Determination of [3H]-2,3,7,8-tetrachlorodibenzo-p-dioxin in human feces to ascertain its relative metabolism in man

Human feces samples from a self-dosing experiment were analyzed by gas chromatography/mass spectrometry (GC/MS) for [3H]-2,3,7,8-tetrachlorodibenzo-p-dioxin (3H-2378-TCDD) to determine that 36-44% of the radioactivity was attributable to the parent compound. This method, using isotope dilution analysis, proved to be difficult due to the unexpectedly higher native 2378-TCDD background which created abnormally large precision ranges around the calculated feces concentrations of 0.1-0.2 pg/g. These results were supported by additional analyses involving the GC/MS chemical cleanup method combined with liquid scintillation counting which showed that at most, 50% of the radioactivity was due to 2378-TCDD metabolites resulting in a minimum metabolism of 50% for these samples.     

Dioxin-binding pentapeptide for use in a high-sensitivity on-bead detection assay

The purpose of this study is to develop a dioxin detection method using a short peptide alternative to an immunoantibody. A full peptide library consisting of 2.5 million possible amino acid combinations was constructed by a solid-phase split synthesis approach using 19 natural amino acids. The peptide beads were subjected to a competitive binding assay between 2,3,7-trichlorodibenzo-p-dioxin and N-NBD-3-(3',4'-dichlorophenoxy)-1-propylamine (NBD-DCPPA) in a buffer containing 20% 1,4-dioxane. Two almost identical pentapeptides, FLDQI and FLDQV, that could bind dioxin were screened from the combinatorial library. NBD-DCPPA and the peptide synthesized on resin beads could be utilized to determine dioxin concentrations. The fluorescence intensity of the beads was measured using fluorescence microscopy to make a calibration curve for the dioxin concentrations. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD) could also detected in the presence of 30% 1,4-dioxane. To optimize the peptide sequence, a one-amino acid-substituted library was prepared using amino acids including nonnatural amino acids. The internal amino acids, LDQ, could not be substituted by any other amino acids. This result indicates that these three side chains are essential to recognize dioxins. The peptide C terminus substituted by phenylglycine showed a 10 times lower detection limit of 2,3,7,8-TeCDD of 150 pM (50 pg/mL) than the original sequence FLDQV. The cross reactivity of the dioxin binding peptides including the secondary derivatives was investigated. Some polycyclic aromatic hydrocarbons bound to the peptide beads, but nonchlorinated dibenzo-p-dioxin and PCB did not. From these results, we demonstrate the potential of short peptides as a practical sensor material targeting low molecular weight compounds such as dioxin.     

Estimation of the biodegradation rate of 2,3,7,8-tetrachlorodibenzo-p-dioxin by using dioxin-degrading fungus, Pseudallescheria boydii

We are developing a bioreactor system for treating dioxin-contaminated soil or water using the dioxin-degrading fungus, Pseudallescheria boydii (P. boydii). In order to design the bioreactor system, this study estimated the rate at which P. boydii degraded 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), which is the most toxic of the dioxins. The experimental results showed that P. boydii degraded 2,3,7,8-TCDD during its logarithmic growth phase, using glucose as a carbon source for growth, and that the growth of P. boydii was not affected by 2,3,7,8-TCDD concentrations usually found at contaminated sites. These results were then used to apply successfully an existing mathematical model to the degradation of 2,3,7,8-TCDD by P. boydii. This allowed an estimation of the rate of degradation of 2,3,7,8-TCDD by P. boydii that can be used in the design of the bioreactor system.     

