Direct sampling mass spectrometry for clinical analysis

Ambient ionisation mass spectrometry for drug and toxin analysis: A review of the recent literature

Ambient ionisation mass spectrometry (AIMS) is a form of mass spectrometry whereby analyte ionisation occurs outside of a vacuum source under ambient conditions. This enables the direct analysis of samples in their native state, with little or no sample preparation and without chromatographic separation. The removal of these steps facilitates a much faster analytical process, enabling the direct analysis of samples within minutes if not seconds. Consequently, AIMS has gained rapid popularity across a diverse range of applications, in particular the analysis of drugs and toxins. Numerous fields rely upon mass spectrometry for the detection and identification of drugs, including clinical diagnostics, forensic chemistry, and food safety. However, all of these fields are hindered by the time-consuming and laboratory-confined nature of traditional techniques. As such, the potential for AIMS to resolve these challenges has resulted in a growing interest in ambient ionisation for drug and toxin analysis. Since the early 2000s, forensic science, diagnostic testing, anti-doping, pharmaceuticals, environmental analysis and food safety have all seen a marked increase in AIMS applications, foreshadowing a new future for drug testing. In this review, some of the most promising AIMS techniques for drug analysis will be discussed, alongside different applications of AIMS published over a 5-year period, to provide a summary of the recent research activity for ambient ionisation for drug and toxin analysis.

Spatial top-down proteomics for the functional characterization of human kidney

Background

The Human Proteome Project has credibly detected nearly 93% of the roughly 20,000 proteins which are predicted by the human genome. However, the proteome is enigmatic, where alterations in amino acid sequences from polymorphisms and alternative splicing, errors in translation, and post-translational modifications result in a proteome depth estimated at several million unique proteoforms. Recently mass spectrometry has been demonstrated in several landmark efforts mapping the human proteoform landscape in bulk analyses. Herein, we developed an integrated workflow for characterizing proteoforms from human tissue in a spatially resolved manner by coupling laser capture microdissection, nanoliter-scale sample preparation, and mass spectrometry imaging.

Results

Using healthy human kidney sections as the case study, we focused our analyses on the major functional tissue units including glomeruli, tubules, and medullary rays. After laser capture microdissection, these isolated functional tissue units were processed with microPOTS (microdroplet processing in one-pot for trace samples) for sensitive top-down proteomics measurement. This provided a quantitative database of 616 proteoforms that was further leveraged as a library for mass spectrometry imaging with near-cellular spatial resolution over the entire section. Notably, several mitochondrial proteoforms were found to be differentially abundant between glomeruli and convoluted tubules, and further spatial contextualization was provided by mass spectrometry imaging confirming unique differences identified by microPOTS, and further expanding the field-of-view for unique distributions such as enhanced abundance of a truncated form (1-74) of ubiquitin within cortical regions.

Conclusions

We developed an integrated workflow to directly identify proteoforms and reveal their spatial distributions. Where of the 20 differentially abundant proteoforms identified as discriminate between tubules and glomeruli by microPOTS, the vast majority of tubular proteoforms were of mitochondrial origin (8 of 10) where discriminate proteoforms in glomeruli were primarily hemoglobin subunits (9 of 10). These trends were also identified within ion images demonstrating spatially resolved characterization of proteoforms that has the potential to reshape discovery-based proteomics because the proteoforms are the ultimate effector of cellular functions. Applications of this technology have the potential to unravel etiology and pathophysiology of disease states, informing on biologically active proteoforms, which remodel the proteomic landscape in chronic and acute disorders.

Portable Instrumentation for Ambient Ionization and Miniature Mass Spectrometers

We critically evaluate the current status of portable mass spectrometry (pMS), particularly where this aligns with ambient ionization. Assessing the field of pMS can be quite subjective, especially in relation to the portable aspects of design, deployment, and operation. In this review, we discuss what it means to be portable and introduce a set of criteria by which pMS and ambient ionization sources can be assessed. Moreover, we consider the recent literature in terms of the most popular and significant advances in portable instrumentation for ambient ionization and miniature mass spectrometers. Finally, emerging trends and exciting future prospects are discussed and some recommendations are offered.

Determination of amino acid metabolic diseases from dried blood spots with a rapid extraction method coupled with nanoelectrospray ionization mass spectrometry

In this work, a rapid extraction method of methanol/water (95:5 v/v) with 0.1% formic acid was developed for extraction of amino acids from dried blood spots (DBS) for inherited metabolic diseases (IMDs). The combination of this extraction procedure with nanoelectrospray ionization mass spectrometry (nESI-MS) was used for the rapid analysis of amino acids. This approach with eliminating the chromatographic separation required only 2 min for the extraction of amino acids from DBS, which simplified the configuration and improved the timeliness. Dependence of the sensitivity on the operating parameters was systematically investigated. The LOD of 91.2-262.5 nmol/L and LOQ of 304-875 nmol/L which were lower than the cut-off values were obtained for amino acids within DBS. The accuracy was determined to be 93.82%-103.07% and the precision was determined to be less than 8.30%. The effectiveness of this method was also compared with the gold standard method (e.g., LC-MS/MS). The desalination mechanism was explored with interference mainly originated from the blood. These findings indicated that the rapid extraction procedure coupled with nESI-MS is capable of screening indicators for IMDs in complex biological samples.

