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Sarretto T, Gardner W, Brungs D, Napaki S, Pigram PJ, Ellis SR. A Machine Learning-Driven Comparison of Ion Images Obtained by MALDI and MALDI-2 Mass Spectrometry Imaging. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:466-475. [PMID: 38407924 DOI: 10.1021/jasms.3c00357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) enables label-free imaging of biomolecules in biological tissues. However, many species remain undetected due to their poor ionization efficiencies. MALDI-2 (laser-induced post-ionization) is the most widely used post-ionization method for improving analyte ionization efficiencies. Mass spectra acquired using MALDI-2 constitute a combination of ions generated by both MALDI and MALDI-2 processes. Until now, no studies have focused on a detailed comparison between the ion images (as opposed to the generated m/z values) produced by MALDI and MALDI-2 for mass spectrometry imaging (MSI) experiments. Herein, we investigated the ion images produced by both MALDI and MALDI-2 on the same tissue section using correlation analysis (to explore similarities in ion images for ions common to both MALDI and MALDI-2) and a deep learning approach. For the latter, we used an analytical workflow based on the Xception convolutional neural network, which was originally trained for human-like natural image classification but which we adapted to elucidate similarities and differences in ion images obtained using the two MSI techniques. Correlation analysis demonstrated that common ions yielded similar spatial distributions with low-correlation species explained by either poor signal intensity in MALDI or the generation of additional unresolved signals using MALDI-2. Using the Xception-based method, we identified many regions in the t-SNE space of spatially similar ion images containing MALDI and MALDI-2-related signals. More notably, the method revealed distinct regions containing only MALDI-2 ion images with unique spatial distributions that were not observed using MALDI. These data explicitly demonstrate the ability of MALDI-2 to reveal molecular features and patterns as well as histological regions of interest that are not visible when using conventional MALDI.
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Affiliation(s)
- Tassiani Sarretto
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia, 2522
| | - Wil Gardner
- Centre for Materials and Surface Science and Department of Mathematical and Physical Sciences, La Trobe University, Bundoora, Australia, 3086
| | - Daniel Brungs
- Graduate School of Medicine, University of Wollongong, Wollongong, Australia, 2522
| | - Sarbar Napaki
- Graduate School of Medicine, University of Wollongong, Wollongong, Australia, 2522
| | - Paul J Pigram
- Centre for Materials and Surface Science and Department of Mathematical and Physical Sciences, La Trobe University, Bundoora, Australia, 3086
| | - Shane R Ellis
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia, 2522
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2
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Steven RT, Burton A, Taylor AJ, Robinson KN, Dexter A, Nikula CJ, Bunch J. Evaluation of Inlet Temperature with Three Sprayer Designs for Desorption Electrospray Ionization Mass Spectrometry Tissue Analysis. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:224-233. [PMID: 38181191 DOI: 10.1021/jasms.3c00332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2024]
Abstract
Mass spectrometry imaging (MSI) allows for the spatially resolved detection of endogenous and exogenous molecules and atoms in biological samples, typically prepared as thin tissue sections. Desorption electrospray ionization (DESI) is one of the most commonly utilized MSI modalities in preclinical research. DESI ion source technology is still rapidly evolving, with new sprayer designs and heated inlet capillaries having recently been incorporated in commercially available systems. In this study, three iterations of DESI sprayer designs are evaluated: (1) the first, and until recently only, commercially available Waters sprayer; (2) a developmental desorption electro-flow focusing ionization (DEFFI)-type sprayer; and (3) a prototype of the newly released Waters commercial sprayer. A heated inlet capillary is also employed, allowing for controlled inlet temperatures up to 500 °C. These three sprayers are evaluated by comparative tissue imaging analyses of murine testes across this temperature range. Single ion intensity versus temperature trends are evaluated as exemplar cases for putatively identified species of interest, such as lactate and glutamine. A range of trends are observed, where intensities follow either increasing, decreasing, bell-shaped, or other trends with temperature. Data for all sprayers show approximately similar trends for the ions studied, with the commercial prototype sprayer (sprayer version 3) matching or outperforming the other sprayers for the ions investigated. Finally, the mass spectra acquired using sprayer version 3 are evaluated by uniform manifold approximation and projection (UMAP) and k-means clustering. This approach is shown to provide valuable insight that is complementary to the presented univariate evaluation for reviewing the parameter space in this study. Full spectral temperature optimization data are provided as supporting data to enable other researchers to design experiments that are optimal for specific ions.
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Affiliation(s)
- Rory T Steven
- National Physical Laboratory Teddington TW11 0LW, U.K
| | - Amy Burton
- National Physical Laboratory Teddington TW11 0LW, U.K
| | - Adam J Taylor
- National Physical Laboratory Teddington TW11 0LW, U.K
| | | | - Alex Dexter
- National Physical Laboratory Teddington TW11 0LW, U.K
| | | | - Josephine Bunch
- National Physical Laboratory Teddington TW11 0LW, U.K
- Imperial College London, Department of Metabolism, Digestion and Reproduction, Sir Alexander Fleming Building, South Kensington Campus, London SW7 2AZ, U.K
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3
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Vandenbosch M, Mutuku SM, Mantas MJQ, Patterson NH, Hallmark T, Claesen M, Heeren RMA, Hatcher NG, Verbeeck N, Ekroos K, Ellis SR. Toward Omics-Scale Quantitative Mass Spectrometry Imaging of Lipids in Brain Tissue Using a Multiclass Internal Standard Mixture. Anal Chem 2023; 95:18719-18730. [PMID: 38079536 DOI: 10.1021/acs.analchem.3c02724] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Mass spectrometry imaging (MSI) has accelerated our understanding of lipid metabolism and spatial distribution in tissues and cells. However, few MSI studies have approached lipid imaging quantitatively and those that have focused on a single lipid class. We overcome this limitation by using a multiclass internal standard (IS) mixture sprayed homogeneously over the tissue surface with concentrations that reflect those of endogenous lipids. This enabled quantitative MSI (Q-MSI) of 13 lipid classes and subclasses representing almost 200 sum-composition lipid species using both MALDI (negative ion mode) and MALDI-2 (positive ion mode) and pixel-wise normalization of each lipid species in a manner analogous to that widely used in shotgun lipidomics. The Q-MSI approach covered 3 orders of magnitude in dynamic range (lipid concentrations reported in pmol/mm2) and revealed subtle changes in distribution compared to data without normalization. The robustness of the method was evaluated by repeating experiments in two laboratories using both timsTOF and Orbitrap mass spectrometers with an ∼4-fold difference in mass resolution power. There was a strong overall correlation in the Q-MSI results obtained by using the two approaches. Outliers were mostly rationalized by isobaric interferences or the higher sensitivity of one instrument for a particular lipid species. These data provide insight into how the mass resolving power can affect Q-MSI data. This approach opens up the possibility of performing large-scale Q-MSI studies across numerous lipid classes and subclasses and revealing how absolute lipid concentrations vary throughout and between biological tissues.
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Affiliation(s)
- Michiel Vandenbosch
- Maastricht MultiModal Molecular Imaging (M4I) Institute, Division of Imaging Mass Spectrometry, Maastricht University, Maastricht 6229ER, Netherlands
| | - Shadrack M Mutuku
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | | | | | | | | | - Ron M A Heeren
- Maastricht MultiModal Molecular Imaging (M4I) Institute, Division of Imaging Mass Spectrometry, Maastricht University, Maastricht 6229ER, Netherlands
| | - Nathan G Hatcher
- Merck & Co., Inc., 770 Sumneytown Pk, West Point, Pennsylvania 19486, United States
| | | | - Kim Ekroos
- Lipidomics Consulting Ltd., Esbo 02230, Finland
| | - Shane R Ellis
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
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4
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Feucherolles M, Le W, Bour J, Jacques C, Duplan H, Frache G. A Comprehensive Comparison of Tissue Processing Methods for High-Quality MALDI Imaging of Lipids in Reconstructed Human Epidermis. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:2469-2480. [PMID: 37843012 PMCID: PMC10623569 DOI: 10.1021/jasms.3c00185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 09/27/2023] [Accepted: 09/29/2023] [Indexed: 10/17/2023]
Abstract
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) has become an important tool for skin analysis, as it allows the simultaneous detection and localization of diverse molecular species within a sample. The use of in vivo and ex vivo human skin models is costly and presents ethical issues; therefore, reconstructed human epidermis (RHE) models, which mimic the upper part of native human skin, represent a suitable alternative to investigate adverse effects of chemicals applied to the skin. However, there are few publications investigating the feasibility of using MALDI MSI on RHE models. Therefore, the aim of this study was to investigate the effect of sample preparation techniques, i.e., substrate, sample thickness, washing, and matrix recrystallization, on the quality of MALDI MSI for lipids analysis of the SkinEthic RHE model. Images were generated using an atmospheric pressure MALDI source coupled to a high-resolution mass spectrometer with a pixel size of 5 μm. Masses detected in a defined region of interest were analyzed and annotated using the LipostarMSI platform. The results indicated that the combination of (1) coated metallic substrates, such as APTES-coated stainless-steel plates, (2) tissue sections of 6 μm thickness, and (3) aqueous washing before HCCA matrix spraying (without recrystallization), resulted in images with a significant signal intensity as well as numerous m/z values. This refined methodology using AP-MALDI coupled to a high-resolution mass spectrometer should improve the current sample preparation workflow to evaluate changes in skin composition after application of dermatocosmetics.
