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The core@shell nanostars composed of star-like Au nanocores with TiO2 shells (Au@TiO2 NSs) are synthesized in a one-pot reaction without any reducing or surface-controlling agents. The Au@TiO2 NSs exhibit strong absorption in the UV region based on the interaction between the Au nanocore and the TiO2 shell, and this optochemical property leads to the efficient laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) analysis of small molecules with low background interference and high reproducible mass signals compared with spherical Au nanoparticles (NPs). The limit of detection and dynamic range values of various analytes also improved with Au@TiO2 NSs compared with those obtained with spherical Au NPs. Our findings successfully demonstrate that Au@TiO2 NSs are a promising matrix for the LDI-TOF-MS analysis of various small molecules as well as synthetic polymers. [ABSTRACT FROM AUTHOR]

The fragmentation of phosphomolybdic acid (PMA) is studied via laser desorption and ionization. It is found that during laser desorption and ionization, acid crystals tend to form cluster-type species of (MoO3)n and HPO3⋅(MoO3)n. Species with the general formula HPO2⋅(MoO3)n and containing Mo5+ and Mo6+ are identified in the mode of positive ion detection. Hydrated H3PMo12O40⋅MoO3⋅4H2O molecular ions are detected in mass spectrometric studies of PMA solutions with a 2,5-dihydroxybenzoic acid matrix. Studying the effect parameters of laser desorption and ionization have on the information content of mass spectra show that peak intensity, laser power, and number of shots are generally in a symbate relationship. The peak intensity depends on the laser power more than on the number of shots. [ABSTRACT FROM AUTHOR]

Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) based on micro/nanostructured materials with different natures has received increasing attention for the analysis of a wide variety of analytes. However, up to now, only a few studies have shown the application of simple platforms in MALDI-MS for the identification of intact proteins. The present work reports on the application of copper oxide particles (Cu2O PS), obtained by a greener route, in combination with low amounts of 2,5-dihydroxybenzoic acid (DHB) as a novel hybrid platform. The combined Cu2O PS@DHB matrix, containing only 2.5 mg mL−1 of particles and 10 mg mL−1 of DHB, was easily applicable in MALDI-MS without surface modification of target plates. Under optimal conditions, the analysis of intact proteins up to 150,000 Da was possible, including immunoglobulin G, bovine serum albumin, and cytochrome C with adequate spot-to-spot signal reproducibility (RSD < 10%). In addition, the analysis of glycopeptides from IgG digests was carried out to prove the multipurpose application of the Cu2O PS@DHB platform in the low m/z range (2500–3000 Da). From the obtained results, it can be concluded that the optical and surface properties of as-synthesized Cu2O PS are likely to be responsible for the superior performance of Cu2O PS@DHB in comparison with conventional matrices. In this sense, the proposed user-friendly methodology opens up the prospect for possible implementation in bioanalysis and diagnostic research. [ABSTRACT FROM AUTHOR]

Background. Study of properties and intermolecular interactions of biologically active compounds which can be used for the purposes of transmembrane drugs delivery is a topical task of modern molecular biophysics. Ascorbyl Palmitate (AP) as a fat-soluble form of vitamin C has recently attracted attention as a promising agent for formation of nanosomes for the “fat insoluble” drug molecules transfer through membranes. However, AP is not sufficiently characterized by up-to-date soft ionization mass spectrometric techniques. Objectives. The aim of the present work is to characterize AP and its intermolecular interactions by a number of mass spectrometric techniques: Electrospray Ionization (ESI), Laser Desorption/Ionization (LDI) and Matrix-Assisted Laser Desorption/Ionization (MALDI). The comparison of these techniques applicability to the study of AP intermolecular interactions as a drug delivery assisting agent is scheduled. Methods. ESI mass spectra are obtained with triple quadrupole Micromass Quattro mass spectrometer. LDI and MALDI experiments are performed by Autoflex II mass spectrometer. Results. In the ESI experiments in the positive ion mode abundant peaks of protonated and cationized AP molecules as well as the peaks of AP clusters nAP•H+ and nAP•Na+ (n=2÷4) are revealed in the mass spectra. This result testifies to the formation of stable noncovalent complexes of the AP molecules in the polar media and confirms the AP ability of formation nanosomes for drug delivery. Analysis of LDI and MALDI mass spectra of AP in positive and negative ion modes shows that in the presence of molecular ions of AP, the peaks of AP dimers or larger AP clusters are not recorded. The ESI probing of the model system containing AP and dipalmitoylphosphatidylcholine (DPPC) reveals stable AP•DPPC•H+ complex which models the AP intermolecular interactions with the phospholipid components of biomembranes and/or liposomes under AP functioning as a drug delivery assisting agent. Conclusions. The current study demonstrates the applicability of all tested mass spectrometric techniques for AP identification in solutions and solid phase, while for the purpose of examining of the AP noncovalent complexes formation and study of AP interactions with biomolecules the ESI is defined as the most effective technique.