Multiple ion isolation and accumulation events for selective chemical noise reduction and dynamic range enhancement in MALDI imaging mass spectrometry

Abundant chemical noise in MALDI imaging mass spectrometry experiments can impede the detection of less abundant compounds of interest. This chemical noise commonly originates from the MALDI matrix as well as other endogenous compounds present in high concentrations and/or with high ionization efficiencies. MALDI imaging mass spectrometry of biological tissues measures numerous biomolecular compounds that exist in a wide range of concentrations in vivo. When ion trapping instruments are used, highly abundant ions can dominate the charge capacity and lead to space charge effects that hinder the dynamic range and detection of lowly abundant compounds of interest. Gas-phase fractionation has been previously utilized in mass spectrometry to isolate and enrich target analytes. Herein, we have characterized the use of multiple continuous accumulations of selected ions (Multi CASI) to reduce the abundance of chemical noise and diminish the effects of space charge in MALDI imaging mass spectrometry experiments. Multi CASI utilizes the mass-resolving capability of a quadrupole mass filter to perform multiple sequential ion isolation events prior to a single mass analysis of the combined ion population. Multi CASI was used to improve metabolite and lipid detection in the MALDI imaging mass spectrometry analysis of rat brain tissue.

Mass Spectrometry Analysis for Clinical Applications: A Review

Mass spectrometry (MS) has become an attractive analytical method in clinical analysis due to its comprehensive advantages of high sensitivity, high specificity and high throughput. Separation techniques coupled MS detection (e.g., LC-MS/MS) have shown unique advantages over immunoassay and have developed as golden criterion for many clinical applications. This review summarizes the characteristics and applications of MS, and emphasizes the high efficiency of MS in clinical research. In addition, this review also put forward further prospects for the future of mass spectrometry technology, including the introduction of miniature MS instruments, point-of-care detection and high-throughput analysis, to achieve better development of MS technology in various fields of clinical application. Moreover, as ambient ionization mass spectrometry (AIMS) requires little or no sample pretreatment and improves the flux of MS, this review also summarizes its potential applications in clinic.

Advances and Emerging Medical Applications of Direct Mass Spectrometry Technologies for Tissue Analysis

Offering superb speed, chemical specificity, and analytical sensitivity, direct mass spectrometry (MS) technologies are highly amenable for the molecular analysis of complex tissues to aid in disease characterization and help identify new diagnostic, prognostic, and predictive markers. By enabling detection of clinically actionable molecular profiles from tissues and cells, direct MS technologies have the potential to guide treatment decisions and transform sample analysis within clinical workflows. In this review, we highlight recent health-related developments and applications of direct MS technologies that exhibit tangible potential to accelerate clinical research and disease diagnosis, including oncological and neurodegenerative diseases and microbial infections. We focus primarily on applications that employ direct MS technologies for tissue analysis, including MS imaging technologies to map spatial distributions of molecules in situ as well as handheld devices for rapid in vivo and ex vivo tissue analysis.

Coupling of Solid-Phase Microextraction Directly to Mass Spectrometry via an Improved Microfluidic Open Interface to Facilitate High-Throughput Determinations

Mass spectrometry analysis can be performed by introducing samples directly to mass spectrometry, allowing the increase of the analysis throughput; however, some disadvantages of direct-to-mass spectrometry analysis include susceptibility to matrix effects and risk of instrument contamination from inadequate sample preparation. Solid-phase microextraction is one of the most suitable sample preparation methods for direct-to-mass spectrometry analysis, as it offers matrix-compatible coatings which ensure analyte enrichment with minimal or no interference from matrix. One of the ways solid-phase microextraction can be coupled directly to mass spectrometry is via a microfluidic open interface. This manuscript reports improvements made to the initial microfluidic open interface design, where the system components have been simplified to mostly commercially available materials. In addition, the analysis of samples has been automated by implementing software that fully controls the analysis workflow, where the washing procedure is optimized to completely reduce the carryover. Herein, the extraction and desorption time profiles from thin and thick SPME devices was studied where the overall workflow consisted of high-throughput sample preparation of 1.3 min per 96 samples and <1 min per sample instrumental analysis.

Direct Coupling of SPME to Mass Spectrometry

Solid-phase microextraction devices are normally analyzed by gas or liquid chromatography. Their use has become increasingly widespread since their introduction in 1990, and nowadays most analytical laboratories use or have used SPME as an efficient and green method to perform analyte extraction and sample clean-up in one step. The SPME technique is intrinsically flexible, and allows for a high degree of optimization with regard to the extracting phase, as well as the way sample is analyzed. Since its introduction, researchers have been trying different ways to transfer analytes extracted from the solid phase to a mass spectrometer, with the aim to increase throughput and reduce solvent, gas usage and costs associated with conventional chromatographic techniques. Furthermore, but not less important, for pure fun of developing new, more efficient and sensitive analytical strategies! This chapter aims at providing a comprehensive overview of the most relevant non-chromatographic mass spectrometric approaches developed for SPME. Technical aspects of each SPME-MS approach will be discussed, highlighting their advantages, disadvantages and future potential developments. Particular emphasis will be given on the most recent direct coupling approaches using novel ionization approaches, and a concise overview of the existing applications will also be provided.

