Evaluation of filter paper collection of urine samples for detection and measurement of organic acidurias by capillary electrophoresis

Targeted and untargeted urinary metabolomics of alkaptonuria patients using ultra high-performance liquid chromatography-tandem mass spectrometry

Alkaptonuria (AKU) is a rare autosomal-recessive disease which is characterized through black urine and ochronosis. It is caused by deficiency of the enzyme Homogentisate 1,2-dioxygenase in the Phenylalanine/Tyrosine degradation pathway which leads to the accumulation of Homogentisic acid (HGA). Urine was provided by AKU patients and healthy controls. Several different methods were developed in this study each with a specific goal. Firstly, a simple and inexpensive RP-UHPLC-UV method for routine monitoring of HGA as a key metabolite employing a Phenylhexyl stationary phase chemistry. Validation was performed in accordance to FDA guidelines and method selectivity was further evaluated via on-line high-resolution sampling 2D-LC-QToF-MS, coupling the Phenylhexyl phase in the first dimension with a C18 phase in the second dimension. Secondly, a targeted and accurate RP-UHPLC-MRM-QTRAP assay, providing quantitative analysis of the relevant pathway metabolites based on a Phenylhexyl stationary phase, and lastly an untargeted HILIC-UHPLC-QToF-MS/MS method with SWATH (sequential window acquisition of all theoretical mass spectra) acquisition employing a sulfobetaine-type HILIC-Z superficially porous particle column, with the aim of uncovering more details about the metabolic profile of this genetic disorder. By untargeted analysis 204 metabolites could be detected and annotated in positive and negative ESI mode in total. Two separate LC methods were employed, differing in their conditions depending on the ionization mode (20 mM ammonium formate as buffer additive adjusted to a pH = 3.5 with formic acid in ESI+ mode and 20 mM ammonium acetate adjusted to a pH = 7.5 with acetic acid in ESI- mode). By effectively combining the aforementioned methods, a comprehensive workflow was developed, allowing the effective analysis of both patient and control urine samples.

New Advances for Newborn Screening of Inborn Errors of Metabolism by Capillary Electrophoresis-Mass Spectrometry (CE-MS)

Expanded newborn screening of inborn errors of metabolism (IEM) based on tandem mass spectrometry (MS/MS) technology is one of the most successful preventative healthcare initiatives for presymptomatic diagnosis and treatment of rare yet treatable genetic diseases in the population. However, confirmatory testing of presumptive screen-positive cases is required using high efficiency separations for improved specificity in order to improve the positive predictive value (PPV) for certain classes of IEMs. Here, we describe recent advances using capillary electrophoresis-mass spectrometry (CE-MS) for reliable second-tier screening or confirmatory testing based on targeted analysis of amino acids, acylcarnitines, nucleosides, and other classes of polar metabolites associated with IEMs. Additionally, nontargeted metabolite profiling enables the identification of unknown biomarkers of clinical significance for other genetic diseases that are currently screened by bioassays and/or mutation panels, such as cystic fibrosis (CF). Noteworthy, CE-MS allows for resolution of isobaric/isomeric interferences without complicated sample handling that is ideal when analyzing volume-restricted biospecimens from neonates/infants, including dried blood spots and sweat specimens. New developments to improve concentration sensitivity, as well as enhance sample throughput and quality control for unambiguous confirmatory testing of IEMs will also be discussed when using multiplexed separations based on multisegment injection-CE-MS.

Quick Diagnosis of Alkaptonuria by Homogentisic Acid Determination in Urine Paper Spots

OBJECTIVES

Two methods are described for homogentisic acid (HGA) determination in dried urine spots (DUS) on paper from Alkaptonuria (AKU) patients, devised for quick early diagnosis. AKU is a rare autosomal recessive disorder caused by deficiency of homogentisate 1,2-dioxygenase, yielding in accumulation of HGA. Its massive excretion causes urine darkening by exposure to air or alkalinization, and is a diagnostic marker. The deposition of polymers produced after HGA oxidation within the connective tissues causes ochronotic arthritis, a degenerative joint disease manifesting in adulthood and only rarely in childhood. No early diagnosis is usually accomplished, awareness following symptom development.

DESIGN AND METHODS

Two methods were designed for HGA determination in DUS: (1) a rapid semi-quantitative reliable method based on colour development in alkali and quantification by comparison with dried paper spots from HGA solutions of known concentration and (2) a quantitative and sensitive HPLC-linked method, previously devised for purine and pyrimidine analysis in urine and plasma.

