| 1. |
- Angerer, Tina B., 1987, et al.
(author)
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Optimizing sample preparation for anatomical determination in the hippocampus of rodent brain by ToF-SIMS analysis
- 2016
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In: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 11:2
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Journal article (peer-reviewed)abstract
- Lipidomics has been an expanding field since researchers began to recognize the signaling functions of lipids and their involvement in disease. Time-of-flight secondary ion mass spectrometry is a valuable tool for studying the distribution of a wide range of lipids in multiple brain regions, but in order to make valuable scientific contributions, one has to be aware of the influence that sample treatment can have on the results. In this article, the authors discuss different sample treatment protocols for rodent brain sections focusing on signal from the hippocampus and surrounding areas. The authors compare frozen hydrated analysis to freeze drying, which is the standard in most research facilities, and reactive vapor exposure (trifluoroacetic acid and NH3). The results show that in order to preserve brain chemistry close to a native state, frozen hydrated analysis is the most suitable, but execution can be difficult. Freeze drying is prone to produce artifacts as cholesterol migrates to surface, masking other signals. This effect can be partially reversed by exposing freeze dried sections to reactive vapor. When analyzing brain sections in negative ion mode, exposing those sections to NH3 vapor can re-establish the diversity in lipid signal found in frozen hydrated analyzed sections. This is accomplished by removing cholesterol and uncovering sulfatide signals, allowing more anatomical regions to be visualized.
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| 2. |
- Li, Xianchan, 1982, et al.
(author)
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Single cell amperometry reveals curcuminoids modulate the release of neurotransmitters during exocytosis from PC12 cells
- 2016
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 781, s. 30-35
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Journal article (peer-reviewed)abstract
- We used single cell amperometry to examine whether curcumin and bisdemethoxycurcumin (BDMC), substances that are suggested to affect learning and memory, can modulate monoamine release from PC12 cells. Our results indicate both curcumin and BDMC need long-term treatment (72 h in this study) to influence exocytosis effectively. By analyzing the parameters calculated from single exocytosis events, it can be concluded that curcumin and BDMC affect exocytosis through different mechanisms. Curcumin accelerates the event dynamics with no significant change of the monoamine amount released from single exocytotic events, whereas BDMC attenuates the amount from single exocytotic event with no significant change of the event dynamics. This comparison of the effect of curcumin and BDMC on exocytosis at the single cell level brings insight into their different mechanisms, which might lead to different biological actions. The effect of curcumin and BDMC on the opening and closing of the exocytotic fusion pore were also investigated. These results might be helpful for understanding the improvement of learning and memory and the anti-depression properties of curcuminoids.
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| 3. |
- Mohammadi, Amir Saeid, 1984, et al.
(author)
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Intact lipid imaging of mouse brain samples: MALDI, nanoparticle-laser desorption ionization, and 40 keV argon cluster secondary ion mass spectrometry
- 2016
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In: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 408:24, s. 6857-6868
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Journal article (peer-reviewed)abstract
- We have investigated the capability of nanoparticle-assisted laser desorption ionization mass spectrometry (NP-LDI MS), matrix-assisted laser desorption ionization (MALDI) MS, and gas cluster ion beam secondary ion mass spectrometry (GCIB SIMS) to provide maximum information available in lipid analysis and imaging of mouse brain tissue. The use of Au nanoparticles deposited as a matrix for NP-LDI MS is compared to MALDI and SIMS analysis of mouse brain tissue and allows selective detection and imaging of groups of lipid molecular ion species localizing in the white matter differently from those observed using conventional MALDI with improved imaging potential. We demonstrate that high-energy (40 keV) GCIB SIMS can act as a semi-soft ionization method to extend the useful mass range of SIMS imaging to analyze and image intact lipids in biological samples, closing the gap between conventional SIMS and MALDI techniques. The GCIB SIMS allowed the detection of more intact lipid compounds in the mouse brain compared to MALDI with regular organic matrices. The 40 keV GCIB SIMS also produced peaks observed in the NP-LDI analysis, and these peaks were strongly enhanced in intensity by exposure of the sample to trifluororacetic acid (TFA) vapor prior to analysis. These MS techniques for imaging of different types of lipids create a potential overlap and cross point that can enhance the information for imaging lipids in biological tissue sections.
