Detection and Seasonal Variations of Huanglongbing Disease in Navel Orange Trees Using Direct Ionization Mass Spectrometry

Ambient mass spectrometry imaging of food natural products by angled direct analysis in real time high-resolution mass spectrometry

Direct surface analysis in ambient conditions provides information on the position and chemical composition of an object at the time of investigation. An angled sampling probe is developed in this work for direct analysis in real time (DART) ionization high-resolution mass spectrometry. The DART ion source and the interface were modified for improved surface resolution, increased ion transfer efficiency, as well as enabling two-dimensional surface scanning. The angled probe DART-MS system was used for investigating a variety of food samples including fruit peels, ginseng root, plant leaves and sections of radish. Abundant signals and distinct chemical profiles are obtained in seconds, and spatial distribution of different molecules across the sample surfaces can be observed. In addition, the developed system can quickly identify the chemical changes when the surfaces were treated. The method is capable of directly evaluating food sample surfaces with different shapes, hardness, and conditions, without any sample pretreatments.

Direct mass spectrometry analysis of biological tissue for diagnosis of thyroid cancer using wooden-tip electrospray ionization

Direct mass spectrometry (MS) analysis of human tissue at the molecular level could gain insight into biomarker discovery and disease diagnosis. Detecting metabolite profiles of tissue sample play an important role in understanding the pathological properties of disease development. Because the complex matrices in tissue samples, complicated and time-consuming sample preparation processes are usually required by conventional biological and clinical MS methods. Direct MS with ambient ionization technique is a new analytical strategy for direct sample analysis with little sample preparation, and has been proven to be a simple, rapid, and effective analytical tools for direct analysis of biological tissues. In this work, we applied a simple, low-cost, disposable wooden tip (WT) for loading tiny thyroid tissue, and then loading organic solvents to extract biomarkers under electrospray ionization (ESI) condition. Under such WT-ESI, the extract of thyroid was directly sprayed out from wooden tip to MS inlet. In this work, thyroid tissue from normal and cancer parts were analyzed by the established WT-ESI-MS, showing lipids were mainly detectable compounds in thyroid tissue. The MS data of lipids obtained from thyroid tissues were further analyzed with MS/MS experiment and multivariate variable analysis, and the biomarkers of thyroid cancer were also investigated.

Direct adsorption sampling and ambient mass spectrometry analysis of tobacco smoke with porous paper strips

Chemical analysis of atmospheric aerosols by conventional analytical methods is usually required to perform complicated and time-consuming sample preparation processes. In recent decades, ambient ionization mass spectrometry (AI-MS) methods have been proven to be simple, rapid, and effective analytical tools for direct analysis of various complex samples. In this work, we applied porous paper filters for direct adsorptive sampling of tobacco smoke, and then the sampled paper filters were performed the emitters of the paper spray ionization (PSI) device. An auto-sampling device was made to control the generation and collection of tobacco smoke. Nicotine, the typical compound of tobacco smoke, was used to optimize the key conditions of auto-sampling. Moreover, different types of tobacco smoke were also compared with multivariate variable analysis, and the makers of tobacco smoke from different sources of tobacco smoke were investigated. By using this method, direct sampling and analysis of a single tobacco sample can be completed within minutes. Overall, our results show that PSI-MS is a powerful tool that integrates collection, extraction, ionization, and identification analytes in smoke.

