Metabolite imaging using matrix-enhanced surface-assisted laser desorption/ionization mass spectrometry (ME-SALDI-MS)

Liu, Qiang; Xiao, Yongsheng; Pagan-Miranda, Coral; Chiu, Yu Matthew; He, Lin

doi:10.1016/j.jasms.2008.09.011

Cited by 60 publications

(56 citation statements)

References 35 publications

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“…An adjustable iris was used to change the diameter of the laser beam, and the final beam size was determined by the largest measurable laser burn-mark left on a substrate under the highest laser fluence provided by the instrument [5]. A 35-m laser beam was used in most experiments, except for DHB-coated garlic section and CHCA-coated mouse brain section, which were imaged under a 90-m laser beam at 100-m stepwise to acquire appreciable signals [6]. CHCA/ANI-coated garlic section was imaged at 50-m stepwise.…”

Section: Ms Instrument Parameters and Data Analysismentioning

confidence: 99%

“…Both characteristics are crucial for detection of low-mass species, rendering ME-SALDI an attractive solution for MS imaging (MSI) of metabolites, especially for those where imaging at high spatial resolution under a reduced laser beam size is desired. Improved MS performance over conventional MALDI and SALDI ionization methods has been demonstrated with enhanced detection sensitivity and a broadened detection mass window [6].However, an inherent challenge associated with matrix-based laser desorption ionization sources is also present in ME-SALDI for MSI applications: it is known that most conventional MALDI matrices slowly vaporize under high vacuum (10 Ϫ7 ϳ10 Ϫ8 Torr) due to their low sublimation points. The loss of materials becomes more severe when the matrix is amorphous-a common form observed when the matrix is deposited by sublimation in a solvent-free fashion.…”

mentioning

confidence: 99%

“…Its applications in tissue imaging have been demonstrated by various groups where porous surfaces or inorganic nanoparticles have been successfully utilized as the energy mediating reagents [3][4][5]. To further improve imaging sensitivity, a hybrid ionization approach, matrix-enhanced SALDI (ME-SALDI), has been recently reported in which conventional matrix molecules were deposited atop a porous SALDI substrate to provide a proton-rich environment for enhanced ionization of desorbed species [6]. The porous SALDI substrate in ME-SALDI is believed to effectively reduce laser flux needed for analyte desorption; consequently few matrix ions and fragments are observed in the resulting spectra.…”

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confidence: 99%

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confidence: 99%

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Ionic matrix for matrix-enhanced surface-assisted laser desorption ionization mass spectrometry imaging (ME-SALDI-MSI)

Liu

2009

J. Am. Soc. Mass Spectrom.

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Matrix-enhanced surface-assisted laser desorption ionization mass spectrometry imaging (ME-SALDI MSI) has been previously demonstrated as a viable approach to improving MS imaging sensitivity. We describe here the employment of ionic matrices to replace conventional MALDI matrices as the coating layer with the aims of reducing analyte redistribution during sample preparation and improving matrix vacuum stability during imaging. In this study, CHCA/ANI (␣-cyano-4-hydroxycinnamic acid/aniline) was deposited atop tissue samples through sublimation to eliminate redistribution of analytes of interest on the tissue surface. The resulting film was visually homogeneous under an optical microscope. Excellent vacuum stability of the ionic matrix was quantitatively compared with the conventional matrix. The subsequently improved ionization efficiency of the analytes over traditional MALDI was demonstrated. The benefits of using the ionic matrix in MS imaging were apparent in the analysis of garlic tissue sections in the ME-SALDI MSI mode. To further improve imaging sensitivity, a hybrid ionization approach, matrix-enhanced SALDI (ME-SALDI), has been recently reported in which conventional matrix molecules were deposited atop a porous SALDI substrate to provide a proton-rich environment for enhanced ionization of desorbed species [6]. The porous SALDI substrate in ME-SALDI is believed to effectively reduce laser flux needed for analyte desorption; consequently few matrix ions and fragments are observed in the resulting spectra. Both characteristics are crucial for detection of low-mass species, rendering ME-SALDI an attractive solution for MS imaging (MSI) of metabolites, especially for those where imaging at high spatial resolution under a reduced laser beam size is desired. Improved MS performance over conventional MALDI and SALDI ionization methods has been demonstrated with enhanced detection sensitivity and a broadened detection mass window [6].However, an inherent challenge associated with matrix-based laser desorption ionization sources is also present in ME-SALDI for MSI applications: it is known that most conventional MALDI matrices slowly vaporize under high vacuum (10 Ϫ7 ϳ10 Ϫ8 Torr) due to their low sublimation points. The loss of materials becomes more severe when the matrix is amorphous-a common form observed when the matrix is deposited by sublimation in a solvent-free fashion. While the loss of matrix under vacuum does not necessarily impose a problem in MALDI profiling experiments where most measurements occur in seconds, it cannot be ignored during MS imaging experiments because of extended interrogation time and the preferred solvent-free approach for matrix deposition [7]. For example, for a commercial MALDI-TOF instrument equipped with a 20-Hz N 2 laser, approximately 720 pixels can be imaged in 1 h when 100 laser shots are averaged per pixel, which translates to ϳ55.6 h of instrument time to examine a 1-cm 2 tissue section with spatial resolution of 50 m, not counting the time spent for translational s...

