Capillary Zone Electrophoresis of 8-Aminopyrene-1,3,6-trisulfonic Acid Labeled Carbohydrates with Online Electrokinetic Sample Cleanup.

Capillary electrophoresis is one of the frequently used separation techniques for the analysis of complex carbohydrates. Since sugars lack chromophore or fluorophore groups, their capillary electrophoresis analysis usually requires tagging by a charged fluorophore. To speed up the derivatization reaction, a large excess of the labeling reagent is typically used; therefore, a purification step is necessary prior to CE analysis using the industry standard low-pH gel-buffer system. In addition to representing an extra sample preparation step with the associated labor and cost, the purification process also holds the risk of losing some of the sample components. In this paper we introduce an online electrokinetic sample cleanup process with electroosmotic flow (EOF)-assisted separation in a bare fused silica capillary using alkaline pH background electrolyte and normal polarity separation voltage. 8-Aminopyrene-1,3,6-trisulfonic acid (APTS)-labeled maltooligosaccharides were analyzed first to understand the complex effect of the downstream EOF and the counter current electromigration of the sample components including the labeling dye. The use of 150 mM caproic acid-253 mM Tris (pH 8.1) running buffer facilitated the entrance of the sample components of interest into the separation capillary, while the excess labeling reagent was excluded and, therefore, did not interfere with the detection. The alkaline caproic acid-Tris running buffer was then applied to the N-glycome analysis of human serum samples, showing excellent separation performance, and more importantly, the extra sample purification step was not required.

Microbead-based extracorporeal immuno-affinity virus capture: a feasibility study to address the SARS-CoV-2 pandemic.

In this paper, we report on the utilization of micro-technology based tools to fight viral infections. Inspired by various hemoperfusion and immune-affinity capture systems, a blood virus depletion device has been developed that offers highly efficient capture and removal of the targeted virus from the circulation, thus decreasing virus load. Single-domain antibodies against the Wuhan (VHH-72) virus strain produced by recombinant DNA technology were immobilized on the surface of glass micro-beads, which were then utilized as stationary phase. For feasibility testing, the virus suspension was flown through the prototype immune-affinity device that captured the viruses and the filtered media left the column. The feasibility test of the proposed technology was performed in a Biosafety Level 4 classified laboratory using the Wuhan SARS-CoV-2 strain. The laboratory scale device actually captured 120,000 virus particles from the culture media circulation proving the feasibility of the suggested technology. This performance has an estimated capture ability of 15 million virus particles by using the therapeutic size column design, representing three times over-engineering with the assumption of 5 million genomic virus copies in an average viremic patient. Our results suggested that this new therapeutic virus capture device could significantly lower virus load thus preventing the development of more severe COVID-19 cases and consequently reducing mortality rate.

Time-Resolved SAXS Study of Polarity- and Surfactant-Controlled Superlattice Transformations of Oleate-Capped Nanocubes During Solvent Removal.

Structural transformations and lattice expansion of oleate-capped iron oxide nanocube superlattices are studied by time-resolved small-angle X-ray scattering (SAXS) during solvent removal. The combination of conductor-like screening model for real solvents (COSMO-RS) theory with computational fluid dynamics (CFD) modeling provides information on the solvent composition and polarity during droplet evaporation. Evaporation-driven poor-solvent enrichment in the presence of free oleic acid results in the formation of superlattices with a tilted face-centered cubic (fcc) structure when the polarity reaches its maximum. The tilted fcc lattice expands subsequently during the removal of the poor solvent and eventually transforms to a regular simple cubic (sc) lattice during the final evaporation stage when only free oleic acid remains. Comparative studies show that both the increase in polarity as the poor solvent is enriched and the presence of a sufficient amount of added oleic acid is required to promote the formation of structurally diverse superlattices with large domain sizes.

The Effect of Sample Glucose Content on PNGase F-Mediated N-Glycan Release Analyzed by Capillary Electrophoresis.

