A paper biosensor for overcoming matrix effects interfering with the detection of sputum pyocyanin with competitive immunoassays

Detecting sputum pyocyanin (PYO) with a competitive immunoassay is a promising approach for diagnosing Pseudomonas aeruginosa respiratory infections. However, it is not possible to perform a negative control to evaluate matrix-effects in competitive immunoassays, and the highly complex sputum matrix often interferes with target detection. Here, we show that these issues are alleviated by performing competitive immunoassays with a paper biosensor. The biosensing platform consists of a paper reservoir, which contains antibody-coated gold nanoparticles, and a substrate containing a competing recognition element, which is a piece of paper modified with an albumin-antigen conjugate. Detection of PYO with a limit of detection of 4.7·10-3 µM and a dynamic range between 4.7·10-1 µM and 47.6 µM is accomplished by adding the sample to the substrate with the competing element and pressing the reservoir against it for 5 min. When tested with patient samples, the biosensor was able to qualitatively differentiate spiked from non-spiked samples, whereas ELISA did not show a clear cut-off between them. Furthermore, the relative standard deviation was lower when determining sputum with the paper-based biosensor. These features, along with a mild liquefaction step that circumvents the use of harsh chemicals or instruments, make our biosensor a good candidate for diagnosing Pseudomonas infections at the bedside through the detection of sputum PYO.

A plasmonic biosensor array exploiting plasmon coupling between gold nanorods and spheres for domoic acid detection via two methods

An immunoassay was developed that utilized plasmonic coupling between immobilised gold nanorods and colloid gold nanospheres to detect the marine toxin domoic acid (DA). The aspect ratio of the nanorods was optimised and the effects of variation in acidity, silver to gold ratio, cetyltrimethylammonium bromide (CTAB) concentration and seed addition in the growth solution on the yield, size variance and LSPR peak position was investigated. Excellent nanorods (size variation < 15%; aspect ratio 3.5-5; yield 0.26-0.35 nM mL^-1) were obtained for the LSPR range 785-867 nm using strong acidic conditions (12 µl HCl (37%)), silver to gold ratio of 1:5, 0.05-0.1 M CTAB and 20-30 µl seed addition to 10 mL of growth solution. One set of nanorods (54.9 X 15.7 nm; LSPR 785 nm) were immobilised onto a silica support and bio-functionalised with DA hapten. Colloid nanospheres (15 nm; LSPR 519 nm) were bio-functionalised with an anti-domoic-acid monoclonal antibody. The functionalised nanoparticles were used to detect DA by plasmon coupling by quantifying the average LSPR shift of individual plasmon couples with hyperspectral imaging or quantifying the pixels count caused by the particle aggregation visible under darkfield microscopy. The first method led to a LSPR blue-shift of ~55 nm caused by the immunoreaction. The second, simpler method, enabled very clear qualitative detection (p < 0.0005) of domoic acid when 10 µM domoic acid was added. Both methods show potential though the novelty and simplicity of the second platform allowing rapid (~30 min) detection with high-throughput possibilities using a simple set-up is of most interest.

An Immunochemical Approach to Quantify and Assess the Potential Value of the Pseudomonas Quinolone Signal as a Biomarker of Infection

Quorum sensing (QS) is a bacterial cell density-based communication system using low molecular weight signals called autoinducers (AIs). Identification and quantification of these molecules could provide valuable information related to the stage of colonization or infection as well as the stage of the disease. With this scenario, we report here for the first time the development of antibodies against the PQS (pseudomonas quinolone signal), the main signaling molecule from the pqs QS system of Pseudomonas aeruginosa, and the development of a microplate-based enzyme-linked immunosorbent assay (ELISA) able of quantifying this molecule in complex biological media in the low nanometer range (LOD, 0.36 ± 0.14 nM in culture broth media). Moreover, the PQS ELISA here reported has been found to be robust and reliable, providing accurate results in culture media. The technique allowed us to follow up the PQS profile of the release of bacterial clinical isolates obtained from patients of different disease status. A clear correlation was found between the PQS immunoreactivity equivalents and the chronic or acute infection conditions, which supports the reported differences on virulence and behavior of these bacterial strains due to their adaptation capability to the host environment. The results obtained point to the potential of the PQS as a biomarker of infection and to the value of the antibodies and the technology developed for improving diagnosis and management of P. aeruginosa infections based on the precise identification of the pathogen, appropriate stratification of the patients according to their disease status, and knowledge of the disease progression.

High-Throughput Immunochemical Method to Assess the 2-Heptyl-4-quinolone Quorum Sensing Molecule as a Potential Biomarker of Pseudomonas aeruginosa Infections

Bacterial quorum sensing (QS) is being contemplated as a promising target for developing innovative diagnostic and therapeutic strategies. Here we report for the first time the development of antibodies against 2-heptyl-4-quinolone (HHQ), a signaling molecule from the pqs QS system of Pseudomonas aeruginosa, involved in the production of important virulent factors and biofilm formation. The antibodies produced were used to develop an immunochemical diagnostic approach to assess the potential of this molecule as a biomarker of P. aeruginosa infection. The ELISA developed is able to reach a detectability in the low nM range (IC₅₀ = 4.59 ± 0.29 nM and LOD = 0.34 ± 0.13 nM), even in complex biological samples such as Müeller Hinton (MH) culture media. The ELISA developed is robust and reproducible and has been found to be specific to HHQ, with little interference from other related alkylquinolones from the pqs QS system. The ELISA has been used to analyze the HHQ production kinetics of P. aeruginosa clinical isolates grown in MH media, pointing to its potential as a biomarker of infection and at the possibility to use the technology developed to obtain additional information about the disease stage.

