A linear-polymer-based lactoferrin-selective recognition element for an ELISA mimic: A proof of concept.

The synthesis of polymers with tailored properties for the recognition of macromolecules such as proteins is challenging. In this work, the synthesis of a new polymer format, a linear polymer (LP), as the selective recognition element for the globular protein lactoferrin (LF) is proposed as a proof-of-concept study. For the synthesis, a solid-phase strategy using the reversible deactivation radical polymerisation (RDRP) mechanism is proposed. This approach, which is usually used in molecular imprinting, involves the immobilisation of LF on the surface of a solid support, but, unlike classical imprinting, a cross-linker in the polymerisation mixture is not required. Consequently, the copolymer is soluble and flexible, thus overcoming the drawbacks associated with traditional synthetic polymers for macromolecule imprinting. This new polymer format has great potential for replacing natural antibodies in bioassays such as enzyme-linked immunosorbent assays (ELISA), dot blot, western blot, or pull-down. In our case, the linear polymer was used as a recognition element to replace natural antibodies in a LF-selective ELISA. The responses of the linear polymer between LF concentrations of 0.1 nM and 0.25 µM were studied, and a significant difference was observed between the non-specific signals and the signals measured in the presence of the polymeric material. Further, the response versus log concentration curves were fitted to a logistic equation, allowing estimation of the EC50 value: 11.8 ± 1.4 nM. We also confirmed the selective detection of LF using the competitive inhibition of the selective LF-biotin conjugate (LF-Bi) binding to the plastic receptor (LP) for closely related proteins (e.g. those having similar molecular weights or isoelectric points) such as human lysozyme, trypsin, and albumin, which are present in human body fluids. The system presents a cross-reactivity value or selectivity of 1.95% for lysozyme, 0.028% for trypsin, and 0.016% for albumin. The applicability of this method for the determination of urine LF levels in inflammatory and infectious diseases of the human urinary tract is also demonstrated.

LC-QQQ-MS routine analysis method for new biomarker quantification in plasma aimed at early chronic kidney disease diagnosis.

Pediatric chronic kidney disease (CKD) is currently assessed using glomerular filtration rate (GFR), which is calculated from different equations based on serum creatinine concentration. However, serum creatinine is affected by several factors and is not reliable enough for the diagnosis of CKD, especially at early stages. Recent targeted and untargeted metabolomics studies found 7 new potential biomarkers that could be useful for early pediatric chronic kidney disease diagnosis. Thus, a new LC-QQQ-MS analytical method has been developed and validated aimed at routine analysis of these 7 potential biomarkers: NG,NG'-dimethyl-l-arginine di(p-hydroxyazobenzene-p'-sulfonate) (SDMA), S-adenosyl-l-methionine (SAM), n-butyryl-l-carnitine (nC4), iso-butyryl-l-carnitine (iC4), citrulline (CIT), creatinine (CNN) and d-erytro-sphingosine-1-phosphate (S1P), in addition to creatinine, the classical biomarker for CKD diagnosis. Then, this analytical method has been used for the quantification of plasma samples from a heterogeneous group of CKD pediatric patients and a control pediatric population. Data analysis of these results showed that it is possible to differentiate between CKD and control populations based on the metabolite concentration in plasma.

Untargeted metabolomics for plasma biomarker discovery for early chronic kidney disease diagnosis in pediatric patients using LC-QTOF-MS.

Pediatric chronic kidney disease (CKD) is a clinical syndrome characterized by renal hypofunction occurring due to gradual and irreversible kidney damage that can further progress over time. New biomarkers may help early diagnosis of pediatric patients suffering from CKD and improve the outcome. Untargeted metabolomics based on LC-QTOF-MS has been used to find new biomarkers for the early diagnosis of CKD in plasma from pediatric patients. In order to avoid any bias in the determination of statistically significant entities as a consequence of the data analysis method followed, two different chemometric approaches have been used, Mass Profiler Professional (MPP) software and Matlab R2015a software. Metabolic fingerprints of control and CKD pediatric patients were compared and five metabolites which showed a significant change common to both data analysis procedures were identified. Sphingosine-1-phosphate, n-butyrylcarnitine, cis-4-decenoylcarnitine and an unidentified feature with 126.0930 m/z were found to be increased in plasma from pediatric patients with CKD, whereas bilirubin was significantly decreased. A partial least squares discriminant analysis model built with these 5 entities classified correctly 96% of the samples. In addition, when considering only early CKD patients against controls, a performance of 97% was obtained. Thus, these promising metabolites could be suitable biomarkers for the early diagnosis of pediatric CKD in a clinical setting.