Protein therapeutics have recently gained high importance in general health care along with applied clinical research. Therefore, it is important to understand the structure-function relationship of these new generation drugs. Asparagine-bound carbohydrates represent an important critical quality attribute of therapeutic glycoproteins, reportedly impacting the efficacy, immunogenicity, clearance rate, stability, solubility, pharmacokinetics and mode of action of the product. In most instances, these linked N-glycans are analyzed in their unconjugated form after endoglycosidase-mediated release, e.g., PNGase F-mediated liberation. In this paper, first, N-glycan release kinetics were evaluated using our previously reported in-house produced 6His-PNGase F enzyme. The resulting deglycosylation products were quantified by sodium dodecyl sulfate capillary gel electrophoresis to determine the optimal digestion time. Next, the effect of sample glucose content was investigated as a potential endoglycosidase activity modifier. A comparative Michaelis-Menten kinetics study was performed between the 6His-PNGase F and a frequently employed commercial PNGase F product with and without the presence of glucose in the digestion reaction mixture. It was found that 1 mg/mL glucose in the sample activated the 6His-PNGase F enzyme, while did not affect the release efficiency of the commercial PNGase F. Capillary isoelectric focusing revealed subtle charge heterogeneity differences between the two endoglycosidases, manifested by the lack of extra acidic charge variants in the cIEF trace of the 6His-PNGase F enzyme, which might have possibly influenced the glucose-mediated enzyme activity differences.

Modification of Hemodialysis Membranes for Efficient Circulating Tumor Cell Capture for Cancer Therapy.

BACKGROUND: It is well known that more than 90% of cancer deaths are due to metastases. However, the entire tumorigenesis process is not fully understood, and it is evident that cells spreading from the primary tumor play a key role in initiating the metastatic process. Tumor proliferation and invasion also elevate the concentration of regular and irregular metabolites in the serum, which may alter the normal function of the entire human homeostasis and possibly causes cancer metabolism syndrome, also referred to as cachexia. METHODS: We report on the modification of commercially available hemodialysis membranes to selectively capture circulating tumor cells from the blood stream by means of immobilized human anti-EpCAM antibodies on the inner surface of the fibers. All critical steps are described that required in situ addition of the immuno-affinity feature to hemodialyzer cartridges in order to capture EpCAM positive circulating tumor cells, which represents ~80% of cancer cell types. RESULTS: The cell capture efficiency of the suggested technology was demonstrated by spiking HCT116 cancer cells both into buffer solution and whole blood and run through on the modified cartridge. Flow cytometry was used to quantitatively evaluate the cell clearance performance of the approach. CONCLUSIONS: The suggested modification has no significant effect on the porous structure of the hemodialysis membranes; it keeps its cytokine removal capability, addressing cachexia simultaneously with CTC removal.

N-Glycosylation Profiling of Human Blood in Type 2 Diabetes by Capillary Electrophoresis: A Preliminary Study.

Currently, diagnosing type 2 diabetes (T2D) is a great challenge. Thus, there is a need to find rapid, simple, and reliable analytical methods that can detect the disease at an early stage. The aim of this work was to shed light on the importance of sample collection options, sample preparation conditions, and the applied capillary electrophoresis bioanalytical technique, for a high-resolution determination of the N-glycan profile in human blood samples of patients with type 2 diabetes (T2D). To achieve the profile information of these complex oligosaccharides, linked by asparagine to hIgG in the blood, the glycoproteins of the samples needed to be cleaved, labelled, and purified with sufficient yield and selectivity. The resulting samples were analyzed by capillary electrophoresis, with laser-induced fluorescence detection. After separation parameter optimization, the capillary electrophoresis technique was implemented for efficient N-glycan profiling of whole blood samples from the diabetic patients. Our results revealed that there were subtle differences between the N-glycan profiles of the diabetic and control samples; in particular, two N-glycan structures were identified as potential glycobiomarkers that could reveal significant changes between the untreated/treated type 2 diabetic and control samples. By analyzing the resulting oligosaccharide profiles, clinically relevant information was obtained, revealing the differences between the untreated and HMG-CoA reductase-inhibitor-treated diabetic patients on changes in the N-glycan profile in the blood. In addition, the information from specific IgG N-glycosylation profiles in T2D could shed light on underlying inflammatory pathophysiological processes and lead to drug targets.

Expanding the capillary electrophoresis-based glucose unit database of the GUcal app.