Rapid Determination of Ethyl Carbamate in Chinese Liquor via a Direct Injection Mass Spectrometry with Time-Resolved Flash-Thermal-Vaporization and Acetone-Assisted High-Pressure Photoionization Strategy

Ethyl carbamate (EC), a carcinogenic compound, is naturally produced in fermented foods and alcoholic beverages. Rapid and accurate measurement of EC is necessary and important for quality control and safety evaluation of Chinese liquor, a traditionally distilled spirit with the highest consumption in China, but it remains a great challenge. In this work, a direct injection mass spectrometry (DIMS) with time-resolved flash-thermal-vaporization (TRFTV) and acetone-assisted high-pressure photoionization (HPPI) strategy has been developed. EC was rapidly separated from the main matrix components, ethyl acetate (EA) and ethanol, by the TRFTV sampling strategy due to the retention time difference of these three compounds with large boiling point differences on the inner wall of a poly(tetrafluoroethylene) (PTFE) tube. Therefore, the matrix effect of EA and ethanol was effectively eliminated. The acetone-assisted HPPI source was developed for efficient ionization of EC through a photoionization-induced proton transfer reaction between EC molecules and protonated acetone ions. The accurate quantitative analysis of EC in liquor was achieved by introducing an internal standard method (ISM) using deuterated EC (d₅-EC). As a result, the limit of detection (LOD) for EC was 8.88 μg/L with the analysis time of only 2 min, and the recoveries ranged from 92.3 to 113.1%. Finally, the prominent capability of the developed system was demonstrated by rapid determination of trace EC in Chinese liquors with different flavor types, exhibiting wide potential applications in online quality control and safety evaluation of not only Chinese liquors but also other liquor and alcoholic beverages.

20 abnormal metabolites of Stage IV Grade C periodontitis was discovered by CPSI-MS

Saliva is a noninvasive biofluid that contains the metabolic signature of severe periodontitis (SP, Stage IV and Grade C). Conductive polymer spray ionization mass spectrometry (CPSI-MS) was used to record a wide range of metabolites within a few seconds, making this technique a promising point-of-care method for the early detection of SP (Stage IV and Grade C). Saliva samples from 31 volunteers, consisting of 16 healthy controls (HC) and 15 patients with SP (Stage IV and Grade C), were collected to identify dysregulated metabolites. Twenty metabolites were screened out, including seven amino acids. Moreover, the results showed that amino acid metabolism is closely related to the development of periodontitis. The present study further confirmed that salivary metabolites in the oral cavity were significantly altered after plaque removal. These results suggest that the combination of CPSI-MS is a feasible tool for preclinical screening of SP (Stage IV and Grade C).

Portable mass spectrometry system: instrumentation, applications, and path to 'omics analysis

Mass spectrometry (MS) is an information rich analytical technique and plays a key role in various 'omics studies. Standard mass spectrometers are bulky and operate at high vacuum, which hinder their adoption by the broader community and utility in field applications. Developing portable mass spectrometers can significantly expand the application scope and user groups of MS analysis. This review discusses the basics and recent advancements in the development of key components of portable mass spectrometers including ionization source, mass analyzer, detector, and vacuum system. Further, major areas where portable mass spectrometers are applied are also discussed. Finally, a perspective on the further development of portable mass spectrometers including the potential benefits for 'omics analysis is provided.

Deeper Understanding of Solvent-Based Ambient Ionization Mass Spectrometry: Are Molecular Profiles Primarily Dictated by Extraction Mechanisms?

Solvent-based ambient ionization mass spectrometry (MS) techniques provide a powerful approach for direct chemical analysis and molecular profiling of biological tissues. While molecular profiling of tissues has been widely used for disease diagnosis, little is understood about how the interplay among solvent properties, matrix effects, and ion suppression can influence the detection of biological molecules. Here, we perform a systematic investigation of the extraction processes of lipids using an ambient ionization droplet microsampling platform to investigate how the physicochemical properties of the solvent systems and extraction time influence molecular extraction and detection. Direct molecular profiling and quantitative liquid chromatography-mass spectrometry (LC-MS) of discrete solvent droplets after surface sampling were investigated to provide insights into extraction and ionization mechanisms. The results of this study suggest that intermolecular interactions such as hydrogen bonding play a major role in extraction and detection of lipids using solvent-based ambient ionization techniques. In addition, extraction time was observed to impact the molecular profiles obtained, suggesting optimization of this parameter can be performed to favor detection of specific analytes.

The application of mass spectrometry method for the study and identification of medically important viruses (review of literature)

It is difficult to overestimate the urgency of the problem of well-timed diagnosis of viral infections. According to the WHO, dozens of outbreaks of viral diseases are recorded annually, both in developing and developed countries. Moreover, the seasonal flu virus alone is capable of infecting up to 20% of the population, even in European countries with a high level of medicine. And the annual number of deaths due to viral infections, according to official statistics, exceeds 600 thousand people around the world. That's why the provision of a reliable and fairly rapid diagnosis of viruses, along with subsequent therapy, makes a significant contribution to reducing the incidence of mortality. Despite the fact that PCR-based methods currently remain the most common method for identifying viruses in clinical practice, as recent experience shows, in addition to the already known disadvantages, in the event of large outbreaks, such test systems may simply not be in the required amount. In this regard, it is necessary to supplement and improve the existing tools for identification and research of clinically significant viruses. The MALDI-TOF mass spectrometry method combines a degree of accuracy and versatility, sufficient both for the identification of clinical strains isolated from patients, and for the study of the phenotypic properties of viruses in research laboratories and centers. This article presents and summarizes the main data on the existing or potential application of the method of time-of-flight mass spectrometry with matrix-associated laser desorption / ionization for the identification or study of viruses.

