Construction and testing of an atmospheric-pressure transmission-mode matrix assisted laser desorption ionisation mass spectrometry imaging ion source with plasma ionisation enhancement

Steven, Rory T.; Shaw, Michael; Murta, Teresa; Green, Felicia M.; Robinson, Kenneth N.; Gilmore, Ian S.; Takáts, Zoltán; Bunch, Josephine

doi:10.1016/j.aca.2018.11.003

Cited by 24 publications

(50 citation statements)

References 41 publications

(54 reference statements)

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“…Briefly, the MALDI-2 process utilizes a secondary laser aligned ~ 400 µm above the primary MALDI-1 ablation surface so that the secondary laser pulses intersect the primary MALDI-1 desorption plume at a given delay time, resulting in ionization of some of the desorbed neutrals. [35][36][37][38][39][40][41][42] The MALDI-2 ionization process is thought to result from a two-photon ionization threshold mechanism that gives rise primarily to protonated species. 34,36,43,44 MALDI-2 has been shown to improve ion yields by more than two orders of magnitude for some lipid classes.…”

Section: Introductionmentioning

confidence: 99%

“…Thus far, MALDI-2 has proven to improve sensitivity for certain molecular classes including liposoluble vitamins, mono-and oligosaccharides, certain lipid classes, and exogenous drugs. 34,36,[38][39][40][41][42][43]45,46 Lipid classes that have been shown to have dramatically increased ion intensities in positive ion mode include hexosylceramides (HexCers), phosphatidylethanolamines (PEs), phosphatidylinositols (PIs), phosphatidylglycerols (PGs), phosphatidylserines (PSs), triacylglycerols (TGs), and cholesterol esters (CEs). 34 Interestingly, other classes of lipids such as phosphatidylcholines (PCs) were not shown to increase significantly with MALDI-2.…”

Section: Introductionmentioning

confidence: 99%

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Effect of MALDI Matrices on Lipid Analyses of Biological Tissues Using MALDI-2 Post-Ionization Mass Spectrometry

McMillen¹,

Fincher²,

Klein³

et al. 2020

Preprint

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<p>Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) allows for highly multiplexed, untargeted detection of many hundreds of analytes from tissue. Recently, laser post-ionization (MALDI-2) has been developed for increased ion yield and sensitivity for lipid IMS. However, the dependence of MALDI-2 performance on the various lipid classes is largely unknown. To understand the effect of the applied matrix on MALDI-2 analysis of lipids, samples including an equimolar lipid standard mixture, various tissue homogenates, and intact rat kidney tissue sections were analyzed using the following matrices: α-cyano-4-hydroxycinnamic acid (CHCA), 2’,5’-dihydroxyacetophenone (DHA), 2’,5’-dihydroxybenzoic acid (DHB), and norharmane (NOR). Lipid signal enhancement of protonated species using MALDI-2 technology varied based on the matrix used. Although signal improvements were observed for all matrices, the most dramatic effects using MALDI-2 were observed using NOR and DHB. For lipid standards analyzed by MALDI-2, NOR provided the broadest coverage, enabling the detection of all 13 protonated standards, including non-polar lipids, whereas DHB gave less coverage but gave the highest signal increase for those lipids recorded. With respect to tissue homogenates and rat kidney tissue, mass spectra were compared and showed that the number and intensity of neutral lipids tentatively identified with MALDI-2 using NOR increased significantly (e.g. 5-fold intensity increase for triacylglycerol). In the cases of DHB with MALDI-2, the number of protonated lipids identified from tissue homogenates doubled with 152 on average compared to 76 with MALDI alone. High spatial resolution imaging (~20 µm) of rat kidney tissue showed similar results using DHB with 125 lipids tentatively identified from MALDI-2 spectra versus just 72 using standard MALDI. From the four matrices tested, NOR provided the greatest increase in sensitivity for neutral lipids (triacylglycerol, diacylglycerol, monoacylglycerol, cholesterol ester) and DHB provided the highest overall number of lipids detected using MALDI-2 technology. </p>

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of MALDI Matrices on Lipid Analyses of Biological Tissues Using MALDI-2 Post-Ionization Mass Spectrometry

McMillen¹,

Fincher²,

Klein³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Briefly, the MALDI-2 process utilizes a secondary laser aligned $400 μm above the primary MALDI-1 ablation surface so that the secondary laser pulses intersect the primary MALDI-1 desorption plume at a given delay time, resulting in ionization of some of the desorbed neutrals. [35][36][37][38][39][40][41][42] The MALDI-2 ionization process is thought to result from a two-photon ionization threshold mechanism that gives rise primarily to protonated species. 34,36,43,44 MALDI-2 has been shown to improve ion yields by more than two orders of magnitude for some lipid classes.…”

Section: Introductionmentioning

confidence: 99%

“…Thus far, MALDI-2 has proven to improve sensitivity for certain molecular classes including liposoluble vitamins, monosaccharide and oligosaccharide, certain lipid classes, and exogenous drugs. 34,36,[38][39][40][41][42][43]45,46 Lipid classes that have been shown to have dramatically increased ion intensities in positive ion mode include hexosylceramides (HexCers), phosphatidylethanolamines (PEs), phosphatidylinositols (PIs), phosphatidylglycerols (PGs), phosphatidylserines (PSs), triacylglycerols (TGs), and cholesterol esters (CEs). 34 Interestingly, other classes of lipids such as phosphatidylcholines (PCs) were not shown to increase significantly with MALDI-2.…”

