetron co-sputtering, via laser ablation quadrupole ion trap time-of-flight mass spectrometry. Furthermore, the stoichiometry of the generated clusters was determined which gives information about individual species present in the plasma plume originating from the interaction of amorphous chalcogenides with high energy laser pulses. Seven different compositions of thin films (Ga content 7.6-31.7 at. %, Sb content 5.2-31.2 at. %, Se content 61.2-63.3 at. %) were studied and in each case about ~50 different clusters were identified in positive and ~20-30 clusters in negative ion mode. Assuming that polymers can influence the laser desorption (laser ablation) process, we have used parafilm as a material to reduce the destruction of the amorphous network structure and/or promote the laser ablation synthesis of heavier species from those of lower mass. In this case, many new and higher mass clusters were identified. The maximum number of (40) new clusters was detected for the Ga-Sb-Se thin film containing the highest amount of antimony (31.2 at. %). This approach opens new possibilities for laser desorption ionization/laser ablation study of other materials. Finally, for selected binary and ternary clusters, their structure was calculated by using density functional theory optimization procedure.

• Publication type
• Journal Article MeSH

The formation of W x O y+●/-● clusters in the gas phase was studied by laser desorption ionization (LDI) and matrix assisted laser desorption ionization (MALDI) of solid WO3. LDI produced (WO3) n+ ●/- ● (n = 1-7) clusters. In MALDI, when using nano-diamonds (NDs), graphene oxide (GO), or fullerene (C60) matrices, higher mass clusters were generated. In addition to (WO3) n-● clusters, oxygen-rich or -deficient species were found in both LDI and MALDI (with the total number of clusters exceeding one hundred ≈ 137). This is the first time that such matrices have been used for the generation of(WO3) n+●/-● clusters in the gas phase, while new high mass clusters (WO3) n-● (n = 12-19) were also detected. Graphical Abstract.

• Keywords
• Fullerene C60, Graphene oxide matrices, Laser desorption ionization, Nano-diamonds, Quadrupole ion trap, TOF mass spectrometry, WO3 clusters,
• Publication type
• Journal Article MeSH

Laser desorption ionization using time-of-flight mass spectrometer afforded with quadrupole ion trap was used to study As2Ch3 (Ch = S, Se, and Te) bulk chalcogenide materials. The main goal of the study is the identification of species present in the plasma originating from the interaction of laser pulses with solid state material. The generated clusters in both positive and negative ion mode are identified as 10 unary (S p+/- and As m+/- ) and 34 binary (As m S p+/- ) species for As2S3 glass, 2 unary (Se q+/- ) and 26 binary (As m Se q+/- ) species for As2Se3 glass, 7 unary (Te r+/- ) and 23 binary (As m Te r+/- ) species for As2Te3 material. The fragmentation of chalcogenide materials was diminished using some polymers and in this way 45 new, higher mass clusters have been detected. This novel approach opens a new possibility for laser desorption ionization mass spectrometry analysis of chalcogenides as well as other materials. Graphical abstract ᅟ.

• Keywords
• Chalcogenides, Clusters, Laser desorption ionization, Structure, Time-of-flight mass spectrometry,
• Publication type
• Journal Article MeSH

Precise calibration in TOF MS requires suitable and reliable standards, which are not always available for high masses. We evaluated inorganic clusters of the monoisotopic elements gold and phosphorus (Au n+/Au n- and P n+/P n-) as an alternative to peptides or proteins for the external and internal calibration of mass spectra in various experimental and instrumental scenarios. Monoisotopic gold or phosphorus clusters can be easily generated in situ from suitable precursors by laser desorption/ionization (LDI) or matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Their use offers numerous advantages, including simplicity of preparation, biological inertness, and exact mass determination even at lower mass resolution. We used citrate-stabilized gold nanoparticles to generate gold calibration clusters, and red phosphorus powder to generate phosphorus clusters. Both elements can be added to samples to perform internal calibration up to mass-to-charge (m/z) 10-15,000 without significantly interfering with the analyte. We demonstrated the use of the gold and phosphorous clusters in the MS analysis of complex biological samples, including microbial standards and total extracts of mouse embryonic fibroblasts. We believe that clusters of monoisotopic elements could be used as generally applicable calibrants for complex biological samples. Graphical Abstract ᅟ.

• Keywords
• Calibration, Gold clusters, Monoisotopic elements, Phosphorus clusters, TOF mass spectrometry,
• Publication type
• Journal Article MeSH