The benefits of carbon black, gold and magnetic nanomaterials for point-of-harvest electrochemical quantification of domoic acid

Gold nanostars (GNST), gold nanospheres (GNP) and carbon black (CB) are chosen as alternative nanomaterials to modify carbon screen-printed electrodes (c-SPEs). The resulting three kinds of modified c-SPEs (GNP-SPE, CB-SPE and GNSP-SPE) were electrochemically and microscopically characterized and compared with standardized c-SPEs after pretreatment with phosphate buffer by pre-anodization (pre-SPE). The results show outstanding electrochemical performance of the carbon black-modified SPEs which show low transient current, low capacitance and good porosity. A competitive chronoamperometric immunoassay for the shellfish toxin domoic acid (DA) is described. The performances of the CB-SPE, GNP-SPE and pre-SPE were compared. Hapten-functionalized magnetic beads were used to avoid individual c-SPE functionalization with antibody while enhancing the signal by creating optimum surface proximity for electron transfer reactions. This comparison shows that the CB-SPE biosensor operated best at a potential near - 50 mV (vs. Ag/AgCl) and enables DA to be determined with a detection limit that is tenfold lower compared to pre-SPE (4 vs. 0.4 ng mL-1). These results show very good agreement with HPLC data when analysing contaminated scallops, and the LOD is 0.7 mg DA kg-1 of shellfish. Graphical abstractSchematic representation of the magnetic bead-based immunoassay for the quantification of domoic acid (DA) in shellfish with nanomaterial-modified screen-printed electrodes. CB, carbon black; GNP, gold nanospheres; GNST, gold nanostars; MB, magnetic beads; DA-mAb, anti-DA monoclonal mouse antibody; HRP-pAb, horseradish conjugated polyclonal goat anti-mouse antibody; DA-BSA, bovine serum albumin conjugated DA; HQ, hydroquinone; BQ, benzoquinone.

Interferometric nanoimmunosensor for label-free and real-time monitoring of Irgarol 1051 in seawater

An interferometric nanobiosensor for the specific and label-free detection of the pollutant Irgarol 1051 directly in seawater has been settled. Due to the low molecular weight of Irgarol pollutant and its expected low concentration in seawater, the sensor is based on a competitive inhibition immunoassay. Parameters as surface biofunctionalization, concentration of the selective antibody and regeneration conditions have been carefully evaluated. The optimized immunosensor shows a limit of detection of only 3 ng/L, well below the 16 ng/L set by the EU as the maximum allowable concentration in seawater. It can properly operate during 30 assay-regeneration cycles using the same sensor biosurface and with a time-to-result of only 20 min for each cycle. Moreover, the interferometric nanosensor is able to directly detect low concentrations of Irgarol 1051 in seawater without requiring sample pre-treatments and without showing any background signal due to sea matrix effect.

Quantification of interacting cognate odorants with olfactory receptors in nanovesicles

This study aims to improve our understanding of the interaction between olfactory receptors and odorants to develop highly selective biosensing devices. Natural nanovesicles (NVs) from Saccharomyces cerevisiae, ~100 nm in diameter, carrying either the human OR17-40 or the chimpanzee OR7D4 olfactory receptor (OR) tagged with the c-myc epitope at their N-terminus, are presented as model systems to quantify the interaction between odorant and olfactory receptors. The level of expression of olfactory receptors was determined at individual NVs using a novel competitive ELISA immunoassay comparing the values obtained against those from techniques involving the solubilization of cell membrane proteins and the identification of c-myc-carrying receptors. Surface Plasmon Resonance (SPR) measurements on L1 Biacore chips indicate that cognate odorants bind to their Ors, thereby quantifying the approximate number of odorants that interact with a given olfactory receptor. The selectivity of OR17-40-carrying NVs towards helional and OR7D4-carrying NVs towards androstenone has been proven in cross-check experiments with non-specific odorant molecules (heptanal and pentadecalactone, respectively) and in control receptors.

Biobarcode assay for the oral anticoagulant acenocoumarol

A novel approach for therapeutic drug monitoring of oral anticoagulants (OA) in clinical samples is reported, based on a NP-based biobarcode assay. The proposed strategy uses specific antibodies for acenocumarol (ACL) covalently bound to magnetic particles (pAb236-MP) and a bioconjugate competitor (hACL-BSA) linked to encoded polystyrene probes (hACL-BSA-ePSP) on a classical competitive immunochemical format. By using this scheme ACL can be detected in low nM range (LOD, 0.96 ± 0.26, N = 3, in buffer) even in complex samples such as serum or plasma (LOD 4 ± 1). The assay shows a high reproducibility (%CV 1.1 day-to-day) and is robust, as it is demonstrated by the fact that ACL can be quantified in complex biological samples with a very good accuracy (slope = 0.97 and R² = 0.91, of the linear regression obtained when analyzing spiked vs measured values). Moreover, we have demonstrated that the biobarcode approach has the potential to overcome one of the main challenges of the multiplexed diagnostic, which is the possibility to measure in a single run biomarker targets present at different concentration ranges. Thus, it has been proven that the signal and the detectability can be modulated by just modifying the oligonucleotide load of the encoded probes. This fact opens the door for combining in the same assay encoded probes with the necessary oligonucleotide load to achieve the detectability required for each biomarker target.

A microfluidic device for the automated electrical readout of low-density glass-slide microarrays

Microarrays are a powerful platform for rapid and multiplexed analysis in a wide range of research fields. Electrical readout systems have emerged as an alternative to conventional optical methods for microarray analysis thanks to its potential advantages like low-cost, low-power and easy miniaturization of the required instrumentation. In this work an automated electrical readout system for low-cost glass-slide microarrays is described. The system enables the simultaneous conductimetric detection of up to 36 biorecognition events by incorporating an array of interdigitated electrode transducers. A polydimethylsiloxane microfluidic structure has been designed that creates microwells over the transducers and incorporates the microfluidic channels required for filling and draining them with readout and cleaning solutions, thus making the readout process fully automated. Since the capture biomolecules are not immobilized on the transducer surface this readout system is reusable, in contrast to previously reported electrochemical microarrays. A low-density microarray based on a competitive enzymatic immunoassay for atrazine detection was used to test the performance of the readout system. The electrical assay shows a detection limit of 0.22±0.03 μg L(-1) similar to that obtained with fluorescent detection and allows the direct determination of the pesticide in polluted water samples. These results proved that an electrical readout system such as the one presented in this work is a reliable and cost-effective alternative to fluorescence scanners for the analysis of low-density microarrays.

