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Graphene-Coated Glass Substrate for Continuous Wave Laser Desorption and Atmospheric Pressure Mass Spectrometric Imaging of Live Hippocampal Tissue
摘要： Atmospheric pressure mass spectrometric (AP-MS) imaging technology combined with an inverted optical microscopic system is a powerful tool for determining the presence and spatial distributions of specific biomolecules of interest in live tissues. Efficient desorption and ionization are essential to acquire mass spectrometric (MS) information in an ambient environment. In this study, we demonstrate a new and efficient desorption process using a graphene-coated glass substrate and a continuous wave (CW) laser for high-resolution AP-MS imaging of live hippocampal tissue. We found that desorption of biomolecules in a live tissue slice was possible with the aid of a graphene-coated glass substrate and indirect application of a 532 nm CW-laser on the graphene substrate. Interestingly, the desorption efficiency of live tissue on the graphene-coated substrate was strongly dependent on the number of graphene layers. Single-layer graphene was found to be the most sensitive substrate for efficient desorption and reproducible high-resolution hippocampal tissue imaging applications. The subsequent ionization process using nonthermal plasma generated sufficient amounts of molecular ions to obtain high-resolution 2-dimensional MS images of the cornu ammonis (CA) and the dentate gyrus (DG) regions of the hippocampus. Therefore, graphene-coated substrates could be a promising platform to induce an efficient desorption process essential for highly reproducible ambient MS imaging.
关键词： Hippocampal tissue,Mass spectrometry imaging,Laser desorption,Graphene-coated substrate,Ambient mass spectrometry
更新于2025-11-25 10:30:42
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An LDI-MSI approach for targeted and untargeted differentiation and assessment of pharmaceutical formulations
摘要： Falsified, counterfeit and adulterated medicines are an endemic problem worldwide that results in both monetary and health-related losses. Developing fast and reliable methods that are able to present a timely result based on the drug’s spectral profile is an effort that is sure to benefit those involved in the whole distribution chain. We propose herein a Laser Desorption/Ionization imaging-based method that provides simple and minimal sample preparation; this method is capable of providing specific markers that characterize adulterations, using as proof of concept one of the most adulterated drug products for oral use, sildenafil. Our approach is able to provide quality markers, which can be applied in the fast screening of any product within the same molecular class. This same strategy may be a useful alternative to provide accurate measurements with high specificity for unraveling contaminants and/or byproducts in virtually any given pharmaceutical product.
关键词： mass spectrometry imaging,LDI,direct analysis,spectral profiles,Falsified medicines
更新于2025-09-23 15:23:52
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Supervised Non-negative Matrix Factorization Methods for MALDI Imaging Applications
摘要： Motivation: Non-negative matrix factorization (NMF) is a common tool for obtaining low-rank approximations of non-negative data matrices and has been widely used in machine learning, e.g., for supporting feature extraction in high-dimensional classification tasks. In its classical form NMF is an unsupervised method, i.e. the class labels of the training data are not used when computing the NMF. However, incorporating the classification labels into the NMF algorithms allows to specifically guide them towards the extraction of data patterns relevant for discriminating the respective classes. This approach is particularly suited for the analysis of mass spectrometry imaging (MSI) data in clinical applications, such as tumor typing and classification, which are amongst the most challenging tasks in pathology. Thus, we investigate algorithms for extracting tumor specific spectral patterns from MSI data by NMF methods. Results: In this paper, we incorporate a priori class labels into the NMF cost functional by adding appropriate supervised penalty terms. Numerical experiments on a MALDI imaging dataset confirm that the novel supervised NMF methods lead to significantly better classification accuracy and stability as compared to other standard approaches.
关键词： MALDI imaging,tumor typing,Non-negative matrix factorization,mass spectrometry imaging,supervised learning
更新于2025-09-23 15:21:01
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Tissue- and sex-specific lipidomic analysis of Schistosoma mansoni using high-resolution atmospheric pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging
摘要： Schistosomes are human pathogens causing the neglected tropical disease schistosomiasis, which occurs worldwide in (sub-)tropical regions. This infectious disease is often associated with poverty, and more than 700 million people are at risk of infection. Exploitation of novel habitats and limited therapeutic options brought schistosomes into research focus. Schistosomes are the only trematodes that have evolved separate sexes. They are covered by their metabolically active tegument, a surface area representing the interface between male and female in their permanent mating contact but also between parasite and host. The tegument comprises, besides others, numerous specific lipid compounds. Limited information is available on the exact lipid composition and its spatial distribution. We used atmospheric-pressure scanning microprobe matrix-assisted laser desorption/ionization (AP-SMALDI) mass spectrometry imaging (MSI) to characterize the Schistosoma mansoni tegument surface in comparison to tissue sections of whole worms or couples. We found that phosphatidylcholines (PC) and specific phosphatidylethanolamines (PE) are significantly more abundant inside the worm body compared to the tegument. On the other hand, the latter was found to be enriched in sphingomyelins (SM), phosphatidylserines (PS), lysophosphatidylcholines (LPC), and specific PE species. We further investigated lipid classes concerning number of carbon atoms in fatty acyl chains as well as the degree of unsaturation and found pronounced differences between the tegument and whole-worm body. Furthermore, differences between male and female teguments were found. The lipid composition of S. mansoni tissues has been investigated in an untargeted, spatially resolved manner for the first time.