GUcal is a standalone application for automatically calculating the glucose unit (GU) values for separated N-glycan components of interest in an electropherogram and suggests their tentative structures by utilizing an internal database. We have expanded the original database of GUcal by integrating all publicly available capillary electrophoresis (CE) data in the GlycoStore collection (https://www.glycostore.org) and with in-house measured GU values. The GUcal app is freely available online (https://www.gucal.hu) and readily facilitates CE-based high throughput GU value determination for first line structural elucidation.

Commentary regarding "Decision support algorithm for the selection of analytical methods in organic compounds detection for future extraterrestrial exploratory missions".

Mátyás et al. recently published their paper entitled as "Decision support algorithm for the selection of analytical methods in organic compounds detection for future extraterrestrial exploratory missions," which we found interesting. However, there are some points of the developed method that need to be refined to get a practical tool for practitioners. In this commentary, we have summarized our suggestions and comments mainly from the chemical/separation point of view.

Tilted pillar array fabrication by the combination of proton beam writing and soft lithography for microfluidic cell capture Part 2: Image sequence analysis based evaluation and biological application.

As a continuation of our previously published work, this paper presents a detailed evaluation of a microfabricated cell capture device utilizing a doubly tilted micropillar array. The device was fabricated using a novel hybrid technology based on the combination of proton beam writing and conventional lithography techniques. Tilted pillars offer unique flow characteristics and support enhanced fluidic interaction for improved immunoaffinity based cell capture. The performance of the microdevice was evaluated by an image sequence analysis based in-house developed single-cell tracking system. Individual cell tracking allowed in-depth analysis of the cell-chip surface interaction mechanism from hydrodynamic point of view. Simulation results were validated by using the hybrid device and the optimized surface functionalization procedure. Finally, the cell capture capability of this new generation microdevice was demonstrated by efficiently arresting cells from a HT29 cell-line suspension.

Effect of the flow profile on separation efficiency in pressure-assisted reversed-polarity capillary zone electrophoresis of anions: Simulation and experimental evaluation.

Capillary electrophoresis connected to electrospray ionization mass spectrometry is a promising combination to analyze complex biological samples. The use of sheathless electrospray ionization interfaces, such as a porous nanoelectrospray capillary emitter, requires the application of forward flow (either by pressure or electroosmosis) to maintain the electrospray process. The analysis of solute molecules with strong negative charges (e.g., aminopyrenetrisulfonate labeled glycans) necessitates a reversed-polarity capillary electrophoresis separation mode, in which case the electroosmotic flow is counter current, thus pressure assistance is necessary. In this study, we compared the effect of forced convection with and without counter electroosmotic flow on the resulting separation efficiency in capillary electrophoresis based on flow profile simulations by computational fluid dynamics technique and by actual experiments. The efficiencies of the detected peaks were calculated from the resulting electropherograms and found approximately 950 000 plates/m for electrophoresis with counter electroosmotic flow, 20 000 plates/m with pressure only (such as would be in open tubular liquid chromatography), and 480 000 plates/m for electrophoresis with simultaneous counter electroosmotic flow and forward pressure assistance, which validates the simulation data.

Triple-Internal Standard Based Glycan Structural Assignment Method for Capillary Electrophoresis Analysis of Carbohydrates.

Despite the ever growing use of capillary electrophoresis in biomedical research and the biopharmaceutical industry, the development of data interpretation methods is lagging behind. In this paper we report the design and implementation of a coinjected triple-internal standard method to alleviate the need of an accompanying run of the maltooligosaccharide ladder for glucose unit (GU) calculation. Based on the migration times of the coinjected standards of maltose, maltotriose, and maltopentadecaose (bracketing the peaks of interest), a data processing approach was designed and developed to set up a virtual ladder that was used for GU calculation. The data processing was tested in terms of the calculated GU values of human IgG glycans, and the resulting relative standard deviation was ≤1.07%. This approach readily supports high-throughput capillary electrophoresis systems by significantly speeding up the processing time for glycan structural assignment.

Numerical modeling of capillary electrophoresis - electrospray mass spectrometry interface design.