Disposable and integrated amperometric immunosensor for direct determination of sulfonamide antibiotics in milk

The preparation and performance of a disposable amperometric immunosensor, based on the use of a selective capture antibody and screen-printed carbon electrodes (SPCEs), for the specific detection and quantification of sulfonamide residues in milk is reported. The antibody was covalently immobilized onto a 4-aminobenzoic acid (4-ABA) film grafted on the disposable electrode, and a direct competitive immunoassay using a tracer with horseradish peroxidase (HRP) for the enzymatic labeling was performed. The amperometric response measured at -0.2 V vs the silver pseudo-reference electrode of the SPCE upon the addition of H(2)O(2) in the presence of hydroquinone (HQ) as mediator was used as transduction signal. The developed methodology showed very low limits of detection (in the low ppb level) for 6 sulfonamide antibiotics tested in untreated milk samples, and a good selectivity against other families of antibiotics residues frequently detected in milk and dairy products. These features, together with the short analysis time (30 min), the simplicity, and easy automation and miniaturization of the required instrumentation make the developed methodology a promising alternative in the development of devices for on-site analysis.

Portable surface plasmon resonance immunosensor for the detection of fluoroquinolone antibiotic residues in milk

An inexpensive and portable surface plasmon resonance (SPR) sensor, SPReeta Evaluation Kit SPR3, has been used to develop a biosensor for the determination of fluoroquinolone antibiotics (FQs) and to demonstrate its performance analyzing FQ residues in milk samples. The SPReeta three-channel gold chips were activated with a mixed self-assembled monolayer (m-SAM) and functionalized with a FQ haptenized protein. Binding of the antibody produced a concentration-dependent increase of the SPR signal as a result of the change in the refraction index. Similarly, the presence of the FQ produced a dose-dependent decrease of the response, which allowed a good limit of detection (LOD) to be obtained (1.0 ± 0.4 μg L(-1) for enrofloxacin in buffer). The response was reproducible in all three channels, on different injections and days, and also between chips. Milk samples could be analyzed after a simple sample treatment involving fat removal by centrifugation and dilution with water. Under these conditions calibration curves were obtained showing that FQ residues can be analyzed in milk samples with an IC(50) value of 26.4 ± 7.2 μg L(-1) and a LOD of 2.0 ± 0.2 μg L(-1) (for enrofloxacin), far below the European Union regulations for this antibiotic family in this matrix. Finally, the paper also demonstrates that the biosensor is able to selectively detect the presence of FQs in milk samples, even in the presence of other antibiotics. Enrofloxacin, ciprofloxacin, and norfloxacin residues were detected in blind samples supplied by Nestlé Co.

Evaluation of immunoassays as an alternative for the rapid determination of pesticides in wine and grape samples

The main objective of this paper is to address the performance of immunochemical assays for the detection of the residues of three pesticides [atrazine, bromopropylate, and 2,4,6-trichlorophenol (TCP)] in real winery samples, such as wine, grapes, and grape juice. Different approaches have been evaluated to minimize interferences from the matrixes, and suitable working protocols have been established in order to achieve the necessary LODs, accuracy, and precision for real samples. A simple dilution of the sample proved to be sufficient for the determination of atrazine and bromopropylate in red and white wine and grape juice at the required levels of concentration. However, for TCP, an SPE procedure has been optimized using amino cartridges. The recoveries were above 85% in all cases, and the LOD values were below the parts per billion level, except for bromopropylate, which ranged between 2 and 50 microg/L, depending on the matrix. The grape matrix effect could be resolved by a simple extraction with methanol. Complete recoveries were obtained, and the final measurement procedures were able to determine selected pesticides below their maximum residue levels. The newly developed methods have been compared with standard chromatographic methods.

Multifunctional nanoparticles--properties and prospects for their use in human medicine

A major aim of medicine has long been the early and accurate diagnosis of clinical conditions, providing an efficient treatment without secondary effects. With the emergence of nanotechnology, the achievement of this goal seems closer than ever. To this end, the development of novel materials and devices operating at the nanoscale range, such as nanoparticles, provides new and powerful tools for imaging, diagnosis and therapy. This review focuses on the significant improvements in performance that nanoparticles offer compared with existing technologies relevant to medicine. Specifically, we address the design of multifunctional nanoparticles as an alternative system for drug and gene delivery, which has great potential for therapy in areas, such as cancer and neuropathologies. Moreover, we discuss the controversy generated by the possible toxic health effects of nanoparticles.

Electrochemical biosensing of pesticide residues based on affinity biocomposite platforms

A novel and very sensitive electrochemical immunosensing strategy for the detection of atrazine based on affinity biocomposite transducers is presented. Firstly, the graphite-epoxy composite transducer was bulk-modified with different universal affinity biomolecules, such as avidin and Protein A. Two strategies for the immobilization of the anti-atrazine antibodies on both biocomposite transducers were evaluated: 'wet-affinity' and 'dry-assisted affinity' immobilization. Finally, the performance of a novel anti-atrazine immunocomposite bulk-modified with anti-atrazine antibodies was also evaluated. The better immobilization performance of the anti-atrazine antibodies was achieved by 'dry-assisted affinity' immobilization on Protein A (2%) graphite-epoxy biocomposite (ProtA(2%)-GEB) as a transducer. The immunological reaction for the detection of atrazine performed on the ProtA(2%)-GEB biosensors is based on a direct competitive assay using atrazine-HRP tracer as the enzymatic label. The electrochemical detection is thus achieved through a suitable substrate and a mediator for the enzyme HRP. This novel strategy was successfully evaluated using spiked orange juice samples. The detection limit for atrazine in orange juices using the competitive electrochemical immunosensing assay was found to be 6 x 10(-3) microgL-1 (0.03 nmolL-1) thus this biosensing method accomplishes by far the LODs required for the European Community directives for potable water and food samples (0.1 microgL-1). This strategy offers great promise for rapid, simple, cost effective, and on-site biosensing of biological, food, and environmental samples.