Recent advances in on-site mass spectrometry analysis for clinical applications

In recent years, mass spectrometry (MS) is increasingly attracting interests for clinical applications, which also calls for technical innovations to make a transfer of MS from conventional analytical laboratories to clinics. The system design and analysis procedure should be friendly for novice users and appliable for on-site clinical diagnosis. In addition, the analysis result should be auto-interpreted and reported in formats much simpler than mass spectra. This motivates new ideas for developments in all the aspects of MS. In this review, we report recent advances of direct sampling ionization and miniature MS system, which have been developed targeting clinical and even point-of-care analysis. We also discuss the trend of the development and provide perspective on the technical challenges raised by diseases such as coronavirus SARS-CoV-2.

A Small Footprint and Robust Interface for Solid Phase Microextraction and Mass Spectrometry Based on Vibrating Sharp-Edge Spray Ionization

Combining solid phase microextraction (SPME) and mass spectrometry (MS) analysis has become increasingly important to many bioanalytical, environmental, and forensic applications due to its simplicity, rapid analysis, and capability of reducing matrix effects for complex samples. To further promote the adoption of SPME-MS based analysis and expand its application scope calls for efficient and convenient interfaces that couple the SPME sample handling with the efficient analyte ionization for MS. Here, we report a novel interface that integrates both the desorption and the ionization steps in one device based on the capillary vibrating sharp-edge spray ionization (cVSSI) method. We demonstrated that the cVSSI is capable of nebulizing liquid samples in a pulled-tip glass capillary with a battery powered function generator. The cVSSI device allows the insertion of a SPME probe into the spray capillary for desorption and then direct nebulization of the desorption solvent in situ. With the integrated interface, we have demonstrated rapid MS analysis of drug compounds from serum samples. Quantitative determination of various drug compounds including metoprolol, pindolol, acebutolol, oxprenolol, capecitabine, and irinotecan was achieved with good linearity (R2 = 0.97-0.99) and limit of detection ranging from 0.25 to 0.59 ng/mL without using a high voltage source. Only 3.5 μL of desorption solvent and 3 min desorption time were needed for the present method. Overall, we demonstrated a portable SPME-MS interface featuring high sensitivity, short analysis time, small footprint, and low cost, which makes it an attractive method for many applications requiring sample cleanup including drug compound monitoring, environmental sample analysis, and forensic sample analysis.

Point-of-care detection of sevoflurane anesthetics in exhaled breath using a miniature TOFMS for diagnosis of postoperative agitation symptoms in children

A miniature TOFMS with MEPEI has been developed for POC diagnosis of postoperative agitation symptoms, and can analyze sevoflurane by direct sampling. The risk is high when the sevoflurane in the exhaled breath is higher than 500 ppmv.

Thermal desorption bridged the gap between dielectric barrier discharge ionization and dried plasma spot samples for sensitive and rapid detection of fentanyl analogs in mass spectrometry

Guided by finite element simulations and 3D-printing, we constructed a semi-covered flat-TD surface for sufficient thermal desorption and ionization of fentanyl analogs from dried plasma/blood spot samples.

Monitoring Retinoblastoma by Machine Learning of Aqueous Humor Metabolic Fingerprinting

The most common intraocular pediatric malignancy, retinoblastoma (RB), accounts for ≈10% of cancer in children. Efficient monitoring can enhance living quality of patients and 5-year survival ratio of RB up to 95%. However, RB monitoring is still insufficient in regions with limited resources and the mortality may even reach over 70% in such areas. Here, an RB monitoring platform by machine learning of aqueous humor metabolic fingerprinting (AH-MF) is developed, using nanoparticle enhanced laser desorption/ionization mass spectrometry (LDI MS). The direct AH-MF of RB free of sample pre-treatment is recorded, with both high reproducibility (coefficient of variation < 10%) and sensitivity (low to 0.3 pmol) at sample volume down to 40 nL only. Further, early and advanced RB patients with area-under-the-curve over 0.9 and accuracy over 80% are differentiated, through machine learning of AH-MF. Finally, a metabolic biomarker panel of 7 metabolites through accurate MS and tandem MS (MS/MS) with pathway analysis to monitor RB is identified. This work can contribute to advanced metabolic analysis of eye diseases including but not limited to RB and screening of new potential metabolic targets toward therapeutic intervention.

Integrated sample desalting, enrichment, and ionization on an omniphobic glass slide for direct mass spectrometry analysis

RATIONALE

Direct and rapid mass spectrometry (MS) analysis is desired for many applications including environmental monitoring, forensic analysis, chemical and biological defense, and point-of-care testing. However, sample pretreatment is often necessary for analyzing targets from complex matrices using MS due to ion suppression. To achieve rapid MS analysis calls for simple and efficient solutions for sample processing and ionization. Here, a simple sample pretreatment and ionization workflow is reported, which achieves sample desalting, enrichment, and ionization on a single glass slide.

METHODS

Desalting is achieved based on crystallization and re-dissolution-induced spontaneous separation of analytes and salt. Efficient sample enrichment is achieved during the crystallization process by modifying the glass surface with an omniphobic coating. Finally, vibrating sharp-edge spray ionization is employed to ionize the target molecules directly on the glass slide. Thus, all the necessary sample operations prior to MS analysis are completed on the sample glass slide.