Capillary electrophoresis hyphenated with electrospray mass spectrometry (CE-ESI-MS) has emerged in the past decade as one of the most powerful bioanalytical techniques. As the sensitivity and efficiency of new CE-ESI-MS interface designs are continuously improving, numerical modeling can play important role during their development. In this review, different aspects of computer modeling and simulation of CE-ESI-MS interfaces are comprehensively discussed. Relevant essentials of hydrodynamics as well as state-of-the-art modeling techniques are critically evaluated. Sheath liquid-, sheathless-, and liquid-junction interfaces are reviewed from the viewpoint of multidisciplinary numerical modeling along with details of single and multiphase models together with electric field mediated flows, electrohydrodynamics, and free fluid-surface methods. Practical examples are given to help non-specialists to understand the basic principles and applications. Finally, alternative approaches like air amplifiers are also included. © 2014 Wiley Periodicals, Inc. Mass Spec Rev 34: 558-569, 2015.

On the electromigration of charged fluorophore-labeled oligosaccharides in polyethylene oxide solutions.

The separation mechanism of charged fluorophore (aminopyrenetrisulfonate)-labeled maltooligosaccharides with α1-4 linkages was studied in polyethylene oxide (PEO) solutions (MW 300 000 Da) with special interest to possible analyte and/or network deformations as well as potential solute-matrix interactions. The electrophoretic mobilities of the 8-aminopyrene-1,3,6-trisulfonate-labeled maltooligosaccharides were found proportional with their MW(-2/3) . The Arrhenius function was used to determine the activation energy needed by the labeled sugars to migrate through the separation media. With increasing solute size, the activation energy (Ea ) values decreased in polymer concentrations above the entanglement threshold of the PEO, while showed apparently independent function at the entanglement threshold. The observed phenomenon was considered as a result of solute-matrix interaction, which could be alleviated by the addition of an organic modifier to the BGE.

Activation energy associated with the electromigration of oligosaccharides through viscosity modifier and polymeric additive containing background electrolytes.

The activation energy related to the electromigration of oligosaccharides can be determined from their measured electrophoretic mobilities at different temperatures. The effects of a viscosity modifier (ethylene glycol) and a polymeric additive (linear polyacrylamide) on the electrophoretic mobility of linear sugar oligomers with α1-4 linked glucose units (maltooligosaccharides) were studied in CE using the activation energy concept. The electrophoretic separations of 8-aminopyrene-1,3,6-trisulfonate-labeled maltooligosaccharides were monitored by LIF detection in the temperature range of 20-50°C, using either 0-60% ethylene glycol (viscosity modifier) or 0-3% linear polyacrylamide (polymeric additive) containing BGEs. Activation energy curves were constructed based on the slopes of the Arrhenius plots. With the use of linear polyacrylamide additive, solute size-dependent activation energy variations were found for the maltooligosaccharides with polymerization degrees below and above maltoheptaose (DP 7), probably due to molecular conformation changes and possible matrix interaction effects.

Enzymatic removal of N-glycans by PNGase F coated magnetic microparticles.

Investigation of protein glycosylation is an important area in biomarker discovery and biopharmaceutical research. Alterations in protein N-glycosylation can be an indication of changes in pathological conditions in the medical field or production parameters of biotherapeutics. Rapid development of these disciplines calls for fast, high-throughput, and reproducible methods to analyze protein N-glycosylation. Currently used methods require either long deglycosylation times or large excess of enzymes. In this paper, we report on the use of PNGase F immobilization onto the surface of magnetic microparticles and their use in rapid and efficient removal of N-glycans from glycoproteins. The use of immobilized PNGase F also allowed reusability of the enzyme-coated beads as the magnetic microparticles can be readily partitioned from the sample by a magnet after each deglycosylation reaction. The efficiency and activity of the PNGase F coated magnetic beads was compared with in-solution enzyme reactions using standard glycoproteins possessing the major N-glycan types of neutral, high mannose, and highly sialylated carbohydrates. The PNGase F coated magnetic beads offered comparable deglycosylation level to the conventional in-solution based method in 10-min reaction times for the model glycoproteins of immunoglobulin G (mostly neutral carbohydrates), ribonuclease B (high mannose type sugars), and fetuin (highly sialylated oligosaccharides) with the special features of easy removal of the enzyme from the reaction mixture and reusability.

Tilted pillar array fabrication by the combination of proton beam writing and soft lithography for microfluidic cell capture: Part 1 Design and feasibility.

