Recent advances in high-throughput quantitative bioanalysis by LC–MS/MS

Quantification for non-targeted LC/MS screening without standard substances

Non-targeted and suspect analyses with liquid chromatography/electrospray/high-resolution mass spectrometry (LC/ESI/HRMS) are gaining importance as they enable identification of hundreds or even thousands of compounds in a single sample. Here, we present an approach to address the challenge to quantify compounds identified from LC/HRMS data without authentic standards. The approach uses random forest regression to predict the response of the compounds in ESI/HRMS with a mean error of 2.2 and 2.0 times for ESI positive and negative mode, respectively. We observe that the predicted responses can be transferred between different instruments via a regression approach. Furthermore, we applied the predicted responses to estimate the concentration of the compounds without the standard substances. The approach was validated by quantifying pesticides and mycotoxins in six different cereal samples. For applicability, the accuracy of the concentration prediction needs to be compatible with the effect (e.g. toxicology) predictions. We achieved the average quantification error of 5.4 times, which is well compatible with the accuracy of the toxicology predictions.

Quantitative of progesterone using isotope dilution-matrix-assisted laser desorption ionization-time of flight mass spectrometry

A quantification assay based on isotope dilution mass spectrometry to determine the concentration of progesterone in human serum was reported. Incorporated with ¹³C₃-progesterone, serum samples were subjected to progesterone extraction and clean-up by C4 solid-phase-extraction columns and hexane-based liquid/liquid extraction, respectively. The cleaned-up serum samples were then subjected to MALDI-TOF mass spectrometry for the quantification of progesterone. In the study, the recovered progesterone concentration determined by the assay showed good robustness and constancy in comparison to conventional radioimmunologic assay. We concluded that the ¹³C₃-progesterone-based quantification assay is a robust method for the measurement of serum progesterone.

Advantages of this technique includes:

• This study describes a MALDI-TOF/MS method for the determination of serum progesterone.

• The technique is simple and easy to apply on MALDI-TOF/MS for serum progesterone analysis.

• The correlation coefficient between MALDI-TOF MS and RIA was 0.981 for serum progesterone.

Bias reduction in the quantitative analysis of a target analyte present in a limited quantity in human plasma using dual-mode heart-cutting two-dimensional liquid chromatography coupled with isotope dilution mass spectrometry

Dual-mode heart-cutting two-dimensional liquid chromatography (DMHC 2D-LC) was applied to isotope dilution mass spectrometry (IDMS) to reduce the bias in the quantitative analysis of a target analyte present in a limited quantity in human plasma. Based on a Waters I-Class LC system, the DMHC 2D-LC system was operated in one- and two-dimensional modes to facilitate the determination of heart-cutting time and the efficient trapping of the target LC eluate. Experiments to determine the feasibility of coupling with IDMS were performed with triple quadrupole mass spectrometry using folic acid standards and/or ¹³ C₅ -folic acid. To validate the performance of the DMHC 2D-LC/IDMS system on a complex sample, human plasma was analyzed for folic acid and the result was compared with that obtained using conventional single-column LC. The total run time of the DMHC 2D-LC system was 20 min, the same as that of the single-column LC system. The peak profile of the spiked ¹³ C₅ -folic acid obtained with single-column LC/MS was affected by matrix effects, but resolved with DMHC 2D-LC/MS, thus improving the accuracy of the analysis. The DMHC 2D-LC/IDMS system showed reliable performance in analyzing the target analyte in human plasma, eliminating matrix effects and saving analysis time.