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Affiliation(s)
- Maureen Feucherolles
- Luxembourg
Institute of Science and Technology (LIST), Molecular and Thermal Analysis, Materials Research
and Technology, L-4422 Belvaux, Luxembourg
| | - William Le
- Luxembourg
Institute of Science and Technology (LIST), Molecular and Thermal Analysis, Materials Research
and Technology, L-4422 Belvaux, Luxembourg
| | - Jérôme Bour
- Luxembourg
Institute of Science and Technology (LIST), Molecular and Thermal Analysis, Materials Research
and Technology, L-4422 Belvaux, Luxembourg
| | - Carine Jacques
- Pierre
Fabre Dermo-Cosmétique et Personal Care, Centre R&D Pierre Fabre, Avenue Hubert Curien, 31025 Toulouse Cedex 01, France
| | - Hélène Duplan
- Pierre
Fabre Dermo-Cosmétique et Personal Care, Centre R&D Pierre Fabre, Avenue Hubert Curien, 31025 Toulouse Cedex 01, France
| | - Gilles Frache
- Luxembourg
Institute of Science and Technology (LIST), Molecular and Thermal Analysis, Materials Research
and Technology, L-4422 Belvaux, Luxembourg
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Metarapi D, van Elteren JT. High-resolution single pulse LA-ICP-MS mapping via 2D sub-pixel oversampling on orthogonal and hexagonal ablation grids - A computational assessment. Talanta 2023; 263:124699. [PMID: 37267882 DOI: 10.1016/j.talanta.2023.124699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 05/16/2023] [Accepted: 05/22/2023] [Indexed: 06/04/2023]
Abstract
Laser beam profiles in analytical laser ablation - inductively coupled plasma - mass spectrometry (LA-ICP-MS) instruments are in general homogenized to produce a flat-top beam profile. However, in practice, they are mostly super-Gaussian in nature, and for small laser beam sizes (<5 μm) they even approach a Gaussian profile. This implies that the amount of surface material sampled by the laser (=ablation volume) directly depends on the beam profile and ablation grid. By contraction of the ablation grid (=sub-pixel mapping) not only more accurate surface sampling is realized, but also a higher pixel density, an improved spatial resolution, and a better signal-to-noise ratio. Although LA sampling is predominantly performed on an orthogonal grid, hexagonal or staggered/interleaved sampling may further improve the image quality as regular hexagons are more compact than squares (=lower perimeter/area) and suffer less from orientation bias (=lower anisotropy). Due to the current limitations of LA stages in executing precise hexagonal sampling with small beam sizes, computational protocols were employed to simulate LA-ICP-MS mapping. Simulation was performed by discrete convolution using the crater profile as the kernel, followed by the application/addition of Poisson/Flicker noise related to the local concentration and instrumental sensitivity/noise. A freely accessible online app was developed (https://laicpms-apps.ki.si/webapps/home/) to study the effect of sampling grid contraction (orthogonal and hexagonal) on the image map quality (spatial resolution and signal-to-noise ratio) by virtual ablation of phantoms. Comparison of experimental LA-ICP-MS maps obtained through orthogonal and hexagonal sampling methods could only be performed using a beam size of 150 μm and a macroscale inkjet-printed resolution target. This was due to the unavailability of precise hexagonal sampling stages and microscale resolution targets, which prevented the use of smaller beam sizes.
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Affiliation(s)
- Dino Metarapi
- Department of Analytical Chemistry, National Institute of Chemistry, Hajdrihova 19, 1000, Ljubljana, Slovenia
| | - Johannes T van Elteren
- Department of Analytical Chemistry, National Institute of Chemistry, Hajdrihova 19, 1000, Ljubljana, Slovenia.
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Lohani V, A.R A, Kundu S, Akhter MDQ, Bag S. Single-Cell Proteomics with Spatial Attributes: Tools and Techniques. ACS OMEGA 2023; 8:17499-17510. [PMID: 37251119 PMCID: PMC10210017 DOI: 10.1021/acsomega.3c00795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 04/12/2023] [Indexed: 05/31/2023]
Abstract
Now-a-days, the single-cell proteomics (SCP) concept is attracting interest, especially in clinical research, because it can identify the proteomic signature specific to diseased cells. This information is very essential when dealing with the progression of certain diseases, such as cancer, diabetes, Alzheimer's, etc. One of the major drawbacks of conventional destructive proteomics is that it gives an average idea about the protein expression profile in the disease condition. During the extraction of the protein from a biopsy or blood sample, proteins may come from both diseased cells and adjacent normal cells or any other cells from the disease environment. Again, SCP along with spatial attributes is utilized to learn about the heterogeneous function of a single protein. Before performing SCP, it is necessary to isolate single cells. This can be done by various techniques, including fluorescence-activated cell sorting (FACS), magnetic-activated cell sorting (MACS), laser capture microdissection (LCM), microfluidics, manual cell picking/micromanipulation, etc. Among the different approaches for proteomics, mass spectrometry-based proteomics tools are widely used for their high resolution as well as sensitivity. This Review mainly focuses on the mass spectrometry-based approaches for the study of single-cell proteomics.
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Affiliation(s)
- Vartika Lohani
- CSIR
Institute of Genomics and Integrative Biology, New Delhi, Delhi 110025, India
- PG Scholar, Department of Pharmacy, Banasthali
Vidyapith, Jaipur, Rajasthan 302001, India
| | - Akhiya A.R
- CSIR
Institute of Genomics and Integrative Biology, New Delhi, Delhi 110025, India
- PG Scholar, Department of Computational
Biology and Bioinformatics, University of
Kerala, Thiruvananthapuram, Kerala 695034, India
| | - Soumen Kundu
- CSIR
Institute of Genomics and Integrative Biology, New Delhi, Delhi 110025, India
- Academy
of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201002, India
| | - MD Quasid Akhter
- CSIR
Institute of Genomics and Integrative Biology, New Delhi, Delhi 110025, India
| | - Swarnendu Bag
- CSIR
Institute of Genomics and Integrative Biology, New Delhi, Delhi 110025, India
- Academy
of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201002, India
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7
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Prysiazhnyi V, Bednařík A, Žalud M, Hegrová V, Neuman J, Preisler J. Fate of Gold Nanoparticles in Laser Desorption/Ionization Mass Spectrometry: Toward the Imaging of Individual Nanoparticles. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:570-578. [PMID: 36917818 PMCID: PMC10080673 DOI: 10.1021/jasms.2c00300] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 02/13/2023] [Accepted: 03/02/2023] [Indexed: 06/14/2023]
Abstract
This study focuses on mapping the spatial distribution of Au nanoparticles (NPs) by laser desorption/ionization mass spectrometry imaging (LDI MSI). Laser interaction with NPs and associated phenomena, such as change of shape, melting, migration, and release of Au ions, are explored at the single particle level. Arrays of dried droplets containing low numbers of spatially segregated NPs were reproducibly prepared by automated drop-on-demand piezo-dispensing and analyzed by LDI MSI using an ultrahigh resolution orbital trapping instrument. To enhance the signal from NPs, an in source gas-phase chemical reaction of generated Au ions with xylene was employed. The developed technique allowed the detecting, chemical characterization, and mapping of the spatial distribution of Au NPs; the ion signals were detected from as low as ten 50 nm Au NPs on a pixel. Furthermore, the Au NP melting dynamics under laser irradiation was monitored by correlative atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM measurements of Au NPs before and after LDI MSI analysis revealed changes in NP shape from a sphere to a half-ellipsoid and total volume reduction of NPs down to 45% of their initial volume.