Plasma biomarker discovery for early chronic kidney disease diagnosis based on chemometric approaches using LC-QTOF targeted metabolomics data.

Chronic kidney disease (CKD) is a progressive pathological condition in which renal function deteriorates in time. The first diagnosis of CKD is often carried out in general care attention by general practitioners by means of serum creatinine (CNN) levels. However, it lacks sensitivity and thus, there is a need for new robust biomarkers to allow the detection of kidney damage particularly in early stages. Multivariate data analysis of plasma concentrations obtained from LC-QTOF targeted metabolomics method may reveal metabolites suspicious of being either up-regulated or down-regulated from urea cycle, arginine methylation and arginine-creatine metabolic pathways in CKD pediatrics and controls. The results show that citrulline (CIT), symmetric dimethylarginine (SDMA) and S-adenosylmethionine (SAM) are interesting biomarkers to support diagnosis by CNN: early CKD samples and controls were classified with an increase in classification accuracy of 18% when using these 4 metabolites compared to CNN alone. These metabolites together allow classification of the samples into a definite stage of the disease with an accuracy of 74%, being the 90% of the misclassifications one level above or below the CKD stage set by the nephrologists. Finally, sex-related, age-related and treatment-related effects were studied, to evaluate whether changes in metabolite concentration could be attributable to these factors, and to correct them in case a new equation is developed with these potential biomarkers for the diagnosis and monitoring of pediatric CKD.

Metabolites and hormones are involved in the intraspecific variability of drought hardening in radiata pine.

Studies of metabolic and physiological bases of plant tolerance and hardening against drought are essential to improve genetic breeding programs, especially in productive species such as Pinus radiata. The exposure to different drought cycles is a highly effective tool that improves plant conditioning, but limited information is available about the mechanisms that modulate this process. To clarify this issue, six P. radiata breeds with well-known differences in drought tolerance were analyzed after two consecutive drought cycles. Survival rate, concentration of several metabolites such as free soluble amino acids and polyamines, and main plant hormones varied between them after drought hardening, while relative growth ratio and water potential at both predawn and dawn did not. Hardening induced a strong increase in total soluble amino acids in all breeds, accumulating mainly those implicated in the glutamate metabolism (GM), especially L-proline, in the most tolerant breeds. Other amino acids from GM such as γ-aminobutyric acid (GABA) and L-arginine (Arg) were also strongly increased. GABA pathway could improve the response against drought, whereas Arg acts as precursor for the synthesis of spermidine. This polyamine showed a positive relationship with the survival capacity, probably due to its role as antioxidant under stress conditions. Finally, drought hardening also induced changes in phytohormone content, showing each breed a different profile. Although all of them accumulated indole-3-acetic acid and jasmonic acid and reduced zeatin content in needles, significant differences were observed regarding abscisic acid, salicylic acid and mainly zeatin riboside. These results confirm that hardening is not only species-dependent but also an intraspecific processes controlled through metabolite changes.

Untargeted metabolomic analysis using liquid chromatography quadrupole time-of-flight mass spectrometry for non-volatile profiling of wines.

The current study presents a method for comprehensive untargeted metabolomic fingerprinting of the non-volatile profile of the Graciano Vitis vinifera wine variety, using liquid chromatography/electrospray ionization time of flight mass spectrometry (LC-ESI-QTOF). Pre-treatment of samples, chromatographic columns, mobile phases, elution gradients and ionization sources, were evaluated for the extraction of the maximum number of metabolites in red wine. Putative compounds were extracted from the raw data using the extraction algorithm, molecular feature extractor (MFE). For the metabolite identification the WinMet database was designed based on electronic databases and literature research and includes only the putative metabolites reported to be present in oenological matrices. The results from WinMet were compared with those in the METLIN database to evaluate how much the databases overlap for performing identifications. The reproducibility of the analysis was assessed using manual processing following replicate injections of Vitis vinifera cv. Graciano wine spiked with external standards. In the present work, 411 different metabolites in Graciano Vitis vinifera red wine were identified, including primary wine metabolites such as sugars (4%), amino acids (23%), biogenic amines (4%), fatty acids (2%), and organic acids (32%) and secondary metabolites such as phenols (27%) and esters (8%). Significant differences between varieties Tempranillo and Graciano were related to the presence of fifteen specific compounds.