Section: Introductionmentioning

confidence: 99%

Effect of MALDI matrices on lipid analyses of biological tissues using MALDI‐2 postionization mass spectrometry

et al. 2020

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Matrix‐assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) allows for highly multiplexed, untargeted detection of many hundreds of analytes from tissue. Recently, laser postionization (MALDI‐2) has been developed for increased ion yield and sensitivity for lipid IMS. However, the dependence of MALDI‐2 performance on the various lipid classes is largely unknown. To understand the effect of the applied matrix on MALDI‐2 analysis of lipids, samples including an equimolar lipid standard mixture, various tissue homogenates, and intact rat kidney tissue sections were analyzed using the following matrices: α‐cyano‐4‐hydroxycinnamic acid, 2′,5′‐dihydroxyacetophenone, 2′,5′‐dihydroxybenzoic acid (DHB), and norharmane (NOR). Lipid signal enhancement of protonated species using MALDI‐2 technology varied based on the matrix used. Although signal improvements were observed for all matrices, the most dramatic effects using MALDI‐2 were observed using NOR and DHB. For lipid standards analyzed by MALDI‐2, NOR provided the broadest coverage, enabling the detection of all 13 protonated standards, including nonpolar lipids, whereas DHB gave less coverage but gave the highest signal increase for those lipids recorded. With respect to tissue homogenates and rat kidney tissue, mass spectra were compared and showed that the number and intensity of neutral lipids tentatively identified with MALDI‐2 using NOR increased significantly (e.g., fivefold intensity increase for triacylglycerol). In the cases of DHB with MALDI‐2, the number of protonated lipids identified from tissue homogenates doubled with 152 on average compared with 76 with MALDI alone. High spatial resolution imaging (~20 μm) of rat kidney tissue showed similar results using DHB with 125 lipids tentatively identified from MALDI‐2 spectra versus just 72 using standard MALDI. From the four matrices tested, NOR provided the greatest increase in sensitivity for neutral lipids (triacylglycerol, diacylglycerol, monoacylglycerol, and cholesterol ester), and DHB provided the highest overall number of lipids detected using MALDI‐2 technology.

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“…Analysis of molecular standards and murine brain tissue sections was performed by this group. 19 In another study, a microwave argon plasma was employed as an ionization source for analyte particles in ion trap mass spectrometry without any sample preparation steps. Three compounds, including pure analytes, analytes in molecularly imprinted polymers (analyte-MIPs), and bioanalytes (drugs) in medical tablets, were analyzed.…”

Section: Introductionmentioning

confidence: 99%

Protein ion yield enhancement in matrix‐assisted laser desorption/ionization mass spectrometry after sample and matrix low‐pressure glow discharge plasma irradiation

Hajiani

Ghassempour

Shokri

2020

Rapid Comm Mass Spectrometry

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Rationale Plasma‐assisted ionization is widely used in mass spectrometry; in this study, a low‐pressure glow discharge is introduced as a new method to improve the detection of large proteins, and bovine serum albumin (BSA) is used as a protein model. The treatment of analyte, matrix, and the matrix/analyte mixture is evaluated under optimal conditions. Methods Low‐pressure radio‐frequency capacitively coupled plasma (RF‐CCP) treatment is utilized in the sample preparation step of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) to enhance the protein MALDI ion signal. Plasma treatment can be an effective tool for enhancing the non‐covalent binding of the analyte with the matrix, incorporation of the analyte into the matrix, production of matrix/analyte crystals, and analyte protonation through plasma activation, resulting in an improved MALDI ion signal. Results Fourier‐transform infrared (FTIR) spectroscopy allows us to distinguish between the functional groups of plasma‐treated and control samples. In addition, optical emission spectroscopy (OES) determines the plasma species, and zeta potential analysis characterizes the potential difference between plasma‐treated and control samples before MALDI‐TOF MS analysis. Plasma‐treated BSA can provide a five‐times enhancement of ion intensity. The combination of the plasma‐treated analyte with the plasma‐treated matrix leads to an increase in the ion intensity by a factor of 14. Conclusions Low‐pressure glow discharge plasma treatment greatly enhances MALDI ion signals, with a noticeable increase in incorporation, co‐crystallization, protonation, and the concentration of the sample functional groups.

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Construction and testing of an atmospheric-pressure transmission-mode matrix assisted laser desorption ionisation mass spectrometry imaging ion source with plasma ionisation enhancement

Cited by 24 publications

References 41 publications

Effect of MALDI Matrices on Lipid Analyses of Biological Tissues Using MALDI-2 Post-Ionization Mass Spectrometry

Effect of MALDI Matrices on Lipid Analyses of Biological Tissues Using MALDI-2 Post-Ionization Mass Spectrometry

Effect of MALDI matrices on lipid analyses of biological tissues using MALDI‐2 postionization mass spectrometry

Protein ion yield enhancement in matrix‐assisted laser desorption/ionization mass spectrometry after sample and matrix low‐pressure glow discharge plasma irradiation

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