The waste stream of low-grade wool is an underutilized source of keratin-rich materials with appropriate methods for upcycling into high value-added products still being an open challenge. In the present work, keratins were precipitated from their water solution to produce hierarchical keratin particles via isoelectric precipitation. Matrix-assisted laser desorption/ionization coupled with time-of-flight tandem mass spectrometry analysis (MALDI-TOF/TOF MS/MS) showed the presence of the amino acid sequence leucine–aspartic acid–valine (LDV) in the extracted keratin. This well-known cell adhesion motif is recognized by the cell adhesion molecule α4β1 integrin. We showed that keratin particles had this tripeptide exposed on the surface and that it could be leveraged, via patterns obtained with microcontact printing, to support and facilitate dermal fibroblast cell adhesion and direct their growth orientation. The zeta potential, isoelectric point, morphological structures, chemical composition, and biocompatibility of keratin particles and the influence of the surfactant sodium dodecyl sulfate (SDS) were investigated. An appropriate ink for microcontact printing of the keratin particles was developed and micron-sized patterns were obtained. Cells adhered preferentially to the patterns, showing how this strategy could be used to functionalize biointerfaces. [ABSTRACT FROM AUTHOR]

The presence of certain microorganisms in dairy products or silage is highly desirable. Among them are probiotic strains of lactic acid bacteria (LAB), which show many beneficial features, including antimicrobial properties that support the development of beneficial microflora; in addition, owing to their biochemical activity, they influence the nutritional, dietary, and organoleptic properties of food products. Before being placed on the market, each strain requires separate testing to determine its probiotic properties and effectiveness. The aim of this study was to isolate LAB strains from a pickled beetroot sample that could be used in the dairy industry and with the potential to be considered as a probiotic in the future. Two strains identified using the MALDI technique were selected—Lactococcus lactis and Weissella cibaria. The optimal growth conditions of the strains were determined, and their proteolytic properties were assessed with the use of the o-PA reagent and spectrophotometry. The lipid profile was analyzed using the SALDI (surface-assisted laser desorption/ionization) technique and silver nanoparticles. High-performance liquid chromatography was used to assess the ability of the strains to synthesize beneficial metabolites, such as B vitamins (B2, B3, and B9) or lactic acid, and gas chromatography was used to analyze the substances responsible for organoleptic properties. Moreover, the ability to inhibit the growth of pathogenic strains was also tested in the selected strains. Both tested strains demonstrated the desired properties of starter cultures for future use in functional food production, showing that fermented plant products can serve as valuable potential probiotic sources. [ABSTRACT FROM AUTHOR]

Plasmonic nanoshells have been acknowledged as efficient nanomaterials for laser desorption/ionization mass spectrometry (LDI-MS) detection of a wide range of small molecules, whereas their applications in mass spectrometry imaging (MSI) are less developed. In this work, we constructed and optimized SiO2@Au nanoshells with tailor-made shell structures and compositions for high-sensitivity LDI-MS analysis and a wide range of MSI applications. Owing to the synergistic effects of plasmonic shells with nanoscale roughness and specific crevice space for the selective trapping of small molecules and cations, SiO2@Au core–shell nanoparticles exhibit superior performance for the detection of a vast diversity of small molecules, including amino acids, oligosaccharides, dyestuff and drugs, peptides, nucleosides, and poly-(ethylene glycols). Compared with organic matrices, this method affords a high reduction in matrix interference, higher analyte coverage, lower detection limits ranging from fmol to pmol, and good repeatability with relative standard deviation (RSD) below 5%. Due to the nanoscale size and homogeneous deposition of SiO2@Au nanoshells, the spatial distribution of various small-molecule metabolites can be visualized in strawberry tissues at a pixel size of 100 μm without imaging artifacts. More valuably, the universality of SiO2@Au-assisted LDI-MSI is further demonstrated for mapping the lipid distribution within the whole-body tissues of zebrafish (Danio rerio), honeybees (Apis cerana), and mouse brain tissues in a spatially resolved manner at pixel sizes of 55, 30, and 50 μm, respectively. These results facilitate the expansion of the abilities of plasmonic core–shell nanoparticles in real-case MSI applications. Taken together, the results indicate that the SiO2@Au nanoshells are expected to be promising and efficient nanomaterials with superior DI efficiency and imaging capabilities, especially in the environmental science and life science fields. [ABSTRACT FROM AUTHOR]

The ligand exchange process on gold nanorods (Au NRs) was explored by using laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS). Cetyltrimethylammonium bromide (CTAB) adsorbed on Au NRs was replaced with alkanethiol derivatives presenting different functional groups. The ligand exchange process was investigated under various conditions, such as in the presence of different functional groups in the ligands and with different concentrations of CTAB. The ligand-exchanged Au NRs were characterized by using a combination of UV–Vis spectroscopy and LDI-TOF-MS. Based on the results, it was revealed that LDI-TOF-MS analysis can provide crucial and distinct information about the degree of ligand exchange on Au NRs. [ABSTRACT FROM AUTHOR]

A facile approach for the synthesis of a silver nanostructured layer for application in surface-assisted laser desorption/ionization mass spectrometry of low-molecular-weight biomolecules was developed using electrochemical deposition. The deposition was carried out using the following silver salts: trifluoroacetate, acetate and nitrate, varying the voltage and time. The plate based on trifluoroacetate at 10 V for 15 min showed intense SALDI-MS responses for standards of various classes of compounds: fatty acids, cyclitols, saccharides and lipids at a concentration of 1 nmol/spot, with values of the signal-to-noise ratio ≥50. The values of the limit of detection were 0.71 µM for adonitol, 2.08 µM for glucose and 0.39 µM for palmitic acid per spot. SEM analysis of the plate showed anisotropic flower-like microstructures with nanostructures on their surface. The reduced chemical background in the low-mass region can probably be explained by the absence of stabilizers and reducing agents during the synthesis. The plate synthesized with the developed approach showed potential for future use in the analysis of low-molecular-weight compounds of biological relevance. The absence of the need for the utilization of sophisticated equipment and the synthesis time (10 min) may benefit large-scale applications of the layer for the detection of various types of small biomolecules. [ABSTRACT FROM AUTHOR]