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Affiliation(s)
- Vadym Prysiazhnyi
- Department
of Chemistry, Faculty of Science, Masaryk
University, 625 00, Brno, Czech
Republic
| | - Antonín Bednařík
- Department
of Chemistry, Faculty of Science, Masaryk
University, 625 00, Brno, Czech
Republic
| | - Michal Žalud
- Department
of Chemistry, Faculty of Science, Masaryk
University, 625 00, Brno, Czech
Republic
| | | | - Jan Neuman
- Nenovision
s. r. o., 612 00, Brno, Czech Republic
| | - Jan Preisler
- Department
of Chemistry, Faculty of Science, Masaryk
University, 625 00, Brno, Czech
Republic
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8
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Bogusiewicz J, Bojko B. Insight into new opportunities in intra-surgical diagnostics of brain tumors. Trends Analyt Chem 2023. [DOI: 10.1016/j.trac.2023.117043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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9
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Bai H, Manni JG, Muddiman DC. Transforming a Mid-infrared Laser Profile from Gaussian to a Top-Hat with a Diffractive Optical Element for Mass Spectrometry Imaging. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:10-16. [PMID: 36542595 PMCID: PMC9975536 DOI: 10.1021/jasms.2c00203] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Many mass spectrometry imaging (MSI) applications such as infrared matrix-assisted electrospray ionization (IR-MALDESI) employ an infrared (IR) laser with a Gaussian profile where laser irradiance is highest in the center and decreases exponentially. To enable full ablation of a square region of interest, oversampling is often needed, which results in nonuniform ablation and leads to decreased image quality. A diffractive optical element (DOE) was integrated into the optical path to generate homogeneous intensity distributions while maintaining laser energy above the ablation threshold, to enable complete sample removal from laser pulses without oversampling. 2D and 3D imaging with the DOE inserted show clear and sharp ablation patterns with satisfactory biological signals gained. Further improvements will optimize the beam profile and generate a square top-hat laser beam for MSI application at higher spatial resolution.
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Affiliation(s)
- Hongxia Bai
- FTMS Laboratory for Human Health Research, Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
| | | | - David C. Muddiman
- FTMS Laboratory for Human Health Research, Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
- Molecular Education, Technology, and Research Innovation Center (METRIC), North Carolina State University, Raleigh, NC 27695 USA
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10
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Kibbe RR, Mellinger AL, Muddiman DC. Novel matrix strategies for improved ionization and spatial resolution using IR-MALDESI mass spectrometry imaging. JOURNAL OF MASS SPECTROMETRY : JMS 2022; 57:e4875. [PMID: 35900350 PMCID: PMC9541679 DOI: 10.1002/jms.4875] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 07/12/2022] [Accepted: 07/15/2022] [Indexed: 05/10/2023]
Abstract
In mass spectrometry imaging (MSI) applications of infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI), an exogenous ice layer is the gold standard for an energy-absorbing matrix. However, the formation of the ice matrix requires additional time and instrument hardware, so glycerol was investigated herein as an alternative to the ice matrix to potentially improve spatial resolution and ionization, while decreasing experiment time. Glycerol solutions of varying concentrations were sprayed over top of rat liver tissue sections for analysis by IR-MALDESI and compared to the typical ice matrix condition. Additionally, we tested if combining the ice matrix and glycerol matrix would further improve analyses. Matrix conditions were evaluated by comparing ion abundance of six lipid species, the laser ablation spot diameter, and number of METASPACE annotations. The ion abundances were also normalized to the volume of tissue ablated to correct for lower abundance values due to less ablated tissue. It was observed that utilizing a 50% glycerol matrix without ice provides improved spatial resolution with lipid abundances and annotations comparable to the ice matrix standard, while decreasing the time required to complete an IR-MALDESI tissue imaging experiment.
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Affiliation(s)
- Russell R. Kibbe
- FTMS Laboratory for Human Health Research, Department of ChemistryNorth Carolina State UniversityRaleighNorth CarolinaUSA
| | - Allyson L. Mellinger
- FTMS Laboratory for Human Health Research, Department of ChemistryNorth Carolina State UniversityRaleighNorth CarolinaUSA
| | - David C. Muddiman
- FTMS Laboratory for Human Health Research, Department of ChemistryNorth Carolina State UniversityRaleighNorth CarolinaUSA
- Molecular Education, Technology and Research Innovation Center (METRIC)North Carolina State UniversityRaleighNorth CarolinaUSA
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11
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Engel KM, Prabutzki P, Leopold J, Nimptsch A, Lemmnitzer K, Vos DRN, Hopf C, Schiller J. A new update of MALDI-TOF mass spectrometry in lipid research. Prog Lipid Res 2022; 86:101145. [PMID: 34995672 DOI: 10.1016/j.plipres.2021.101145] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/06/2021] [Accepted: 12/29/2021] [Indexed: 01/06/2023]
Abstract
Matrix-assisted laser desorption and ionization (MALDI) mass spectrometry (MS) is an indispensable tool in modern lipid research since it is fast, sensitive, tolerates sample impurities and provides spectra without major analyte fragmentation. We will discuss some methodological aspects, the related ion-forming processes and the MALDI MS characteristics of the different lipid classes (with the focus on glycerophospholipids) and the progress, which was achieved during the last ten years. Particular attention will be given to quantitative aspects of MALDI MS since this is widely considered as the most serious drawback of the method. Although the detailed role of the matrix is not yet completely understood, it will be explicitly shown that the careful choice of the matrix is crucial (besides the careful evaluation of the positive and negative ion mass spectra) in order to be able to detect all lipid classes of interest. Two developments will be highlighted: spatially resolved Imaging MS is nowadays well established and the distribution of lipids in tissues merits increasing interest because lipids are readily detectable and represent ubiquitous compounds. It will also be shown that a combination of MALDI MS with thin-layer chromatography (TLC) enables a fast spatially resolved screening of an entire TLC plate which makes the method competitive with LC/MS.
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Affiliation(s)
- Kathrin M Engel
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - Patricia Prabutzki
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - Jenny Leopold
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - Ariane Nimptsch
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - Katharina Lemmnitzer
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - D R Naomi Vos
- Center for Biomedical Mass Spectrometry and Optical Spectroscopy (CeMOS), Mannheim University of Applied Sciences, Paul-Wittsack-Strasse 10, D-68163 Mannheim, Germany
| | - Carsten Hopf
- Center for Biomedical Mass Spectrometry and Optical Spectroscopy (CeMOS), Mannheim University of Applied Sciences, Paul-Wittsack-Strasse 10, D-68163 Mannheim, Germany
| | - Jürgen Schiller
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany.
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12
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Ding X, Liu K, Shi Z. LASER DESORPTION/ABLATION POSTIONIZATION MASS SPECTROMETRY: RECENT PROGRESS IN BIOANALYTICAL APPLICATIONS. MASS SPECTROMETRY REVIEWS 2021; 40:566-605. [PMID: 32770707 DOI: 10.1002/mas.21649] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/07/2020] [Accepted: 07/16/2020] [Indexed: 06/11/2023]
Abstract
Lasers have long been used in the field of mass spectrometric analysis for characterization of condensed matter. However, emission of neutrals upon laser irradiation surpasses the number of ions. Typically, only one in about one million analytes ejected by laser desorption/ablation is ionized, which has fueled the quest for postionization methods enabling ionization of desorbed neutrals to enhance mass spectrometric detection schemes. The development of postionization techniques can be an endeavor that integrates multiple disciplines involving photon energy transfer, electrochemistry, gas discharge, etc. The combination of lasers of different parameters and diverse ion sources has made laser desorption/ablation postionization (LD/API) a growing and lively research community, including two-step laser mass spectrometry, laser ablation atmospheric pressure photoionization mass spectrometry, and those coupled to ambient mass spectrometry. These hyphenated techniques have shown potentials in bioanalytical applications, with major inroads to be made in simultaneous location and quantification of pharmaceuticals, toxins, and metabolites in complex biomatrixes. This review is intended to provide a timely comprehensive view of the broadening bioanalytical applications of disparate LD/API techniques. We also have attempted to discuss these applications according to the classifications based on the postionization methods and to encapsulate the latest achievements in the field of LD/API by highlighting some of the very best reports in the 21st century. © 2020 John Wiley & Sons Ltd.