Quality by design applied to olanzapine and quetiapine LC-MS/MS bioanalysis

One major challenge in quantifying drugs in biological matrices is to manage interfering compounds. A technique such liquid chromatography coupled to mass spectrometry in tandem (LC-MS/MS) is especially suitable for this application due to its high sensitivity and selectivity in detecting low concentrations of analytes in a complex system. Due to the complexity of LC-MS/MS systems, a number of experimental parameters must be optimized to provide an adequate separation and detection of the analyte. In the present work, a design of experiments approach was developed to optimize an LC-MS/MS-based bioanalytical method to extract olanzapine (OLZ) and quetiapine (QTP) from human plasma. Three steps for the optimization process were conducted: central composite face-centered design to optimize chromatographic parameters (Step 1), ionization in mass spectrometry (Step 2) and a full 32 factorial design to optimize analyte extraction conditions (Step 3). After the optimization process, resolutions and QTP and OLZ retention time (2.3 and 4, respectively) were optimum with pH of 4.7 and 85.5% of acetonitrile for the chromatographic step. Mass spectrometry optimization step provided an increase of (±50%) in the average peak area with high signal-to-noise relationship for the analytes studied. The proposed extraction method was 70% more efficient than the initial method for all drugs analyzed.

Simultaneous Determination of Schisandrin and Promethazine with Its Metabolite in Rat Plasma by HPLC-MS/MS and Its Application to a Pharmacokinetic Study

This study aimed to develop a selective, simple, and sensitive HPLC-MS/MS method for the simultaneous determination of schisandrin and promethazine (PMZ) with its metabolite in rat plasma, which was further used for a pharmacokinetic herb-drug interaction study. HPLC-MS/MS analyses were performed on an Agilent Technologies 1290 LC and a 6410 triple quadrupole mass spectrometer. The following parameters, the lower limit of quantification (LLOQ), calibration curve, accuracy, precision, stability, matrix effect, and recovery, were validated. The linear range of the developed method for PMZ, its metabolite promethazine sulfoxide (PMZSO), and schisandrin in rat plasma was 0.5-200 ng/mL (R 2 > 0.995), with an LLOQ of 0.5 ng/mL, which completely met the determination requirements of biosamples. The intra- and interday precision (RSD, %) was below 13.31% (below 16.67% for the LLOQ) in various plasma, whose accuracy (bias, %) was from -8.52% to 11.40%, which were both within an acceptable range. This method was successfully applied to a pharmacokinetic herb-drug interaction study after oral administration of PMZ with or without S. chinensis water extract. The results demonstrated that coadministration with the S. chinensis water extract might affect the pharmacokinetic behaviors of PMZ. In turn, when taken together with PMZ, the pharmacokinetic parameters of schisandrin, the main active component of S. chinensis, were also affected. The method established in the current study was selective, simple, sensitive, and widely available with good linearity, high accuracy and precision, and a stable sample preparation process. Moreover, this analytical method provides a significant approach for the investigation of herb-drug interaction between S. chinensis and PMZ. The potential pharmacokinetic herb-drug interaction of PMZ- and schisandrin-containing preparations should be noted.

Challenges and Advances in the Fabrication of Monolithic Bioseparation Materials and their Applications in Proteomics Research

High-performance liquid chromatography integrated with tandem mass spectrometry (HPLC-MS/MS) has become a powerful technique for proteomics research. Its performance heavily depends on the separation efficiency of HPLC, which in turn depends on the chromatographic material. As the "heart" of the HPLC system, the chromatographic material is required to achieve excellent column efficiency and fast analysis. Monolithic materials, fabricated as continuous supports with interconnected skeletal structure and flow-through pores, are regarded as an alternative to particle-packed columns. Such materials are featured with easy preparation, fast mass transfer, high porosity, low back pressure, and miniaturization, and are next-generation separation materials for high-throughput proteins and peptides analysis. Herein, the recent progress regarding the fabrication of various monolithic materials is reviewed. Special emphasis is placed on studies of the fabrication of monolithic capillary columns and their applications in separation of biomolecules by capillary liquid chromatography (cLC). The applications of monolithic materials in the digestion, enrichment, and separation of phosphopeptides and glycopeptides from biological samples are also considered. Finally, advances in comprehensive 2D HPLC separations using monolithic columns are also shown.