Renal cell carcinoma (RCC) is a very aggressive and often fatal heterogeneous disease that is usually asymptomatic until late in the disease. There is an urgent need for RCC specific biomarkers that may be exploited clinically for diagnostic and prognostic purposes. Serum and urine samples were collected from patients with diagnosed kidney cancer and assessed with gold nanoparticle enhanced target (AuNPET) surface assisted-laser desorption/ionization mass spectrometry (SALDI MS) based metabolomics and statistical analysis. A database search allowed providing assignment of signals for the most promising features with a satisfactory value of the area under the curve and accuracy. Four potential biomarkers were found in urine and serum samples to distinguish clear cell renal cell carcinoma (ccRCC) from controls, 4 for the ccRCC with and without metastases, and 6 metabolites to distinguish low and high stages or grades. This pilot study suggests that serum and urine metabolomics based on AuNPET-LDI MS may be useful in distinguishing types, grades and stages of human RCC. [ABSTRACT FROM AUTHOR]

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) emerges as an effective method for analyzing small molecules. At the current stage, its application is still limited by its detection sensitivity. According to the mechanism of SALDI-MS, the sensitivity highly depends on the laser desorption/ionization (LDI) efficiency. In this study, we adjust the localized surface plasmon resonance (LSPR) between particles by changing the gap, thereby improving the efficiency of LDI. The gaps of nanoparticles can be adjusted by the ionic strength in the solution. With the decrease of the gaps, the thermal effect of the nanoparticles is gradually enhanced and the number of excited electrons is also increased, which improves the sensitivity of SALDI-MS. The prepared substrate with optimized gaps has wide applicability for the detection of small biomolecules and dye molecules. Moreover, the substrate can successfully detect trace small molecules in complex samples. The analysis of sulfonamide in lake water shows the commendable performance of the substrate. The relative standard deviations (RSD) of spot-to-spot and batch-to-batch are 3.73% and 7.22% respectively, confirming the high reproducibility and the detection limit is as low as 100 pM, indicating the high sensitivity of the substrate. The results demonstrate that adjusting the LSPR of metal nanoparticles is a promising method for improving the performance of SALDI-MS. [Display omitted] • Homogeneous AuNPs were prepared on the substrate. • The gaps of AuNPs were optimized by changing the ionic strength. • The substrate demonstrated remarkable sensitivity and reproducibility. • The substrate could be used for practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon nanocoating and lithium cationization facilitate laser desorption/ionization of lignans. • High signal intensity allowed for structural studies of lignans by tandem SALDI MS. • Post-source decay, high-, and low-energy CID fragmentation techniques were used. • Rapid and low-cost method for screening of lignans in plant biomass was proposed. • The developed approach was successfully tested on real coniferous knotwood extracts. Lignans are one of the most widespread classes of plant secondary metabolites possessing unique biological activities. The search for new sources of such compounds, their screening and identification in plant biomass is an urgent task, requiring the use of advanced analytical methods. In the present study, matrix-free surface assisted laser desorption/ionization (SALDI) mass spectrometry was proposed for its solution. The combination of carbon nanocoating sputtered on a target plate with lithium cationization allowed obtaining high-quality mass spectra of eight coniferous wood lignans with different bonds between aromatic units (secoisolariciresinol, matairesinol, 7-hydroxymatairesinol, nortrachelogenin, pinoresinol, guaiacylglycerol- β -guaiacyl ether, dehydrodihydrodiisoeugenol, and divanillin). Three types of fragmentation methods (post-source decay, high- and low-energy collision induced dissociation) for the first time were implemented on two types of MALDI instruments. Regardless of tandem mass spectrometry technique, lignans demonstrated the similar fragmentation patterns including the cleavage of bonds between aromatic units with the formation of mostly lithiated product ions. The low-energy collision induced dissociation in quadrupole ion trap provided the most informative tandem mass spectra and multi-stage fragmentation capabilities in structural studies. On this basis, an approach to rapid, high-throughput, and low-cost screening and tentative identification of lignans including isomeric compounds in plant biomass was developed and successfully tested on real samples of pine, fir, spruce, and larch knotwood extracts. [ABSTRACT FROM AUTHOR]

The presence of certain microorganisms in dairy products or silage is highly desirable. Among them are probiotic strains of lactic acid bacteria (LAB), which show many beneficial features, including antimicrobial properties that support the development of beneficial microflora; in addition, owing to their biochemical activity, they influence the nutritional, dietary, and organoleptic properties of food products. Before being placed on the market, each strain requires separate testing to determine its probiotic properties and effectiveness. The aim of this study was to isolate LAB strains from a pickled beetroot sample that could be used in the dairy industry and with the potential to be considered as a probiotic in the future. Two strains identified using the MALDI technique were selected—Lactococcus lactis and Weissella cibaria. The optimal growth conditions of the strains were determined, and their proteolytic properties were assessed with the use of the o-PA reagent and spectrophotometry. The lipid profile was analyzed using the SALDI (surface-assisted laser desorption/ionization) technique and silver nanoparticles. High-performance liquid chromatography was used to assess the ability of the strains to synthesize beneficial metabolites, such as B vitamins (B2, B3, and B9) or lactic acid, and gas chromatography was used to analyze the substances responsible for organoleptic properties. Moreover, the ability to inhibit the growth of pathogenic strains was also tested in the selected strains. Both tested strains demonstrated the desired properties of starter cultures for future use in functional food production, showing that fermented plant products can serve as valuable potential probiotic sources.

Abstract Nutriology relies on advanced analytical tools to study the molecular compositions of food and provide key information on sample quality/safety. Small nutrients detection is challenging due to the high diversity and broad dynamic range of molecules in food samples, and a further issue is to track low abundance toxins. Herein, we developed a novel plasmonic matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) approach to detect small nutrients and toxins in complex biological emulsion samples. Silver nanoshells (SiO2@Ag) with optimized structures were used as matrices and achieved direct analysis of ~ 6 nL of human breast milk without any enrichment or separation. We performed identification and quantitation of small nutrients and toxins with limit-of-detection down to 0.4 pmol (for melamine) and reaction time shortened to minutes, which is superior to the conventional biochemical method currently in use. The developed approach contributes to the near-future application of MALDI MS in a broad field and personalized design of plasmonic materials for real-case bio-analysis.