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Affiliation(s)
- Xuelu Ding
- Department of Pharmaceutical Analysis, School of Pharmacy, Qingdao University, Qingdao, 266021, China
| | - Kun Liu
- Department of Pharmaceutical Analysis, School of Pharmacy, Qingdao University, Qingdao, 266021, China
| | - Zhenyan Shi
- Department of Pharmaceutical Analysis, School of Pharmacy, Qingdao University, Qingdao, 266021, China
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13
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Taylor M, Lukowski JK, Anderton CR. Spatially Resolved Mass Spectrometry at the Single Cell: Recent Innovations in Proteomics and Metabolomics. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:872-894. [PMID: 33656885 PMCID: PMC8033567 DOI: 10.1021/jasms.0c00439] [Citation(s) in RCA: 131] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/20/2021] [Accepted: 01/25/2021] [Indexed: 05/02/2023]
Abstract
Biological systems are composed of heterogeneous populations of cells that intercommunicate to form a functional living tissue. Biological function varies greatly across populations of cells, as each single cell has a unique transcriptome, proteome, and metabolome that translates to functional differences within single species and across kingdoms. Over the past decade, substantial advancements in our ability to characterize omic profiles on a single cell level have occurred, including in multiple spectroscopic and mass spectrometry (MS)-based techniques. Of these technologies, spatially resolved mass spectrometry approaches, including mass spectrometry imaging (MSI), have shown the most progress for single cell proteomics and metabolomics. For example, reporter-based methods using heavy metal tags have allowed for targeted MS investigation of the proteome at the subcellular level, and development of technologies such as laser ablation electrospray ionization mass spectrometry (LAESI-MS) now mean that dynamic metabolomics can be performed in situ. In this Perspective, we showcase advancements in single cell spatial metabolomics and proteomics over the past decade and highlight important aspects related to high-throughput screening, data analysis, and more which are vital to the success of achieving proteomic and metabolomic profiling at the single cell scale. Finally, using this broad literature summary, we provide a perspective on how the next decade may unfold in the area of single cell MS-based proteomics and metabolomics.
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Affiliation(s)
- Michael
J. Taylor
- Environmental Molecular Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Jessica K. Lukowski
- Environmental Molecular Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Christopher R. Anderton
- Environmental Molecular Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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Müller MA, Kompauer M, Strupat K, Heiles S, Spengler B. Implementation of a High-Repetition-Rate Laser in an AP-SMALDI MSI System for Enhanced Measurement Performance. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:465-472. [PMID: 33370109 DOI: 10.1021/jasms.0c00368] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Matrix-assisted laser desorption/ionization mass spectrometry imaging is a promising tool in the life sciences for obtaining spatial and chemical information from complex biological samples. State-of-the-art setups combine high mass resolution and high mass accuracy with high lateral resolution, offering untargeted insights into biochemical processes on the single-cell length scale. Despite recent technological breakthroughs, the sensitivity and acquisition speed of many setups are often in competition with achievable pixel resolutions below 25 μm. New measurement modes were developed by implementing a high-repetition-rate laser into an AP-SMALDI10 ion source, coupled to an orbital trapping mass spectrometer. These new MSI modes allow for a modular use of the new setup. We demonstrate that the system allows single cell features to be visualized in mouse brain tissue sections at a pixel resolution of 5 μm and an imaging speed of 18 pixels/s. Furthermore, the analytical sensitivity was improved in another measurement mode by applying multiple pulses of a highly focused laser beam over larger square pixels ≥25 μm edge length, increasing ion signal intensities up to 20-fold on tissue and decreasing the limit of detection by 1 order of magnitude.
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Affiliation(s)
- Max A Müller
- Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Mario Kompauer
- Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Kerstin Strupat
- Thermo Fisher Scientific (Bremen) GmbH, 28199 Bremen, Germany
| | - Sven Heiles
- Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Bernhard Spengler
- Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, 35392 Giessen, Germany
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15
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Debeljak Ž, Niehoff AC, Bandjak A, Mandić D, Bošnjak B, Heffer M, Mrđenović S, Marković I, Zjalić M, Šerić V. MALDI TOF Mass Spectrometry Imaging of Blood Smear: Method Development and Evaluation. Int J Mol Sci 2021; 22:ijms22020585. [PMID: 33430160 PMCID: PMC7827909 DOI: 10.3390/ijms22020585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 01/05/2021] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to develop and evaluate matrix assisted LASER desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry imaging (MSI) of blood smear. Integrated light microscope and MALDI IT-TOF mass spectrometer, together with a matrix sublimation device, were used for analysis of blood smears coming from healthy male donors. Different blood plasma removal, matrix deposition, and instrumental settings were evaluated using the negative and positive ionization modes while agreement between the light microscopy images and the lateral distributions of cellular marker compounds served as the MSI quality indicator. Red and white blood cells chemical composition was analyzed using the differential m/z expression. Five seconds of exposure to ethanol followed by the 5 min of 9-aminoacridine or α-cyano-4-hydroxycinnamic acid deposition, together with two sets of instrumental settings, were selected for the MALDI TOF MSI experiments. Application of the thin and transparent matrix layers assured good correspondence between the LASER footprints and the preselected regions of interest. Cellular marker m/z signals coincided well with the appropriate cells. A metabolite databases search using the differentially expressed m/z produced hits which were consistent with the respective cell types. This study sets the foundations for application of blood smear MALDI TOF MSI in clinical diagnostics and research.
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Affiliation(s)
- Željko Debeljak
- Clinical Institute of Laboratory Diagnostics, Osijek University Hospital, J. Huttlera 4, 31 000 Osijek, Croatia; (Ž.D.); (A.B.); (D.M.); (V.Š.)
- Department of Pharmacology, Faculty of Medicine, JJ Strossmayer University of Osijek, J. Huttlera 4, 31 000 Osijek, Croatia
| | - Ann-Christin Niehoff
- European Innovation Center, Shimadzu Europa GmbH, Albert-Hahn-Straße 6-10, 47269 Duisburg, Germany;
| | - Ana Bandjak
- Clinical Institute of Laboratory Diagnostics, Osijek University Hospital, J. Huttlera 4, 31 000 Osijek, Croatia; (Ž.D.); (A.B.); (D.M.); (V.Š.)
| | - Dario Mandić
- Clinical Institute of Laboratory Diagnostics, Osijek University Hospital, J. Huttlera 4, 31 000 Osijek, Croatia; (Ž.D.); (A.B.); (D.M.); (V.Š.)
- Department of Medical Chemistry, Biochemistry and Clinical Chemistry, Faculty of Medicine, JJ Strossmayer University of Osijek, J. Huttlera 4, 31 000 Osijek, Croatia
| | - Bojana Bošnjak
- Clinical Institute of Transfusion Medicine, Osijek University Hospital, J. Huttlera 4, 31 000 Osijek, Croatia;
- Department of Microbiology, Parasitology and Clinical Laboratory Diagnostics, Faculty of Medicine, JJ Strossmayer University of Osijek, J. Huttlera 4, 31 000 Osijek, Croatia
| | - Marija Heffer
- Department of Medical Biology and Genetics, Faculty of Medicine, JJ Strossmayer University of Osijek, J. Huttlera 4, 31 000 Osijek, Croatia; (M.H.); (M.Z.)
| | - Stefan Mrđenović
- Department of Hematology, Internal Medicine Clinic, Osijek University Hospital, J. Huttlera 4, 31 000 Osijek, Croatia;
- Department of Internal Medicine, Family Medicine and History of Medicine, Faculty of Medicine Osijek, JJ Strossmayer University of Osijek, J. Huttlera 4, 31 000 Osijek, Croatia
| | - Ivana Marković
- Clinical Institute of Laboratory Diagnostics, Osijek University Hospital, J. Huttlera 4, 31 000 Osijek, Croatia; (Ž.D.); (A.B.); (D.M.); (V.Š.)