Identification of in vitro and in vivo potential metabolites of novel cardiovascular and adrenolytic drugs by liquid chromatography-mass spectrometry with the aid of experimental design

Drug metabolism in liver microsomes was studied in vitro using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Relevant drug was incubated with dog, human and rat liver microsomes (DLMs, HLMs, RLMs) along with NADPH, and the reaction mixture was analyzed by LC-MS/MS to obtain specific metabolic profile. GRACE analytical C18 column, Vision HT (50 × 2 mm, 1.5 μm) was implemented with acetonitrile and water (+ 5 mM ammonium acetate) in a gradient mode as the mobile phase at a flow 0.4 mL.min−1. Different phase I and phase II metabolites were detected and structurally described. The metabolism of the studied drugs occurred via oxidation, hydroxylation and oxidative deamination processes. Conjugates with the glucuronic acid and sulfate were also observed as phase II biotransformation. The central composite design (CCD) showed that factors, such as time incubation, liver microsomal enzymes concentration and NADPH concentration, along with drying gas temperature, nebulizer gas pressure and capillary voltage significantly affected the final response of the method. This study describes the novel information about the chemical structure of the potential metabolites of selected biologically active compounds, which provide vital data for further pharmacokinetic and in vivo metabolism studies.

Quantification of total and unbound cefuroxime in plasma by ultra-performance liquid chromatography tandem mass spectrometry in a cohort of critically ill patients with hypoalbuminemia and renal failure

Background

Pharmacokinetic studies of cefuroxime by ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) have been limited to measurements of total concentrations. Here, we developed a robust method for quantifying total and unbound cefuroxime concentrations using UPLC‐MS/MS and ultrafiltration in critically ill patients with hypoalbuminemia and renal failure.

Methods

Method validation included accuracy, linearity, precision, repeatability, recovery, and limit of quantification (LOQ). Feasibility of the method was performed on samples obtained from randomly selected intensive care unit (ICU) patients. Total and unbound cefuroxime concentrations were quantified using UPLC‐MS/MS. Sampling times were categorized as trough (180‐1 min prior to administration), peak (10‐30 min after administration), mid (30‐360 min after administration), and continuous (sampling during administration). Pharmacokinetic/pharmacodynamic (PK/PD) targets were unbound cefuroxime concentrations above 4 times the minimum inhibitory concentration (32 mg/L).

Results

Intra‐assay and inter‐assay precision was <3%. Recovery was 99.7%‐100.3%, and LOQ was 0.1 mg/L. We included 11 patients (median age 72 years (range 54‐77). Median albumin serum concentrations and eGFR were 19 g/L (range 11‐40 g/L) and 48 mL/min/1.73 m² (range 7‐115 mL/min/1.73 m²), respectively. Median trough and mid concentrations of total cefuroxime were 22.27 mg/L (range 5.42‐54.03 mg/L) and 71.49 mg/L (range 53.87‐73.86 mg/L), and median unbound fraction was 75.42% (range 27.36%‐99.75%). Median unbound cefuroxime concentrations were 11.94 mg/L (range 3.85‐32.39 mg/L) (trough) and 55.62 mg/L (range 10.03‐62.62 mg/L) (mid).

Conclusion

The method is precise and accurate according to ISO 15189 and within the clinical range of cefuroxime (0.5‐100 mg/L). The method was applied in ICU patients and is suitable for TDM on unbound cefuroxime concentrations.

Emerging molecular biology tools and strategies for engineering natural product biosynthesis

Natural products and their related derivatives play a significant role in drug discovery and have been the inspiration for the design of numerous synthetic bioactive compounds. With recent advances in molecular biology, numerous engineering tools and strategies were established to accelerate natural product synthesis in both academic and industrial settings. However, many obstacles in natural product biosynthesis still exist. For example, the native pathways are not appropriate for research or production; the key enzymes do not have enough activity; the native hosts are not suitable for high-level production. Emerging molecular biology tools and strategies have been developed to not only improve natural product titers but also generate novel bioactive compounds. In this review, we will discuss these emerging molecular biology tools and strategies at three main levels: enzyme level, pathway level, and genome level, and highlight their applications in natural product discovery and development.

