The analysis of human amniotic fluid using capillary electrophoresis

Capillary electrophoresis of small ions and molecules in less conventional human body fluid samples: A review

In recent years, advances in sensitive analytical techniques have encouraged the analysis of various compounds in biological fluids. While blood serum, blood plasma and urine still remain the golden standards in clinical, toxicological and forensic science, analyses of other body fluids, such as breast milk, exhaled breath condensate, sweat, saliva, amniotic fluid, cerebrospinal fluid, or capillary blood in form of dried blood spots are becoming more popular. This review article focuses on capillary electrophoresis and microchip electrophoresis of small ions and molecules (e.g. inorganic cations/anions, basic/acidic drugs, small acids/bases, amino acids, peptides and other low molecular weight analytes) in various less conventional human body fluids and hopes to stimulate further interest in the field.

Early prediction of macrosomia based on an analysis of second trimester amniotic fluid by capillary electrophoresis

AIM

To identify, using capillary electrophoresis and chemometrics, early biomarkers in human amniotic fluid of large-for-gestational-age (LGA) infants.

MATERIALS & METHODS

Second trimester amniotic fluid samples, obtained from mothers undergoing age-related amniocentesis, were analyzed by capillary electrophoresis. Electropherogram data were aligned using correlation-optimized warping. A genetic algorithm using a Bayesian evaluation function and a leave-one-out cross-validation strategy for two birth outcomes: appropriate-for-gestational-age (AGA) versus LGA infants.

RESULTS

LGA (n = 23) was differentiated from AGA (n = 86) with a sensitivity of 100% and a specificity of 98% using only two wavelets. The first wavelet is associated with albumin and the second wavelet with an unknown small molecule.

CONCLUSION

The approach developed herein allows LGA fetuses to be metabolically distinguished from AGA fetuses early in pregnancy and indicates that the birth of a LGA infant is already associated with an altered biochemical profile by the second trimester.

Prediction of gestational diabetes mellitus based on an analysis of amniotic fluid by capillary electrophoresis

Aim: To detect gestational diabetes mellitus biomarkers in human amniotic fluid collected for age-related genetic testing using capillary electrophoresis and a sophisticated data analysis methodology. Materials & methods: Amniotic fluid samples were separated by capillary electrophoresis. Samples were classified using a genetic algorithm with Bayesian benefit function. The best model maximized the sensitivity and specificity and employed a leave-one-out cross-validation strategy. Results: Gestational diabetes mellitus (GDM; n = 14) was distinguished from non-GDM (n = 95) with 86% sensitivity and 99% specificity using two wavelets. These wavelets were located in the unresolved protein region and on the edge of the maternally derived albumin peak. Conclusion: GDM is a maternal pathology; however, it was shown that it alters the biochemical profile of amniotic fluid. Testing for GDM is normally carried out at 24–28 weeks, but changes can be detected at 15 weeks gestation, suggesting that GDM onset occurs early in gestation.

Pregnancy-specific protein B (PSPB), progesterone and some biochemical attributes concentrations in the fetal fluids and serum and its relationship with fetal and placental characteristics of Iraqi riverine buffalo (Bubalus bubalis)

This study was carried out to demonstrate the pregnancy-specific protein B (PSPB), progesterone and some biochemical parameters concentrations in amniotic fluid, allantoic fluid and fetal serum collected from slaughtered Iraqi riverine pregnant buffaloes at three different months of gestation (6th, 7th and 8th). Ten out of 22 adult buffaloes of 4.6 ± 0.97 years old were used in this study. The buffaloes were mated naturally by monitoring the estrus cycles via appearance of vaginal fluids and mounting by bulls. Pregnancy was checked for these buffaloes by non-returning to estrus for three estrus cycles and assured by rectal palpation on day 61 post-mating (PM). Buffaloes were slaughtered at three different periods of gestation (three at 6th month, four at 7th month and three at 8th month of gestation) to verify the progesterone and PSPB as well as some blood attributes levels (glucose, cholesterol, total protein, albumin, globulins and albumin: globulins ratio) in amniotic fluid (AF), allantoic fluid (LF) and fetal serum (FS). Progesterone was higher (P<0.01) in LF at the 8th month of gestation and lower in FS during the 7th and 8th months of pregnancy. PSPB concentrations were greater in FS (6th and 8th months in particular) than in both AF and LF. The overall mean of cholesterol concentration was higher in FS (P<0.05) followed by AF and LF that had the lowest concentration. The FS exhibited higher total protein during the three gestation periods. Most of fetal and placental measurements increased as the pregnancy advanced. In conclusion, these results described, for the first time, the PSPB and progesterone concentrations and blood characteristics in fetal fluids and serum in water riverine buffaloes during different stages of pregnancy. Progesterone concentrations were greater in allantoic fluid than in other fluids. In contrast, PSPB and other blood attributes were higher in fetal serum than other fluids of Iraqi riverine buffaloes. These findings reflect the changes in hormones, proteins and other metabolites during different gestation periods.