Part per trillion determination of atrazine in natural water samples by a surface plasmon resonance immunosensor

A new immunoassay for continuously monitoring atrazine in water has been developed. It uses a portable biosensor platform based on surface plasmon resonance (SPR) technology. This immunoassay is based on the binding inhibition format with purified polyclonal antibodies, with the analyte derivative covalently immobilized on a gold sensor surface. An alkanethiol self-assembled monolayer (SAM) was formed on the gold-coated sensor surface in order to obtain a reusable sensing surface. The low detection limit for the optimized assay, calculated as the concentration that produces a 10% decrease in the blank signal, is 20 ng/L. A complete assay cycle, including regeneration, is accomplished in 25 min. Additionally, a study of the matrix effects of different types of wastewater was performed. All measurements were carried out with the SPR sensor system (beta-SPR) commercialised by the company Sensia, S.L. (Spain). The small size and low response time of the beta-SPR platform would allow it to be used in real contaminated locations. The immunosensor was evaluated and validated by measuring the atrazine content of 26 natural samples collected from Ebro River. Solid-phase extraction followed by gas chromatography coupled to mass spectrometric detection (SPE-GC-MS) was used to validate the new immunoassay.

Influence of mineral metabolism parameters on pulse pressure in healthy subjects

BACKGROUND

The role of mineral metabolism in cardiovascular pathologies has been studied almost exclusively in chronic kidney disease patients. There are no studies that relate mineral metabolism to pulse pressure in healthy populations.

METHODS

692 subjects were initially selected. After applying clinical exclusion criteria, 659 subjects were recruited. Creatinine clearance was then calculated to detect subjects with occult chronic kidney disease. Statistical analysis was applied to the remaining population after excluding subjects with occult chronic kidney disease (n = 466). Pulse pressure, creatinine clearance, calcium, phosphorus, intact parathormone, 25-hydroxivitamin D3 and Bsm I genotype of the vitamin D receptor were determined. Means and frequencies were compared by ANOVA and Chi-square, respectively. Multivariate analysis was applied to the whole population and then to Caucasians, Sub-Saharans, Caucasian men and Caucasian women separately. Pulse pressure (PP) was the dependent variable, and adjustments were made for clinical and laboratory data.

RESULTS

The prevalence of occult chronic kidney disease was 32%. In subjects without kidney disease, phosphorus and vitamin D were independent predictors of elevated PP in Caucasian males whereas Bsm I genotype of the vitamin D was an independent predictor of elevated PP in the Caucasian population in both genders. No covariable showed relationship with PP in Sub-Saharan subjects.

CONCLUSION

Mineral metabolism influences pulse pressure in Caucasian men.

Biomonitoring human exposure to organohalogenated substances by measuring urinary chlorophenols using a high-throughput screening (HTS) immunochemical method

The widespread contamination of the environment by persistent organochlorinated substances is well-known. High-throughput immunochemical methods may improve routine assessment of the exposure of the population to these chemicals by analyzing urinary biomarkers. Trichlorophenols (TCP) have often been considered as biomarkers of many organochlorinated compounds. With the aim to assess exposure of the population to these substances a high-throughput immunosorbent solid-phase extraction (HTS-IS-SPE) procedure coupled to ELISA for simultaneous analyses of 2,4,6-TCP immunoreactivity equivalents (2,4,6-TCP-IR equiv) in multiple hydrolyzed urine samples has been developed. Around 100 urine samples can be processed simultaneously with an inter- and intraassay precision lower than 23% CV and a limit of detection of 0.3 microg L(-1). The analyses by HTS-IS-SPE-ELISA and HTS-IS-SPE-GC/MS of urine samples (N = 117) collected from three different population groups point to a broad exposure of the Catalonian population to organohalogenated substances including the recently emerging organobrominated pollutants. Environment and edible products seem to be the most likely sources of exposure, since excretion of 2,4,6-TCP-IR equiv has been found to be independent from the occupational sector. An excellent correlation was observed between the 2,4,6-TCP-IR equiv determined by HTS-IS-SPE-ELISA and the concentrations measured by HTS-IS-SPE-GC/MS (R2 = 0.912). The results show that immunochemical screening methods, based on the quantification of urinary biomarkers, can be excellent tools for exposure assessment. The HTS-IS-SPE-ELISA presented here has proved to be efficient, precise, accurate, rapid, and specific, which opens up the possibility for a broad variety of applications where routine testing of large number of samples is required.

Analysis of nonylphenol: advances and improvements in the immunochemical determination using antibodies raised against the technical mixture and hydrophilic immunoreagents

The development of an enzyme-linked immunosorbent assay (ELISA) for the detection of technical nonylphenol (NP) is reported. The preparation of specific antibodies has been addressed using an immunizing hapten with a four-carbon atom spacer arm placed at the ortho position that preserves both the hydroxyl group and the complexity of the branched nonyl chain mixture of the technical NP. The synthesis of the immunizing hapten 5-(2-hydroxy-5-nonylphenyl)-pentanoic acid has been accomplished through a four-step synthetic pathway using the NP commercial technical mixture as the starting material. Three types of competitor haptens have also been prepared depending on the location of the spacer arm: in ortho position to the phenol group (type A), attached to the oxygen atom (type B), and in para position, substituting the nonyl chain (type C). Drawbacks produced by the hydrophobicity of the NP or of the hapten derivatives have been circumvented by using a highly hydrophilic carrier molecule such as a high-molecular-weight aminodextran as a coating support for antigen in an indirect ELISA format. A reproducible and sensitive indirect competitive ELISA has been finally obtained, reaching a limit of detection of 2.3 +/- 0.9 microg L(-1) and an IC50 value of 29 +/- 5 microg L(-1) (both N = 16). A coefficient of variation of 11% for assays performed on different days (N = 5; IC50 = 30 +/- 3 microg L(-1)) demonstrates the assay reproducibility. The assay also recognizes the nonylphenol polyethoxylates to a different degree depending on the length of the ethoxylate chain. Recovery values in the range between 96 and 100% have been obtained using spiked blind aqueous samples although the sample preparation procedure used has been shown to have a great influence on the method accuracy. A preliminary evaluation of the analytical protocol established has been performed using real water samples.