- Department of Medical Chemistry, Biochemistry and Clinical Chemistry, Faculty of Medicine, JJ Strossmayer University of Osijek, J. Huttlera 4, 31 000 Osijek, Croatia
- Correspondence: ; Tel.: +385-(031)-511-641
| | - Milorad Zjalić
- Department of Medical Biology and Genetics, Faculty of Medicine, JJ Strossmayer University of Osijek, J. Huttlera 4, 31 000 Osijek, Croatia; (M.H.); (M.Z.)
| | - Vatroslav Šerić
- Clinical Institute of Laboratory Diagnostics, Osijek University Hospital, J. Huttlera 4, 31 000 Osijek, Croatia; (Ž.D.); (A.B.); (D.M.); (V.Š.)
- Department of Medical Chemistry, Biochemistry and Clinical Chemistry, Faculty of Medicine, JJ Strossmayer University of Osijek, J. Huttlera 4, 31 000 Osijek, Croatia
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16
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Lin HY, Dyakov YA, Lee YT, Ni CK. Temperature Dependence of Desorbed Ions and Neutrals and Ionization Mechanism of Matrix-Assisted Laser Desorption/Ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:95-105. [PMID: 32239933 DOI: 10.1021/jasms.0c00101] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two separate temperature-dependent experiments were performed to investigate the ionization mechanism of ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) of matrix 2,5-dihydroxybenzoic acid (2,5-DHB). First, the angular resolved intensity and velocity distributions of neutrals desorbed from the 2,5-DHB solid sample through UV laser (355 nm) pulse irradiation were measured using a rotating quadrupole mass spectrometer. Second, the desorbed neutrals, at an angle normal to the surface, and the desorbed ions were simultaneously detected for each laser shot using the quadrupole mass spectrometer and a time-of-flight mass spectrometer, respectively. Both experiments were conducted at two initial temperatures: 100 and 300 K. The measurements from these two experiments were used to calculate the initial temperature dependence of the ion-to-neutral ratio. The results closely agreed with the predictions of the temperature-dependent ion-to-neutral ratio using the thermal model, indicating that thermally induced proton transfer is the dominant reaction that generates initial ions of 2,5-DHB in UV-MALDI.
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Affiliation(s)
- Hou-Yu Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Yuri A Dyakov
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Yuan Tseh Lee
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Chi-Kung Ni
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
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17
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Abstract
Mass spectrometry imaging (MSI) is a label-free molecular imaging technique allowing an untargeted detection of a broad range of biomolecules and xenobiotics. MSI enables imaging of the spatial distribution of proteins, peptides, lipids and metabolites from a wide range of samples. To date, this technique is commonly applied to tissue sections in cancer diagnostics and biomarker development, but also molecular histology in general. Advances in the methodology and bioinformatics improved the resolution of MS images below the single cell level and increased the flexibility of the workflow. However, MSI-based research in virology is just starting to gain momentum and its full potential has not been exploited yet. In this review, we discuss the main applications of MSI in virology. We review important aspects of matrix-assisted laser desorption/ionization (MALDI) MSI, the most widely used MSI technique in virology. In addition, we summarize relevant literature on MSI studies that aim to unravel virus-host interactions and virus pathogenesis, to elucidate antiviral drug kinetics and to improve current viral disease diagnostics. Collectively, these studies strongly improve our general understanding of virus-induced changes in the proteome, metabolome and metabolite distribution in host tissues of humans, animals and plants upon infection. Furthermore, latest MSI research provided important insights into the drug distribution and distribution kinetics, especially in antiretroviral research. Finally, MSI-based investigations of oncogenic viruses greatly increased our knowledge on tumor mass signatures and facilitated the identification of cancer biomarkers.
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Affiliation(s)
- Luca D Bertzbach
- Institute of Virology, Freie Universität Berlin, Berlin, Germany
| | | | - Axel Karger
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
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18
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Bringing SEM and MSI Closer Than Ever Before: Visualizing Aspergillus and Pseudomonas Infection in the Rat Lungs. J Fungi (Basel) 2020; 6:jof6040257. [PMID: 33143040 PMCID: PMC7711807 DOI: 10.3390/jof6040257] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/15/2020] [Accepted: 10/26/2020] [Indexed: 11/16/2022] Open
Abstract
A procedure for processing frozen rat lung tissue sections for scanning electron microscopy (SEM) from deeply frozen samples initially collected and stored for matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was developed. The procedure employed slow thawing of the frozen sections while floating on the surface and melting in a fixative solution. After the float-washing step, the sections were dehydrated in a graded ethanol series and dried in a critical point dryer. The SEM generated images with well-preserved structures, allowing for monitoring of bacterial cells and fungal hyphae in the infected tissue. Importantly, the consecutive nonfixed frozen sections were fully compatible with MALDI-MSI, providing molecular biomarker maps of Pseudomonas aeruginosa. The protocol enables bimodal image fusion in the in-house software CycloBranch, as demonstrated by SEM and MALDI-MSI.
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19
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Validation of MALDI-MS imaging data of selected membrane lipids in murine brain with and without laser postionization by quantitative nano-HPLC-MS using laser microdissection. Anal Bioanal Chem 2020; 412:6875-6886. [PMID: 32712813 PMCID: PMC7496020 DOI: 10.1007/s00216-020-02818-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/08/2020] [Accepted: 07/14/2020] [Indexed: 12/23/2022]
Abstract
MALDI mass spectrometry imaging (MALDI-MSI) is a widely used technique to map the spatial distribution of molecules in sectioned tissue. The technique is based on the systematic generation and analysis of ions from small sample volumes, each representing a single pixel of the investigated sample surface. Subsequently, mass spectrometric images for any recorded ion species can be generated by displaying the signal intensity at the coordinate of origin for each of these pixels. Although easily equalized, these recorded signal intensities, however, are not necessarily a good measure for the underlying amount of analyte and care has to be taken in the interpretation of MALDI-MSI data. Physical and chemical properties that define the analyte molecules’ adjacencies in the tissue largely influence the local extraction and ionization efficiencies, possibly leading to strong variations in signal intensity response. Here, we inspect the validity of signal intensity distributions recorded from murine cerebellum as a measure for the underlying molar distributions. Based on segmentation derived from MALDI-MSI measurements, laser microdissection (LMD) was used to cut out regions of interest with a homogenous signal intensity. The molar concentration of six exemplary selected membrane lipids from different lipid classes in these tissue regions was determined using quantitative nano-HPLC-ESI-MS. Comparison of molar concentrations and signal intensity revealed strong deviations between underlying concentration and the distribution suggested by MSI data. Determined signal intensity response factors strongly depend on tissue type and lipid species. Graphical abstract ![]()
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20
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Boskamp MS, Soltwisch J. Charge Distribution between Different Classes of Glycerophospolipids in MALDI-MS Imaging. Anal Chem 2020; 92:5222-5230. [DOI: 10.1021/acs.analchem.9b05761] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Marcel S. Boskamp
- Institute of Hygiene, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Jens Soltwisch
- Institute of Hygiene, Westfälische Wilhelms-Universität Münster, Münster, Germany
- Interdisciplinary Center for Clinical Research (IZKF), Westfälische Wilhelms-Universität Münster, Münster, Germany
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21
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Heiles S, Kompauer M, Müller MA, Spengler B. Atmospheric-Pressure MALDI Mass Spectrometry Imaging at 213 nm Laser Wavelength. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:326-335. [PMID: 32031384 DOI: 10.1021/jasms.9b00052] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
First results for a new atmospheric-pressure matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging source operating at 213 nm laser wavelength are presented. The activation of analytes in the 213 nm MALDI process at atmospheric pressure was evaluated and compared to results for 337 nm MALDI and electrospray ionization using thermometer molecules. Different sample preparation techniques for nicotinic acid, the matrix with the highest ionization efficiency at 213 nm of all tested matrices, were evaluated and optimized to obtain small crystal sizes, homogenous matrix layer sample coverage, and high ion signal gains. Mass spectrometry imaging experiments of phospholipids in mouse tissue sections in positive- and negative-ion mode with different lateral resolutions and the corresponding pre-/post-mass spectrometry imaging workflows are presented. The use of custom-made objective lenses resulted in sample ablation spot diameters of on average 2.9 μm, allowing mass spectrometry imaging experiments to be performed with 3 μm pixel size without oversampling. The ion source was coupled to an orbital trapping mass spectrometer offering high mass resolution (>100.000), high mass accuracy (≤ ±2 ppm), and high sensitivity (single pixel on-tissue tandem MS from 6.6 μm2 ablation area). The newly developed 213 nm atmospheric-pressure MALDI source combines the high mass resolution and high mass accuracy performance characteristics of orbital trapping mass spectrometers with high lateral resolution (pixel size ∼3 μm) mass spectrometry imaging.