Bioanalysis of Targeted Nanoparticles in Monkey Plasma via LC-MS/MS

This work represents the first reporting of a comprehensive bioanalytical GLP methodology detailing the mass spectrometric quantitation of PF-05212384 dosed as a targeted polymeric encapsulated nanoparticle (PF-07034663) to monkeys. Polymeric nanoparticles are a type of drug formulation that enables the sustained release of an active therapeutic agent (payload) for targeted delivery to specific sites of action such as cancer cells. Through the careful design and engineering of the nanoparticle formulation, it is possible to improve the biodistribution and safety of a given therapeutic payload in circulation. However, the bioanalysis of nanoparticles is challenging due to the complexity of the nanoparticle drug formulation itself and the number of pharmacokinetic end points needed to characterize the in vivo exposure of the nanoparticles. Gedatolisib, also known as PF-05212384, was reformulated as an encapsulated targeted polymeric nanoparticle. The bioanalytical assays were validated to quantitate both total and released PF-05212384 derived from the encapsulated nanoparticle (PF-07034663). Assay performance calculated from quality control samples in three batch runs demonstrated intraday precision and accuracy within 10.3 and 12.2%, respectively, and interday precision and accuracy within 9.1 and 8.5%, respectively. This method leveraged automation to ease the burden of a laborious and complicated sample pretreatment and extraction procedure. The automated method was used to support a preclinical safety study in monkeys in which both released and total PF-05212384 concentrations were determined in over 1600 monkey plasma study samples via LC-MS/MS.

Capillary microsampling in mice: effective way to move from sparse sampling to serial sampling in pharmacokinetics profiling

Pharmacokinetic studies are an integral part of drug discovery and development. Mice are the commonly used species for pharmacokinetics studies during early discovery studies. Conventionally, composite PK profiles are obtained from mice studies due to the physiological limitations of the total blood volume that can be drawn over a certain period.With advancements in bioanalytical instrumentation and in blood sampling techniques, analysis with small volume (<50 µL) became feasible enabling serial blood sampling from the mouse for PK studies. The objective of the current study was to develop and establish a serial blood sampling technique in mouse and compare it with the conventional sparse sampling method (composite PK) following oral administration of widely used NSAIDs, diclofenac, celecoxib and tenoxicam, into Swiss Albino mice.The pharmacokinetic parameters of all three probe drugs by serial blood sampling were comparable with that of sparse sampling method. There was no significant difference between the whole blood concentration time profiles of all three drugs between serial sampling and sparse sampling suggesting serial blood sampling method can be easily implemented for mice PK studies.Serial blood sampling technique requires use of fewer number of animals, less quantity of test compound and reduces the possible dosing errors as fewer number of animals need to be dosed resulting in quality PK data and enabling comparison of inter-animal differences in PK profile.

Simulation of phase I metabolism reactions of selected calcium channel blockers by human liver microsomes and photochemical methods with the use of Q-TOF LC/MS

The in vitro phase I metabolism of perhexiline and flunarizine, two calcium channel blockers was investigated during this study with the use of human liver microsomes (HLM) method compared with TiO₂, WO₃ and ZnO catalyzed photochemical reaction. In order to determine the structures of metabolites an quadrupole time-of-flight mass spectrometry combined with liquid chromatography (Q-TOF LC/MS) system was used. The obtained high resolution mass spectra enabled to identify thirteen products of metabolism of selected drugs including three not yet described metabolites of perhexiline and two new metabolites of flunarizine. The vast majority of metabolites were confirmed also with the participation of photocatalytic approach of the drug metabolism simulation. The comparison of all metabolic profiles made with the use of computational methods drew attention particularly to TiO₂ and WO₃ catalyzed photochemical reaction as similar to HLM incubation. Additionally, in silico toxicity assessment of the detected transformation products of the analyzed substances was also evaluated.

A concise review of quantification methods for determination of vitamin K in various biological matrices

Vitamin K is an essential nutrient in the body and involved in numerous physiological and pathophysiological functions. Both the lack and surplus of vitamin K can put human health at risk. Therefore, it becomes necessary to monitor vitamin K concentrations in different biomatrices through establishing sensitive and specific analytical methods. This review collectively describes an updated overview of the sample pretreatment methodologies and methods for quantitative determination of vitamin K that have been used in last two decades. High Performance Liquid Chromatography (HPLC) is commonly utilized as a standard for separation of vitamin K in combination with different detection including spectroscopic, spectrometric, fluorometric and mass spectroscopy. Recent progress in sample pretreatment technologies and quantitation methodologies have enhanced the ability to identify and quantitate vitamin K in biomatrices to further advance our understanding of the role of this vitamin in human health and disease.

