Selective Plate-Based Assay for Trace EDTA Analysis via Boron Trifluoride-methanol Derivatization UHPLC-QqQ-MS/MS Enabling Biologic and Vaccine Processes.

The employment of ethylenediaminetetraacetic acid (EDTA) across several fields in chemistry and biology has required the creation of a high number of quantitative assays. Nonetheless, the determination of trace EDTA, especially in biologics and vaccines, remains challenging. Herein, we introduce an automated high-throughput approach based on EDTA esterification in 96-well plates using boron trifluoride-methanol combined with rapid analysis by ultra-high-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). Derivatization of EDTA to its methyl ester (Me-EDTA) serves to significantly improve chromatographic performance (retention, peak shape, and selectivity), while also delivering a tremendous enhancement of sensitivity in the positive ion mode electrospray ionization (ESI+). This procedure, in contrast to previous EDTA methods based on complexation with metal ions, is not affected by high concentration of other metals, buffers, and related salts abundantly present in biopharmaceutical processes (e.g., iron, copper, citrate, etc.). Validation of this assay for the determination of ng·mL-1 level EDTA in monoclonal antibody and vaccine products demonstrated excellent performance (repeatability, precision, and linear range) with high recovery from small sample volumes while also providing an advantageous automation-friendly workflow for high-throughput analysis.

Lipid imaging within the normal rat kidney using silver nanoparticles by matrix-assisted laser desorption/ionization mass spectrometry.

The well-characterized cellular and structural components of the kidney show distinct regional compositions and distribution of lipids. In order to more fully analyze the renal lipidome we developed a matrix-assisted laser desorption/ionization mass spectrometry approach for imaging that may be used to pinpoint sites of changes from normal in pathological conditions. This was accomplished by implanting sagittal cryostat rat kidney sections with a stable, quantifiable and reproducible uniform layer of silver using a magnetron sputtering source to form silver nanoparticles. Thirty-eight lipid species including seven ceramides, eight diacylglycerols, 22 triacylglycerols, and cholesterol were detected and imaged in positive ion mode. Thirty-six lipid species consisting of seven sphingomyelins, 10 phosphatidylethanolamines, one phosphatidylglycerol, seven phosphatidylinositols, and 11 sulfatides were imaged in negative ion mode for a total of seventy-four high-resolution lipidome maps of the normal kidney. Thus, our approach is a powerful tool not only for studying structural changes in animal models of disease, but also for diagnosing and tracking stages of disease in human kidney tissue biopsies.

Cellular membrane phospholipids act as a depository for quaternary amine containing drugs thus competing with the acetylcholine/nicotinic receptor.

We previously demonstrated that ammonium- or guanidinium-phosphate interactions are key to forming noncovalent complexes (NCXs) through salt bridge formation with G-protein coupled receptors (GPCR), which are immersed in the cell membrane's lipids. The present work highlights MALDI ion mobility coupled to orthogonal time-of-flight mass spectrometry (MALDI IM oTOF MS) as a method to determine qualitative and relative quantitative affinity of drugs to form NCXs with targeted GPCRs' epitopes in a model system using, bis-quaternary amine based drugs, α- and ß- subunit epitopes of the nicotinic acetylcholine receptor' (nAChR) and phospholipids. Bis-quaternary amines proved to have a strong affinity for all nAChR epitopes and negatively charged phospholipids, even in the presence of the physiological neurotransmitter acetylcholine. Ion mobility baseline separated isobaric phosphatidyl ethanolamine and a matrix cluster, providing an accurate estimate for phospholipid counts. Overall this technique is a powerful method for screening drugs' interactions with targeted lipids and protein respectively containing quaternary amines and guanidinium moieties.

Reverse-Phase Ultra-Performance Chromatography Method for Oncolytic Coxsackievirus Viral Protein Separation and Empty to Full Capsid Quantification.