RESULTS

Efficient sample enrichment on the omniphobic glass slide is first visualized using food dyes. The benefits of the desalting and enrichment steps for detecting macrolide antibiotics in 1× phosphate buffered saline (PBS) solutions are demonstrated by comparing samples with different treatment procedures. Finally, quantification of macrolide antibiotics from PBS and serum samples is demonstrated. A linear range between 2 nM and 10 μM has been achieved for the serum sample with a limit of detection of 1 nM.

CONCLUSIONS

A simple, flexible, low-cost, and highly integrated workflow for detecting target molecules from complex matrices using MS is demonstrated. This method will be valuable to many applications that require rapid and efficient MS analysis of complex samples.

Mass Spectrometric Biosensing: A Powerful Approach for Multiplexed Analysis of Clinical Biomolecules

Rapid and sensitive detection of clinical biomolecules in a multiplexed fashion is of great importance for accurate diagnosis of diseases. Mass spectrometric (MS) approaches are exceptionally suitable for clinical analysis due to its high throughput, high sensitivity, and reliable qualitative and quantitative capabilities. To break through the bottleneck of MS technique for detecting high-molecular-weight substances with low ionization efficiency, the concept of mass spectrometric biosensing has been put forward by adopting mass spectrometric chips to recognize the targets and mass spectrometry to detect the signals switched by the recognition. In this review, the principle of mass spectrometric sensing, the construction of different mass tags used for biosensing, and the typical combination mode of mass spectrometric imaging (MSI) technique are summarized. Future perspectives including the design of portable matching platforms, exploitation of novel mass tags, development of effective signal amplification strategies, and standardization of MSI methodologies are proposed to promote the advancements and practical applications of mass spectrometric biosensing.

Rapid Screening of COVID-19 Directly from Clinical Nasopharyngeal Swabs Using the MasSpec Pen

The outbreak of COVID-19 has created an unprecedent global crisis. While the polymerase chain reaction (PCR) is the gold standard method for detecting active SARS-CoV-2 infection, alternative high-throughput diagnostic tests are of a significant value to meet universal testing demands. Here, we describe a new design of the MasSpec Pen technology integrated to electrospray ionization (ESI) for direct analysis of clinical swabs and investigate its use for COVID-19 screening. The redesigned MasSpec Pen system incorporates a disposable sampling device refined for uniform and efficient analysis of swab tips via liquid extraction directly coupled to an ESI source. Using this system, we analyzed nasopharyngeal swabs from 244 individuals including symptomatic COVID-19 positive, symptomatic negative, and asymptomatic negative individuals, enabling rapid detection of rich lipid profiles. Two statistical classifiers were generated based on the lipid information acquired. Classifier 1 was built to distinguish symptomatic PCR-positive from asymptomatic PCR-negative individuals, yielding a cross-validation accuracy of 83.5%, sensitivity of 76.6%, and specificity of 86.6%, and validation set accuracy of 89.6%, sensitivity of 100%, and specificity of 85.3%. Classifier 2 was built to distinguish symptomatic PCR-positive patients from negative individuals including symptomatic PCR-negative patients with moderate to severe symptoms and asymptomatic individuals, yielding a cross-validation accuracy of 78.4%, specificity of 77.21%, and sensitivity of 81.8%. Collectively, this study suggests that the lipid profiles detected directly from nasopharyngeal swabs using MasSpec Pen-ESI mass spectrometry (MS) allow fast (under a minute) screening of the COVID-19 disease using minimal operating steps and no specialized reagents, thus representing a promising alternative high-throughput method for screening of COVID-19.

Point-of-Care Therapeutic Drug Monitoring for Precision Dosing of Immunosuppressive Drugs

BACKGROUND

Immunosuppressive drugs (ISD) are an essential tool in the treatment of transplant rejection and immune-mediated diseases. Therapeutic drug monitoring (TDM) for determination of ISD concentrations in biological samples is an important instrument for dose personalization for improving efficacy while reducing side effects. While currently ISD concentration measurements are performed at specialized, centralized facilities, making the process complex and laborious for the patient, various innovative technical solutions have recently been proposed for bringing TDM to the point-of-care (POC).

CONTENT

In this review, we evaluate current ISD-TDM and its value, limitations, and proposed implementations. Then, we discuss the potential of POC-TDM in the era of personalized medicine, and provide an updated review on the unmet needs and available technological solutions for the development of POC-TDM devices for ISD monitoring. Finally, we provide concrete suggestions for the generation of a meaningful and more patient-centric process for ISD monitoring.

SUMMARY

POC-based ISD monitoring may improve clinical care by reducing turnaround time, by enabling more frequent measurements in order to obtain meaningful pharmacokinetic data (i.e., area under the curve) faster reaction in case of problems and by increasing patient convenience and compliance. The analysis of the ISD-TDM field prompts the evolution of POC testing toward the development of fully integrated platforms able to support clinical decision-making. We identify 4 major areas requiring careful combined implementation: patient usability, data meaningfulness, clinicians' acceptance, and cost-effectiveness.