Prostaglandins E2 and F2α levels in human menstrual fluid by online Solid Phase Extraction coupled to Liquid Chromatography tandem Mass Spectrometry (SPE-LC-MS/MS)

This paper reports an online SPE-LC-MS/MS method for the simultaneous quantification of prostaglandins (PGE₂ and PGF_2α) in menstrual fluid samples. To meet this goal human peripheral serum was used as surrogate matrix. The analytes were trapped on an OASIS HLB cartridge for 3 min, for sample cleanup and enrichment, and then transferred during only 42 s to an HSS T3 C18 analytical column, for separation and analysis. Prostaglandins (PGs) were detected by selected reaction monitoring in negative ion mode, PGE₂ (m/z 351 → 315) and PGF_2α (m/z 353 → 193) using isotope-labeled internal standard (PGE₂-d₄, m/z 355 → 319). The concentration linear range was of 10.34-1.034 ng mL^-1 and the lower limit of quantification (LLOQ) was 10.34 ng mL^-1 for both PGs. Validation parameters were successfully assessed according to the European Medicines Agency guideline (EMA), also comprising the FDA normative. The method showed no matrix effect and process efficiency around 100%, in addition to only 15 min of analysis time with lower solvent consumption. The method application was carried out using two menstrual fluid sample groups: control (n = 15) and treatment group (n = 7; samples from women that used Tahiti lemon juice). The PGF_2α levels were found to be higher in treated group than in control group (p ≤ 0.05), denoting an effect of the intake of Tahiti lemon juice on the menstrual inflammatory process. The on-line method herein reported could be useful for the analysis of PGs from large research studies.

Quantitation of escitalopram and its metabolites by liquid chromatography-tandem mass spectrometry in psychiatric patients: New metabolic ratio establishment

Therapeutic drug monitoring (TDM) is used to determine the concentration of drug in plasma/serum to adjust the dose of the therapeutic drug. Selective and sensitive analytical methods are used to determine drug and metabolite levels for the successful application of TDM. The aim of the study was to develop and validate using LC-MS/MS to analyse quantitative assay of escitalopram (S-CT) and metabolites in human plasma samples. In order to provide a convenient and safe treatment dose, it was aimed to determine the levels of S-CT and its metabolites in the patients' plasma. A new method with short sample preparation and analysis time was developed and validated using LC-MS/MS to analyse quantitative assay of S-CT and its metabolites in plasma. Also, plasma samples of 30 patients using 20 mg S-CT between the ages of 18 and 65 years were analysed by the validated method. The mean values of S-CT, demethyl escitalopram and didemethyl escitalopram in plasma of patients were 27.59, 85.52 and 44.30 ng/mL, respectively. At the end of the analysis, the metabolic ratio of S-CT and metabolites was calculated. It is considered that the method for the quantitative analysis of S-CT and its metabolites in human plasma samples may contribute to the literature on account of its sensitive and easy application. Additionally, the use of our data by physicians will contribute to the effective drug treatment for their patients who take S-CT.

Recent advances of online coupling of sample preparation techniques with ultra high performance liquid chromatography and supercritical fluid chromatography

Ultra high performance liquid chromatography and supercritical fluid chromatography techniques are favored because of their high efficiency and fast analysis speed. Although many sample preparation techniques have been coupled with common liquid chromatography online, the online coupling of sample preparation with the two popular chromatography techniques have gained increasing attention owing to the increasing requirements of efficiency and sensitivity. In this review, we have discussed and summarized the recent advances of the online coupling of sample preparation with ultra high performance liquid chromatography and supercritical fluid chromatography techniques. The main sample preparation techniques that have been coupled with ultra high performance liquid chromatography online are solid-phase extraction and in-tube solid-phase microextraction, while solid-phase extraction and supercritical fluid extraction are the main techniques that have been coupled with supercritical fluid chromatography online. Especially, the strategies for online coupling of sample preparation with chromatography techniques were summarized. Typical applications and growing trends of the online coupling techniques were also discussed in detail. With the increasing demands of improving the efficiency, throughput, and analytical capability toward complex samples of the analysis methods, online coupling of sample preparation with chromatography techniques will acquire further development.