Picogram level quantitation of 2,3,7,8-tetrachlorodibenzo-p-dioxin in fish extracts by capillary gas chromatography/matrix isolation/Fourier transform infrared spectrometry

For the first time, gas chromatography/matrix isolation/Fourier transform infrared spectrometry (GC/MI/FTIR) has been reported to confirm the identity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2378-TCDD) and to quantify its level in fish extracts in the 170-220 pg range "on disk". When expressed on a fish tissue basis, analyte levels ranged from 15 to 45 pg/g. Spectroscopic identification was based on the position and relative intensity of seven absorption bands. Optical alignment as well as performance evaluation and optimization of the GC/MI/FTIR system are described. The use of [13C12]2378-TCDD as an internal standard was essential for quantitation, and quality assurance controls were used to verify system performance. GC/MI/FTIR quantitation of 2378-TCDD was compared with that independently found by GC with electron capture detection. Recovery of 2378-TCDD averaged 52% (n = 8, 30% relative standard deviation) for fish extracts.     

Photodegradation of tetra- and hexachlorodibenzo-p-dioxins

This study examined the direct photolysis and photocatalytic processes for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin (1,2,3,6,7,8-HxCDD). The photocatalytic procedure was performed on the TiO₂ film under irradiation with 365 nm UV and the compounds were immobilized on TiO₂/solid phase. No 2,3,7,8-substituted PCDD/Fs products were detected in photocatalytic process under the experimental conditions. The reaction rate constants were 0.3256 h⁻¹ for 2,3,7,8-TCDD (2000 ng) in UV/TiO₂ reaction, 0.2474 h⁻¹ for 1,2,3,6,7,8-HxCDD (2000 ng) in UV/TiO₂ reaction and 0.0666 h⁻¹ for 1,2,3,6,7,8-HxCDD (50 ng) under direct UV irradiation. For 1,2,3,6,7,8-HxCDD (50 ng) in a UV/TiO₂ reaction, the degradation is too fast to determine the reaction rate. The photocatalytic process was faster than direct photolysis for the same chlorinated PCDDs, and the rate decreased with increasing PCDDs quantity. The photocatalytic rate of the PCDDs decreased with increasing chlorination extent. The confirmed intermediates of 1,2,3,6,7,8-HxCDD in direct photolysis, 1,2,3,7,8-PeCDD and 2,3,7,8-TCDD both were formed by the loss of a longitudinal chlorine nearest the oxygen atom. The quantity of 1,2,3,7,8-PeCDD and toxic equivalency quantity (TEQ) declined after 10 h of UV irradiation. The proposed dechlorination pathway of 1,2,3,6,7,8-HxCDD was via 1,2,3,7,8-PeCDD to 2,3,7,8-TCDD. Formation of trace concentrations of 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (1,2,3,4,7,8-HxCDD) and 1,2,3,7,8,9-hexachlorodibenzo-p-dioxin (1,2,3,7,8,9-HxCDD) from 1,2,3,6,7,8-HxCDD appears to be a minor side reaction.     

Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans in primipara breast milk from Taiwan: estimation of dioxins and furans intake for breastfed infants

Postnatal exposure to dioxins in breastfed infants occurs mainly during breast-feeding. The exposure to a substantial amount of endocrine disruptors in the early days of life may cause long-term health effects. Test subjects were healthy and primiparous mothers with a mean age of 28 (S.D. = 3.8) in 2001. The PCDD/F congeners were analyzed in the breast milk using gas chromatograph/high resolution mass spectrometry. The mean level of PCDD/Fs was 7.4 pg-WHO-TEQ/g lipid, which is significantly lower than the level found in individuals from other countries. The total PCDD WHO-TEQ levels in breast milk had a significant positive association with maternal age and a slightly negative association with perinatal BMI (body mass index of the period before and after the delivery). The estimated daily intake of 10.5 pg-WHO-TEQ/kg/day from individual breast milk was predicted for a breastfed infant at 6 months of age with proper assumption of 8 kg body weight, 854 milk per day of consumption, 95% of dioxin absorption rate, and linear decline of dioxin during lactation. Based on the lower WHO-TEQ levels in the breast milk, breast-feeding should still be encouraged and continued in Taiwan.     