Ambient Ionization Mass Spectrometry: Application and Prospective

Mass spectrometry (MS) is a formidable analytical tool for the analysis of non-polar to polar compounds individually and/or from mixtures, providing information on the molecular weights and chemical structures of the analytes. During the last more than one-decade, ambient ionization mass spectrometry (AIMS) has developed quickly, producing a wide range of platforms and proving scientific improvements in a variety of domains, from biological imaging to quick quality control. These methods have made it possible to detect target analytes in real time without sample preparation in an open environment, and they can be connected to any MS system with an atmospheric pressure interface. They also have the ability to analyze explosives, illicit drugs, disease diagnostics, drugs in biological samples, adulterants in food and agricultural products, reaction progress, and environmental monitoring. The development of novel ambient ionization techniques, such as probe electrospray ionization, paper spray ionization, and fiber spray ionization, employed even at picolitre to femtolitre solution levels to provide femtogram to attogram levels of the target analytes. The special characteristic of this ambient ion source, which has been extensively used, is the noninvasive property of PESI of examination of biological real samples. The results in the current review supports the idea that AIMS has emerged as a pioneer in MS-based approaches and that methods will continue to be developed along with improvements to existing ones in the near future.

Molecular signatures between citrus and Candidatus Liberibacter asiaticus

Citrus Huanglongbing (HLB), also known as citrus greening, is one of the most devastating citrus diseases worldwide. Candidatus Liberibacter asiaticus (CLas) is the most prevalent strain associated with HLB, which is yet to be cultured in vitro. None of the commercial citrus cultivars are resistant to HLB. The pathosystem of Ca. Liberibacter is complex and remains a mystery. In this review, we focus on the recent progress in genomic research on the pathogen, the interaction of host and CLas, and the influence of CLas infection on the transcripts, proteins, and metabolism of the host. We have also focused on the identification of candidate genes for CLas pathogenicity or the improvements of HLB tolerance in citrus. In the end, we propose potentially promising areas for mechanistic studies of CLas pathogenicity, defense regulators, and genetic improvement for HLB tolerance/resistance in the future.

In vivo solid-phase microextraction swab-mass spectrometry for multidimensional analysis of human saliva

Solid phase microextraction (SPME) is one of the most powerful sample preparation techniques for analyte extraction and enrichment from complex matrices. SPME fibers are commonly used to extract analytes from collected samples. Following our recent work on development of in vivo SPME swab that integrates an SPME fiber and a medical swab (Anal Chim Acta, 2020, 1124, 71-77), the multiple SPME fibers inserted into a medical swab (multiple-SPME swab) is further developed to couple with different mass spectrometry (MS) approaches for multidimensional analysis of human saliva in this work. The new features of cotton ball and SPME fiber of multiple-SPME swab are investigated. Biomarker discovery and disease diagnosis using multiple-SPME swab are also demonstrated. The present study shows that direct coupling multiple-SPME swab with different MS-based approaches could be simple and versatile in vivo method to expand the classes of analytes extracted simultaneously from human saliva.

Contactless electrospray ionization mass spectrometry for direct detection of analytes in living organisms

In this study, we developed contactless electrospray ionization mass spectrometry (ESI-MS) for in vivo analysis of living organisms in different applications. The in vivo sampling and direct analysis processess of living organisms were integrated into an operation that only requires the organism close to MS inlet that was applied to a high voltage. Living plants and animals were directly induced to generate spray ionization. Direct detection and in vivo monitoring of metabolites and chemical residues in various living organisms were successfully demonstrated. Analysis of a single sample could be completed within 30 s. Overall, contactless ESI-MS provides an attractive in vivo method to straightforward investigation of living organisms.

Mass spectrometry imaging as a potential technique for diagnostic of Huanglongbing disease using fast and simple sample preparation

Huanglongbing (HLB) is a disease of worldwide incidence that affects orange trees, among other commercial varieties, implicating in great losses to the citrus industry. The disease is transmitted through Diaphorina citri vector, which inoculates Candidatus Liberibacter spp. in the plant sap. HLB disease lead to blotchy mottle and fruit deformation, among other characteristic symptoms, which induce fruit drop and affect negatively the juice quality. Nowadays, the disease is controlled by eradication of sick, symptomatic plants, coupled with psyllid control. Polymerase chain reaction (PCR) is the technique most used to diagnose the disease; however, this methodology involves high cost and extensive sample preparation. Mass spectrometry imaging (MSI) technique is a fast and easily handled sample analysis that, in the case of Huanglongbing allows the detection of increased concentration of metabolites associated to the disease, including quinic acid, phenylalanine, nobiletin and sucrose. The metabolites abieta-8,11,13-trien-18-oic acid, suggested by global natural product social molecular networking (GNPS) analysis, and 4-acetyl-1-methylcyclohexene showed a higher distribution in symptomatic leaves and have been directly associated to HLB disease. Desorption electrospray ionization coupled to mass spectrometry imaging (DESI-MSI) allows the rapid and efficient detection of biomarkers in sweet oranges infected with Candidatus Liberibacter asiaticus and can be developed into a real-time, fast-diagnostic technique.