Relative hypoparathyroidism induced by interferon treatment in a hemodialysis patient

Several authors have documented beneficial effects of interferon (IFN) in chronic hepatitis C virus (HCV) infection among the dialysis population. Reports about mineral metabolism disturbances during IFN treatment are scarce, especially in dialysis patients. We report the case of a 49-year-old woman on hemodialysis with chronic HCV infection who developed significant decrease in serum calcium (Ca) and phosphorus (P) levels accompanied by relative hypoparathyroidism while being under treatment with alpha-IFN. These changes were closely related to IFN treatment, because they disappeared after INF was discontinued, reaching Ca and P levels which were similar to those of the pre-IFN period. Because IFN may induce immune disorders, several autoimmune markers were analyzed. All of them were negative or within the normal range. To further explore these mineral metabolism disturbances, a number ofparathyroid hormone (PTH) secretion-inhibiting factors, such as aluminum, magnesium, 25-hydroxyvitamin D, and calcitriol were excluded as a cause for these changes. We suggest that mineral metabolism should be carefully observed during interferon treatment in dialysis patients.

[Differential effect of vitamin D analogues on the proliferation of vascular smooth muscle cells]

Atherosclerosis is the principal cause of myocardial infarction, stroke, and peripheral vascular disease, accounting for nearly half of all mortality in developed countries. The excessive growth of vascular smooth muscle cells is an important component in the development of atherosclerotic lesion. The direct effect of calcitriol and vitamin D analogs on the VSMCs proliferation is not clear. In this study we have analysed if calcitriol, Paricalcitol (19-nor-1,25-dihydroxy-vitamin D2) and EB1089 (experimental analog used as anticancerous) modify proliferation and the expression of vitamin D receptor (VDR) gene that is regulated at the transcriptional level by itself in the VSMCs. VSMCs proliferation was analysed by BrdU incorporation and VDR gene expression using RT-PCR. VSMCs proliferation was stimulated when calcitriol was added to the culture. VSMCs proliferation was significantly lower with analogs at the same dose. With regard to the functional study, the expression of VDR gene was upregulated by calcitriol at a concentration of 100 nM. There were no changes in this expression with the analogs. In conclusion, calcitriol, do not modify VSMCs proliferation. Therefore, Paricalcitol could have a minor proliferating effect on the wall of vessels that vitamin D.

[Influence of the vitamin D receptor gene polymorphism and 25-hydroxyvitamin D on arterial pressure in health individuals]

The role of vitamin D in the regulation of blood pressure is unclear. There are no studies that relate Bsm I polymorphism with blood pressure.

OBJECTIVE

To analyze if Bsm I polymorphism and 25-hydroxyvitamin D (25OHD3) influence blood pressure in healthy individuals with normal blood pressure.

METHODS

Systolic (SBP) and diastolic (DBP) blood pressure, Body Mass Index (BMI), plasma creatinine, serum calcium, serum phosphorus, serum iPTH, serum 25OHD3 and Bsm I genotype were determined in 590 healthy individuals (260 men and 330 women). Data were analysed using a multiple linear regression model. SBP and DBP were defined as dependent variables and the rest of variables as independent.

RESULTS

Gender was strongly associated with both SBP (beta: -12.01, p: 0.000) and DBP (beta: -4.78, p: 0.000). Therefore, a separate analysis was performed according to gender. In males, SBP was associated with BMI (beta: 0.83, p: 0.001), 25OHD3, (beta: 0.36, p: 0.000) and genotype (beta: -3.90, p: 0.002); and DBP with 25OHD 3 (beta: 0.16, p: 0.018) and age (beta: 0.28, p: 0.000). Differences of blood pressure among the three genotypes were explored by analysis of variance. SBP was higher in men with bb genotype than in the other genotypes (p: 0.007). In females, 25OHD3 and genotype were not associated with blood pressure.

CONCLUSIONS

Healthy men with higher levels of vitamin D have higher levels of SBP and DBP. Moreover, men with bb genotype have the highest levels of SBP. Blood pressure levels in women are not influenced by vitamin D nor by Bsml genotype. Our data suggest a possible pathophysiological interaction between vitamin D and sex hormones in blood pressure control.

Immunochemical determination of 2,4,6-trichloroanisole as the responsible agent for the musty odor in foods. 1. Molecular modeling studies for antibody production

Nine antisera have been raised against 2,4,6-trichloroanisole (2,4,6-TCA) by immunizing them with three different haptens. With the spacer arm at the meta position, hapten A (3-(2,4,6-trichloro-3-methoxyphenyl)propanoic acid) preserved all of the functional groups of the target analyte. In hapten B (5-(2,4,6-trichlorophenoxy)pentanoic acid), the spacer was placed in the molecule substituting the methoxy group. Finally, hapten C (3-(3,5-dichloro-4-methoxyphenyl)propanoic acid) held the spacer arm at the para position instead of the chlorine atom of the target analyte. Using theoretical models, we have studied how the molecular geometry and the electronic distribution are affected by the introduction of the linker. The evaluation of the avidity of the resulting antibodies demonstrates that the orientation produced by the spacer arm must also be considered an essential aspect. The screening for competitive assays performed after synthesizing a battery of heterologous competitors has provided with these antibodies eight indirect enzyme-linked immunosorbent assays with acceptable properties. From the number of assays obtained, their maximal absorbance, their signal-to-noise ratio, the slope, and the IC(50) values obtained, it can be concluded that hapten C provided the best antibodies.

Immunochemical determination of 2,4,6-trichloroanisole as the responsible agent for the musty odor in foods. 2. Immunoassay evaluation

Immunoassays for 2,4,6-trichloroanisol (TCA) have been evaluated. The assays were developed after raising antibodies against three different immunizing haptens (1). Lack of reproducibility has been one of the main problems of these assays. Precision was worse on these assays, reaching lower limits of detection. The high lipophilicity of TCA and its, consequently, low water solubility have been found to be the major cause of this problem. A reliable microplate-based enzyme-linked immunosorbent assay (ELISA) has been set after consideration of the TCA physicochemical features and evaluation of important parameters affecting immunoassay performance. The immunoassay uses As78 (developed against hapten B-KLH) and C9-OVA as the coating antigen. The selectivity is high although the brominated analogue 2,4,6-TBA is also recognized. In buffered media containing 7% ethanol, the resulting assay shows a good accuracy with an IC(50) value of 0.53 microgram L(-)(1) and a limit of detection of 0.044 microgram L(-)(1). Red and white wine samples caused important interferences in the immunoassay demonstrating the necessity of a cleanup procedure prior to the ELISA.

