An isotope dilution capillary electrophoresis/tandem mass spectrometry (CE-MS/MS) method for the simultaneous measurement of choline, betaine, and dimethylglycine concentrations in human plasma

Detection of choline in biological fluids from patients on haemodialysis by an amperometric biosensor based on a novel anti-interference bilayer

A new and highly selective amperometric biosensor able to analyse choline in clinical samples from patients suffering from renal diseases and receiving repetitive haemodialysis treatment is described. The proposed biosensor is based on choline oxidase immobilized by co-crosslinking onto a novel anti-fouling and anti-interferent membrane. Between the several polymeric films electrosynthesized on a Pt electrode whose permselective behaviours were here investigated, those based on overoxidized polypyrrole/poly(o-aminophenol) bilayer revealed the most effective in rejecting common interferents usually present in biological fluids. The so realized biosensor showed notably analytical performances, displaying linear choline responses up to 100 μM, a sensitivity of 156 nA mM^-1 mm^-2 and a limit of detection, calculated at a signal-to-noise ratio equal to 3, of 1 μM; further, the within-a-day coefficients of variation for replicate (n = 3) were 2.7% and 1.2% at 100 μM and 10 μM choline levels, respectively. The remarkable performances and anti-interference behaviour allowed us the use of the proposed biosensor for the selective and fouling-free detection of choline in dialysate coming from patients on haemodialysis and even in their unpretreated human sera. Preliminary results gave choline levels in good agreement with the expected values.

Recent advances in capillary electrophoresis-mass spectrometry: Instrumentation, methodology and applications

Capillary electrophoresis (CE) offers fast and high-resolution separation of charged analytes from small injection volumes. Coupled to mass spectrometry (MS), it represents a powerful analytical technique providing (exact) mass information and enables molecular characterization based on fragmentation. Although hyphenation of CE and MS is not straightforward, much emphasis has been placed on enabling efficient ionization and user-friendly coupling. Though several interfaces are now commercially available, research on more efficient and robust interfacing with nano-electrospray ionization (ESI), matrix-assisted laser desorption/ionization (MALDI) and inductively coupled plasma mass spectrometry (ICP) continues with considerable results. At the same time, CE-MS has been used in many fields, predominantly for the analysis of proteins, peptides and metabolites. This review belongs to a series of regularly published articles, summarizing 248 articles covering the time between June 2016 and May 2018. Latest developments on hyphenation of CE with MS as well as instrumental developments such as two-dimensional separation systems with MS detection are mentioned. Furthermore, applications of various CE-modes including capillary zone electrophoresis (CZE), nonaqueous capillary electrophoresis (NACE), capillary gel electrophoresis (CGE) and capillary isoelectric focusing (CIEF) coupled to MS in biological, pharmaceutical and environmental research are summarized.

Recent advances in amino acid analysis by capillary electromigration methods: June 2015-May 2017

In the tenth edition of this article focused on recent advances in amino acid analysis using capillary electrophoresis, we describe the most important research articles published on this topic during the period from June 2015 to May 2017. This article follows the format of the previous articles published in Electrophoresis. The new developments in amino acid analysis with CE mainly describe improvements in CE associated with mass spectrometry. Focusing on applications, we mostly describe clinical works, although metabolomics studies are also very important. Finally, works focusing on amino acids in food and agricultural applications are also described.

Fluorescence Imaging of Streptococcus pneumoniae with the Helix pomatia agglutinin (HPA) As a Potential, Rapid Diagnostic Tool

Streptococcus pneumoniae is a common human pathogen and a major causal agent of life-threatening infections that can either be respiratory or non-respiratory. It is well known that the Helix pomatia (edible snail) agglutinin (HPA) lectin shows specificity for terminal αGalNAc residues present, among other locations, in the Forssman pentasaccharide (αGalNAc1→3βGalNAc1→3αGal1→4βGal1→4βGlc). Based on experiments involving choline-independent mutants and different growth conditions, we propose here that HPA recognizes the αGalNAc terminal residues of the cell wall teichoic and lipoteichoic acids of S. pneumoniae. In addition, experimental evidence showing that pneumococci can be specifically labeled with HPA when growing as planktonic cultures as well as in mixed biofilms of S. pneumoniae and Haemophilus influenzae has been obtained. It should be underlined that pneumococci were HPA-labeled despite of the presence of a capsule. Although some non-pneumococcal species also bind the agglutinin, HPA-binding combined with fluorescence microscopy constitutes a suitable tool for identifying S. pneumoniae and, if used in conjunction with Gram staining and/or other suitable technique like antigen detection, it may potentially facilitate a fast and accurate diagnosis of pneumococcal infections.

A simplified LC-MS/MS method for rapid determination of cycloserine in small-volume human plasma using protein precipitation coupled with dilution techniques to overcome matrix effects and its application to a pharmacokinetic study

Matrix effects have been a major concern when developing LC-MS/MS methods for quantitative bioanalysis of cycloserine. Sample handling procedures including solid phase extraction or derivatization have been reported previously by researchers to overcome matrix effects of cycloserine. In the present study, the possibility of reducing matrix effects of cycloserine using protein precipitation coupled with dilution techniques was investigated. Plasma samples were pretreated by protein precipitation with methanol followed by a 40-fold dilution with methanol-water (50:50, v/v). The analyte and the internal standard (mildronate) were chromatographed on a Shim-pack XR-ODS (100 mm × 2.0 mm, 2.2 μm) column using methanol-0.01% formic acid (70:30, v/v) as mobile phase and detected by multiple reaction monitoring mode via positive electrospray ionization. The total run time was only 2 min per sample. The suppression of cycloserine response was reduced with the matrix effects ranging between 80.5 and 87.9%. A lower limit of quantification (LLOQ) of 0.300 μg/mL was achieved using only 10 μL of plasma. The intra- and inter-day precisions were less than 4.8% and the accuracy ranged from -2.6 to 6.6%. The method was successfully applied to a pharmacokinetic study of cycloserine in 30 healthy Chinese male subjects after oral administration of a single dose of cycloserine at 250, 500 and 750 mg under fasting conditions. The newly developed method is simpler, faster, cost-effective, and more robust than previously reported LC-MS/MS methods.