Solute accumulation and elastic modulus changes in six radiata pine breeds exposed to drought.

Drought is one of the main abiotic factors that determine forest species growth, survival and productivity. For this reason, knowledge of plant drought response and the identification of physiological traits involved in stress tolerance will be of interest to breeding programs. In this work, several Pinus radiata D. Don breeds from different geographical origins were evaluated along a water stress period (4 weeks) and subsequent rewatering (1 week), showing different responses among them. Leaf water potential (Ψ(leaf)) and osmotic potential decreases were accompanied by a variation in the total relative water content (RWC, %). The most tolerant breeds presented the lowest leaf water potential and RWC at turgor loss point, and showed the lowest elastic modulus (ε) values. A high ε value was a characteristic of a less-drought-tolerant plant and was related to membrane alterations (high electrolyte leakage percentages) that could favor cell water loss. Of the group of solutes that contributed to osmotic adjustment, soluble carbohydrates were the most abundant, although stressed plants also increased their content of free amino acids [mainly proline (Pro) and glutamic acid (Glu), and γ-aminobutyric acid (GABA)] and free polyamines. In addition, the most sensitive breeds had a higher GABA/Glu ratio. After rewatering, Pro and GABA were higher in rehydrated plants than in controls.

Sensitive determination of triazines in underground waters using stir bar sorptive extraction directly coupled to automated thermal desorption and gas chromatography-mass spectrometry.

An automated thermal desorption-gas chromatography-mass spectrometry method for the determination of triazin herbicides in aqueous solution with excellent sensitivity was developed. The method is based on the use of stir bar sorptive extraction. The main parameters such as extraction time, sample volume, the addition of salt and organic modifiers, desorption temperature, desorption flow and desorption time which affect the efficiency of the proposed methodology are fully discussed. The proposed method is sensitive and shows a good linearity within a range of 10-10000 ng L(-1) with correlation coefficients higher than 0.998. Quantitation limits are, in all cases, below the limits accepted by European legislation for human waters consumption and ranging between 11.3 ng L(-1) and 0.7 ng L(-1). The repetitivity, expressed as a relative standard deviation, has values of lower than 8% for all analytes. Using this method, determination of 10 triazines in underground water samples was successfully performed. The average concentrations obtained in the analysis of the spiked samples at two different levels of concentration correspond to mean recoveries ranging from 94.4+/-5.1% to 106.0+/-6.3% for a significance level of 0.05.

Stereoselective determination of demethyl- and didemethyl-citalopram in rat plasma and brain tissue by liquid chromatography with fluorescence detection using precolumn derivatization.

A rapid and sensitive HPLC enantioselective method with fluorescence detection was developed to determine (-)-(R) and (+)-(S) enantiomers of the metabolites of citalopram, demethyl- and didemethyl-citalopram in plasma and brain tissue. This assay involves pre-column chiral derivatization with (-)-(R)-1-(1-naphthyl)ethyl isocyanate followed by separation on a normal-phase silica column. The developed liquid-liquid extraction procedure permits quantitative determination of analytes with recoveries ranged between 81 and 88% with intra- and inter-day relative standard deviations less than 10.5%. Linearity was obtained over the concentration range 5-1000 ng/mL and 100-10,000 ng/g for spiked drug-free plasma and brain tissue, respectively, with detection limits lower than 2.1 ng/mL and 42.8 ng/g.

Solid-phase microextraction coupled with high performance liquid chromatography using on-line diode-array and electrochemical detection for the determination of fenitrothion and its main metabolites in environmental water samples.

The aim of this study was to develop a methodology for the analysis of the insecticide fenitrothion and its two main environmental metabolites, fenitrooxon and 3-methyl-4-nitrophenol. For this purpose, a solid-phase microextraction (SPME) method coupled to high performance liquid chromatography (LC) was optimized. Two on-line detectors, diode array (DAD) and direct current amperometrical (DCAD) were used in order to determine sensitivity and selectivity. The effects of the extraction parameters, including exposure and desorption time, pH, temperature, salt concentration and desorption mode on the extraction efficiency were studied. A satisfactory reproducibility for extractions from samples at 20 ppb-level with RSD < 12.5% (n = 10) was obtained. The calibration graphs were linear in the range of 10-1000 microg l(-1) and detection limits for the target compounds were between 1.2 and 11.8 microg l(-1) depending on which detector was used. The method was applied for determining fenitrothion and both its metabolites in river waters which run through forest areas near to aerial application of the pesticide.