Powders of boron, magnesium and tungsten before and after mechanochemical activation are studied via laser desorption/ionization. It is found that the activation process removes low molecular weight hydrocarbon impurities and high molecular weight clusters of oxides and hydroxides. It is shown that this technique allows determination of clusters in a wide range of masses. [ABSTRACT FROM AUTHOR]

Carbon fiber (CNF), prepared by carbonization of electrospun polyacrylonitrile (PAN) fibers, is systematically investigated as a mediator to replace conventional organic matrices for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). CNF exhibits a high salt tolerance, sensitivity, and resolution for organic matrix-free laser desorption/ionization time-of-flight mass spectrometry (LDI-MS) analysis of various analytes under both positive and negative ionization modes. Especially, saccharides, a neutral molecule having low negative ionization efficiency, are successfully detected with CNF. Taken together, this study clearly demonstrates CNF is a promising material to develop an efficient and universal platform for LDI-MS analysis regardless of preferential ionization modes of analytes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bimetallic plasmonic array was self-assembled at liquid–liquid interface. • The array facilitated affinity-based capture and signal amplification in MS analysis. • Fast and accurate quantification of nucleosides was achieved using trace biofluids. Metabolites, depicting physiological and pathophysiological state, underpin diverse disease-associated phenomena. Metabolite detection offers insights for identifying disease biomarkers and monitoring treatment responses, thereby facilitating early disease diagnosis and personalized medicine. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) holds promise in molecular profiling, with advanced materials emerging as efficient matrices for metabolite detection. Yet, their preferences in analyzing various metabolites have not been systematically explored, hindering the development of matrices for suitable clinical practice. Herein, we report plasmonic array assisted MS for fast and direct quantification of specific metabolites in human biofluids. Plasmonic array is prepared by self-assembling hybrid bimetallic alloys at liquid–liquid interfaces. Large scale screening of 37 metabolites exhibited LDI preferences of plasmonic array especially for nucleosides. Plasmonic array enables sensitive and selective detection of nucleosides, due to the synergistic effect via alloy composition and chemical interactions without the use of costly antibodies. Consequently, accurate quantification is achieved with a recovery rate of 103.18 % ± 3.78 % for inosine, consuming a trace amount of serum as low as 4 μL within seconds. This work provides useful guidelines for matrix design in the MALDI MS analysis of metabolites toward biomedical applications. [ABSTRACT FROM AUTHOR]

According to the matrix-free laser desorption/ionization time-of-flight mass spectrometric data, the reaction of benzimidazole with bis(iodomethyl)tetramethyldisiloxane at different temperatures leads to the formation of linear and cyclic organosilicon systems containing benzimidazole fragments. The structures of the major and minor products were determined by analysis of the fragmentation patterns in the field-free space. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have drawn great interest in recent decades due to their fascinating structures, unusual physical properties, versatile modification strategies, and biological compatibilities. In this review, we describe recent progress in the application of MOFs to matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Owing to their high porosities, specific affinities, and photon absorption capacities, MOFs can be used as solid adsorbents to selectively capture peptides (including endogenous peptides, phosphopeptides, and glycopeptides) and as matrices in MALDI MS. Current developments in and future prospects for this field of research are also discussed. [ABSTRACT FROM AUTHOR]

Upon laser irradiation, sulfur extracts chemically bound copper from its compounds, and forms Cu x S y − clusters, supporting Goldschmidt's classification that copper is a chalcophile. Moreover, an array of Cu–S ion clusters (with m / z ratios extending to over 8000) are formed when a mixture of copper and sulfur is irradiated with UV light. Samples of elemental copper, upon laser irradiation under negative-ion LDI-MS conditions, do not generate noticeable signals for copper-bearing gaseous ions. In contrast, a several thousand-fold enhancement of the generated ion current was observed when freshly made mixtures of copper and sulfur powders were laser-ablated. Time-of-flight mass spectra recorded showed a range of peaks with m / z ratios extending to over m / z 8000, indicating the formation in situ of an array of Cu–S ion clusters by a chemical reaction that takes place between the two elements upon laser irradiation. Evidently, sulfur acts as a potent reactive matrix and generates at least three distinguishable series of ion clusters: Cu 1 S x − (x = 2, 3, 4...), Cu 2 S y − (y = 3, 4, 5...), and Cu 3 S z − (z = 3, 4, 5...). Laser ablation of CuS alone did not produce signals beyond m / z 600. Some of the high-mass ions formed in this manner were isobaric; consequently, composite peaks were observed under low-resolution MS conditions. Under high-resolution conditions, however, we were able to separate and determine the composition of some isobaric mixtures. For example, the peak recorded at m / z 287 was resolved to two peaks that represented primarily the 63Cu 2 65Cu32S 3 − and 63Cu32S 7 − ions. Intriguingly, the spectra recorded from many copper-containing minerals mixed with sulfur were remarkably similar to those acquired from copper-and-sulfur mixtures, which demonstrated that elemental sulfur has the ability to extract chemically bound copper even from its compounds, and form gas-phase Cu–S clusters of varying composition. [ABSTRACT FROM AUTHOR]