Design, fabrication, integration, and feasibility test results of a novel microfluidic cell capture device is presented, exploiting the advantages of proton beam writing to make lithographic irradiations under multiple target tilting angles and UV lithography to easily reproduce large area structures. A cell capture device is demonstrated with a unique doubly tilted micropillar array design for cell manipulation in microfluidic applications. Tilting the pillars increased their functional surface, therefore, enhanced fluidic interaction when special bioaffinity coating was used, and improved fluid dynamic behavior regarding cell culture injection. The proposed microstructures were capable to support adequate distribution of body fluids, such as blood, spinal fluid, etc., between the inlet and outlet of the microfluidic sample reservoirs, offering advanced cell capture capability on the functionalized surfaces. The hydrodynamic characteristics of the microfluidic systems were tested with yeast cells (similar size as red blood cells) for efficient capture.

Effect of Separation Temperature on Structure Specific Glycan Migration in Capillary Electrophoresis.

Temperature dependent differential migration shifts were studied in capillary electrophoresis between linear (maltooligosaccharides) and branched (sialylated, neutral and core fucosylated biantennary IgG glycans) carbohydrates. Background electrolytes without as well as with low and high molecular weight additives (ethylene glycol, linear polyacrylamide and poly(ethylene oxide)) were investigated for this phenomena in the temperature range of 20-50 °C. Glucose unit (GU) value shifts were observed with increasing temperature for the all IgG glycans both in additive-free and additive-containing background electrolytes, emphasizing the importance of tight temperature control during glycosylation analysis by capillary electrophoresis. The activation energy concept was applied to understand the structure specific electrophoretic migration of the different sugar molecules. Activation energy values were derived from the slopes of the Arrhenius plots of logarithmic mobility vs reciprocal absolute temperature and compared for the linear and branched sugars as well as for the various background electrolyte additives.

GUcal: An integrated application for capillary electrophoresis based glycan analysis.

Recent emergence in the use of monoclonal antibody therapeutics and other glycoprotein biopharmaceuticals requires high-throughput, robust, and automated techniques for their glycosylation analysis. Capillary electrophoresis is one of the high-performance methods of choice; however, while the necessary instrumentation is well developed, the related bioinformatics tools are lacked behind. In this paper, we introduce an integrated toolset dubbed as GUcal, to automatically calculate the glucose unit (GU) values for all sample components of interest in an electropherogram with a concomitant database search for structural assignment. The database comprises CE GUs and suggested structures of N-glycans released from human IgG. The app is freely available online (www.lendulet.uni-pannon.hu/gucal) and readily facilitates CE-based glycan analysis.

Simulation-based design of a microfabricated pneumatic electrospray nebulizer.

A microfabricated pneumatic electrospray nebulizer has been developed and evaluated using computer simulations and experimental measurements of the MS signals. The microdevice under development is designed for electrospray MS interfacing without the need to fabricate an electrospray needle and can be used as a disposable or an integral part of a reusable system. The design of the chip layout was supported by computational fluid dynamics simulations. The tested microdevices were fabricated in glass using conventional photolithography, followed by wet chemical etching and thermal bonding. The performance of the microfabricated nebulizer was evaluated by means of TOF-MS with a peptide mixture. It was demonstrated that the nebulizer, operating at supersonic speed of the nebulizing gas, produced very stable nanospray (900 nL/min) as documented by less than 0.1% (SE) fluctuation in total mass spectrometric signal intensity.

Recent advances in the analysis of human milk oligosaccharides by liquid phase separation methods.

Human milk is a complex, dynamically changing biological fluid, which contains a large amount of non-conjugated carbohydrates, referred to as human milk oligosaccharides (HMOs). These HMOs are very important for the infants as they play important roles in the formation of the gut microbiome, the immune system and support brain development. HMOs show highly complex structural diversity due to numerous linkage possibilities of the building monosaccharides. In order to elucidate their structure-function relationship and to develop more effective infant formulas, cutting-edge analytical technologies are in great demand. In this paper, we review the current strategies for HMO analysis based on liquid phase separation methods. High performance liquid chromatography, capillary electrophoresis and their hyphenation with mass spectrometry are critically reviewed, emphasizing their advantages and disadvantages from practical point of views. Recent advances of the methods are categorized according to their application fields.