The characterization of PCDDs, PCDFs and coplanar PCBs during the past 50 years in Gwangyang Bay, South Korea

The PCDD/DFs and coplanar PCBs (co-PCBs) in sediment samples from Gwangyang Bay in South Korea was investigated. The total concentration of dioxins and their toxic equivalent quantity (TEQ; calculated with the WHO 2005 Toxic Equivalency Factors) value in the surface sediment of the outer site (261 pg g(-1) TOC, 4.4 pg-TEQ g(-1)) were 3-fold higher than the inner site (90 pg g(-1) TOC, 1.1 pg-TEQ g(-1)) in the Bay. The dioxin in the sediment samples was found to come from a mixture of the impurities of pentachlorophenol (PCP), chloronitrofen (CNP) and combustion based on the result of hierarchical cluster analysis (HCA). These dioxin sources have been influenced by the characterization associated with this region which was both an agricultural-centered and industrial-centered area. According to principal component analysis (PCA) related to the Kow values for the congener-specific composition of co-PCBs in the sediment core, the Kanechlor (KC)-500 and the atmospheric deposition were identified as the possible sources. The maximum burden in the sediment core was 1.3 kg for 1967-1974 and the total burdens of PCDD/DFs and co-PCBs in the sediment core were estimated to be 6.6 kg during the past 50 years. The cumulative burdens of dioxin are still increasing in Gwangyang Bay.     

Evaluation of technology for wastes and soils contaminated with dioxins,furans, and related substances

The objectives of the U.S. EPA Dioxin-Engineering program are: (a) to conduct basic/ applied research on the behavior of 2,3,7,8-TCDD in contaminated soils, applying this knowledge to methods useful for the in-situ stabilization of such soils and investigating the viability of special organisms or chemical reagents for the destruction of this artifact and related toxic chemicals; and (b) to develop and evaluate, both in the laboratory and in the field, technologies for the detoxification, destruction, or control of PCDD-contaminated liquids and soils.Resource levels for the program amount to $3.3 million for 1984–1986 with an additional $7.2 million from the Superfund to accelerate this program and provide quality assurance/control support to the data gathering and certification efforts.In approximately one and one-half years, significant contributions have been made in the following areas:• Sorption/desorption characteristics of 2,3,7,8–TCDD in contaminated soils have been investigated.• In-situ stabilization techniques for soils are being evaluated.• Phanerochaete chrysosporium, a white rot fungus, has shown the ability to degrade 2,3,7,8-TCDD in laboratory experiments.• Shallow mines for contaminated soils have been evaluated and the concept appears technically and environmentally feasible.• Field testing of the EPA Mobile Incineration System in Missouri is continuing. Destruction and removal efficiencies of > 99.9999% were achieved; ash and scrubber water were delisted.• Alkali polyethelene glycolate reagents are being studied and results are encouraging.     

Arsenic inhibits induction of cytochrome P450 1A1 by 2,3,7,8-tetrachlorodibenzo-p-dioxin in human hepatoma cells

The aim of this study was to examine the arsenic effect on activation of aryl hydrocarbon receptor (AhR)-mediated gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in human hepatoma cells. The human hepatoma Huh7 cells were treated with sodium arsenite (NaAsO2) from 0.5 to 20 microM for 24 h. Our data revealed that NaAsO2 < or = 10 microM caused no significant cytotoxic effect on Huh7 cells (p>0.05). We also established a dioxin-responsive element (DRE)-mediated Chemical Activated LUciferase eXpression (CALUX) cell line, Huh7-DRE-Luc, by stable transfection of Huh7 with a DRE-driven firefly luciferase reporter plasmid (4xDRE-TATA-Luc). Treatments of Huh7-DRE-Luc and Huh7 with NaAsO2 attenuated the 2,3,7,8-TCDD-induced DRE-CALUX and cytochrome P450 1A1 (CYP1A1) activations, respectively, in a dose-dependent manner. We found that the calculated CALUX-toxic equivalent (TEQ) levels induced by cotreatment of NaAsO2 > or = 3.0 microM and 10 nM 2,3,7,8-TCDD were significantly lower than that induced by 2,3,7,8-TCDD alone (p<0.05). In the present study, we demonstrated that arsenic not only inhibited the TCDD-induced CYP1A1 activation but also interfered with DRE-CALUX bioassay in human hepatoma cells. Our finding also suggests that extensive cleanup of sample for removal of any possible interfering factor is critical to guarantee the accuracy of dioxin-TEQ levels using DRE-CALUX bioassay.     