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Section: Ms Instrument Parameters and Data Analysismentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Ionic matrix for matrix-enhanced surface-assisted laser desorption ionization mass spectrometry imaging (ME-SALDI-MSI)

Liu

2009

J. Am. Soc. Mass Spectrom.

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“…We were therefore surprised to discover in the present work that MALDI-MS detection of RNA oligonucleotides can be extended to higher mass ranges by using unmodified fused silica instead of metal targets. Activated fused silica or other target materials, such as carbon, metal oxides, or nanoparticles, have been used in matrix-free techniques to improve detection or eliminate matrix interference in detection of low molecular weight analytes [3][4][5][6][7][8][9][10], but improved detection of polymers at the higher end of the molecular weight range is unexpected.…”

Section: Introductionmentioning

confidence: 99%

Signal Enhancement of Abiotically-Synthesized RNA Oligonucleotides and other Biopolymers using Unmodified Fused Silica in MALDI-MS

Cassidy

Dong

Joshi

et al. 2011

J. Am. Soc. Mass Spectrom.

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Metal is the standard desorption platform for MALDI-MS but other surfaces have been shown to offer advantages for particular types of analytes or applications. One such substrate is fused silica, which has been employed for matrix-free detection of low mass analytes and for affinity MALDI-MS in which binding ligands are immobilized at the fused silica surface. The present work reports improved MALDI-MS detection of RNA oligonucleotides, including polyA, polyU, and polyA/U, at the high end of the mass range when unmodified fused silica is used instead of stainless steel as the MALDI target. The RNA oligonucleotides were abiotically synthesized from activated monomers on catalytic clay surfaces. Further investigation found enhanced signals as well for other anionic biopolymers, including DNA oligonucleotides and heparin. Enhancement also was observed for dextran, which is neutral, indicating that the effect is not restricted to anionic biopolymers. Among more general analytical applications, the results are particularly relevant to rapid screening of abiotic RNA polymerization toward elucidating pathways to life on Earth.

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Imaging Mass Spectrometry

Remoortere¹,

Jones²,

Deelder³

et al. 2012

Encyclopedia of Drug Metabolism and Interactions

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Imaging mass spectrometry combines the chemical specificity and parallel detection of mass spectrometry with microscopic imaging capabilities. The ability to simultaneously obtain images from all analytes detected, from atomic to macromolecular ions, allows the analyst to probe the chemical organization of a sample and to correlate this with physical features. The sensitivity of the ionization step, sample preparation, the spatial resolution, and the speed of the technique are all important parameters that affect the type of information obtained. Recently, significant progress has been made in each of these steps for both secondary ion mass spectrometry (SIMS) and matrix-assisted laser desorption/ionization (MALDI) imaging of biological samples. Examples demonstrating localization of proteins in tumors, a reduction of lamellar phospholipids in the region binding two single celled organisms, and sub-cellular distributions of several biomolecules have all contributed to an increasing upsurge in interest in imaging mass spectrometry. Here we review many of the instrumental developments and methodological approaches responsible for this increased interest, compare and contrast the information provided by SIMS and MALDI imaging, and discuss future possibilities.

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Metabolite imaging using matrix-enhanced surface-assisted laser desorption/ionization mass spectrometry (ME-SALDI-MS)

Cited by 60 publications

References 35 publications

Ionic matrix for matrix-enhanced surface-assisted laser desorption ionization mass spectrometry imaging (ME-SALDI-MSI)

Ionic matrix for matrix-enhanced surface-assisted laser desorption ionization mass spectrometry imaging (ME-SALDI-MSI)

Signal Enhancement of Abiotically-Synthesized RNA Oligonucleotides and other Biopolymers using Unmodified Fused Silica in MALDI-MS

Imaging Mass Spectrometry

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