Longitudinal Transcriptomic, Proteomic, and Metabolomic Analysis of Citrus limon Response to Graft Inoculation by Candidatus Liberibacter asiaticus

Presymptomatic detection of citrus trees infected with Candidatus Liberibacter asiaticus (CLas), the bacterial pathogen associated with Huanglongbing (HLB; citrus greening disease), is critical to controlling the spread of the disease. To test whether infected citrus trees produce systemic signals that may be used for indirect disease detection, lemon (Citrus limon) plants were graft-inoculated with either CLas-infected or control (CLas-) budwood, and leaf samples were longitudinally collected over 46 weeks and analyzed for plant changes associated with CLas infection. RNA, protein, and metabolite samples extracted from leaves were analyzed using RNA-Seq, mass spectrometry, and 1H NMR spectroscopy, respectively. Significant differences in specific transcripts, proteins, and metabolites were observed between CLas-infected and control plants as early as 2 weeks post graft (wpg). The most dramatic differences between the transcriptome and proteome of CLas-infected and control plants were observed at 10 wpg, including coordinated increases in transcripts and proteins of citrus orthologs of known plant defense genes. This integrated approach to quantifying plant molecular changes in leaves of CLas-infected plants supports the development of diagnostic technology for presymptomatic or early disease detection as part of efforts to control the spread of HLB into uninfected citrus groves.

Schirmer Paper Noninvasive Microsampling for Direct Mass Spectrometry Analysis of Human Tears

Rapid and sensitive detection of metabolites and chemical residues in human tears is highly beneficial for understanding eye health. In this study, Schirmer paper was used for noninvasive microsampling of human tears, and then paper spray mass spectrometry (PSMS) was performed for direct analysis of human tears. Schirmer PSMS was successfully used for rapid diagnosis of dry-eye syndrome by detecting the volume and metabolites of human tears. Drugs of abuse, therapeutic drugs, and pharmacodynamics in human tears were also investigated by Schirmer PSMS. Furthermore, specific markers of environmental exposures in the air to human eyes, including volatile organic compounds, aerosol, and smoke, were unambiguously sampled and detected in human tears using Schirmer PSMS. Excellent analytical performances were achieved, including single-use, low-sample consumption (1.0 μL), rapid analysis (the whole analytical procedure completed within 3 min), high sensitivity (absolute limit of detection less than or equal to 0.5 pg, signal-to-noise ratio greater than or equal to 3), good reproducibility (relative standard deviation less than 10%, n = 3), and accurate quantitation (average deviation less than 3%, n = 3). Overall, our results showed that Schirmer PSMS is a highly effective method for direct tear analysis and is expected to be a convenient tool for human tear analysis in significant clinical applications.

Direct Detection of Lysozyme in Viscous Raw Hen Egg White Binding to Sodium Dodecyl Sulfonate by Reactive Wooden-tip Electrospray Ionization Mass Spectrometry

Direct characterization of native protein binding to ligands in raw biological samples is a challenging task, because the ligand solution might induce proteins to aggregation, flocculation and denaturation. In this work, we developed a reactive wooden-tip electrospray ionization mass spectrometry (ESI-MS) for formation and characterization of protein-ligand complexes upon rapid mixing in electrospray droplets. Raw viscous hen egg white (HEW) was directly loaded onto a wooden tip to induce spray ionization, and sodium dodecyl sulfonate (SDS) solution was directly loaded into the HEW spray by a pipette tip, and thus lysozyme-DS complexes were then formed in the electrospray droplets and were detected subsequently by mass spectrometry. The new approach was successfully applied to investigate interaction of SDS and native lysozyme in electrospray droplets of standard solution and raw egg white. Our results showed that wooden-tip ESI-MS is a promising method to form and characterize protein-ligand complexes.