A solution of fullerene C 60 in N -methylpyrrolidone (NMP) presents a suitable system for obtaining fullerene's clusters with the tunable size. However, the mechanism of fullerenes interaction with polar NMP molecules is still elusive. Herein, we present the measured laser desorption/ionization mass spectra (LDI MS) of the precipitates produced from C 60 /NMP solutions of different age in comparison with the typical spectra of C 60 crystallized from toluene and benzene. The distinctive characteristics of the C 60 /NMP mass spectra were identified and carefully examined. The number of characteristic peaks and their relative intensities in the spectra strongly depend on the age of initial C 60 /NMP solutions. This effect was attributed to the specific C 60 -NMP interactions in the solution, namely to the formation of charge-transfer complexes of C 60 with NMP molecules followed by fullerene cluster formation. The results of additional measurements carried out by means of small-angle X-ray scattering (SAXS), nuclear magnetic resonance (NMR), UV–Vis absorption spectroscopy together with the density functional theory (DFT) calculations are in accord with the proposed hypothesis. Unlabelled Image • State of C 60 in N -methylpyrrolidone solution studied using MS, SAXS, NMR, UV, DFT • С 60 /NMP MS spectra qualitatively different from C 60 /TL and C 60 /BZ • Number of characteristic peaks in MS spectra depends on age of C 60 /NMP solutions. • Formation of C 60 -NMP complexes is revealed experimentally and qualified using DFT. • The relation of complexes and cluster growth discovered [ABSTRACT FROM AUTHOR]

Abstract Herein, a robust and homogeneous porous poly(3,4-ethylenedioxythiophene)/graphene (PEDOT/graphene) thin film surface-assisted laser desorption/ionization (SALDI) functional platform was prepared through a rapid and facile in-situ photopolymerization method. The graphene-embedded PEDOT skeleton well circumvented the aggregation-related problems in the traditional carbon-based SALDI method which combined with time-of-flight mass spectrometer (TOF MS). As a result, the reproducibility and quantitative capacity of the SALDI platform were significantly improved. Furthermore, the highly efficient adsorption performance of the PEDOT/graphene thin film was demonstrated in terms of in vitro and in vivo solid-phase microextraction (SPME) extraction. It showed that porous morphology with abundant graphene doping favored the adsorption and enrichment of target analytes. Owing to the excellent adsorption capability of the PEDOT/graphene thin film and the inherent strong laser absorption ability of graphene, expected SALDI effect (3–13 times higher than the commercial nanomaterial-assisted LDI plate) and quantitative analysis (linear range 0.5–100 μg L−1) of the PEDOT/graphene functional surfaces were achieved. As for the real-world applications, we deployed the PEDOT/graphene thin film SALDI platform for the analysis of five estrogens in biological samples at microliter-volume level, without tedious sample preparation procedures. Satisfactory recoveries ranging from 60.6% to 99.0% were obtained. The present study suggested that the graphene-embedded PEDOT skeleton with porous morphology would be developed as promising coating for the adsorption of analytes of interest. Additionally, the combination of PEDOT with graphene not only expanded the application fields of PEDOT, but also offered an efficient strategy for preparing homogeneous functional surfaces to realize the quantitative analysis in SALDI method. Graphical abstract fx1 Highlights • Robust and homogeneous porous PEDOT/graphene based SALDI platform was prepared via an in-situ photopolymerization method. • The graphene-embedded PEDOT skeleton well circumvented the aggregation-related problems. • The high-efficiency adsorption performance of the PEDOT/graphene thin film was demonstrated by in vitro and in vivo SPME. • The analyses of estrogens in biosamples at μL-volume level without tedious sample preparation procedures were realized. [ABSTRACT FROM AUTHOR]

Matrix-assisted laser desorption/ionization (MALDI) has been considered as one of the most powerful analytical tools for mass spectrometry (MS) analysis of large molecular weight compounds such as proteins, nucleic acids, and synthetic polymers thanks to its high sensitivity, high resolution, and compatibility with high-throughput analysis. Despite these advantages, MALDI cannot be applied to MS analysis of small molecular weight compounds (2 carbon domains surrounded by sp3 carbon matrix. Chemical modification of GO can precisely tune its physicochemical properties, and it can be readily incorporated with other functional nanomaterials. In this review, the advances of GO derivatives and their nanohybrid structures as alternatives to organic matrices are summarized to demonstrate their potential and practical aspect for MALDI-TOF-MS analysis of small molecules.

We demonstrate the performance of the degradation analysis of N,N″‐Di(1‐naphthyl)‐N,N″‐diphenyl‐(1,1″‐biphenyl)‐4,4″‐diamine (NPB) by laser desorption/ionization time of flight mass spectrometry (LDI‐TOF MS), which is a rapid and accurate technique for material identification. The difference of normal and degraded areas of NPB was clearly shown in mass spectra. Degraded areas were visualized by using LDI‐TOF MS imaging with high spatial resolution of 5 μm. Positive and negative mass spectra of 9,10‐Di(1‐naphthyl)anthracene (α‐ADN) with 98%(HPLC) purity were obtained to determine impurities in OLED materials. The bromine ion that generated impurities during the synthetic process was detected in the negative spectrum of α‐ADN. This technique provides a convenient method to validate the performance and stability of OLED device. [ABSTRACT FROM AUTHOR]

Surface-assisted laser desorption/ionization mass spectrometry on gold nanoparticle enhanced target (AuNPET) technique was used for metabolomic analysis and secondary metabolites detection of two mould strains – Aspergillus versicolor and Penicillium chrysogenum in model conditions on microbiological malt extract agar medium. Results obtained with the use of AuNPET-based mass spectrometry technique were compared with traditional matrix-assisted laser desorption/ionization (MALDI) method based on α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) matrices. Gold nanoparticle enhanced target method enabled effective ionization of microbial cellular extract ingredients without interference from the matrix and also improved calibration of spectra resulting in the detection of much higher amount of characteristic metabolites for studied organisms than MALDI. [ABSTRACT FROM AUTHOR]