RESULTS

Colour intensity developed by DUS after alkali addition was proportional to HGA concentration, and calculated amounts were in good agreement with quantitative analysis performed by RP-HPLC on DUS and on urines as such.

CONCLUSIONS

DUS, often used for different diagnostic purpose, are easily prepared and safely delivered. The simple and quick colour method proposed provides reliable HGA assessment and is fit for large screening. HGA concentration determined in 10 AKU patient DUS by both methods 1 and 2 was in agreement with direct urine assay and in the range reported by literature.A reliable HGA quantification based on colour development in paper urine spots is validated by HPLC-linked HGA quantification, and proposed as a quick diagnostic tool for AKU patients.

State-of-the-art dried blood spot analysis: an overview of recent advances and future trends

Dried blood spots have become a popular method in a variety of micro blood-sampling techniques in the life sciences sector, consequently competing with the field of conventional, invasive blood sampling by venepuncture. Dried blood spots are widely applied in numerous bioanalytical assays and have gained a significant role in the screening of inherited metabolic diseases, in PK and PD modeling; in the treatment and diagnosis of infectious diseases; and in therapeutic drug monitoring. Recent technological developments such as automation, online extraction, mass spectrometric direct analysis and also conventional dried blood spot bioanalysis, as well as future developments in dried blood spot bioanalysis are highlighted and presented in this article.

Storage of oral fluid as dried spots on alginate and chitosan foam – a new concept for oral fluid collection

Background: In recent years, there has been a major focus on analyzing drug substances from dried µl volumes of biological fluids, commonly known as dried matrix spotting. Results: 10 µl oral fluid, spiked with five basic drugs, was collected and stored as dried spots on alginate and chitosan foam, and subsequently dissolved; the drugs were thereafter isolated with electromembrane extraction and analyzed by LC–MS. The correlation coefficients were above 0.9885 for all drugs in the range 25–1000 ng/ml. The reported RSD values were below 15%. Conclusion: Storage of oral fluid as dried spots on alginate and chitosan foam have been investigated for the first time. The extract obtained after electromembrane extraction was directly compatible with LC–MS, and apparently free from coextracted matrix components.

Expanded newborn screening of inborn errors of metabolism by capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS)

Expanded newborn screening of inborn errors of metabolism (IEM) based on tandem mass spectrometry technology has emerged as one of the most successful preventative healthcare initiatives for presymptomatic diagnosis and treatment of rare yet treatable genetic diseases. However, confirmatory testing using methods with improved specificity is required in clinical laboratories to improve the positive predictive value for certain classes of IEMs due to their high rates of false positives. Here, we describe recent advances for comprehensive profiling of amino acids and acylcarnitines derived from dried blood spot extracts or plasma using capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) that allows for resolution of major isobaric/isomeric interferences without complicated sample handling. The integration of online sample preconcentration together with desalting in CE-ESI-MS enables the direct analysis of hydrophilic amino acids, surface-active acylcarnitines, as well as labile thiols under a single format when using a simple aqueous buffer electrolyte system.

Capillary electrophoresis for short chain organic acids in faeces Reference values in a Mediterranean elderly population

There is increasing evidence that gut microflora and fermentation processes in the large intestine are important for health, and that health-promoting effects are mediated by fermentation products. Usually analytical methods for these compounds are tedious. A simple and rapid procedure of aqueous extraction from the stools has been optimized. After extraction, an aliquot of the aqueous layer was directly injected into the capillary electrophoresis equipment. Oxalic, formic, fumaric, 2-ketoglutaric, succinic, citric, acetic, propionic, 2-ketoisovaleryc, butyric, isovaleric lactic, glyceric 2-hydroxybutyric, and valeric acids were separated and identified. Electrophoretic conditions were: phosphate buffer 234 mM pH 6.10 with 12% (v/v) methanol with a coated capillary at -10 kV of applied potential. The method was validated for a representative group of compounds: acetic, propionic butyric, 2-hydroxybutiric, isovaleric, and oxalic acids, including the comparison of results with ionic chromatography. Finally 136 samples from healthy humans aged 60-80, both male and female living in Spain, were measured. They could be used as reference values for further studies.

