Mass Spectrometry Imaging of low Molecular Weight Compounds in Garlic (Allium sativum L.) with Gold Nanoparticle Enhanced Target

Fiber Laser-Generated Silver-109 Nanoparticles for Laser Desorption/Ionization Mass Spectrometry of Illicit Drugs

Cannabinoids and opioids are the most prominently used drugs in the world, with fentanyl being the main cause of drug overdose-related deaths. Monitoring drug use in groups as well as in individuals is an important forensic concern. Analytical methods, such as mass spectrometry (MS), have been found most useful for the identification of drug abuse on a small and large scale. Pulsed fiber laser 2D galvoscanner laser-generated nanomaterial (PFL 2D GS LGN) was obtained from monoisotopic silver-109. Nanomaterial was used for laser desorption/ionization mass spectrometry of selected illicit drug standards with standard high-resolution reflectron-based time-of-flight MALDI apparatus. Δ9-THC, 11-OH-THC, 11-COOH-THC, fentanyl, codeine, 6-monoacetylmorphine (6-MAM), heroin, tramadol, and methadone were chosen as test compounds. Illicit drugs were tested in a concentration range from 100 μg/mL to 10 pg/mL, equating to 50 μg to 50 fg per measurement spot. For all analyzed compounds, identification and quantification by silver-109-assisted laser desorption/ionization (LDI) MS was possible, with uncommon [M + 109Ag3]+ and [M - H]+ ions present for certain structures. The results of the quantitative analysis of drugs using silver-109 PFL 2D GS LGN for LDI MS are presented. Laser-generated NPs are proven to be useful for the analysis of selected drugs, with exceptionally good results for fentanyl monitoring in a broad range of concentrations.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2017-2018

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2018. Also included are papers that describe methods appropriate to glycan and glycoprotein analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, new methods, matrices, derivatization, MALDI imaging, fragmentation and the use of arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Most of the applications are presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and highlights the impact that MALDI imaging is having across a range of diciplines. MALDI is still an ideal technique for carbohydrate analysis and advancements in the technique and the range of applications continue steady progress.

Surface-assisted laser desorption/ionization mass spectrometry imaging: A review

In the last decades, surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) has attracted increasing interest due to its unique capabilities, achievable through the nanostructured substrates used to promote the analyte desorption/ionization. While the most widely recognized asset of SALDI-MS is the untargeted analysis of small molecules, this technique also offers the possibility of targeted approaches. In particular, the implementation of SALDI-MS imaging (SALDI-MSI), which is the focus of this review, opens up new opportunities. After a brief discussion of the nomenclature and the fundamental mechanisms associated with this technique, which are still highly controversial, the analytical strategies to perform SALDI-MSI are extensively discussed. Emphasis is placed on the sample preparation but also on the selection of the nanosubstrate (in terms of chemical composition and morphology) as well as its functionalization possibilities for the selective analysis of specific compounds in targeted approaches. Subsequently, some selected applications of SALDI-MSI in various fields (i.e., biomedical, biological, environmental, and forensic) are presented. The strengths and the remaining limitations of SALDI-MSI are finally summarized in the conclusion and some perspectives of this technique, which has a bright future, are proposed in this section.

Mass spectrometry imaging for direct visualization of components in plants tissues

Mass spectrometry is considered the most informative technique for components identification and has been widely adopted in plant sciences. However, the spatial distribution of compounds in the plant, which is vital for the exploration of plant physiological mechanisms, is missed in MS analysis. In recent years, mass spectrometry imaging has brought a great breakthrough in plant analysis because it can determine both the molecular compositions and spatial distributions, which is conducive to understand functions and regulation pathways of specific components in plants. Mass spectrometry imaging analysis of plant tissue is toward high sensitivity, high spatial resolution, and even single-cell analysis. Despite many challenges and technical barriers, such as difficulties of sample pretreatment caused by morphological diversity of plant tissues, obstacles for high spatial resolution imaging, and so on, lots of researches have contributed to remarkable progress, including improvement in tissue preparation, matrix innovation, and ionization mode development. This review focuses on the advances of mass spectrometry imaging analysis of plants in the last 5 years, including commonly used ionization techniques, technical advances, and recent applications of mass spectrometry imaging in plants.

A fast and effective approach for the discrimination of garlic origin using wooden-tip electrospray ionization mass spectrometry and multivariate classification

This paper presents the combination of wooden-tip electrospray ionization mass spectrometry (WTESI-MS) and multivariate pattern recognition methods (principal component analysis, PCA and partial least squares discriminant analysis, PLS-DA) for the rapid and reliable discrimination, via chemical fingerprints, of garlic origin. A total of 312 garlic samples grown in different countries (Brazil, China, Argentina, Spain, and Chile) were studied. The methodology was based on a direct sampling approach, which relies on loading the sample by penetrating the garlic cloves with a pre-wetted wooden tip, followed by direct prompt analysis by WTESI-MS. Thus, no sample preparation is needed, which prevents the degradation of important metabolites and increases the analytical throughput. Parameters that affects the WTESI were optimized and the best performance in terms of signal stability and intensity was achieved using the positive ion mode. Most of the ions in WTESI mass spectra were assigned to amino acids, sugars, organosulfur compounds, and lipids. The discriminative model showed good performance (accuracy rates between 81.9% and 98.6%) and enabled identifying diagnostic ions for garlic samples from different origins. The differentiation and classification of garlic origin is of major importance as this food flavoring product is widely consumed, with worldwide trade representing billions of dollars every year, and is very often the subject of fraud.