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Affiliation(s)
- Sven Heiles
- Institute of Inorganic and Analytical Chemistry , Justus Liebig University Giessen , 35392 Giessen , Germany
| | - Mario Kompauer
- Institute of Inorganic and Analytical Chemistry , Justus Liebig University Giessen , 35392 Giessen , Germany
| | - Max A Müller
- Institute of Inorganic and Analytical Chemistry , Justus Liebig University Giessen , 35392 Giessen , Germany
| | - Bernhard Spengler
- Institute of Inorganic and Analytical Chemistry , Justus Liebig University Giessen , 35392 Giessen , Germany
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22
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Bowman AP, Bogie JFJ, Hendriks JJA, Haidar M, Belov M, Heeren RMA, Ellis SR. Evaluation of lipid coverage and high spatial resolution MALDI-imaging capabilities of oversampling combined with laser post-ionisation. Anal Bioanal Chem 2019; 412:2277-2289. [PMID: 31879798 PMCID: PMC7118047 DOI: 10.1007/s00216-019-02290-3] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 11/04/2019] [Accepted: 11/18/2019] [Indexed: 01/28/2023]
Abstract
Matrix-assisted laser desorption/ionisation-mass spectrometry imaging (MALDI-MSI) is a powerful technique for visualising the spatial locations of lipids in biological tissues. However, a major challenge in interpreting the biological significance of local lipid compositions and distributions detected using MALDI-MSI is the difficulty in associating spectra with cellular lipid metabolism within the tissue. By-and-large this is due to the typically limited spatial resolution of MALDI-MSI (30–100 μm) meaning individual spectra represent the average spectrum acquired from multiple adjacent cells, each potentially possessing a unique lipid composition and biological function. The use of oversampling is one promising approach to decrease the sampling area and improve the spatial resolution in MALDI-MSI, but it can suffer from a dramatically decreased sensitivity. In this work we overcome these challenges through the coupling of oversampling MALDI-MSI with laser post-ionisation (MALDI-2). We demonstrate the ability to acquire rich lipid spectra from pixels as small as 6 μm, equivalent to or smaller than the size of typical mammalian cells. Coupled with an approach for automated lipid identification, it is shown that MALDI-2 combined with oversampling at 6 μm pixel size can detect up to three times more lipids and many more lipid classes than even conventional MALDI at 20 μm resolution in the positive-ion mode. Applying this to mouse kidney and human brain tissue containing active multiple sclerosis lesions, where 74 and 147 unique lipids are identified, respectively, the localisation of lipid signals to individual tubuli within the kidney and lipid droplets with lesion-specific macrophages is demonstrated. Graphical abstract ![]()
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Affiliation(s)
- Andrew P Bowman
- Maastricht MultiModal Molecular Imaging (M4I) Institute, Division of Imaging Mass Spectrometry, Maastricht University, Universiteitssingel 50, 6629, ER, Maastricht, The Netherlands
| | - Jeroen F J Bogie
- Department of Immunology and Biochemistry, Biomedical Research Institute, Hasselt University, 3590, Diepenbeek, Belgium
| | - Jerome J A Hendriks
- Department of Immunology and Biochemistry, Biomedical Research Institute, Hasselt University, 3590, Diepenbeek, Belgium
| | - Mansour Haidar
- Department of Immunology and Biochemistry, Biomedical Research Institute, Hasselt University, 3590, Diepenbeek, Belgium
| | | | - Ron M A Heeren
- Maastricht MultiModal Molecular Imaging (M4I) Institute, Division of Imaging Mass Spectrometry, Maastricht University, Universiteitssingel 50, 6629, ER, Maastricht, The Netherlands
| | - Shane R Ellis
- Maastricht MultiModal Molecular Imaging (M4I) Institute, Division of Imaging Mass Spectrometry, Maastricht University, Universiteitssingel 50, 6629, ER, Maastricht, The Netherlands.
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23
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Holzlechner M, Eugenin E, Prideaux B. Mass spectrometry imaging to detect lipid biomarkers and disease signatures in cancer. Cancer Rep (Hoboken) 2019; 2:e1229. [PMID: 32729258 PMCID: PMC7941519 DOI: 10.1002/cnr2.1229] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 11/04/2019] [Accepted: 11/07/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Current methods to identify, classify, and predict tumor behavior mostly rely on histology, immunohistochemistry, and molecular determinants. However, better predictive markers are required for tumor diagnosis and evaluation. Due, in part, to recent technological advancements, metabolomics and lipid biomarkers have become a promising area in cancer research. Therefore, there is a necessity for novel and complementary techniques to identify and visualize these molecular markers within tumors and surrounding tissue. RECENT FINDINGS Since its introduction, mass spectrometry imaging (MSI) has proven to be a powerful tool for mapping analytes in biological tissues. By adding the label-free specificity of mass spectrometry to the detailed spatial information of traditional histology, hundreds of lipids can be imaged simultaneously within a tumor. MSI provides highly detailed lipid maps for comparing intra-tumor, tumor margin, and healthy regions to identify biomarkers, patterns of disease, and potential therapeutic targets. In this manuscript, recent advancement in sample preparation and MSI technologies are discussed with special emphasis on cancer lipid research to identify tumor biomarkers. CONCLUSION MSI offers a unique approach for biomolecular characterization of tumor tissues and provides valuable complementary information to histology for lipid biomarker discovery and tumor classification in clinical and research cancer applications.
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Affiliation(s)
- Matthias Holzlechner
- Department of Neuroscience, Cell Biology, and AnatomyThe University of Texas Medical Branch at Galveston (UTMB)GalvestonTexas
| | - Eliseo Eugenin
- Department of Neuroscience, Cell Biology, and AnatomyThe University of Texas Medical Branch at Galveston (UTMB)GalvestonTexas
| | - Brendan Prideaux
- Department of Neuroscience, Cell Biology, and AnatomyThe University of Texas Medical Branch at Galveston (UTMB)GalvestonTexas
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24
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Confirmation of sub-cellular resolution using oversampling imaging mass spectrometry. Anal Bioanal Chem 2019; 411:7935-7941. [DOI: 10.1007/s00216-019-02212-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 10/04/2019] [Accepted: 10/11/2019] [Indexed: 01/26/2023]
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Robinson KN, Steven RT, Race AM, Bunch J. The Influence of MS Imaging Parameters on UV-MALDI Desorption and Ion Yield. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:1284-1293. [PMID: 30949969 DOI: 10.1007/s13361-019-02193-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 02/12/2019] [Accepted: 03/11/2019] [Indexed: 06/09/2023]
Abstract
Ultraviolet matrix-assisted laser desorption/ionization mass spectrometry imaging (UV-MALDI MSI) is a widely used technique for imaging molecular distributions within biological systems. While much work exists concerning desorption in UV-MALDI MS, the effects of commonly varied parameters for imaging applications (repetition rate, use of continuous raster mode and raster speed), which determine spatial resolution and limits of detection for the technique, remain largely unknown. We use multiple surface characterization modalities to obtain quantitative measurements of material desorption and analyte ion yield in thin film model systems of two matrix compounds, arising from different UV-MALDI MSI sampling conditions. Observed changes in resulting ablation feature point to matrix-dependent spatial resolution and laser-induced matrix modification effects. Analyte ion yields of 10-9 to 10-6 are observed. Complex changes in ion yield, between spot and raster sampling and arising from varied laser repetition rate and raster speed, are observed. Graphical Abstract.
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Affiliation(s)
- Kenneth N Robinson
- National Centre of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory, Teddington, UK
- Advanced Materials and Healthcare Technologies Division (AMHT), University of Nottingham, Nottingham, UK
| | - Rory T Steven
- National Centre of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory, Teddington, UK.
| | - Alan M Race
- National Centre of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory, Teddington, UK
| | - Josephine Bunch
- National Centre of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory, Teddington, UK.
- Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, UK.