Oncolytic virus immunotherapy is emerging as a novel therapeutic approach for cancer treatment. Immunotherapy clinical drug candidate V937 is currently in phase I/II clinical trials and consists of a proprietary formulation of Coxsackievirus A21 (CVA21), which specifically infects and lyses cells with overexpressed ICAM-1 receptors in a range of tumors. Mature Coxsackievirus virions, consisting of four structural virion proteins, (VPs) VP1, VP2, VP3, and VP4, and the RNA genome, are the only viral particles capable of being infectious. In addition to mature virions, empty procapsids with VPs, VP0, VP1, and VP3, and other virus particles are produced in V937 production cell culture. Viral protein VP0 is cleaved into VP2 and VP4 after RNA genome encapsidation to form mature virions. Clearance of viral particles containing VP0, and quantification of viral protein distribution are important in V937 downstream processing. Existing analytical methods for the characterization of viral proteins and particles may lack sensitivity or are low throughput. We developed a sensitive and robust reverse-phase ultra-performance chromatography method to separate, identify, and quantify all five CVA21 VPs. Quantification of virus capsid concentration and empty/full capsid ratio was achieved with good linearity, accuracy, and precision. ClinicalTrials.gov ID: NCT04521621 and NCT04152863.

Advancing Structure Characterization of PS-80 by Charge-Reduced Mass Spectrometry and Software-Assisted Composition Analysis.

The commercially available Polysorbate 80 (PS-80) is a highly heterogeneous product. It is a complex and structurally diverse mixture consisting of polymeric species containing polyoxyethylenes (POEs), fatty acid esters, with/or without a carbohydrate core. The core is primarily sorbitan, with some isosorbide and sorbitol. Depending on the sources of fatty acids and the degrees of esterification, multiple combinations of fatty acid esters are commonly observed. A number of POE intermediates, such as polyoxyethylene glycols, POE-sorbitans, POE-isosorbides, and an array of fatty acid esters from these intermediates remain in the raw material as well. The complex composition of PS-80 is difficult to control and poses a significant characterization challenge for its use in the pharmaceutical industry. Here, we present a novel solution for PS-80 characterization using ultra high-performance liquid chromatography coupled with charge-reduction high resolution mass spectrometry. Post column co-infusion of triethylamine focused the signal into mainly singly charged molecular ions and reduced the extent of in-source fragmentation, resulting in a simpler ion map and enhanced measurement of PS-80 species. The data processing workflow is designed to programmatically identify PS-80 component classes and reduce the burden of manually analyzing complex MS data. The 2-dimensional graphical representation of the data helps visualize these features. Together, these innovative methodologies enabled us to analyze components in PS-80 with unprecedented detail and shall be a useful tool to study formulation and stability of pharmaceutical preparations. The power of this approach was demonstrated by comparing the composition of PS-80 obtained from different vendors.

An In Vitro Study of Aromatic Stacking of Drug Molecules.

In this paper, drug-drug chemical interactions between two different aromatic compounds were studied by mass spectrometry. Specifically, we examined non-covalent complexes (NCX) between paclitaxel, a chemotherapeutic compound, and medications widely used in palliative care for depression, psychosis, and anxiety. It is unknown whether psychotropic medications directly interact with paclitaxel. Here, we use a simple and rapid electrospray ionization mass spectrometry in vitro assay, which has been predictive in the case of neuropeptides, to measure the relative strength of non-covalent interactions. This chemical interaction is most likely due to the overlap of aromatic rings of π-orbitals between paclitaxel and five commonly used medications: diazepam, clonozepam, sertraline, fluoxetine, and haloperidol. Molecular modeling illustrates that differences in the stability of the NCXs are likely due to the distance between the aromatic rings present in both the paclitaxel and antidepressant medications. Graphical Abstract.

Mass Spectrometric Imaging of Ceramide Biomarkers Tracks Therapeutic Response in Traumatic Brain Injury.

Traumatic brain injury (TBI) is a serious public health problem and the leading cause of death in children and young adults. It also contributes to a substantial number of cases of permanent disability. As lipids make up over 50% of the brain mass and play a key role in both membrane structure and cell signaling, their profile is of particular interest. In this study, we show that advanced mass spectrometry imaging (MSI) has sufficient technical accuracy and reproducibility to demonstrate the anatomical distribution of 50 µm diameter microdomains that show changes in brain ceramide levels in a rat model of controlled cortical impact (CCI) 3 days post injury with and without treatment. Adult male Sprague-Dawley rats received one strike and were euthanized 3 days post trauma. Brain MS images showed increase in ceramides in CCI animals compared to control as well as significant reduction in ceramides in CCI treated animals, demonstrating therapeutic effect of a peptide agonist. The data also suggests the presence of diffuse changes outside of the injured area. These results shed light on the extent of biochemical and structural changes in the brain after traumatic brain injury and could help to evaluate the efficacy of treatments.

Laser Desorption/Ionization Mass Spectrometric Imaging of Endogenous Lipids from Rat Brain Tissue Implanted with Silver Nanoparticles.