Platform development for expression and purification of stable isotope labeled monoclonal antibodies in Escherichia coli

The widespread use of monoclonal antibodies (mAbs) as a platform for therapeutic drug development in the pharmaceutical industry has led to an increased interest in robust experimental approaches for assessment of mAb structure, stability and dynamics. The ability to enrich proteins with stable isotopes is a prerequisite for the in-depth application of many structural and biophysical methods, including nuclear magnetic resonance (NMR), small angle neutron scattering, neutron reflectometry, and quantitative mass spectrometry. While mAbs can typically be produced with very high yields using mammalian cell expression, stable isotope labeling using cell culture is expensive and often impractical. The most common and cost-efficient approach to label proteins is to express proteins in Escherichia coli grown in minimal media; however, such methods for mAbs have not been reported to date. Here we present, for the first time, the expression and purification of a stable isotope labeled mAb from a genetically engineered E. coli strain capable of forming disulfide bonds in its cytoplasm. It is shown using two-dimensional NMR spectral fingerprinting that the unlabeled mAb and the mAb singly or triply labeled with ¹³C, ¹⁵N, ²H are well folded, with only minor structural differences relative to the mammalian cell-produced mAb that are attributed to the lack of glycosylation in the Fc domain. This advancement of an E. coli-based mAb expression platform will facilitate the production of mAbs for in-depth structural characterization, including the high resolution investigation of mechanisms of action.

Development of a LC-MS method for simultaneous determination of amoxicillin and metronidazole in human serum using hydrophilic interaction chromatography (HILIC)

A method was developed for the determination of amoxicillin and metronidazole in human serum. The procedure used was hydrophilic interaction chromatography (HILIC) followed by mass spectrometric (MS) detection. Chromatographic separation was achieved on a ZIC-HILIC column and the mobile phase consisted of a mixture of 0.1% (v/v) formic acid in water and 0.1% (v/v) formic acid in acetonitrile. The method was validated with regard to selectivity, accuracy, precision, calibration, lower limit of quantification (LOQ), extraction recovery and matrix effect. The LOQs were 0.0138 and 0.008 μg/ml for amoxicillin and metronidazole respectively, while for quantification purposes linearity was achieved in the range of 0.1 μg/ml to 6.4 μg/ml for both drugs with correlation coefficients >0.9990. The intraday precision (expressed as %RSD) and the accuracy (expressed as the % deviation from the nominal value) was <15% for both antibiotics at all QC levels. Extraction recoveries for both drugs and internal standards were >80%, while a considerable matrix effect (<60%) was observed for amoxicillin. Finally, the method was applied to the determination of amoxicillin and metronidazole concentrations in serum for 20 patients.

Application of solid phase microextraction followed by liquid chromatography-mass spectrometry in the determination of antibiotic drugs and their metabolites in human whole blood and tissue samples

A sensitive, rapid and specific analytical method using high performance liquid chromatography coupled with mass spectrometry (HPLC-QqQ-MS) was developed to determine selected antibiotic drugs and their metabolites (amoxicillin, cefotaxime, ciprofloxacin, clindamycin and metronidazole; amoxycilloic acid, 4-hydroxyphenyl glycyl amoxicillin, desacetyl cefotaxime, 3-desacetyl cefotaxime lactone, ciprofloxacin N-oxide, N-demethylclindamycin, clindamycin sulfoxide, and hydroxy metronidazole) in human whole blood and vascularized tissue after single oral administration. The samples were prepared by solid phase microextraction with C18 fibers (SPME_C18) and determined on a GRACE analytical C18 column, Vision HT (50 × 2 mm, 1.5 μm) at the flow rate of 0.4 mL min^-1 using water and acetonitrile (containing 0.1% formic acid) as the mobile phase. The proposed method was successfully applied in a pharmacokinetic study of the selected antibiotic drugs and their metabolites in real human samples. Additionally, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF-MS) was used for identification and qualification analysis of the target compounds.