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26
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Schmitt ND, Rawlins CM, Randall EC, Wang X, Koller A, Auclair JR, Kowalski JM, Kowalski PJ, Luther E, Ivanov AR, Agar NY, Agar JN. Genetically Encoded Fluorescent Proteins Enable High-Throughput Assignment of Cell Cohorts Directly from MALDI-MS Images. Anal Chem 2019; 91:3810-3817. [PMID: 30839199 PMCID: PMC6827431 DOI: 10.1021/acs.analchem.8b03454] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) provides a unique in situ chemical profile that can include drugs, nucleic acids, metabolites, lipids, and proteins. MSI of individual cells (of a known cell type) affords a unique insight into normal and disease-related processes and is a prerequisite for combining the results of MSI and other single-cell modalities (e.g. mass cytometry and next-generation sequencing). Technological barriers have prevented the high-throughput assignment of MSI spectra from solid tissue preparations to their cell type. These barriers include obtaining a suitable cell-identifying image (e.g. immunohistochemistry) and obtaining sufficiently accurate registration of the cell-identifying and MALDI-MS images. This study introduces a technique that overcame these barriers by assigning cell type directly from mass spectra. We hypothesized that, in MSI from mice with a defined fluorescent protein expression pattern, the fluorescent protein's molecular ion could be used to identify cell cohorts. A method was developed for the purification of enhanced yellow fluorescent protein (EYFP) from mice. To determine EYFP's molecular mass for MSI studies, we performed intact mass analysis and characterized the protein's primary structure and post-translational modifications through various techniques. MALDI-MSI methods were developed to enhance the detection of EYFP in situ, and by extraction of EYFP's molecular ion from MALDI-MS images, automated, whole-image assignment of cell cohorts was achieved. This method was validated using a well-characterized mouse line that expresses EYFP in motor and sensory neurons and should be applicable to hundreds of commercially available mice (and other animal) strains comprising a multitude of cell-specific fluorescent labels.
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Affiliation(s)
- Nicholas D. Schmitt
- Department of Chemistry and Chemical Biology, and Barnett Institute of Chemical and Biological Analysis, Northeastern University, Boston, MA, 02115, USA
- These authors contributed equally to this work
| | - Catherine M. Rawlins
- Department of Chemistry and Chemical Biology, and Barnett Institute of Chemical and Biological Analysis, Northeastern University, Boston, MA, 02115, USA
- These authors contributed equally to this work
| | - Elizabeth C. Randall
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Xianzhe Wang
- Department of Chemistry and Chemical Biology, and Barnett Institute of Chemical and Biological Analysis, Northeastern University, Boston, MA, 02115, USA
| | - Antonius Koller
- Department of Chemistry and Chemical Biology, and Barnett Institute of Chemical and Biological Analysis, Northeastern University, Boston, MA, 02115, USA
| | - Jared R. Auclair
- Department of Chemistry and Chemical Biology, and Barnett Institute of Chemical and Biological Analysis, Northeastern University, Boston, MA, 02115, USA
- Biopharmaceutical Analysis Training Laboratory (BATL), Northeastern University Innovation Campus, Burlington, MA, 01803, USA
| | | | | | - Ed Luther
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115, USA
| | - Alexander R. Ivanov
- Department of Chemistry and Chemical Biology, and Barnett Institute of Chemical and Biological Analysis, Northeastern University, Boston, MA, 02115, USA
| | - Nathalie Y.R. Agar
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, 02115, USA
- Department of Neurosurgery, Brigham and Women’s Hospital, Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 02115, USA
| | - Jeffrey N. Agar
- Department of Chemistry and Chemical Biology, and Barnett Institute of Chemical and Biological Analysis, Northeastern University, Boston, MA, 02115, USA
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115, USA
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27
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Li G, Cao Q, Liu Y, DeLaney K, Tian Z, Moskovets E, Li L. Characterizing and alleviating ion suppression effects in atmospheric pressure matrix-assisted laser desorption/ionization. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33:327-335. [PMID: 30430670 PMCID: PMC6353668 DOI: 10.1002/rcm.8358] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Revised: 09/14/2018] [Accepted: 11/11/2018] [Indexed: 05/05/2023]
Abstract
RATIONALE As a powerful ambient ion source, atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) enables direct analysis at atmospheric pressure/temperature and minimal sample preparation. With the increasing usage of AP-MALDI sources with Orbitrap instruments, systematic characterization of the extent of ion suppression effect (ISE) in AP-MALDI-Orbitrap mass spectrometry imaging (MSI) is desirable. Recently, a new low-pressure MALDI platform has been introduced that reportedly provided better sensitivity. While extensive research efforts have been devoted to improving spatial resolution, fewer studies focused on the characterization and sensitivity improvement of these MALDI platforms that, coupled with high-resolution Orbitraps, provide powerful strategy for MSI. METHODS We compared the analytical performance of AP and low-pressure (subatmospheric) MALDI sources to study the effect of pressure control in the ion source. Using a model peptide/protein mixture, we systematically evaluated the factors influencing ISE. Furthermore, the effect of laser spot size was evaluated through tissue imaging analysis of lipids and neuropeptides. The effects of ion suppression and laser spot size have also been examined by comparing the number of identified molecular species during MSI analysis. RESULTS Several key operating parameters including source pressure, laser energy, laser repetition rate, and microscopic slide coating materials were optimized to minimize the ISE. Under the optimal conditions, the subatmospheric AP-MALDI-Orbitrap platform with high spatial and mass spectral resolution enabled significantly improved coverage of several lipid and neuropeptide families in the MS analysis of mouse brain tissue sections. CONCLUSIONS The new SubAP-MALDI source coupled with an Orbitrap mass spectrometer was established as a viable platform for in situ endogenous biomolecular analysis with increased sensitivity compared with conventional AP-MALDI sources as evidenced by the confident identification of neuropeptides from mouse brain imaging analyses. The alleviated ISE was key to substantial performance improvement due to optimized intermediate pressure conditions and better ion collection by the ion funnel.
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Affiliation(s)
- Gongyu Li
- School of Pharmacy, University of Wisconsin-Madison, Madison, WI, 53705, USA
| | - Qinjingwen Cao
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Yang Liu
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Kellen DeLaney
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Zichuan Tian
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | | | - Lingjun Li
- School of Pharmacy, University of Wisconsin-Madison, Madison, WI, 53705, USA
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Contact Information for Corresponding Author: Prof. Dr. Lingjun Li, School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, Wisconsin 53705-2222, USA;, Phone: +1-608-265-8491;, Fax: +1-608-262-5345;,
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28
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Michno W, Wehrli PM, Blennow K, Zetterberg H, Hanrieder J. Molecular imaging mass spectrometry for probing protein dynamics in neurodegenerative disease pathology. J Neurochem 2018; 151:488-506. [PMID: 30040875 DOI: 10.1111/jnc.14559] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 07/03/2018] [Accepted: 07/12/2018] [Indexed: 12/14/2022]
Abstract
Recent advances in the understanding of basic pathological mechanisms in various neurological diseases depend directly on the development of novel bioanalytical technologies that allow sensitive and specific chemical imaging at high resolution in cells and tissues. Mass spectrometry-based molecular imaging (IMS) has gained increasing popularity in biomedical research for mapping the spatial distribution of molecular species in situ. The technology allows for comprehensive, untargeted delineation of in situ distribution profiles of metabolites, lipids, peptides and proteins. A major advantage of IMS over conventional histochemical techniques is its superior molecular specificity. Imaging mass spectrometry has therefore great potential for probing molecular regulations in CNS-derived tissues and cells for understanding neurodegenerative disease mechanism. The goal of this review is to familiarize the reader with the experimental workflow, instrumental developments and methodological challenges as well as to give a concise overview of the major advances and recent developments and applications of IMS-based protein and peptide profiling with particular focus on neurodegenerative diseases. This article is part of the Special Issue "Proteomics".