[Porphyria cutanea tarda, hemodialysis and HCV hepatopathy]

Porphyria cutanea tarda is treated with phlebotomies in the absence of renal failure. However, in patients on maintenance hemodialysis, this will lead to the need for high doses of erythropoietin. We describe the case of a 63-year-old hemodialysis patient who had chronic hepatitis C virus and developed porphyria cutanea tarda after iron overload due to repeated transfusions. She was treated with erythropoietin and phlebotomies reaching clinical remission 4 months after beginning treatment.

Competitive quenching fluorescence immunoassay for chlorophenols based on laser-induced fluorescence detection in microdroplets

An improved biomonitoring system for the analysis of 2,4,6-trichlorophenol (TCP) in urine samples has been developed. The principle of the biosensor device is the detection of laser-induced fluorescence (LIF) in single microdroplets by a homogeneous quenching fluorescence immunoassay (QFIA). The competitive immunoassay occurs in microdroplets (d = 58,4 microm) produced by a piezoelectric generator system with 10-microm-diameter orifice. A continuous Ar ion laser (488 nm) excites the fluorescent tracer; its fluorescence is detected by a spectrometer attached to a 512 x 512 cooled, charge-coupled device camera. Fluorescence is quenched by specific binding of TCP polyclonal antibodies to the fluorescent tracer (hapten A-fluorescein); the quenching effect is diminished by the presence of the analyte. Thus, an increase in the signal is produced in a positive dose-dependent manner when TCP is present in the sample. In 10 mM PBS buffer, the IC50 of the LIF-microdroplet QFIA is 0.45 microg L(-1) reaching a LOD of 0.04 microg L(-1). The QFIA with the same reagents performed in microtiter plate format achieved a LOD of 0.36 microg L(-1) in buffer solution. Performance in human urine was similar to that observed in the buffer. A LOD of 1.6 ,g L(-1), with a dynamic range between 4 and 149.5 microg L(-1) in urine, was obtained without any sample treatment other than dilution with the assay buffer. The detectability achieved is sufficient for occupational exposure risk assessment.

Influence of vitamin D receptor gene polymorphisms on mortality risk in hemodialysis patients

The BsmI polymorphism of the vitamin D receptor (VDR) gene influences mineral metabolism and the course of cancers and infections. The poly-A polymorphism is in linkage disequilibrium with BsmI and could be responsible for clinical associations attributed to BsmI. The objective of this work is to study the influence of VDR polymorphisms on survival of 143 prevalent hemodialysis (HD) patients followed up for 4 years. Chi-square test was used to study the association between survival and these polymorphisms. Cox analysis was performed, adjusting for comorbid conditions in the entire HD population, groups of patients on HD therapy for less than 5 and 3 years before entering 4 years of observation, patients without diabetes, and patients treated with calcitriol. Survival was analyzed by means of Kaplan-Meier according to BsmI genotypes. Results showed a strong influence of the BsmI polymorphism on survival. The bb genotype was overrepresented among survivors (45.7%) compared with nonsurvivors (21.6%), and Cox analysis showed a significant influence of age, diabetes, calcitriol treatment, and BsmI polymorphism in all groups (in the entire population, Exp(B): BB, 3.9; and Bb, 3 with respect to bb), and also of phosphorus in patients without diabetes and calcitriol-treated patients. Survival means by Kaplan-Meier were as follows: BB, 983 days; Bb, 1,152 days; and bb, 1,290 days (log-rank P = 0.01). The BsmI polymorphism influences survival in HD patients, whereas the poly-A and FokI polymorphisms do not.

Influence of Bsml vitamin D receptor gene polymorphism on the response to a single bolus of calcitrol in hemodialysis patients

AIMS

BsmI polymorphism of the vitamin D receptor gene has been linked to hyperparathyroidism severity and calcitriol levels. The aim of this study was to analyze the response to a single bolus of calcitriol in hemodialysis patients with the BB and bb genotype.

PATIENTS

Twenty homozygous BsmI hemodialysis patients (9 BB and 11 bb).

METHODS

Hyperparathyroidism was assessed comparing basal PTH levels, and in 17 patients, also measuring the inhibition with hypercalcemia. Patients were given a bolus of calcitriol and PTH in absolute terms and in percentages relative to the baseline values at 24, 48 and 72 hours after the bolus were measured. All biochemical parameters were compared between genotypes with univariant ANOVA and additionally, PTH relative values were compared with general factorial analysis of variance, adjusting for calcium and phosphorus. Means were also compared within each genotype between consecutive determinations with non-parametric Wilcoxon analysis, using each patient as his/her own control. The response to calcitriol was also assessed by the area under the curve for each patient and was subsequently compared between genotypes.

RESULTS

There were no differences on hyperparathyroidism severity between the groups. The BB genotype showed a better response than bb to calcitriol 72 hours after the bolus (percentage relative to basal PTH value: BB: 63%, bb: 88.6%, p = 0.03; BB vs bb with univariant ANOVA). When general factorial analysis of variance was applied, adjusting for serum calcium and phosphorus, genotype showed a significant influence on the response to calcitriol at 72 hours (p = 0.04). When each patient was used as his/her own control, the BB genotype showed a significant decrease in PTH levels at 48 and 72 hours (p = 0.00 baseline vs 48 h, and p = 0.01 baseline vs 72h) whereas the bb did not.

CONCLUSIONS

BsmI polymorphism of the VDR gene induces differences on the response to a single bolus of calcitriol independently of calcium and phosphorus.