Speciation of volatile aromatic and chlorinated hydrocarbons in an urban atmosphere using TCT-GC/MS.

Several aromatic and chlorinated volatile hydrocarbons (VOCs) were measured in Vitoria-Gasteiz City (Spain) throughout the years 1999 and 2002 in order to find out the concentration of these pollutants in urban air. These VOCs were retained in Tenax TA, subsequently desorpted by using a thermal desorption cold trap injector (TCT), and thereafter analyzed by gas chromatography/mass spectrometry (GC/MS). This analytical methodology permits the determination of 42 VOCs at very low concentrations, although only 32 of them were found in the urban air of the city (ranging from 205.51 to 0.01 microg m(-3)), with high reproducibility (%RSD lower than 10%). Twenty-four-hour samples were taken each sampling day to ascertain their total daily concentration, and rigorous quality controls were carried out to check the representativeness of sampling. Results of this exhaustive study show that toluene (T), xylenes (X), ethylbenzene (E), and benzene (B) were, respectively, the most abundant of these VOCs in the urban area during that period. The total concentration of BTEX represented, on average, more than 72.6% of the VOC total concentration, with the highest concentrations being reached in autumn, except for benzene and derived compounds (in winter). Benzene was the minority BTEX pollutant, its yearly mean concentration being less than the maximum established by the European Directive 2000/69/CE (5 microg m(-3)).

Optimization and validation of a method of analysis for fenitrothion and its main metabolites in forestry air samples using sorbent tubes with thermal desorption cold trap injection and gas chromatography-mass spectrometry.

An analytical methodology using thermal-desorption cold trap (TCT) and GC-MS was developed for the determination of the insecticide fenitrothion and its main metabolites, 3-methyl-4-nitrophenol and fenitrooxon, in forestry atmospheres. The sampled atmosphere was pumped through a glass tube containing 100 mg of Tenax adsorbent at a flow rate of 50 ml min(-1). Adsorption/thermal desorption and breakthrough experiments were performed to test the ability to quantitatively trap the compounds. The detection limits of method for these compounds ranged between 1.6 and 2.1 ng m(-3). This methodology was developed to evaluate the persistence of fenitrothion in forest atmospheres after treatment. Spray application at 21.5 mg active ingredient m(-2) resulted in atmosphere levels of the insecticide of 78.3 ng m(-3) (after 2 h of application). Within 2-4 days following treatment, the presence of fenitrooxon fell to 50-55%. During this period residues of metabolites began to appear, disappearing 19 days later.

Coupling solid-phase microextraction and high-performance liquid chromatography for direct and sensitive determination of halogenated fungicides in wine.

A solid-phase microextraction (SPME) method coupled to high-performance liquid chromatography with diode array detection (HPLC-DAD) for the analysis of six organochlorine fungicides (nuarimol, triadimenol, triadimefon, folpet, vinclozolin and penconazole) in wine was developed. For this purpose, polydimethylsiloxane-divinylbenzene-coated fibers were utilized and all factors affecting throughput, precision, and accuracy of the SPME method were investigated and optimized. These factors include: matrix influence, extraction and desorption time, percentage of ethanol, pH, salt effect and desorption mode. The performed analytical procedure showed detectability ranging from 4 to 27 microg l(-1) and precision from 2.4 to 14.2% (as intra-day relative standard deviation, RSD) and 4.7-25.7% (as inter-day RSD) depending on the fungicide. The results demonstrate the suitability of the SPME-HPLC-DAD method to analyze these organochlorine fungicides in red wine.

Multimembrane carbon fiber microelectrodes for amperometric determination of serotonin in human urine.

An electrochemical sensor for the determination of serotonin in urine was prepared using Ni(II)-phthalocyanine and Nafion to modify the surface of a 4 mm length carbon fiber microelectrode. The resultant sensor was found to improve the response towards this neuronal amine versus the microelectrode without the polymer films. Different polymerization conditions, as well as different conditioning solutions and buffer systems, were investigated in order to optimize the response of the electrodes. Square wave voltammetry (SWV) is proposed as a direct method for determination of serotonin in human urine, after a solid-liquid extraction process. The proposed method enables a detection limit for serotonin of 0.80 +/- 0.04 microgram L-1 to be achieved at a reduction potential of 0.35 V, with an overall prediction error of 2.2% and recoveries of 93%.

Persistence of the insecticide Dimilin 45 ODC on conifer forest foliage in an Atlantic-climate ecosystem.