Rapid simultaneous ultrasensitive immunodetection of five bacterial toxins

Rapid ultrasensitive detection of gastrointestinal pathogens presents a great interest for medical diagnostics and epidemiologic services. Though conventional immunochemical and polymerase chain reaction (PCR)-based methods are sensitive enough for many applications, they usually require several hours for assay, whereas as sensitive but more rapid methods are needed in many practical cases. Here, we report a new microarray-based analytical technique for simultaneous detection of five bacterial toxins: the cholera toxin, the E. coli heat-labile toxin, and three S. aureus toxins (the enterotoxins A and B and the toxic shock syndrome toxin). The assay involves three major steps: electrophoretic collection of toxins on an antibody microarray, labeling of captured antigens with secondary biotinylated antibodies, and detection of biotin labels by scanning the microarray surface with streptavidin-coated magnetic beads in a shear-flow. All the stages are performed in a single flow cell allowing application of electric and magnetic fields as well as optical detection of microarray-bound beads. Replacement of diffusion with a forced transport at all the recognition steps allows one to dramatically decrease both the limit of detection (LOD) and the assay time. We demonstrate here that application of this "active" assay technique to the detection of bacterial toxins in water samples from natural sources and in food samples (milk and meat extracts) allowed one to perform the assay in less than 10 min and to decrease the LOD to 0.1-1 pg/mL for water and to 1 pg/mL for food samples.     

Bioremediation of PCDD/Fs-contaminated municipal solid waste incinerator fly ash by a potent microbial biocatalyst

Removal of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from fly ash poses a serious problem. In the study presented here, we used a microbial biocatalyst which is a mixture of 4 bacterial and 5 fungal dioxin-degrading strains. The ability of this biocatalyst to bioremediate PCDD/Fs from contaminated municipal solid waste incinerator (MSWI) fly ash was examined by solid-state fermentation under laboratory conditions. Treatment of MSWI fly ash with the microbial biocatalyst for 21 days resulted in a 68.7% reduction in total toxic PCDD/Fs. Further analyses revealed that the microbial biocatalyst also removed 66.8% of the 2,3,7,8-substituted congeners from the fly ash. During the treatment period, the presence of the individual strains composing the microbial biocatalyst was monitored by the amplification of strain-specific DNA sequences followed by denaturing gradient gel electrophoresis (DGGE). This analysis showed that all of the bacterial and fungal strains composing this dioxin-degrading microbial mixture maintained under the dioxin treatment conditions. These results demonstrate that this microbial biocatalyst could potentially be used in the bioremediation of PCDD/Fs from contaminated fly ash.     

Detection and confirmation of staphylococcal enterotoxin B in apple juice and milk using piezoelectric-excited millimeter-sized cantilever sensors at 2.5 fg/mL