An ultrasensitive electrochemical sensor for the detection of acetaminophen via a three-dimensional hierarchical nanoporous gold wire electrode

Acetaminophen is one of the most commonly used non-steroidal anti-inflammatory drugs worldwide. However, due to the increasing popularity of this drug, overdosing and the contamination of ambient waterways have emerged as major issues. Here, we report on a reliable, ultrasensitive, and easy-to-use sensor for the electrochemical detection of acetaminophen. This sensor employs a gold wire electrode with a unique three-dimensional hierachical nanoporous structure, fabricated using a dissolution, disproportion and deposition procedure. In consideration of optimal sensitivity and reproducibility, the most suitable nanoporous gold electrode was employed for the detection of acetamiophen among a set of nanoporous electrodes made under different reaction times. It was found that the pore size, film thickness, and electrochemically active surface area (ECSA) played major roles in the fouling resistance of the developed sensor. The ECSA of the selected sensor was increased by 15.8 times after the post-treatment. The 3D nanoporous electrode demonstrated excellent performance for the detection of acetaminophen with a low detection limit of 3.37 nM, and a strong anti-interference capability. The developed nanoporous Au electrode proved effective for the detection of acetaminophen in real sheep serum, which confirmed its promising application for medical diagnostics and pollutant surveilliance in source waters.

Solvent-resistant microfluidic paper-based analytical device/spray mass spectrometry for quantitative analysis of C18 -ceramide biomarker

We developed a highly efficient and low-cost organic solvents-resistant microfluidic paper-based analytical device (μPAD) coupled with paper spray mass spectrometry (PS-MS) for quantitative determination of C₁₈ -ceramide as a prognostic biomarker for several diseases. Several models of μPAD patterns have been examined to select the most resistant and efficient microchannel barriers, which can provide continuous spray at ionization zone and prevent "coffee ring" effect. Moreover, the developed μPAD has enabled the analysis of low concentration of C₁₈ -ceramide because of the maximum supply of deposited analyte through microchannel. The MS results confirmed the formation of doubly and singly charged metal ion complexes between ceramide and different metal ions. Notably, the complexation that occurs between lithium ions and C₁₈ -ceramide showed a high relative abundance compared with other formed complexes. Taking into account the relative abundance of complex [Cer + Li]⁺ at 572.8 m/z, it can be considered as a stable ion and therefore be used for the analysis of C₁₈ -ceramide at low concentrations. Complexation of C₁₈ -ceramide and lithium confirmed with quantum chemical calculations. The proposed method represents good linearity with a regression coefficient of 0.9956 for the analysis of C₁₈ -ceramide and reaches a limit of detection to 0.84 nM. It has been adapted successfully for practical application in human serum samples with high recovery values in range of 92%-105%. The developed μPAD-MS technique provides clear advantages by reducing the experimental steps and simplifying the operation process and enables to identify subnanomolar concentration of C₁₈ -ceramide in human serum samples.

Hyphenated sample preparation-electrospray and nano-electrospray ionization mass spectrometry for biofluid analysis

Stand-alone electrospray ionization mass spectrometry (ESI-MS) has been advancing through enhancements in throughput, selectivity and sensitivity of mass spectrometers. Unlike traditional MS techniques which usually require extensive offline sample preparation and chromatographic separation, many sample preparation techniques are now directly coupled with stand-alone MS to enable outstanding throughput for bioanalysis. In this review, we summarize the different sample clean-up and/or analyte enrichment strategies that can be directly coupled with ESI-MS and nano-ESI-MS for the analysis of biological fluids. The overview covers the hyphenation of different sample preparation techniques including solid phase extraction (SPE), solid phase micro-extraction (SPME), slug flow micro-extraction/nano-extraction (SFME/SFNE), liquid extraction surface analysis (LESA), extraction electrospray, extraction using digital microfluidics (DMF), and electrokinetic extraction (EkE) with ESI-MS and nano-ESI-MS.

One-step hexaplex immunoassays by on-line paper substrate-based electrospray ionization mass spectrometry for combined cancer biomarker screening

Mass spectrometry (MS) is attractive as a multiplexed immunoassay readout benefiting from its high sensitivity, speed and mass resolution. Here, a simple paper-based hexaplex immunoassay with an on-line MS readout was proposed, using functionalized paper as the immune substrates, along with rhodamine-based mass tags assembled on gold nanoparticles prepared as the mass probes (MPs). Simultaneous immune capture and labeling were conducted in one step on paper substrates in 96-well plates with a high throughput within 30 minutes, and the on-line efficient dissociation of the mass tags highly facilitated the hexaplex readout of the immune signals by a newly established on-line paper substrate-based electrospray ionization-MS setup. Six MPs were synthesized for the simultaneous quantification of six important cancer protein markers (cancer antigen 15-3, cancer antigen 19-9, carcinoma embryonic antigen, cancer antigen 125, human epididymis protein 4, and alpha fetoprotein) using only 10 μL serum, presenting satisfactory sensitivity, accuracy and specificity. This platform was further tested in screening for the six biomarkers in serum samples of patients with breast, liver and gastric cancers, showing its high potential for sensitive and specific early cancer diagnosis.

Emerging Chromatography-Free High-Throughput Mass Spectrometry Technologies for Generating Hits and Leads

Mass spectrometry (MS) detection can offer unmatched selectivity and sensitivity. The use of MS without chromatography greatly increases the throughput, making it suitable for high throughput screening. However, the trade-offs of direct MS detection need to be carefully evaluated along with the development of novel strategies to ensure successful implementation. In this review, we will discuss the pros and cons of chromatography-free MS and discuss some of the currently used and future technologies being investigated to enable high-throughput MS.