Supercritical fluid chromatography: a promising alternative to current bioanalytical techniques

During the last years, chemistry was involved in the worldwide effort toward environmental problems leading to the birth of green chemistry. In this context, green analytical tools were developed as modern Supercritical Fluid Chromatography in the field of separative techniques. This chromatographic technique knew resurgence a few years ago, thanks to its high efficiency, fastness and robustness of new generation equipment. These advantages and its easy hyphenation to MS fulfill the requirements of bioanalysis regarding separation capacity and high throughput. In the present paper, the technical aspects focused on bioanalysis specifications will be detailed followed by a critical review of bioanalytical supercritical fluid chromatography methods published in the literature.

Peptidome analysis of amniotic fluid from pregnancies with preeclampsia

Preeclampsia (PE), a life-threatening, complicated pregnancy-associated disease, has recently become a research focus in obstetrics. However, the peptidome of the amniotic fluid in PE patients has rarely been investigated. The present study used peptidomic profiling to perform a comparative analysis of human amniotic fluid between normal and PE pregnancies. Centrifugal ultrafiltration and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was combined with isotopomeric dimethyl labels to gain a deeper understanding of the role of proteins and the peptidome in the onset of PE. Following ultrafiltration and LC-MS/MS, 352 peptides were identified. Of these, 23 peptides were observed to be significantly differentially expressed (6 downregulated and 17 upregulated; P<0.05). Using Gene Ontology and Blastp analyses, the functions and biological activities of these 23 peptides were identified and revealed to include autophagy, signal transduction, receptor activity, enzymatic activity and nucleic acid binding. In addition, a bibliographic search revealed that some of the identified peptides, including Titin, are crucial to the pathogenesis underlying PE. The present study identified 23 peptides expressed at significantly different levels in the amniotic fluid of PE and normal pregnancies. A comprehensive peptidome analysis is more efficient than a simple biomarker analysis at revealing deficiencies and improving the detection rate in diseases. These analyses therefore provide a substantial advantage in applications aimed at the discovery of disease-specific biomarkers.

Decreased Prostaglandin D2 Levels in Major Depressive Disorder Are Associated with Depression-Like Behaviors

BACKGROUND

Prostaglandin (PG) D2 is the most abundant prostaglandin in the mammalian brain. The physiological and pharmacological actions of PGD2 in the central nervous system seem to be associated with some of the symptoms exhibited by patients with major depressive disorder. Previous studies have found that PGD2 synthase was decreased in the cerebrospinal fluid of major depressive disorder patients. We speculated that there may be a dysregulation of PGD2 levels in major depressive disorder.

METHODS

Ultra-performance liquid chromatography-tandem mass spectrometry coupled with a stable isotopic-labeled internal standard was used to determine PGD2 levels in the plasma of major depressive disorder patients and in the brains of depressive mice. A total of 32 drug-free major depressive disorder patients and 30 healthy controls were recruited. An animal model of depression was constructed by exposing mice to 5 weeks of chronic unpredictable mild stress. To explore the role of PGD2 in major depressive disorder, selenium tetrachloride was administered to simulate the change in PGD2 levels in mice.

RESULTS

Mice exposed to chronic unpredictable mild stress exhibited depression-like behaviors, as indicated by reduced sucrose preference and increased immobility time in the forced swimming test. PGD2 levels in the plasma of major depressive disorder patients and in the brains of depressive mice were both decreased compared with their corresponding controls. Further inhibiting PGD2 production in mice resulted in an increased immobility time in the forced swimming test that could be reversed by imipramine.

CONCLUSION

Decreased PGD2 levels in major depressive disorder are associated with depression-like behaviors.