Quantitative analysis of nerve growth factor in the amniotic fluid during chick embryonic development

Nerve growth factor (NGF) and most neurotrophic factors support the proliferation and survival of particular types of neurons. Besidesthe pivotal role of NGF in the development of neuronal cells, it also has important functions on non-neuronal cells. The amnion surrounds the embryo, providing an aqueous environment for the embryo. A wide range of proteins has been identified in human amniotic fluid (AF). In this study, total protein concentration (TPC) and NGF level in AF samples from chick embryos were measured using a Bio-Rad protein assay, enzyme linked immunosorbent assay (ELISA) and Western blot. TPC increased from days E10 to day E18. There was a rapid increase in AF TPC on day E15 when compared to day E16. No significant changes in NGF levels have been seen from day E10 to day E14. There was a rapid increase in NGF content on days E15 and E16, and thereafter the levels decreased from day E16 to day E18. Since, NGF is important in brain development and changes in AF NGF levels have been seen in some CNS malformations, changes in the TPC and NGF levels in AF during chick embryonic development may be correlated with cerebral cortical development. It is also concluded that NGF is a constant component of the AF during chick embryogenesis.

Capillary electrophoresis of human follicular fluid

Some of the major serum proteins that are also found in follicular fluid, including transferrin, alpha-macroglobulin and albumin, are thought to play a role in oocyte maturation. This study set out to identify proteins in human follicular fluid by capillary zone electrophoresis and to investigate their relationship to follicular/oocyte maturity and fertility outcome. 176 individual follicular fluid samples, from 30 women undertaking in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI), were run using an optimized capillary zone electrophoresis method that gave a good separation of sixteen peaks in most samples. Nine of the peaks were identified and quantified but seven remain unknown and require further proteomic identification. Of the identified protein peaks, levels of each were corrected for follicular volume and total content calculated. No significant difference in protein levels was found with regard to oocyte recovery and fertilization. Protein concentrations tended to decrease as the follicular sphere increased whilst total content in follicular fluid increased in proportion to size. This is consistent with simple transudation across a sphere surface area which does not increase in proportion to the follicular fluid. This is not true of the concentration and content pattern of other proteins/biomolecules which are produced by follicular cells locally. In conclusion, neither concentration nor absolute levels of nine major proteins identified in follicular fluids correlated with oocyte presence and fertility outcome. Future work to remove more concentrated proteins (e.g. albumin) would enhance separation of smaller peaks and identification of the unknown molecules.

Metabolite profiling of human amniotic fluid by hyphenated nuclear magnetic resonance spectroscopy

The metabolic profiling of human amniotic fluid (HAF) is of potential interest for the diagnosis of disorders in the mother or the fetus. In order to build a comprehensive metabolite database for HAF, hyphenated NMR has been used, for the first time, for systematic HAF profiling. Experiments were carried out using reverse-phase (RP) and ion-exchange liquid chromatography (LC), in order to detect less and more polar compounds, respectively. RP-LC conditions achieved good separation of amino acids, some sugars, and xanthines. Subsequent NMR and MS analysis enabled the rapid identification of 30 compounds, including 3-methyl-2-oxovalerate and 4-aminohippurate identified in HAF for the first time, to our knowledge. Under ion-exchange LC conditions, a different set of 30 compounds was detected, including sugars, organic acids, several derivatives of organic acids, and amino acids. In this experiment, five compounds were identified for the first time in HAF: D-xylitol, amino acid derivatives (N-acetylalanine, N-acetylglycine, 2-oxoleucine), and isovalerate. The nonendogenous nature of some metabolites (caffeine, paraxanthine, D-xylitol, sorbitol) is discussed. Hyphenated NMR has allowed the rapid detection of approximately 60 metabolites in HAF, some of which are not detectable by standard NMR due to low abundance (microM) and signal overlap thus enabling an extended metabolite database to be built for HAF.

Online coupling of capillary electrophoresis with mass spectrometry for the identification of biomarkers for clinical diagnosis

Proteomic screening of complex biologic samples is of increasing importance in clinical research and diagnosis. In the postgenomic area it is evident that changes of the composition of body fluids, as well as post-translational modifications of proteins and peptides, provide more information than genetic typing. The study of these changes allows the state of health or disease of particular organs, and consequently, the whole organism, to be described. This review describes the application of capillary electrophoresis coupled online to an electrospray ionization time-of-flight mass spectrometer to the analysis of body fluids obtained from patients for the identification of biomarkers for diagnostic purposes.