Dynamic Range Expansion by Gas-Phase Ion Fractionation and Enrichment for Imaging Mass Spectrometry

In the analysis of biological tissue by imaging mass spectrometry (IMS), the limit of detection and dynamic range are of paramount importance in obtaining experimental results that provide insight into underlying biological processes. Many important biomolecules are present in the tissue milieu in low concentrations and in complex mixtures with other compounds of widely ranging abundances, challenging the limits of analytical technologies. In many IMS experiments, the ion signal can be dominated by a few highly abundant ion species. On trap-based instrument platforms that accumulate ions prior to mass analysis, these high abundance ions can diminish the detection and dynamic range of lower abundance ions. Herein, we describe two strategies for combating these challenges during IMS experiments on a hybrid QhFT-ICR MS. In one iteration, the mass resolving capabilities of a quadrupole mass filter are used to selectively enrich ions of interest via a technique previously termed continuous accumulation of selected ions. Second, we have introduced a supplemental dipolar AC waveform to the quadrupole mass filter of a commercial QhFT-ICR mass spectrometer to perform selected ion ejection prior to the ion accumulation region. This setup allows the selective ejection of the most abundant ion species prior to ion accumulation, thereby greatly improving the molecular depth with which IMS can probe tissue samples. The gain in sensitivity of both of these approaches roughly scales with the number of accumulated laser shots up to the charge capacity of the ion accumulation cell. The efficiencies of these two strategies are described here by performing lipid imaging mass spectrometry analyses of a rat brain.

MINIATURIZATION IN MASS SPECTROMETRY

Expectations for continuous miniaturization in mass spectrometry are not declining for years. Portable instruments are highly welcome by the industry, science, space agencies, forensic laboratories, and many other units. All are striving for the small, cheap, and as good as possible instruments. This review describes the recent developments of miniature mass spectrometers and also provides selected applications where these devices are used. Upcoming perspectives of further development are also discussed. @ 2019 John Wiley & Sons Ltd. Mass Spec Rev.

Analysis of biofluids by paper spray-MS in forensic toxicology

Direct ambient ionization techniques have been developed with the aim to reduce the complexity of mass spectrometry analysis by minimizing sample preparation and chromatographic separation. In this context, paper spray-MS (PS-MS) is an innovative approach that provides faster and cheaper analysis of biofluids by the addition of the sample directly to a paper. In forensic toxicology, the analytical workflow for the detection and quantification of drugs of abuse is onerous, including sample treatment, extraction and clean up, especially regarding complex biological matrices. PS-MS allows the detection of analytes of toxicological interest in blood, plasma and urine using low sample volume. This review aims to discuss the potential use, advances and challenges of PS-MS in forensic toxicology.

Single Cell Metabolomics: A Future Tool to Unmask Cellular Heterogeneity and Virus-Host Interaction in Context of Emerging Viral Diseases

Viral emergence is an unpredictable but obvious event, particularly in the era of climate change and globalization. Efficient management of viral outbreaks depends on pre-existing knowledge and alertness. The potential hotspots of viral emergence often remain neglected and the information related to them is insufficient, particularly for emerging viruses. Viral replication and transmission rely upon usurping the host metabolic machineries. So altered host metabolic pathways can be exploited for containment of these viruses. Metabolomics provides the insight for tracing out such checkpoints. Consequently introspection of metabolic alteration at virus-host interface has evolved as prime area in current virology research. Chromatographic separation followed by mass spectrometry has been used as the predominant analytical platform in bulk of the analyses followed by nuclear magnetic resonance (NMR) and fluorescence based techniques. Although valuable information regarding viral replication and modulation of host metabolic pathways have been extracted but ambiguity often superseded the real events due to population effect over the infected cells. Exploration of cellular heterogeneity and differentiation of infected cells from the nearby healthy ones has become essential. Single cell metabolomics (SCM) emerges as necessity to explore such minute details. Mass spectrometry imaging (MSI) coupled with several soft ionization techniques such as electrospray ionization (ESI), laser ablation electrospray ionization (LAESI), matrix assisted laser desorption/ionization (MALDI), matrix-free laser desorption ionization (LDI) have evolved as the best suited platforms for SCM analyses. The potential of SCM has already been exploited to resolve several biological conundrums. Thus SCM is knocking at the door of virus-host interface.

Targeted Quantification of Peptides Using Miniature Mass Spectrometry

Proteomics by mass spectrometry (MS) allows for the identification of amino acid/peptide sequences in complex mixtures. Peptide analysis and quantitation enables screening of protein biomarkers and targeted protein biomarker analysis for clinical applications. Whereas miniature mass spectrometers have primarily demonstrated point-of-care analyses with simple procedures aiming at drugs and lipids, it would be interesting to explore their potential in analyzing proteins and peptides. In this work, we adapted a miniature MS instrument for peptide analysis. A mass range as wide as 100-2000 m/z was achieved for obtaining peptide spectra using this instrument with dual linear ion traps. MS² and MS³ can be performed to analyze a wide range of peptides. The parameters of pressure, electric potentials, and solution conditions were optimized to analyze peptides with molecular weights between 900 and 1800 Da. The amino acid sequences were identified using both beam-type and in-trap collision-induced dissociation, and the results were comparable to those obtained by a commercial quadrupole time-of-flight mass spectrometer. With product ion monitoring scan mode, peptide quantitation was performed with a limit of detection of 20 nM achieved for the Met peptide. The method developed has also been applied to the analysis of the trypsin-digested cell lysate of SKBR3 cells with a low expression level of the Met gene.