In this work, a novel strategy for highly efficient detection of small molecules with a homogeneous carbon nanosphere film-spot (HCNFs) was carried out for the first time by negative surface-assisted laser desorption/ionization time-of-flight mass spectroscopy (SALDI-TOF MS). The HCNFs was fabricated by monolayer oxidized carbon nanospheres (OCS) self-assembling on laser desorption/ionization (LDI) target. With the HCNFs, no background interference and exclusive deprotonated ([M−H] − ) peaks of analytes were obtained for a wide range of small biomolecules including fatty acids, amino acids, nucleobases, traditional Chinese medicines, and anti-cancer drugs in the negative SALDI-TOF MS. Comparing with other carbon-based matrices as well as the organic matrix, the monolayer OCS film exhibited various advantages including fewer interfering fragments, stronger signal intensities, and higher detection sensitivity. Moreover, with the improved spotting homogeneity of the HCNFs, “sweet-spot” searching on LDI target was avoided and good reproducibility was obtained in the LDI-TOF MS analysis. This study is expanding the application of carbon nanospheres and providing a promising approach for rapid analysis of small molecules with none-interference and good reproducibility. [ABSTRACT FROM AUTHOR]

Mass spectrometric imaging (MSI) has received considerable attention in recent years, since it allows the molecular mapping of various compound classes, such as proteins, peptides, glycans, secondary metabolites, lipids, and drugs in animal, human, or plant tissue sections. In the present study, the application of laser-based MSI analysis of secondary plant metabolites to monitor their transport from the grass leaves of Dactylis glomerata, over the crop of the grasshopper Chorthippus dorsatus to its excrements, and finally in the soil solution is described. This plant-herbivore-soil pathway was investigated under controlled conditions by using laboratory mesocosms. From six targeted secondary plant metabolites (dehydroquinic acid, quinic acid, apigenin, luteolin, tricin, and rosmarinic acid), only quinic acid, and dehydroquinic acid, an in-source-decay (ISD) product of quinic acid, could be traced in nearly all compartments. The tentative identification of secondary plant metabolites was performed by MS/MS analysis of methanol extracts prepared from the investigated compartments, in both the positive and negative ion mode, and subsequently compared with the results generated from the reference standards. Except for tricin, all secondary metabolites could be tentatively identified by this approach. Additional liquid-chromatography mass spectrometry (LC-MS) experiments were carried out to verify the MSI results and revealed the presence of quinic acid only in grass and chewed grass, whereas apigenin-hexoside-pentoside and luteolin-hexoisde-pentoside could be traced in the grasshopper body and excrement extracts. In summary, the MSI technique shows a trade-off between sensitivity and spatial resolution. [ABSTRACT FROM AUTHOR]

Matrix-assisted laser desorption/ionization (MALDI), a soft ionization method, coupling with time-of-flight mass spectrometry (TOF MS) has become an indispensible tool for analyzing macromolecules, such as peptides, proteins, nucleic acids and polymers. However, the application of MALDI for the analysis of small molecules (<700 Da) has become the great challenge because of the interference from the conventional matrix in low mass region. To overcome this drawback, more attention has been paid to explore interference-free methods in the past decade. The technique of applying nanomaterials as matrix of laser desorption/ionization (LDI), also called nanomaterial-assisted laser desorption/ionization (nanomaterial-assisted LDI), has attracted considerable attention in the analysis of low-molecular weight compounds in TOF MS. This review mainly summarized the applications of different types of nanomaterials including carbon-based, metal-based and metal-organic frameworks as assisted matrices for LDI in the analysis of small biological molecules, environmental pollutants and other low-molecular weight compounds. [ABSTRACT FROM AUTHOR]

Two new versions of surface-assisted laser desorption/ionization method are considered. One version is based on a combination of this method with thermal desorption sample injection and may be applied for determination of chemical compounds that are transformed into a gas phase without decomposition by heating. Another version is based on laser-induced electron-transfer desorption/ionization and could be used for determination of compounds with low proton affinity. The possibilities of the new approaches are illustrated by the example of determination of aminoacids, medical compounds, chlorophyll, as well as gold in sulfide ores. [ABSTRACT FROM AUTHOR]

The ability of single or several cells introduction onto substrate simply would be a useful tool for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). In this study, we aimed to establish a sample introduction method for pattering cells to the substrate by inkjet technology. Inkjet driving, substrate surface and relative humidity were optimized for single or several cells introduction. Single type cell solution and MALDI matrix solution were automatically printed onto ITO glass substrate which was hydrophobic modified under humidity controlled condition. Then the substrate was inserted to MALDI-MS and cells sample solution provided several peaks from phospholipids. The inkjet technique enables us to print single and subcellular on the substrate with the range of a few hundred micrometers. This diameter would be useful for targeting by laser of MALDI-MS. Our technique provides a new platform for MALDI-MS analysis in single or several cells to get a wide information from one sample. [ABSTRACT FROM AUTHOR]

Aging of secondary organic aerosol (SOA) particles formed from OH– initiated oxidation of ethylbenzene in the presence of high mass (100–300 μg/m 3 ) concentrations of (NH 4 ) 2 SO 4 seed aerosol was investigated in a home-made smog chamber in this study. The chemical composition of aged ethylbenzene SOA particles was measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with a Fuzzy C-Means (FCM) clustering algorithm. Experimental results showed that nitrophenol, ethyl-nitrophenol, 2,4-dinitrophenol, methyl glyoxylic acid, 5-ethyl-6-oxo-2,4-hexadienoic acid, 2-ethyl-2,4-hexadiendioic acid, 2,3-dihydroxy-5-ethyl-6-oxo-4-hexenoic acid, 1H-imidazole, hydrated N-glyoxal substituted 1H-imidazole, hydrated glyoxal dimer substituted imidazole, 1H-imidazole-2-carbaldehyde, N-glyoxal substituted hydrated 1H-imidazole-2-carbaldehyde and high-molecular-weight (HMW) components were the predominant products in the aged particles. Compared to the previous aromatic SOA aging studies, imidazole compounds, which can absorb solar radiation effectively, were newly detected in aged ethylbenzene SOA in the presence of high concentrations of (NH 4 ) 2 SO 4 seed aerosol. These findings provide new information for discussing aromatic SOA aging mechanisms. [ABSTRACT FROM AUTHOR]