The oil formulation of diflubenzuron (Dimilin 45 ODC) persisted for 10-12 weeks on the foliage of a conifer forest in an Atlantic-climate ecosystem. Within 22-30 days following treatment, 55-80% of the insecticide had been removed from the foliage. During this period, the concentration of diflubenzuron was higher than 370 ng g(-1). Aerial application at 56.3 g of Al ha(-1) resulted in deposition levels of the insecticide ranging from 867.5 to 1824.4 ng g(-1), depending upon forest characteristics. The results showed that aerial application is only a suitable technique for the treatment of forest areas with dense foliage and/or high tree density and no more than 15% of tree-free area. The only metabolite detected was 2,6-difluorobenzamide, and this persisted on foliage until the first rainfalls occurred. An empirical mathematical correlation was found to express the influence of meteorological variables--rainfall, solar radiation and temperature--on the persistence of the insecticide. These results suggested that degradation of diflubenzuron on foliage could be due to photodegradation. Some recommendations were made to optimize the deposition of the insecticide on foliage and to minimize its persistence and the off-site spray drift.

Solid-phase microextraction for the determination of systemic and non-volatile pesticides in river water using gas chromatography with nitrogen-phosphorous and electron-capture detection.

A solid-phase microextraction (SPME) method combined with gas chromatography with nitrogen-phosphorous and electron capture detection for the analysis of the pesticides terbumeton, metribuzine, isomethiozine, pyridafenthion and triadimenol in river water has been developed. For this purpose, polyacrylate and polydimethylsiloxane coated fibres have been utilised and the factors affecting throughput, precision and accuracy of the SPME method have been investigated and optimised. These factors include: matrix influence, adsorption time, pH, salt effect, desorption time, temperature and also the lapse of time between sampling and injection. The performed analytical procedure showed detectability ranging from 2.0 ng l(-1) to 3.0 microg l(-1) and precision from 1.9 to 27.7% (as relative standard deviation) depending on the pesticide, the fibre and the detector used. The results demonstrate the suitability of the SPME method to analyse these non-volatile pesticides in river water.

Determination of the insecticide pyridafenthion in river water, soils and wine by adsorptive stripping voltammetry.

Solid-phase extraction or liquid-liquid extraction has been combined with adsorptive stripping voltammetry at a hanging mercury drop electrode to isolate, determine, quantify and recover trace concentrations of pyridafenthion in water, wine and soil. A systematic study of the experimental parameters affecting the stripping response was carried out by differential pulse voltammetry. By using an accumulation potential of 400 mV and an accumulation time of 540 s, the limit of detection was 0.17 microgram l-1 and the relative standard deviation (n = 10) was 1.9% at a concentration level of 8.5 micrograms l-1. Different methods are proposed which eliminate matrix interferences. These results have been applied to the systematic study of this compound in water, wine and soil. The lowest detectable concentration for pyridafenthion is 34 micrograms l-1 in water, 102 micrograms l-1 in wine and 80 micrograms kg-1 in soil. Recoveries of the pyridafenthion from supplied environmental samples were in all cases higher than 92% with a relative standard deviation lower than 3%.

Joint determination of todralazine and acetazolamide in human serum by differential pulse polarography.

Differential pulse polarography (DPP) is proposed as a direct method for the quantitation of todralazine and acetazolamide in human serum. The method was applied to the determination of these drugs in human serum, after a liquid-liquid extraction process. This extraction process together with the use of the standard additions method is essential for the elimination of the matrix effect. The proposed method enables detection limits of 0.107 microgram ml-1 for acetazolamide and 0.111 microgram ml-1 for todralazine to be achieved at reduction potentials of -0.59 and -0.86 V, respectively, using Britton-Robinson buffer (pH 1.65) as the supporting electrolyte.

Use of derivatization reactions with adsorptive stripping voltammetry for determining fotemustine in biological samples.

A method is described for determining the new fotemustine antineoplastic in human serum. The method is based on the derivatization of the original molecule by means of diazotization and coupling reactions. The derivatization product is determined by means of adsorptive stripping voltammetry. The calibration graphs were linear over the range 6 x 10(-9)-8 x 10(-7) and 6 x 10(-10)-8 x 10(-8) M, according to whether the coupling reagent was 1-naphthylamine or 1-naphthol, respectively. At the same time, the detection limits are 4.1 x 10(-9) and 1.4 x 10(-10) M, respectively. The method was applied to determine this antineoplastic in human serum, after a liquid-liquid extraction process, from which recovery factors of 95.6% has been obtained.