Determination of free amino acids and related compounds in amniotic fluid by capillary electrophoresis with contactless conductivity detection

A capillary electrophoretic (CE) method with contactless conductivity detection (CCD) has been developed for the determination of free amino acids (AAs) in the amniotic fluid. Apart from 20 proteinogenic AAs, 12 other biogenic compounds have been identified including ethanolamine, choline, beta-alanine, 2-aminobutyric acid, 4-aminobutyric acid, creatinine, ornithine, carnitine, citrulline, 4-hydroxyproline, 1-methylhistidine and 3-methylhistidine. The running electrolyte consisted of 1.7 M acetic acid and 0.1% hydroxyethyl-cellulose (pH 2.15). An addition of acetonitrile to the sample improved the separation of AAs significantly and permitted an increase in the amount of the sample injected. As a result, the sensitivity of the determination increased and the limit of detection (LOD) decreased by a factor of ca. 4, as compared with our previous study. The LOD values were between 1.5 microM (arginine) and 6.7 microM (aspartic acid). The CE/CCD method has then been applied to clinical analyses of the amniotic fluid collected from 20 pregnant women aged over 35 years and 24 pregnant women with whom abnormal foetus development was suspected. The latter group of women was found to exhibit systematically enhanced amniotic levels of most of the AAs studied.

Capillary electrophoresis-mass spectrometry as a powerful tool in clinical diagnosis and biomarker discovery

Proteome analysis is now emerging as key technology for deciphering biological processes and the discovery of biomarkers for diseases from tissues and body fluids. The complexity and wide dynamic range of protein expression poses a formidable challenge to both peptide separation technologies and mass spectrometry (MS). Here we review the efforts that have been undertaken to date, focussing on capillary electrophoresis coupled to mass spectrometry (CE-MS). We discuss CE-MS from an application point of view evaluating its merits and vices in regard to biomarker discovery and clinical applications. As examples, we present the use of CE-MS for the determination of protein patterns in urine, serum, and other body fluids. Finally, the benefits and limitations of CE-MS for the analysis of proteins in clinical samples are discussed against the background of alternative technologies.

Total protein concentration in human amniotic fluid is negatively associated with infant birth weight

Our objectives were 2-fold: 1) to assess the concentration and distribution of total protein in human amniotic fluid (AF) using 3 standard assays [Bradford, bicinchoninic acid solution (BCA), and Lowry] and 2) to establish whether these total protein concentrations were associated with and predictive of infant birth weight. Birth outcomes were determined using recently developed birth-weight-for-gestational-age categories (percentiles) for fetal growth where infants < 10% were classified as SGA (small-for-gestational-age), those between 10 and 90% as appropriate-for-gestational-age (AGA) and those infants >/= 90% as large-for-gestational-age (LGA). AF samples were collected from women undergoing routine amniocentesis for genetic testing (mean = 15 +/- 0.04 wk, range 12-20 wk), frozen, and later analyzed for total protein in 617 singleton-expectant mothers in Montréal, QC, Canada. Maternal and fetal characteristics were obtained from questionnaires and medical chart review. Mothers giving birth to LGA infants had uniformly lower AF protein concentrations at 12-20 wk gestation compared with AF protein concentrations for mothers of AGA infants. Multiple regression analyses demonstrated that total AF protein, collected during routine amniocentesis and later analyzed by the Lowry method, was negatively associated with birth weight at term in our population. These data suggest that one or more AF proteins might emerge as biomarkers of fetal growth.

Chiral separation of gemifloxacin in sodium-containing media using chiral crown ether as a chiral selector by capillary and microchip electrophoresis

Chiral crown ether, (+)-(18-crown-6)-tetracarboxylic acid (18C6H(4)), is an effective chiral selector for resolving enantiomeric primary amines owing to the difference in affinities between 18C6H(4) and each of the amine enantiomers. In addition to the destacking effect of sodium ion in the sample solution, the strong affinity of sodium ion to the polyether ring of crown ether is unfavorable to chiral capillary electrophoresis using 18C6H(4) as a chiral selector. In this report, the chiral separation of gemifloxacin dissolved in a saline sample matrix using 18C6H(4) was investigated. Adding a chelating agent, ethylenediaminetetraacetic acid (EDTA), to the run buffer greatly improved the separation efficiencies and peak shapes. The successful chiral separation of gemifloxacin in a urinary solution was demonstrated for both capillary and microchip electrophoresis.