Pneumatically Sprayed Gold Nanoparticles for Mass Spectrometry Imaging of Neurotransmitters

Using citrate-capped gold nanoparticles (AuNPs) for laser desorption ionization mass spectrometry (LDI-MS) is an approach that has demonstrated broad applicability to ionization of different classes of molecules. Here, we show a simple AuNP-based approach for the ionization of neurotransmitters. Specifically, the detection of acetylcholine, dopamine, epinephrine, glutamine, 4-aminobutyric acid, norepinephrine, octopamine, and serotonin was achieved at physiologically relevant concentrations in serum and homogenized tissue. Additionally, pneumatic spraying of AuNPs onto tissue sections facilitated mass spectrometry imaging (MSI) of rabbit brain tissue sections, zebrafish embryos, and neuroblastoma cells for several neurotransmitters simultaneously using this quick and simple sample preparation. AuNP LDI-MS achieved mapping of neurotransmitters in fine structures of zebrafish embryos and neuroblastoma cells at a lateral spatial resolution of 5 μm. The use of AuNPs to ionize small aminergic neurotransmitters in situ provides a fast, high-spatial resolution method for simultaneous detection of a class of molecules that typically evade comprehensive detection with traditional matrixes.

Application of Mass Spectrometry Imaging for Visualizing Food Components

Consuming food is essential for survival, maintaining health, and triggering positive emotions like pleasure. One of the factors that drive us toward such behavior is the presence of various compounds in foods. There are many methods to analyze these molecules in foods; however, it is difficult to analyze the spatial distribution of these compounds using conventional techniques, such as mass spectrometry combined with high-performance liquid chromatography or gas chromatography. Mass spectrometry imaging (MSI) is a two-dimensional ionization technology that enables detection of compounds in tissue sections without extraction, purification, separation, or labeling. There are many methods for ionization of analytes, including secondary ion mass spectrometry, matrix-assisted laser desorption/ionization, and desorption electrospray ionization. Such MSI technologies can provide spatial information on the location of a specific analyte in food. The number of studies utilizing MSI technologies in food science has been increasing in the past decade. This review provides an overview of some of the recent applications of MSI in food science and related fields. In the future, MSI will become one of the most promising technologies for visualizing the distribution of food components and for identifying food-related factors by their molecular weights to improve quality, quality assurance, food safety, nutritional analysis, and to locate administered food factors.

Assessing the potential of sputtered gold nanolayers in mass spectrometry imaging for metabolomics applications

Mass spectrometry imaging (MSI) is a molecular imaging technique that maps the distribution of molecules in biological tissues with high spatial resolution. The most widely used MSI modality is matrix-assisted laser desorption/ionization (MALDI), mainly due to the large variety of analyte classes amenable for MALDI analysis. However, the organic matrices used in classical MALDI may impact the quality of the molecular images due to limited lateral resolution and strong background noise in the low mass range, hindering its use in metabolomics. Here we present a matrix-free laser desorption/ionization (LDI) technique based on the deposition of gold nanolayers on tissue sections by means of sputter-coating. This gold coating method is quick, fully automated, reproducible, and allows growing highly controlled gold nanolayers, necessary for high quality and high resolution MS image acquisition. The performance of the developed method has been tested through the acquisition of MS images of brain tissues. The obtained spectra showed a high number of MS peaks in the low mass region (m/z below 1000 Da) with few background peaks, demonstrating the ability of the sputtered gold nanolayers of promoting the desorption/ionization of a wide range of metabolites. These results, together with the reliable MS spectrum calibration using gold peaks, make the developed method a valuable alternative for MSI applications.

Recent advances in matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI) for in situ analysis of endogenous molecules in plants

INTRODUCTION

Mass spectrometry imaging (MSI) as a label-free and powerful imaging technique enables in situ evaluation of a tissue metabolome and/or proteome, becoming increasingly popular in the detection of plant endogenous molecules.

OBJECTIVE

The characterisation of structure and spatial information of endogenous molecules in plants are both very important aspects to better understand the physiological mechanism of plant organism.

METHODS

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) is a commonly-used tissue imaging technique, which requires matrix to assist in situ detection of a variety of molecules on the surface of a tissue section. In previous studies, MALDI-MSI was mostly used for the detection of molecules from animal tissue sections, compared to plant samples due to cell structural limitations, such as plant cuticles, epicuticular waxes, and cell walls. Despite the enormous progress that has been made in tissue imaging, there is still a challenge for MALDI-MSI suitable for the imaging of endogenous compounds in plants.

RESULTS

This review summarises the recent advances in MALDI-MSI, focusing on the application of in situ detection of endogenous molecules in different plant organs, i.e. root, stem, leaf, flower, fruit, and seed.

CONCLUSION

Further improvements on instrumentation sensitivity, matrix selection, image processing and sample preparation will expand the application of MALDI-MSI in plant research.