Development and application of immunoaffinity chromatography for the determination of the triazinic biocides in seawater

The development of an immunoaffinity chromatography (IAC) procedure for the selective extraction of the anti-fouling agent Irgarol 1051 [2-(tert.-butylamino)-4-(cyclopropylamino)-6-(methylthio)-1,3,5-triazine] from seawater is described. The anti-Irgarol 1051 antibodies were covalently bound to agarose-based beads support. IAC column capacities were higher than 400 ng and ethanol-water (70:30) was selected as eluting mixture. After percolation of 250 ml of water sample containing Irgarol 1051 at environmental levels (ng l(-1) ), the breakthrough volume was still not achieved. Other triazine herbicides percolated through the IAC column showed good recoveries. Thus, this IAC procedure may be useful to extract related compounds. The developed IAC column was applied to real seawater samples and compared with RP-C18 cartridges. The limit of detection (LOD) reached by using the IAC procedure was twenty times lower than the LOD achieved by the RP-C 18 cartridges using the same detection system. Irgarol 1051 was detected at ng l(-1) levels in the Barcelona marina (northwestern Mediterranean Sea). An acceptable correlation between enzyme-linked immunosorbent assay and gas chromatography with nitrogen-phosphorus detection was observed, thus analysis of Irgarol 1051 can be performed by either one of the methods. In this work, further confirmation of the analyte identity for real samples was accomplished by gas chromatography-electron impact mass spectrometry.

Development of an immunochemical technique for the analysis of trichlorophenols using theoretical models

An immunoassay has been developed for trichlorophenol analysis on the basis of theoretical chemistry modeling studies. These data have allowed us to choose the optimum chemical structure of the immunizing hapten according to realistic similarities with the target analyte. The synthesis of this hapten and the subsequent application of an appropriate immunization protocol have lead to the production of polyclonal antibodies against the target analyte. A homologous direct competitive ELISA has been developed that can be carried out in about 1 h. It has a limit of detection of 0.2 +/- 0.06 microg/L (1.01 +/- 0.3 nM) and it has been proven to tolerate a wide range of ionic strengths and pH values. Thus, the assay has acceptable features in samples with ionic strength between 4 and 56 mS/cm and pH values between 5.5 and 9.5. Studies on the selectivity of this immunoassay have demonstrated a high recognition of the corresponding brominated analogues. Other phenolic compounds do not interfere significantly in the analysis of 2,4,6-trichorophenol using this immunochemical technique. The accuracy of the assay has been evaluated using certified and spiked samples.

Vitamin D receptor genotype influences parathyroid hormone and calcitriol levels in predialysis patients

BACKGROUND

BsmI vitamin D receptor (VDR) gene polymorphism has been associated with the severity of hyperparathyroidism in patients on hemodialysis. The aim of this study was to analyze the influence of this polymorphism on parathyroid function and serum calcitriol levels in patients with different degrees of chronic renal failure (CRF) before dialysis.

METHODS

A total of 248 CRF patients, divided into three groups according to creatinine clearance (CCr; mild CRF group> 60 to </=85 ml/min, N = 54; moderate CRF group> 35 to </=60 ml/min, N = 113; severe CRF group> 10 to </=35 ml/min, N = 81), had their serum intact parathyroid hormone (iPTH) and calcitriol levels measured and BsmI genotype frequencies estimated by polymerase chain reaction (PCR) analysis. Diabetics, those on treatment with steroids, vitamin D or derivatives, and phosphorus binding agents were excluded. All those with serum calcium levels of <2.25 mmol/liter or> 2.5 mmol/liter and serum phosphorus levels of> 1.6 mmol/liter or who needed phosphorus binding agents were excluded. The statistical analysis was done with the general factorial analysis of variance entering first PTH and then calcitriol as the dependent variable; the genotype (BB, Bb and bb), sex and CCr group were defined as factors; and covariables included serum calcium, serum phosphorus, 1/creatinine versus time slope, PTH when calcitriol was the dependent variable, and calcitriol when PTH was the dependent variable.

RESULTS

When serum PTH levels were entered as the dependent variable, serum calcium, CCr group, and the interaction of genotype with the CCr group were found to be significant factors (P = 0.025, P <0.001 and P = 0.039, respectively). When serum calcitriol levels were entered as the dependent variable, genotype, the interaction of genotype with CCr, the CCr group, and the 1/creatine versus time slope were found to be significant (P = 0.027, P = 0.028, P <0.001 and P = 0.044, respectively). The marginal means of PTH, adjusted with the general factorial analysis of variance across the three groups were: (a) mild CRF group, BB 5.3 pmol/liter (CI 0 to 13.8), Bb 5.5 pmol/liter (CI 2 to 9), bb 5.4 pmol/liter (CI 0.6 to 10.2); (b) moderate CRF group, BB 6.2 pmol/liter (CI 1.5 to 10.9), Bb 7.8 pmol/liter (CI 5.3 to 10.3), bb 7.5 pmol/liter (CI 4.8 to 10.1); (c) severe CRF group, BB 9.3 pmol/liter (CI 4.2 to 14.3), Bb 17.1 pmol/liter (CI 13.9 to 20.2), bb 21.9 pmol/liter (CI 18.7 to 25.2). The marginal means of calcitriol adjusted with the general factorial analysis of variance across the three groups were: (a) mild CRF group, BB 47 pg/ml (CI 37 to 57), Bb 40.9 pg/ml (CI 37 to 44.8), bb 32.6 pg/ml (CI 26.8 to 38. 4); (b) moderate CRF group, BB 24.1 pg/ml (CI 18.3 to 29.8), Bb 26.6 pg/ml (CI 23.5 to 29.7), bb 25.3 pg/ml (CI 22 to 28.6); (c) severe CRF group, BB 27.4 pg/ml (CI 21.3 to 33.5), Bb 19.4 pg/ml (CI 15.5 to 23.2), bb 20.4 pg/ml (CI 16.1 to 24.7).

CONCLUSION

The progression of hyperparathyroidism is slower in predialysis patients with BB genotypes than in the other genotypes. Also, calcitriol levels are less reduced in the BB genotype, which may act to lessen the severity of secondary hyperparathyroidism.