Rapid and high-throughput screening of multi-residue pharmaceutical drugs in bovine tissue using solid phase microextraction and direct analysis in real time-tandem mass spectrometry (SPME-DART-MS/MS)

Direct Analysis in Real Time (DART) has become a popular research area in food safety monitoring due to its unique characteristics that allow rapid and high-throughput screening of complex matrices with minimal sample preparation. The current research aimed to investigate the detection and quantitation capabilities of solid phase microextraction (SPME) and DART coupled to tandem mass spectrometry MS/MS for a large number of pharmaceutical drugs covering a wide range of physico-chemical properties (log P, -1.22-5.97) in complex animal-food matrices such as beef tissue. 53% of the 98 target analytes selected initially could be efficiently ionized by DART and quantified at or below the Canadian maximum residue limits (MRLs) and US regulatory tolerances in bovine muscle. Despite using only two internal standards for correction, promising results were obtained for these analytes, where 62% of the detected analytes achieved linear correlation coefficients >0.99 within the evaluated range of concentrations (0.25-3X, where X corresponds to the MRL for each target analyte). In addition, more than 92% of the detected analytes achieved average accuracies within the 70-120% range of their true concentrations and intraday repeatability RSDs ≤25% at the 0.5X, 1X, and 2X concentration levels. The fully automated sample preparation workflow allowed for total extraction and analysis times as short as 1 min time per sample. While DART has limited capabilities in terms of analyte coverage, this research highlights the potential usefulness of SPME-DART-MS/MS as a method for rapid analysis in food safety monitoring applications.

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.

Optimization of Coated Blade Spray for Rapid Screening and Quantitation of 105 Veterinary Drugs in Biological Tissue Samples

Rapid and efficient determination of contaminants at trace levels in tissue samples has become an unmet need around the globe. Coated blade spray (CBS) extraction/ionization is a technology capable of performing, with a single device, enrichment of analytes present in complex matrices, as well as the direct interface and introduction of said analytes into the mass spectrometer via electrospray ionization. To facilitate the challenging rapid tissue screening, we describe for the first time the use of a very thin layer of biocompatible polyacrylonitrile as a CBS device undercoating to make metal surface biocompatible. This add-on is meant to protect the portion of the uncoated stainless-steel of the blade that is normally exposed to the matrix, consequently becoming susceptible to adhesion of matrix macromolecules, cells, and fat. In addition, we present for the first time the use of CBS in negative ionization mode for quantitative purposes. The optimized CBS workflow allows for rapid and high-throughput screening and quantitation of 105 veterinary drugs in homogenized bovine tissue in both negative and positive ionization mode in one single run using a single CBS device with analysis times as short as 1 min per sample when 96 extractions are simultaneously conducted. While only two internal standards were used for correction, one per ionization mode, excellent accuracy and precision were achieved, with more than 90% of analytes falling within the 70-120% range of their true concentrations and yielding RSD ≤ 25% at three validation levels. The majority of analytes achieved linear correlation coefficients >0.99, and all 105 analytes were able to meet both Canadian and U.S. regulatory levels.

Applications of Mass Spectrometry for Clinical Diagnostics: The Influence of Turnaround Time

This critical review discusses how the need for reduced clinical turnaround times has influenced chemical instrumentation. We focus on the development of modern mass spectrometry (MS) and its application in clinical diagnosis. With increased functionality that takes advantage of novel front-end modifications and computational capabilities, MS can now be used for non-traditional clinical analyses, including applications in clinical microbiology for bacteria differentiation and in surgical operation rooms. We summarize here recent developments in the field that have enabled such capabilities, which include miniaturization for point-of-care testing, direct complex mixture analysis via ambient ionization, chemical imaging and profiling, and systems integration.

Oxidative stress and abnormal bioactive lipids in early cystic fibrosis lung disease

BACKGROUND

Clinical data indicate that airway inflammation in children with cystic fibrosis (CF) arises early, is associated with structural lung damage, and predicts progression. In bronchoalveolar lavage fluid (BALF) from CFTR mutant mice, several aspects of lipid metabolism are abnormal that contributes to lung disease. We aimed to determine whether lipid pathway dysregulation is also observed in BALF from children with CF, to identify biomarkers of early lung disease and potential therapeutic targets.

METHODS

A comprehensive panel of lipids that included Sphingolipids, oxylipins, isoprostanes and lysolipids, all bioactive lipid species known to be involved in inflammation and tissue remodeling, were measured in BALF from children with CF (1-6 years, N = 33) and age-matched non-CF patients with unexplained inflammatory disease (N = 16) by HPLC-MS/MS. Lipid data were correlated with chest CT scores and BALF inflammation biomarkers.

RESULTS

The ratio of long chain to very long chain ceramide species (LCC/VLCC) and lysolipid levels were enhanced in CF compared to non-CF patients, despite comparable neutrophil counts and bacterial load. In CF patients both LCC/VLCC and lysolipid levels correlated with inflammation and chest CT scores. The ceramide precursors Sphingosine, Sphinganine, Sphingomyelin, correlated with inflammation, whilst the oxidative stress marker isoprostane correlated with inflammation and chest CT scores. No correlation between lipids and current bacterial infection in CF (N = 5) was observed.

CONCLUSIONS

Several lipid biomarkers of early CF lung disease were identified, which point toward potential disease monitoring and therapeutic approaches that can be used to complement CFTR modulators.