Capillary electrophoresis for caffeine and pyroglutamate determination in coffees

In a preliminary study pyroglutamate showed to be over 10 times increased in some lyophilised coffees with respect to brewed or filtered coffees, and probably that increase is related to some stage of the industrial process. Pyroglutamate is known to have a number of remarkable cognitive enhancing effects, which could be also related to the properties of coffee traditionally associated to caffeine. Pyroglutamate improves memory and learning and has anti-anxiety effects in rats. Therefore, a method has been developed and validated for the simultaneous determination of caffeine and pyroglutamate in coffee by capillary electrophoresis. Separation conditions employed MECK conditions with 50 mM borate buffer at pH 9.5 with 130 mM SDS. The applied potential was 10 kV and detection was performed at 200 nm. Afterwards, 10 soluble coffees from the market were measured and caffeine and pyroglutamate levels were compared. Those coffees with higher pyroglutamate with or without caffeine were preliminarily tested for sedative/stimulant properties and cognition enhancing effects in mice. The most relevant finding was a partial reversal of scopolamine-induced amnesia in the passive avoidance paradigm after oral administration of one coffee.

N-benzyloxycarbonyl-l-proline: An in vitro and in vivo inhibitor of prolidase

Prolidase deficiency (PD) is a recessive disorder of the connective tissue caused by mutations in the prolidase, a specific peptidase, cleaving the dipeptides with a C-terminal prolyl and hydroxyprolyl residue. PD is a complex syndrome characterized mainly by intractable skin lesions, recurrent respiratory infections and mental retardation. The relation between prolidase biological functions and the disease is still largely unknown. We studied the effect of a prolidase inhibitor, N-benzyloxycarbonyl-l-proline (Cbz-Pro), in vitro on prolidase from human fibroblasts and in vivo on murine erythrocytes prolidase. A 90% inhibition was detected incubating cellular extracts at 1:1 ratio of Gly-Pro substrate: Cbz-Pro inhibitor. Pulse experiments performed incubating human fibroblasts with 6 mM Cbz-Pro revealed that the inhibitor uptake was completed in about 1 min. The Cbz-Pro uptake was saturable and pH dependent. Long-term incubation of fibroblasts with Cbz-Pro caused mitochondria depolarization and increased cellular death as reported for long-term culture of fibroblasts from PD patients. An inhibitory effect of Cbz-Pro has also been shown in vivo. Our results demonstrated that Cbz-Pro is a potent inhibitor of prolidase in cultured fibroblasts and it can be used in vivo to better characterize the prolidase enzyme and further investigate PD physiopathology.

Capillary electrophoresis for the analysis of short-chain organic acids in coffee

A simple and rapid capillary electrophoresis method for low-molecular mass carboxylic acids measurement in coffee has been optimised and validated. Regarding separation conditions, phosphate concentration in the background electrolyte, surfactant type [cetyltrimethylammonium bromide (CTAB), tetradecyltri methylammonium bromide (TTAB) and hexadimethrine bromide (HDB)], percentages of organic modifier and pH were assayed. The best conditions were: 500 mM phosphate buffer at pH 6.25 with CTAB 0.5 mM. The separation was carried out with an uncoated fused-silica capillary (57 cm x 50 microm i.d.) which was operated at -10 kV potential. Detection was performed at 200 nm. In such conditions 17 short-chain organic acids: oxalic, formic, fumaric, mesaconic, succinic, maleic, malic, isocitric, citric, acetic, citraconic, glycolic, propionic, lactic, furanoic, pyroglutamic, quinic acids plus nitrate were separated, identified and measured. Validation parameters of the method allow us to consider it lineal, accurate and precise and, therefore, reliable for its employment in food composition studies or for quality control. Results in coffees with different industrial treatment allow the detection of important differences in the organic acid profile.

Capillary electrophoresis for the determination of organic acidurias in body fluids: a review

A systematic review of the literature on capillary electrophoresis applied to short chain organic acid analysis in body fluids has been conducted with special interest on those acids related to inborn errors of metabolism. The technique is briefly described, as well as the choice of the main analytical parameters: sample pre-treatment, polarity, capillary type, background electrolyte, and detection. The applications described in the literature are listed and the main features of the technique are discussed.

Capillary electrophoresis for short-chain organic acids and inorganic anions in different samples

This review article is a comprehensive survey of capillary electrophoresis methods developed for the measurement of short-chain organic acids and inorganic anions in a wide variety of matrices, such as food and beverages, environmental, industry, and other applications, as well as clinical applications in body fluids such as urine, plasma or cerebrospinal fluid. Details of sample pretreatment and of electrophoretic conditions have been collected in tables, arranged by the type of matrix. Strategies employed for method development for the analysis of these compounds by capillary electrophoresis in real samples are discussed.