Inorganic seed particles have relatively large surface area, and play an important role in the formation and aging of secondary organic aerosol (SOA). The effects of dry (NH)SO which is the most commonly found in urban atmosphere on the aged benzene SOA were qualitatively studied utilizing aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with Fuzzy C-Means (FCM) clustering algorithm in this study. Experimental results indicated that nitrophenol, oxocarboxylic acid, epoxide products are the predominant components in the aged benzene SOA in the presence of low concentration (about 10 μg m) of dry (NH)SO. These aged products are the same as the previously obtained aged benzene SOA without (NH)SO seed aerosol, indicating that low concentration of dry (NH)SO acts just as the nucleation or condensation center of the SOA, and do not affect the chemical composition of SOA. However, 1 H-imidazole, 1 H-imidazole-2-carbaldehyde, hydrated 1 H-imidazole-2-carbaldehyde, 2,2′-biimidazole, hydrated N-glyoxal substituted 1 H-imidazole, N-glyoxal substituted hydrated 1 H-imidazole-2- carbaldehyde, hydrated mono glyoxal substituted hydrated 1 H-imidazole-2-carboxaldehyde, mono glyoxal substituted 2,2-biimidazole and hydrated glyoxal dimer substituted imidazole which are formed from ammonium ion reaction with glyoxal are the major particulate products in the aged benzene SOA in the presence of high concentration (about 100 μg m) of dry (NH)SO. The retention of water on the dry (NH)SO particles creates ammonium ion, which can promote the formation of high-molecular-weight (HMW) products through multiphase reactions such as hydration and polymerization of aldehydes form from OH-initiated oxidation of benzene. [ABSTRACT FROM AUTHOR]

With a coating of gold nanoparticles (AuNPs), over-the-counter (OTC) drugs and Chinese herbal medicine granules in KBr pellets could be analyzed by Fourier Transform Infra-red (FT-IR) spectroscopy and Surface-assisted Laser Desorption/Ionization mass spectrometry (SALDI-MS). FT-IR spectroscopy allows fast detection of major active ingredient (e.g., acetaminophen) in OTC drugs in KBr pellets. Upon coating a thin layer of AuNPs on the KBr pellet, minor active ingredients (e.g., noscapine and loratadine) in OTC drugs, which were not revealed by FT-IR, could be detected unambiguously using AuNPs-assisted LDI-MS. Moreover, phytochemical markers of Coptidis Rhizoma (i.e. berberine, palmatine and coptisine) could be quantified in the concentrated Chinese medicine (CCM) granules by the SALDI-MS using standard addition method. The quantitative results matched with those determined by high-performance liquid chromatography with ultraviolet detection. Being strongly absorbing in UV yet transparent to IR, AuNPs successfully bridged FT-IR and SALDI-MS for direct analysis of active ingredients in the same solid sample. FT-IR allowed the fast analysis of major active ingredient in drugs, while SALDI-MS allowed the detection of minor active ingredient in the presence of excipient, and also quantitation of phytochemicals in herbal granules. [ABSTRACT FROM AUTHOR]

Carbon nanomaterials have attracted great interest over past decades owing to their unique physical properties, versatile functionalization chemistry, and biological compatibility. In this article, we review recent progress in application of carbon nanomaterials in laser desorption/ionization mass spectrometry (LDI MS). Various types of carbon nanomaterials, including fullerenes, carbon nanotubes, graphene, carbon nanodots, nanodiamond, nanofibers, nanohorns, and their derivative forms, are involved. The applications of these materials as new matrices or probes in matrix-assisted or surface-enhanced laser desorption/ionization mass spectrometry (MALDI or SELDI MS) are discussed. Finally, we summarize current challenges and give our perspectives on the future of applications of carbon nanomaterials in LDI MS. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Laser desorption/ionization (LDI) has been an essential ionization means for biological mass spectrometry (MS). It relies on an energy transfer medium to adsorb the light energy and convert it into other forms of energy to desorb and ionize analyte molecules. Noble metal nanomaterials, which are well-known as plasmonic nanomaterials and exhibit unique plasmonic effects, have been increasingly used in LDI. Various mechanisms were proposed; however, the mechanisms remain to be elucidated and verified, especially for biomolecules. Herein, we proposed a plasmon-induced charge transfer desorption/ionization (PICTDI) mechanism. Upon being shined with a laser beam, plasmonic nanoparticles, such as gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) or their mixture, transfer charges (electrons, protons or other cations) from the nanoparticles to surrounding analytes through surface plasmon, leading to analyte desorption and ionization. Hybrid plasmon-excited LDI surpassed single plasmon-excited mode, which can be proved in both positive and negative ion mode and confirmed by a variety of biomolecules, from nucleosides to saccharides to short peptides. This mechanism provides a sound understanding and a useful guideline for rational design of new plasmonic charge transfer nanomedia. [Display omitted] • A mechanism called plasmon-induced charge-transfer desorption/ionization was proposed. • The mechanism was verified by theoretical simulation and experimental evidence. • Both positive and negative ionization mode of the proposed mechanism was demonstrated. [ABSTRACT FROM AUTHOR]

The article discusses the authors' establishment of a time-of-flight mass spectrometric (TOF MS) facility to analyze decomposition products of energetic molecules (EMs) including tetrazole derivatives, and to study the decomposition behavior of EMS. It details the matrix-assisted laser desorption/ionization (MALDI) and LDI experiments performed with energetic tetrazole derivatives which were of interest for the application of high performance explosives and fast burning propellants.