Electrostatic Spray Ionization from 384-Well Microtiter Plates for Mass Spectrometry Analysis-Based Enzyme Assay and Drug Metabolism Screening

We have realized the direct ionization of samples from wells of microtiter plates under atmospheric conditions for mass spectrometry analysis without any liquid delivery system or any additional interface. The microtiter plate is a commercially available 384-well plate without any modification, working as a container and an emitter for electrostatic spray ionization of analytes. The approach provides high throughput for the large batches of reactions and both the qualitative and quantitative analysis of a single compound or mixture. The limits of detection in small drug molecules, peptides, and proteins are similar in comparison with standard direct infusion electrospray ionization. The analysis time per well is only seconds. These analytical merits benefit many microtiter plate-based studies, such as combinatorial chemistry and high throughput screening in enzyme assay or drug metabolism. Herein, we illustrate the application in enzyme assay using tyrosine oxidation catalyzed by tyrosinase in the presence or absence of inhibitors. The potential application in drug development is also demonstrated with cytochrome P450-catalyzed metabolic reactions of two drugs in microtiter plates followed with direct ESTASI-MS/MS-based characterization of the metabolism products.

Rapid quantification of free and glucuronidated THCCOOH in urine using coated well plates and LC–MS/MS analysis

Aim: Generally, urine drug testing for cannabis abuse involves measuring total concentrations of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) obtained by enzymatic and/or alkaline hydrolysis of THCCOOH-glucuronide. As hydrolysis can be inconsistent and incomplete, direct measurement of the two metabolites is preferable. Methodology & results: We developed a high-throughput LC–MS/MS method for simultaneous quantification of free and glucuronidated THCCOOH in urine using coated 96-well plates for analyte extraction and column-switching chromatography. Excellent separation of the two analytes was achieved within 2.5 min, with linear ranges from 5 to 2000 μg/l for THCCOOH and from 10 to 4000 μg/l for THCCOOH-glucuronide. Conclusion: The method was successfully validated and applied to authentic urine samples from cannabis consumers, demonstrating its applicability for routine cannabinoid testing.

Dried blood spot testing for seven steroids using liquid chromatography-tandem mass spectrometry with reference interval determination in the Korean population

Background

Conventional screening for congenital adrenal hyperplasia (CAH) using immunoassays generates a large number of false-positive results. A more specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been introduced to minimize unnecessary follow-ups. However, because of limited data on its use in the Korean population, LC-MS/MS has not yet been incorporated into newborn screening programs in this region. The present study aims to develop and validate an LC-MS/MS method for the simultaneous determination of seven steroids in dried blood spots (DBS) for CAH screening, and to define age-specific reference intervals in the Korean population.

Methods

We developed and validated an LC-MS/MS method to determine the reference intervals of cortisol, 17-hydroxyprogesterone, 11-deoxycortisol, 21-deoxycortisol, androstenedione, corticosterone, and 11-deoxycorticosterone simultaneously in 453 DBS samples. The samples were from Korean subjects stratified by age group (78 full-term neonates, 76 premature neonates, 89 children, and 100 adults).

Results

The accuracy, precision, matrix effects, and extraction recovery were satisfactory for all the steroids at three concentrations; values of intra- and inter-day precision coefficients of variance, bias, and recovery were 0.7-7.7%, -1.5-9.8%, and 49.3-97.5%, respectively. The linearity range was 1-100 ng/mL for cortisol and 0.5-50 ng/mL for other steroids (R²>0.99). The reference intervals were in agreement with the previous reports.

Conclusions

This LC-MS/MS method and the reference intervals validated in the Korean population can be successfully applied to analyze seven steroids in DBS for the diagnosis of CAH.

A whole-molecule immunocapture LC–MS approach for the in vivo quantitation of biotherapeutics

Aim: Large-molecule biotherapeutic quantitation in vivo by LC–MS has traditionally relied on enzymatic digestion followed by quantitation of a ‘surrogate peptide’ to infer whole-molecule concentration. MS methods presented here measure the whole molecule and provide a platform to better understand the various circulating drug forms by allowing for variant quantitation. Results: An immunocapture LC–MS method for quantitation of a biotherapeutic monoclonal antibody from human plasma is presented. Sensitivity, precision and accuracy for each molecular portion are presented along with an example of glycoform variant quantitation. Conclusion: The method is presented as a basic platform to be further developed for Good Practice (GxP) applications, critical quality attribute analysis or general understanding of molecular forms present as required for the wide range of drug development processes.