Mass spectrometry imaging (MSI) of tissue implanted with silver nanoparticulate (AgNP) matrix generates reproducible imaging of lipids in rodent models of disease and injury. Gas-phase production and acceleration of size-selected 8 nm AgNP is followed by controlled ion beam rastering and soft landing implantation of 500 eV AgNP into tissue. Focused 337 nm laser desorption produces high quality images for most lipid classes in rat brain tissue (in positive mode: galactoceramides, diacylglycerols, ceramides, phosphatidylcholines, cholesteryl ester, and cholesterol, and in negative ion mode: phosphatidylethanolamides, sulfatides, phosphatidylinositol, and sphingomyelins). Image reproducibility in serial sections of brain tissue is achieved within <10% tolerance by selecting argentated instead of alkali cationized ions. The imaging of brain tissues spotted with pure standards was used to demonstrate that Ag cationized ceramide and diacylglycerol ions are from intact, endogenous species. In contrast, almost all Ag cationized fatty acid ions are a result of fragmentations of numerous lipid types having the fatty acid as a subunit. Almost no argentated intact fatty acid ions come from the pure fatty acid standard on tissue. Graphical Abstract ᅟ.

Ethanol Induced Brain Lipid Changes in Mice Assessed by Mass Spectrometry.

Alcohol abuse is a chronic disease characterized by the consumption of alcohol at a level that interferes with physical and mental health and causes serious and persistent changes in the brain. Lipid metabolism is of particular interest due to its high concentration in the brain. Lipids are the main component of cell membranes, are involved in cell signaling, signal transduction, and energy storage. In this study, we analyzed lipid composition of chronically ethanol exposed mouse brains. Juvenile (JUV) and adult (ADU) mice were placed on a daily limited-access ethanol intake model for 52 days. After euthanasia, brains were harvested, and total lipids were extracted from brain homogenates. Samples were analyzed using high resolution mass spectrometry and processed by multivariate and univariate statistical analysis. Significant lipid changes were observed in different classes including sphingolipids, fatty acids, lysophosphatidylcholines, and other glycerophospholipids.

Mass spectrometry imaging of rat brain lipid profile changes over time following traumatic brain injury.

BACKGROUND: Mild traumatic brain injury (TBI) is a common public health issue that may contribute to chronic degenerative disorders. Membrane lipids play a key role in tissue responses to injury, both as cell signals and as components of membrane structure and cell signaling. This study demonstrates the ability of high resolution mass spectrometry imaging (MSI) to assess sequences of responses of lipid species in a rat controlled cortical impact model for concussion. NEW METHOD: A matrix of implanted silver nanoparticles was implanted superficially in brain sections for matrix-assisted laser desorption (MALDI) imaging of 50µm diameter microdomains across unfixed cryostat sections of rat brain. Ion-mobility time-of-flight MS was used to analyze and map changes over time in brain lipid composition in a rats after Controlled Cortical Impact (CCI) TBI. RESULTS: Brain MS images showed changes in sphingolipids near the CCI site, including increased ceramides and decreased sphingomyelins, accompanied by changes in glycerophospholipids and cholesterol derivatives. The kinetics differed for each lipid class; for example ceramides increased as early as 1 day after the injury whereas other lipids changes occurred between 3 and 7 days post injury. COMPARISON WITH EXISTING METHOD(S): Silver nanoparticles MALDI matrix is a sensitive new tool for revealing previously undetectable cellular injury response and remodeling in neural, glial and vascular structure of the brain. CONCLUSIONS: Lipid biochemical and structural changes after TBI could help highlighting molecules that can be used to determine the severity of such injuries as well as to evaluate the efficacy of potential treatments.

MALDI-Ion Mobility Mass Spectrometry of Lipids in Negative Ion Mode.