关键词： mass spectrometry imaging,phosphatidylserines,phosphatidylethanolamines,sphingomyelins,lipidomic analysis,Schistosoma mansoni,tegument,phosphatidylcholines,lysophosphatidylcholines
更新于2025-09-23 15:21:01
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MALDI MS Imaging at Acquisition Rates Exceeding 100 Pixels per Second
摘要： The practicality of matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) applied to molecular imaging of biological tissues is limited by the analysis speed. Typically, a relatively low speed of stop-and-go micromotion of XY stages is considered as a factor substantially reducing the rate with which fresh sample material can be supplied to the laser spot. The sample scan rate in our laboratory-built high-throughput imaging TOF mass spectrometer was significantly improved through the use of a galvanometer-based optical scanner performing fast laser spot repositioning on a target plate. The optical system incorporated into the ion source of our MALDI TOF mass spectrometer allowed focusing the laser beam via a modified grid into a 10-μm round spot. This permitted the acquisition of high-resolution MS images with a well-defined pixel size at acquisition rates exceeding 100 pixel/s. The influence of selected parameters on the total MS imaging time is discussed. The new scanning technique was employed to display the distribution of an antitumor agent in 3D colorectal adenocarcinoma cell aggregates; a single MS image comprising 100 × 100 pixels with 10-μm lateral resolution was recorded in approximately 70 s.
关键词： MSI,TOF,Mass spectrometry imaging,High throughput,Laser beam scanning,Colorectal adenocarcinoma,3D cell aggregates,Spheroids,Grid ion source,MALDI
更新于2025-09-23 15:21:01
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Unique Distribution of Diacyl-, Alkylacyl-, and Alkenylacyl-Phosphatidylcholine Species Visualized in Pork Chop Tissues by Matrix-Assisted Laser Desorption/Ionizationa??Mass Spectrometry Imaging
摘要： Phosphatidylcholine (PC) is the major phospholipid in meat and in?uences meat qualities, such as healthiness. PC is classi?ed into three groups based on the bond at the sn-1 position: Diacyl, alkylacyl, and alkenylacyl. To investigate their composition and distribution in pork tissues, including longissimus thoracis et lumborum (loin) spinalis muscles, intermuscular fat, and transparent tissues, we performed matrix-assisted laser desorption/ionization–mass spectrometry imaging (MALDI–MSI). Eleven diacyl-, seven alkylacyl-, and six alkenylacyl-PCs were identi?ed using liquid chromatography (LC)-tandem MS (MS/MS) analysis. Despite many alkylacyl- and alkenylacyl-PC species sharing identical m/z values, we were able to visualize these PC species using MALDI–MSI. Diacyl- and alkylacyl- and/or alkenylacyl-PC species showed unique distribution patterns in the tissues, suggesting that their distribution patterns were dependent on their fatty acid compositions. PCs are a major dietary source of choline in meat, and the amount was signi?cantly higher in the muscle tissues. Consumption of choline mitigates age-related memory decline and neurodegenerative diseases; therefore, the consumption of pork muscle tissues could help to mitigate these diseases. These results support the use of MALDI–MSI analysis for assessing the association between PC species and the quality parameters of meat.