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Affiliation(s)
- Wojciech Michno
- Department of Psychiatry and Neurochemistry, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden
| | - Patrick M Wehrli
- Department of Psychiatry and Neurochemistry, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden
| | - Kaj Blennow
- Department of Psychiatry and Neurochemistry, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden.,Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden
| | - Henrik Zetterberg
- Department of Psychiatry and Neurochemistry, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden.,Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden.,Department of Neurodegenerative Disease, UCL Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute at UCL, London, UK
| | - Jörg Hanrieder
- Department of Psychiatry and Neurochemistry, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden.,Department of Neurodegenerative Disease, UCL Institute of Neurology, University College London, London, UK.,Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden
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29
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New insights into mechanisms of material ejection in MALDI mass spectrometry for a wide range of spot sizes. Sci Rep 2018; 8:7755. [PMID: 29773805 PMCID: PMC5958139 DOI: 10.1038/s41598-018-25946-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 04/25/2018] [Indexed: 01/22/2023] Open
Abstract
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is widely used for the analysis of large biomolecules in numerous applications. The technique utilizes nanosecond-long laser pulses at various spot sizes to eject and ionize large molecules embedded in a highly absorptive chemical matrix. Despite the methods name, ‘molecular desorption’ from the matrix crystal surface is not the sole mechanism discussed for material ejection in MALDI, but additional ablation of larger clusters has been reported. Here we present results on the influence of laser fluence and spot size on the mechanisms of the initial material ejection in MALDI and subsequent plume development. We used a laser-based postionization (MALDI-2) as well as a complementary photoacoustic method to monitor the material ejection step. The photoacoustic data reveal a quasi-thermal sublimation process up to a transition fluence. Above this threshold fluence additional ablation processes are observed. Complementary investigations on plume dynamics by MALDI-2 showed an ejection of predominantly fast particles for desorption conditions while ablation produces considerably slower ejecta. Additionally the presented results revealed a peculiar influence of the spot size on analyte fragmentation as well as plume development and allows for new insights into the unexplained spot size effect reported for MALDI.
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30
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Robinson KN, Steven RT, Bunch J. Matrix Optical Absorption in UV-MALDI MS. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:501-511. [PMID: 29468418 DOI: 10.1007/s13361-017-1843-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 10/31/2017] [Accepted: 11/01/2017] [Indexed: 05/03/2023]
Abstract
In ultraviolet matrix-assisted laser desorption/ionization mass spectrometry (UV-MALDI MS) matrix compound optical absorption governs the uptake of laser energy, which in turn has a strong influence on experimental results. Despite this, quantitative absorption measurements are lacking for most matrix compounds. Furthermore, despite the use of UV-MALDI MS to detect a vast range of compounds, investigations into the effects of laser energy have been primarily restricted to single classes of analytes. We report the absolute solid state absorption spectra of the matrix compounds α-cyano-4-hydroxycinnamic acid (CHCA), para-nitroaniline (PNA), 2-mercaptobenzothiazole (MBT), 2,5-dihydroxybenzoic acid (2,5-DHB), and 2,4,6-trihydroxyacetophenone (THAP). The desorption/ionization characteristics of these matrix compounds with respect to laser fluence was investigated using mixed systems of matrix with either angiotensin II, PC(34:1) lipid standard, or haloperidol, acting as representatives for typical classes of analyte encountered in UV-MALDI MS. The first absolute solid phase spectra for PNA, MBT, and THAP are reported; additionally, inconsistencies between previously published spectra for CHCA are resolved. In light of these findings, suggestions are made for experimental optimization with regards to matrix and laser wavelength selection. The relationship between matrix optical cross-section and wavelength-dependant threshold fluence, fluence of maximum ion yield, and R, a new descriptor for the change in ion intensity with fluence, are described. A matrix cross-section of 1.3 × 10-17 cm-2 was identified as a potential minimum for desorption/ionization of analytes. Graphical Abstract ᅟ.
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Affiliation(s)
- Kenneth N Robinson
- National Center of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory, Teddington, UK
- Advanced Materials and Healthcare Technologies Division, University of Nottingham, Nottingham, UK
| | - Rory T Steven
- National Center of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory, Teddington, UK
| | - Josephine Bunch
- National Center of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory, Teddington, UK.
- Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, UK.
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31
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Niehaus M, Schnapp A, Koch A, Soltwisch J, Dreisewerd K. New Insights into the Wavelength Dependence of MALDI Mass Spectrometry. Anal Chem 2017. [PMID: 28636332 DOI: 10.1021/acs.analchem.7b01744] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The interplay between the wavelength of the laser and the absorption profile of the matrix constitutes a crucial factor in matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). Numerous studies have shown that typically best analytical results are obtained if the laser wavelength matches the UV absorption band of the matrix in the solid state well. However, many powerful matrices exhibit peak absorptions which differ notably from the standard MALDI laser wavelengths of 337, 349, and 355 nm, respectively. Here we used two wavelength-tunable lasers to investigate the MALDI wavelength dependence with a selected set of such matrices. We studied 3-hydroxypicolinic acid (3-HPA), 2,4,6-trihydroxyacetophenon (THAP), dithranol (1,8-dihydroxy-10H-anthracen-9-on), 2-(4'-hydroxybenzeneazo)benzoic acid (HABA), and 6-aza-2-thiothymine (ATT). For analyte systems we investigated DNA oligomers (3-HPA), phospholipids (dithranol, THAP, HABA), and non-covalent peptide-peptide and protein-peptide complexes (ATT). We recorded analyte ion and total ion counts as a function of wavelength and laser fluence between 213 and 600 nm. Although the so-generated comprehensive heat maps generally corroborated the previously made findings, several fine features became notable. For example, despite a still high optical absorption exhibited by some of the matrices in the visible wavelength range, ion yields generally dropped strongly, indicating a change in ionization mechanism. Moreover, the non-covalent complexes were optimally detected at wavelengths corresponding to a relatively low optical absorptivity of the ATT matrix, presumably because of ejection of a particular cold MALDI plume. Our comprehensive data shed useful light into the MALDI mechanisms and could assist in further methodological advancement of the technique.
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Affiliation(s)
- Marcel Niehaus
- Institute for Hygiene, Biomedical Mass Spectrometry, University of Münster , D-48149 Münster, Germany
| | - Andreas Schnapp
- Institute for Hygiene, Biomedical Mass Spectrometry, University of Münster , D-48149 Münster, Germany
| | - Annika Koch
- Institute for Hygiene, Biomedical Mass Spectrometry, University of Münster , D-48149 Münster, Germany
| | - Jens Soltwisch
- Institute for Hygiene, Biomedical Mass Spectrometry, University of Münster , D-48149 Münster, Germany.,Interdisciplinary Center for Clinical Research (IZKF), University of Münster , D-48149 Münster, Germany
| | - Klaus Dreisewerd
- Institute for Hygiene, Biomedical Mass Spectrometry, University of Münster , D-48149 Münster, Germany.,Interdisciplinary Center for Clinical Research (IZKF), University of Münster , D-48149 Münster, Germany
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32
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Feenstra AD, Dueñas ME, Lee YJ. Five Micron High Resolution MALDI Mass Spectrometry Imaging with Simple, Interchangeable, Multi-Resolution Optical System. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:434-442. [PMID: 28050871 DOI: 10.1007/s13361-016-1577-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 11/17/2016] [Accepted: 12/08/2016] [Indexed: 05/18/2023]
Abstract
High-spatial resolution mass spectrometry imaging (MSI) is crucial for the mapping of chemical distributions at the cellular and subcellular level. In this work, we improved our previous laser optical system for matrix-assisted laser desorption ionization (MALDI)-MSI, from ~9 μm practical laser spot size to a practical laser spot size of ~4 μm, thereby allowing for 5 μm resolution imaging without oversampling. This is accomplished through a combination of spatial filtering, beam expansion, and reduction of the final focal length. Most importantly, the new laser optics system allows for simple modification of the spot size solely through the interchanging of the beam expander component. Using 10×, 5×, and no beam expander, we could routinely change between ~4, ~7, and ~45 μm laser spot size, in less than 5 min. We applied this multi-resolution MALDI-MSI system to a single maize root tissue section with three different spatial resolutions of 5, 10, and 50 μm and compared the differences in imaging quality and signal sensitivity. We also demonstrated the difference in depth of focus between the optical systems with 10× and 5× beam expanders. Graphical Abstract ᅟ.
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Affiliation(s)
- Adam D Feenstra
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA
- Ames Laboratory-US DOE, Ames, IA, 50011, USA
| | - Maria Emilia Dueñas
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA
- Ames Laboratory-US DOE, Ames, IA, 50011, USA
| | - Young Jin Lee
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA.
- Ames Laboratory-US DOE, Ames, IA, 50011, USA.
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