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| 4. |
- Mohammadi, Amir Saeid, 1984
(author)
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Label free analysis and spatial distribution of molecular lipids in brain tissue and cells using mass spectrometry imaging
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Lipids are important inherent components in brain and cell membranes, which play significant biological roles in cell function. Identification and localization of specific biomolecules such as peptides and lipids within cellular membranes is currently a major challenge in metabolomics and biological studies. With recent technological and methodological improvements, imaging mass spectrometry methods including secondary ion mass spectrometry (SIMS) and matrix-assisted laser desorption ionization (MALDI) have become promising techniques to identify and map different lipid species in tissue sections and cells. In biological investigations SIMS and MALDI often provide complementary information. SIMS provides detection of small molecules at high spatial resolution, whereas MALDI is capable of ionizing larger molecules in a sample, albeit at reduced spatial resolution. I present a sample preparation technique with gold and silver nanoparticles (NPs) compatible with both SIMS and MALDI, which provides potential complementary detection in lipid analysis by both NP-laser desorption ionization and SIMS techniques. Although these MS techniques have associated abilities there are some limitations with each method. In the technical approaches of this thesis for mass spectrometry imaging methods, I have investigated the limitations, improvements and technical developments in MALDI and SIMS, which can maximize the information available for biomolecular imaging in brain tissue sections and cells. In MALDI, analyte detection is sometimes limited due to the mass interferences from the organic matrix and the spatial resolution can also be limited by the wet organic matrix deposition on the sample surface. I show images of delocalized lipid standards (as a limitation in wet matrix deposition method in MALDI) by developing a test device. In this work, Au nanoparticles deposited (in nanoparticle-LDI) as an alternative to organic matrix have been shown to provide advantages in different lipid analysis and imaging. I investigate the lipid information that can be obtained by NP-LDI compared to two different organic matrices deposited by sublimation (as a dry matrix application method) in which each technique can be used to detect a variety of lipid species. As biological samples such as brain tissue are not favorable for a vacuum environment, the techniques for developing of sample preparation in SIMS imaging have been investigated to overcome these sample preparation challenges. Newly developed high-energy gas cluster ion beams (GCIBs) have been investigated as a primary ion source in SIMS. This offers a potent imaging technique to obtain maximum information on intact lipid species and extend the useful mass range for SIMS imaging in biological samples compared to NP-LDI and MALDI. In this work, high energy Ar GCIBs show potential abilities for ionizing the molecular ions of lipids. The second main objective is to apply high energy GCIB SIMS imaging as a promising technique to investigate changes in lipids in the cell membrane induced by application of Cisplatin, a chemotherapeutic agent that also can affect cognition. This work is aimed at gaining a better understanding of the biochemical mechanisms understanding the role of lipids in cognition.
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| 5. |
- Phan, Nhu TN, 1981, et al.
(author)
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Laser Desorption Ionization Mass Spectrometry Imaging of Drosophila Brain Using Matrix Sublimation versus Modification with Nanoparticles
- 2016
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 88:3, s. 1734-1741
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Journal article (peer-reviewed)abstract
- Laser desorption ionization mass spectrometry (LDI-MS) is used to image brain lipids in the fruit fly, Drosophila, a common invertebrate model organism in biological and neurological studies. Three different sample preparation methods, including sublimation with two common organic matrixes for matrix-assisted laser desorption ionization (MALDI) and surface assisted laser desorption ionization (SALDI) using gold nano particles, are examined for sample profiling and imaging the fly brain. Recrystallization with trifluoroacetic acid following matrix deposition in MALDI is shown to increase the incorporation of biomolecules with one matrix, resulting in more efficient ionization, but not for the other matrix. The key finding here is that the mass fragments observed for the fly brain slices with different surface modifications are significantly different. Thus, these approaches can be combined to provide complementary analysis of chemical composition, particularly for the small metabolites, diacylglycerides, phosphatidylcholines, and triacylglycerides, in the fly brain. Furthermore, imaging appears to be beneficial using modification with gold nanoparticles in place of matrix in this application showing its potential for cellular and subcellular imaging. The imaging protocol developed here with both MALDI and SALDI provides the best and most diverse lipid chemical images of the fly brain to date with LDI.
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