Fast-switching high-voltage porous-tip electrospray ionization mass spectrometry for rapid detection of antirheumatic drugs in adulterated herbal dietary supplements

RATIONALE

Herbal dietary supplements (HDSs) adulterated with undeclared synthetic drugs can lead to serious health problems METHODS: A fast-switching positive/negative high-voltage (+/- HV) was developed to apply on electrospray ionization mass spectrometry (ESI-MS) with porous tips for rapid screening of five antirheumatic drugs in antirheumatic HDSs. The fast-switching (switch-time: 100 ms) negative and positive ions were alternately generated to perform full-MS and tandem-MS analysis, providing an effective method for rapid detection of analytes in whichever mode of detection was most suitable (negative or positive ion mode). The use of different tips and solvents was also optimized in this work.

RESULTS

The limits of detection of the five antirheumatic drugs were found to be less than 0.1 ng/g (S/N > 3). The reproducibility of the five drugs was measured to be 10.0-23.3% (n = 5). A single sample analysis could be completed within 1 min. Rapid screening of a total of 28 real HDS samples collected from the market was examined by the fast-switching HV substrate-tip ESI-MS method, and the screening result was further validated by conventional liquid chromatography/mass spectrometry.

CONCLUSIONS

Overall, our results demonstrated that fast-switching HV substrate-tip ESI-MS is a rapid, reliable, and effective method for simultaneous screening of various analytes in complex samples.

Vibrating tip spray ionization mass spectrometry for direct sample analysis

In this work, a vibrating tip spray ionization source was developed for direct mass spectrometric analysis of raw samples under voltage-free condition. A solid tip was mounted on a vibrator, and the solid tip was placed on the front of MS inlet. Liquid, viscous, and bulk solid samples could be directly loaded on the tip-end surface, and then a drop of solvent at microliter level was subsequently loaded on the tip for dissolution and extraction of analytes, and a vibrator was then started to atomize and ionize the analytes under ambient condition. We demonstrated vibrating tip spray mass spectrometry in various applications, including food safety, pharmaceutical analysis, and forensic science. Furthermore, in situ analysis of biological tissues and in vivo analysis of living plants were conveniently performed, due to voltage-free. Different vibration frequencies and solvent compositions were investigated. The analytical performances, including sensitivity, reproducibility, and linear range, were investigated. The ionization process and mechanism were also discussed in this work.

Laser irradiation desorption of microcystins from protein complex in fish tissue and liquid chromatography-tandem mass spectrometry analysis

Microcystins are a group of cyanotoxins which interact with the C-terminal region of PP1 and PP2A proteins, so denaturation and inactivation are necessary for breaking covalent binding to release microcystins. In this study, a novel extraction method was developed by laser irradiation desorption of microcystins from fish protein. The sample was mixed with aqueous methanol and irradiated by a 450 nm laser, with an optimized value of laser power density at 8 W and exposure time at 5 min. ThenLC-MS/MS was applied for the determination of microcystins in fish extracts. The ionization behaviors of microcystins were investigated firstly, and doubly charged microcystins were selected as precursor ions in multiple reaction monitoring scan for quantification. This proposed quantitative method was well validated in terms of selectivity, linearity, sensitivity, accuracy, recovery, and stability. The successful application of this LC-MS/MS method showed its ability for the analysis of microcystins in low concentration, and it would be of significant interest for environmental and food safety applications to ensure the safety of fish and related products.