Effective detection of low molecular weight compounds in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is often hindered by matrix interferences in the low m/z region of the mass spectrum. Here, we show that monolayer-protected gold nanoparticles (AuNPs) can serve as alternate matrices for the very sensitive detection of low molecular weight compounds such as amino acids. Amino acids can be detected at low fmol levels with minimal interferences by properly choosing the AuNP deposition method, density, size, and monolayer surface chemistry. By inkjet-printing AuNPs at various densities, we find that AuNP clusters are essential for obtaining the greatest sensitivity. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report a novel platform using optimized SiO 2 @Au core–shell structures as matrices for highly efficient laser desorption/ionization mass spectrometry analysis of small biomolecules (MW < 700 Da). Owing to the designer structure, SiO 2 @Au nanoshells can achieve low detection-of-limits (~ pmol–fmol) in mass spectrometry and selective laser desorption/ionization in bio-mixtures towards diverse small molecules. By further surface modification with aptamers, Apt-SiO 2 @Au nanoshells allowed simultaneously targeted enrichment and detection of kanamycin with a detection limit at 200 pM. Our work not only starts new applications of SiO 2 @Au nanoshells in mass spectrometry, but also contributes to advanced analysis of either a group of small molecules or one target small molecule from complex bio-samples in a pre-designed manner for bio-diagnostics. From the Clinical Editor Existing methods for the detection of small molecules are often not sensitive enough. Here, the authors developed aptamer functionalized SiO2@Au nanoshells for use in mass spectrometry, with very low detection limits. The new platform appeared to be simple and efficient and should be applicable in detection of clinical samples. [ABSTRACT FROM AUTHOR]

The trace detection, bulk quantification, and chemical imaging of inorganic explosives and components was demonstrated utilizing in-source collision induced dissociation (CID) coupled with laser desorption/ionization mass spectrometry (LDI-MS). The incorporation of in-source CID provided direct control over the extent of adduct and cluster fragmentation as well as organic noise reduction for the enhanced detection of both the elemental and molecular ion signatures of fuel-oxidizer mixtures and other inorganic components of explosive devices. Investigation of oxidizer molecular anions, specifically, nitrates, chlorates, and perchlorates, identified that the optimal in-source CID existed at the transition between fragmentation of the ionic salt bonds and molecular anion bonds. The chemical imaging of oxidizer particles from latent fingerprints was demonstrated, including both cation and anion components in positive and negative mode mass spectrometry, respectively. This investigation demonstrated LDI-MS with in-source CID as a versatile tool for security fields, as well as environmental monitoring and nuclear safeguards, facilitating the detection of elemental and molecular inorganic compounds at nanogram levels. [ABSTRACT FROM AUTHOR]

Secondary organic aerosol (SOA) from the photooxidation of aromatic compounds is a very complex mixture containing products with a different chemical nature that are dependent on aging processes. Aging of SOA particles formed from OH-initiated oxidation of benzene was investigated in a home-made smog chamber in this study. The chemical composition of aged benzene SOA particles were measured using aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with Fuzzy C-Means (FCM) clustering algorithm. Experimental results showed that nitrophenol, dinitrophenol, nitrocatechol, dinitrocatechol, 6-oxo-2,4-hexadienoic acid, 2,4-hexadiendioic acid, 2,3-dihydroxy-6-oxo-4-hexenoic acid, 2,3-epoxy-4-hexendioic acid, 2,3-epoxy-4,5-dihydroxy-hexanedioic acid and high-molecular-weight (HMW) components were the predominant products in the aged particles. Compared to offline method such as liquid chromatography mass spectrometry (LC-MS) measurement, the real-time ALTOFMS detection approach coupled with the FCM data processing algorithm can make cluster analysis of SOA successfully and provide more information of products. The present results also indicate that benzene SOA aging proceeds through the oxidation of the internal double bond of ring-opened products, phenolic compounds, and acid-catalyzed heterogeneous reactions of carbonyl products. The possible reaction mechanisms leading to these aged products were also discussed and proposed. [ABSTRACT FROM AUTHOR]

An aerosol laser time of flight mass spectrometer (ALTOFMS) that can be used for real-time measurement of the size and composition of individual aerosol particles has been designed and utilized to provide on-line measurement of secondary organic aerosol (SOA) particles resulted from Cl-initiated oxidation of toluene in smog chamber. Both the size and chemical compositions of individual aerosol particles were obtained in real-time. According to a large number of single aerosol diameters and mass spectra, the size distribution and chemical composition of aerosol were determined statistically. Experimental results indicate that aerosol particles produced from Cl-initiated oxidation of toluene were predominantly in the form of PM 2.5 particles, and nine positive laser desorption/ionization mass spectra peaks: m/z 18, 29, 30, 44, 46, 52, 65, 77, and 94 may come from the fragment ions of the products of the SOA: aromatic aldehydes, aromatic acids, phenolic compounds, and nitrogenated organic compounds. These results were in good agreement with those ones from previous Cl-initiated oxidation of toluene. These were demonstrated that ALTOFMS is a useful tool to reveal the formation and transformation processes of SOA particles in smog chamber. [ABSTRACT FROM AUTHOR]

Density functional theory method with functional B3LYP and 6-31G (d,p) basis set has been used to examine the possible structures of acridine orange fragments resulting from laser irradiation of dye adsorbed on the surface of thermoexfoliated graphite under mass spectrometric experiment. The structures and thermodynamic parameters of these fragments have been found as well as the order of their formation. [ABSTRACT FROM AUTHOR]