A 69-year-old woman with intermittent claudication and elevated ESR

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Validation of an immunoassay method for the determination of traces of carbaryl in vegetable and fruit extracts by liquid chromatography with photodiode array and mass spectrometric detection

A competitive enzyme-linked immunosorbent assay (ELISA) method for carbaryl quantitation in crop extracts was validated by liquid chromatography (LC) with diode array detection (DAD). For this purpose, six crops (banana, carrot, green bean, orange, peach and potato) were chosen for recovery and reproducibility studies. The general sample preparation included extraction with methanol followed by liquid-liquid partitioning and clean-up on Celite-charcoal adsorbent column of the vegetable extracts. ELISA samples consisted of a diluted LC extract in assay phosphate buffer (pH 7.5). The potential effect of methanol in these samples was evaluated. It was observed that a maximum content of 10% methanol present in the assay buffer could be tolerated without expressive losses in the ELISA performance. Under these conditions, a IC50 approximately 1.48 micrograms l-1 was obtained. A minimum matrix effect with a 1:50 dilution of the methanolic extracts in assay buffer was noticed, except for green bean samples that inhibited completely the assay. For the vegetable extracts, the ELISA sensitivities varied from 3.9 to 5.7 micrograms l-1, and good recoveries (82-96%) with R.S.D.s ranging from 5.7 to 12.1% were found. An excellent correlation between the LC-DAD and ELISA techniques was obtained. The confirmation of the carbaryl in less concentrated samples was achieved by LC-mass spectrometry interfaced with atmospheric pressure chemical ionisation. The [M + H]+ = 202 and [M + H-57]+ = 145 ions, equivalent to the protonated molecular and 1-naphthol ions, respectively, were used to carbaryl identification in these samples.

Influence of the hapten design on the development of a competitive ELISA for the determination of the antifouling agent Irgarol 1051 at trace levels

Enzyme-linked immunosorbent assays (ELISAs) with a high detectability have been developed for determination of the antifouling agent Irgarol 1051. The features of the resulting assays have been rationalized by using molecular mechanic calculations (MM2+) to correlate the chemical structure of different immunizing haptens and the corresponding avidities of the obtained antisera. The ability of Irgarol 1051 to compete for the antibody binding sites with 11 horseradish peroxidase enzyme tracers, differing in the chemical structures of the hapten, has been investigated. The present paper demonstrates that high-quality antibodies and, therefore, immunoassays reaching very low detection limits could be predicted by molecular modeling studies of the analyte conformations and of the immunizing haptens' geometries, hydrogen-bonding capabilities, and electronic distributions. Two of the ELISAs obtained have been optimized to obtain reproducible immunoassays. The dynamic ranges of both assays are between 30 and 200 ng/L, and the limits of detection are approximately 16 ng/L. The reported immunoassays have been evaluated and validated by analyzing spiked and real seawater samples. Irgarol 1051 has been found to be present in two of the geographical locations analyzed at concentration levels dependent on the time of year. The analytical results obtained with these immunoassays have been validated by chromatographic methods.

Priming and inducing effects of interleukin-3 on histamine release from cord-blood basophils

The effect of interleukin-3 (IL-3) on histamine release from cord and adult blood basophils were evaluated. Leukocyte suspensions, obtained from adult patients with respiratory allergy (n = 15), normal adult subjects (n = 15), and neonates with (n = 15) and without (n = 19) atopic disposition, were stimulated with anti-IgE, fMLP, and IL-3. IgE-mediated histamine release was significantly higher in adult patients, either allergic or normal, than in neonates with or without atopic disposition. A trend toward higher fMLP-induced histamine release was found in allergic adult subjects. IL-3 had a weak direct histamine-releasing activity in allergic adult subjects and in neonates, but not in normal adult donors. A significant enhancing effect of IL-3 on histamine release induced by anti-IgE was observed in neonates with and without atopic disposition and in normal adult subjects, but not in atopic adult patients. IL-3 exerted a priming effect also when basophils were stimulated with fMLP, without any significant difference between neonates and adult subjects. Passive sensitization with IgE-rich serum resulted in a significant increase in anti-IgE-induced, but not in IL-3-induced, histamine release from cord-blood basophils. In conclusion, IL-3 primes cord-blood as well as adult blood basophils for a consecutive anti-IgE- or fMLP-induced histamine release and its activity is not limited by the low density of membrane IgE in cord-blood basophils.

Enzyme-linked immunosorbent assay for the specific detection of the mercapturic acid metabolites of naphthalene

The measurement of metabolites constitutes a useful tool for detection of exposure and in pharmacokinetic studies. Epoxidation with subsequent glutathione conjugation and mercapturic acid formation is an important deactivation pathway for naphthalene, a toxin which presumably causes lung disease. The mercapturic acid conjugates of naphthalene [NaphMA (1), N-acetyl-S-(1,2-dihydro-1-hydroxy-2-naphthyl)cysteine (1a), and N-acetyl-S-(1,2-dihydro-2-hydroxy-1-naphthyl)cysteine (1b)], its most important urinary metabolites, and other structurally related derivatives, such as N-acetyl-S-(1,2,3,4-tetrahydro-2-hydroxy-1-naphthyl) cysteine (2), N-acetyl-S-(3-hydroxy-1,2,3,4-tetrahydro-2-naphthyl)cysteine (3), and N-acetyl-S-(2-hydroxy-1-phenylethyl)cysteine (4a) and N-acetyl-S-(2-hydroxy-2-phenylethyl)cysteine (4b) as an isomeric mixture, were synthesized to develop an ELISA (enzyme-linked immunosorbent assay) for the specific detection of NaphMA (1). Compound 1, as an isomeric mixture, was used to raise antibodies by immunizing six rabbits with the corresponding KLH (keyhole limpet hemocyanin) and BSA (bovine serum albumin) derivatives (1KLH and 1BSA). The remaining compounds were covalently attached to BSA, conalbumin, and ovalbumin to be used as coating antigens. The best assay was obtained in a homologous system combining serum Ab2357 (1KLH) and 1BSA as coating antigen. The immunoassay has an I50 of 4-6 ng/mL and a detection limit of 1-2 ng/mL. Because of the known instability of the mercapturic acid conjugate of naphthalene 1, leading to the fully aromatic compound 20, a system involving HPLC is described to check the stability of the NaphMA stock solutions used in the assay. Cross-reactivity studies show high specificity toward the NaphMA. Other related compounds as well as the dehydrated derivative 20 are not recognized by the antibody in this ELISA system.