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.

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.

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.

[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.

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.