Profiling and imaging MALDI mass spectrometry (MS) allows detection and localization of biomolecules in tissue, of which lipids are a major component. However, due to the in situ nature of this technique, complexity of tissue and need for a chemical matrix, the recorded signal is complex and can be difficult to assign. Ion mobility adds a dimension that provides coarse shape information, separating isobaric lipids, peptides, and oligonucleotides along distinct familial trend lines before mass analysis. Previous work using MALDI-ion mobility mass spectrometry to analyze and image lipids has been conducted mainly in positive ion mode, although several lipid classes ionize preferentially in negative ion mode. This work highlights recent data acquired in negative ion mode to detect glycerophosphoethanolamines (PEs), glycerophosphoserines (PSs), glycerophosphoglycerols (PGs), glycerolphosphoinositols (PIs), glycerophosphates (PAs), sulfatides (STs), and gangliosides from standard tissue extracts and directly from mouse brain tissue. In particular, this study focused on changes in ion mobility based upon lipid head groups, composition of radyl chain (# of carbons and double bonds), diacyl versus plasmalogen species, and hydroxylation of species. Finally, a MALDI-ion mobility imaging run was conducted in negative ion mode, resulting in the successful ion mapping of several lipid species.

Extraction and purification of depurinated benzo[a]pyrene-adducted DNA bases from human urine by immunoaffinity chromatography coupled with HPLC and analysis by LC/quadrupole ion-trap MS.

In this paper, we describe implementation and testing of an immunoaffinity (IA) column for rapid and selective extraction of 7-(benzo[a]pyren-6-yl)adenine (BP-6-N7Ade) and 7-(benzo[a]pyren-6-yl)guanine (BP-6-N7Gua) from urine, where BP is benzo[a]pyrene. The BP radical cation is a carcinogenic metabolite that reacts with double-stranded DNA, producing depurinated BP-adducted DNA bases excreted in urine. The expected modified nucleobases are BP-6-N7Gua, BP-6-N7Ade, and 8-(benzo[a]pyren-6-yl)guanine (BP-6-C8Gua), and they may serve as important biomarkers for DNA damage by PAHs. IA extracts of urine from a cigarette smoker and a nonsmoker contained less than 5% of contaminants present in Sep-Pak extracts and, unlike the latter, were suitable for analytical HPLC. IA extraction achieved 75-95% recovery of BP-6-N7Gua (10 fmol/mL) and BP-6-N7Ade (1 fmol/mL) added to urine samples. Tandem mass spectrometry of IA/HPLC fractions of urine from two coal smoke-exposed women at high risk for lung cancer demonstrated the presence of 20 and 50 fmol BP-6-N7Gua per mL of urine. Unexposed controls were negative. With proposed modifications, the IA-based protocol can achieve a detection limit of 0.1 fmol/mL urine, which is sufficient for routine quantification of BP-adducted bases in urine of cigarette smokers. This procedure may allow screening of persons at risk for lung cancer associated with exposure to PAH in cigarette and other forms of smoke.

Electron ionization mass spectrometry of citrus limonoids.

Electron ionization (EI) mass spectrometry was used to differentiate four structurally closely related citrus limonoid aglycones, including limonin, nomilin, obacunone, and deacetylnomilin. The limonoids were isolated and purified from citrus seeds. Structures of major fragment ions were elucidated by high-resolution mass spectrometry (HRMS) and fragmentation pathways were proposed. The fragmentation patterns observed in the EI spectra can be used as important references for the positive characterization of limonoid aglycones.

Structural differentiation of diastereomeric benzo[ghi]fluoranthene adducts of deoxyadenosine by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and postsource decay.

The product ion formation characteristics of four diastereomeric deoxyadenosine adducts formed by the reaction of the syn and anti diastereomers of trans-3,4-dihydroxy-5,5a-epoxy-3,4,5,5a-tetrahydrobenzo[ghi]fluoranthene are studied by matrix-assisted laser desorption ionization and postsource decay (PSD) to determine fragmentation pathways that may permit differentiation of their structures. The two adducts derived from each diol-epoxide with DNA differ in structure based on the cis/trans arrangement of the 3'-hydroxyl group on the benzo[ghi]fluoranthene (B[ghi]F) and the adenine base bound to the B[ghi]F 5a carbon. The two adduct diastereomers with the cis adenine-3'-hydroxyl configuration produce product ions at m/z 394 and m/z 510 formed by the loss of water that are not observed in the PSD spectra of the two trans isomers. The data suggest a mechanism of water loss that is initiated by a hydrogen-bonding interaction between the charge-bearing proton on the N1 atom and the 3'-hydroxyl oxygen on the polycyclic aromatic hydrocarbon (PAH). Fragmentation is initiated by the transfer of the adenine N1 proton from the nitrogen to the PAH 3'-hydroxyl oxygen and inductive cleavage of the C3-O(3) bond to form a benzylic carbocation on B[ghi]F. The proposed mechanism is supported by semiempirical molecular modeling calculations.