关键词： mass spectrometry imaging (MSI),lipid distribution,phosphatidylcholines,liquid chromatography-tandem mass spectrometry (LC-MS/MS),pork,matrix-assisted laser desorption/ionization (MALDI)
更新于2025-09-23 15:19:57
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Application of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging for Evaluating the Quality of Fish Fillets
摘要： Consumption of fish is rapidly increasing worldwide. It is important to evaluate fish fillet quality because fish undergoes physical and chemical changes during frozen storage. Fish fillets exhibit formaldehyde (FA) accumulation from the decomposition of trimethylamine N-oxide. FA is a powerful protein denaturant; thus, it is important to avoid FA buildup during fish processing to preserve fish quality, especially texture. To determine where FA accumulates, in order to maintain the quality of fish fillets, we performed matrix-assisted laser desorption/ionization mass spectrometry imaging, aiming to identify muscle-derived peptides, which reflect conditions such as denaturation and/or aggregation. We used frozen sections from which lipophilic molecules were washed out and detected various peptide peaks. Furthermore, we tried to identify indices to represent fish fillet softening by protease treatment. We could detect characteristic peaks owing to FA and protease treatment; the findings were consistent with the results of texture profiles showing fish fillet’s real solidity. These molecules might thus serve as effective markers to evaluate fish fillet quality.
关键词： mass spectrometry imaging,peptide,matrix-assisted laser desorption/ionization,protease,formaldehyde
更新于2025-09-23 15:19:57
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Phospholipid imaging of zebrafish exposed to fipronil using atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry
摘要： Mass spectrometry imaging can effectively detect and reflect the information of molecular spatial distribution, and has been widely used for in situ analysis of endogenous or exogenous molecules in organisms. The present work applied the atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry (AP-MALDI-MS) in the imaging of whole zebrafish slices exposed to fipronil. The chemical fingerprints in the range of m/z 600-950 showed significant differences in phospholipids between the fipronil exposed and untreated zebrafish groups. The major perturbed phospholipids were identified as PC(34:2), PC(34:1), PC(34:2)+Na, PC(36:4), PC(38:6), and PS(18:0/22:6), PI(18:0/20:4), PI(18:1/20:4) etc. Our results indicated that the exposure of fipronil obviously affected the phospholipid metabolism of zebrafish, especially of the fish eye region. Our work provides a new method or possibility for toxicological study and related metabolic analysis of pesticides in animals.
关键词： Fipronil,In vivo Phospholipids,Mass spectrometry imaging,MALDI,Zebra fish
更新于2025-09-19 17:13:59
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Mass spectrometry imaging of thin-layer chromatography plates using laser desorption/low-temperature plasma ionisation
摘要： Thin-layer chromatography (TLC) is a classic method for the separation and analysis of complex mixtures. Biological assays, chemical derivatisation and spectroscopy techniques are compatible with TLC and provide extra information about isolated compounds. However, coupling TLC to mass spectrometry is hampered by the difficulty to desorb the analytes from the silica surfaces. In this study, we used a multimodal ion source for laser desorption (LD) and low-temperature plasma (LTP) post-ionisation. Efficient desorption was reached by covering the TLC plates with activated carbon. Regions of interest can be analysed by spots, by lines or by area. We show the separation of methylxanthines from coffee, tea and cocoa preparations by TLC, with subsequent mass spectrometry imaging (MSI). Using a lateral resolution of 400 mm × 400 mm, allowed the acquisition of 21,895 spectra in 2.4 h (2.5 pixels/s). Further, we demonstrate the possibility of direct mass fragmentation studies and quantification. We mounted the system on an Open LabBot with a theoretical lateral resolution of 12.5 mm and performed the visualisation of ions of interest and the pixel-wise review of mass spectra with our free software RmsiGUI (https://bitbucket.org/lababi/rmsigui). This non-proprietary and modular platform enables the cost-efficient adaption of the system and further development by the community.
关键词： mass spectrometry imaging,thin-layer chromatography,low-temperature plasma,laser desorption,ambient ionisation
更新于2025-09-19 17:13:59
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Silicon‐Based Laser Desorption Ionization Mass Spectrometry for the Analysis of Biomolecules: A Progress Report
摘要： Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is widely used in the biomedical field for the label-free analysis of molecules such as drugs, lipids, peptides, proteins, and biological tissues for molecular imaging. However, organic matrices used in traditional MALDI-MS applications introduce excessive interferences in the low m/z range. For this reason, nanostructured materials—and in particular silicon-based LDI strategies—have become a promising alternative, since they provide a much weaker background. Herein, the recent developments in fabrication, functionalization, and practical applications of silicon-based LDI-MS methods are reviewed. Also the basic requirements of silicon-based substrates for optimal LDI analysis by providing an overview of the LDI mechanisms that use silicon-based substrates instead of organic matrices are reported. Finally, the considerable potential of silicon-based substrates is discussed, giving suggestions for topics for future research.
关键词： silicon nanostructures,laser desorption ionization (LDI),surface functionalization,mass spectrometry imaging (MSI)
更新于2025-09-19 17:13:59