A sensitive and reliable method for the detection of a model toxin, staphylococcal enterotoxin B (SEB) in buffer, apple juice, and milk is shown using piezoelectric-excited, millimeter-sized cantilever (PEMC) sensors. Limit of detection in spiked milk and apple juice samples is 10 and 100 fg, respectively. PEMC sensors (2 mm(2)) are prepared by immobilizing a polyclonal antibody specific to SEB, which was exposed to 1 mL of 1% milk and apple juice containing 10 fg-10 ng. Sensor response to 100 fg, 1 pg, and 10 pg of SEB in apple juice resulted in resonance frequency decreases of 113 +/- 18 (n = 4), 308 +/- 24 (n = 4), and 521 +/- 20 (n = 2) Hz, respectively. In milk, 10 fg, 100 fg, 1 pg, and 10 pg of SEB resulted in resonance frequency decreases of 126 +/- 18 (n = 2), 143 +/- 35 (n = 4), 310 +/- 32 (n = 5), and 557 +/- 25 (n = 2) Hz, respectively. Positive detection of SEB in the sample solution was observed within the first 20 min. The responses of the sensor to positive (SEB present, but no antibody on sensor), negative (SEB absent, antibody on sensor), and buffer (SEB absent, antibody on sensor) controls were -17 +/- 10 (n = 3), -9 +/- 5 (n = 3), and -6 +/- 12 (n = 18) Hz, respectively. Positive verification of SEB detection was confirmed by two methods: (1) low-pH buffer release caused increase in resonance frequency, and (2) second antibody binding to SEB attached to sensor that caused further resonance frequency decrease. The significance of these results is that PEMC sensors can reliably detect SEB at 10-100 fg (effective concentration of 2.5 and 25 fg/mL) in complex fluids without sample preparation or the use of labeled reagents.     

Signal enhancement in antibody microarrays using quantum dots nanocrystals: application to potential Alzheimer's disease biomarker screening

The performance of cadmium-selenide/zinc-sulfide (CdSe@ZnS) quantum dots (QDs) and the fluorescent dye Alexa 647 as reporter in an assay designed to detect apolipoprotein E (ApoE) has been compared. The assay is a sandwich immunocomplex microarray that functions via excitation by visible light. ApoE was chosen for its potential as a biomarker for Alzheimer's disease. The two versions of the microarray (QD or Alexa 647) were assessed under the same experimental conditions and then compared to a conventional enzyme-linked immunosorbent assay (ELISA) targeting ApoE. The QDs proved to be highly effective reporters in the microarrays, although their performance strongly varied in function of the excitation wavelength. At 633 nm, the QD microarray gave a limit of detection (LOD) of ～247 pg mL(-1); however, at an excitation wavelength of 532 nm, it provided a LOD of ～62 pg mL(-1), five times more sensitive than that of the Alexa microarray (～307 pg mL(-1)) and seven times more than that of the ELISA (～470 pg mL(-1)). Finally, serial dilutions from a human serum sample were assayed with high sensitivity and acceptable precision and accuracy.     

Two trace analytical methods for determination of hydroxylated PCBs and other halogenated phenolic compounds in eggs from Norwegian birds of prey

Two new trace analytical methods are presented for identification and quantification of phenolic compounds in complex biological matrixes such as bird of prey eggs. One method is based on derivatization with methyl chloroformate prior to GC/high-resolution MS (HRMS) analysis in electron impact ionization mode. Alternatively, the underivatized phenolic analytes were separated and detected by HPLC coupled to time-of-flight MS (TOF-MS) in the negative ion electrospray ionization mode. For both methods, the egg samples were homogenized and dried with acidified sodium sulfate, cold column-extracted, and cleaned up by gel permeation chromatography and subsequently a Florisil column. Recovery rates for pentachlorophenol (PCP), tetrabromobisphenol A (TBBPA), and selected hydroxylated PCBs (HO-PCBs) from spiked hen's eggs (spiking level 1 ng/g of wet weight (ww)) were in the range of 56-98% for the HPLC/MS method and 57-108% for GC/MS including derivatization. Typical detection limits of the HPLC/TOF-MS method were 5 pg/g ww (1-2 pg injected) for HO-PCBs and PCP and 20 pg/g ww (3 pg injected) for TBBPA. The GC/HRMS method achieved detection limits of approximately 1 pg/g ww in predatory bird eggs for all analytes (0.2 pg injected for derivatized TBBPA and 0.05 pg injected for derivatized HO-PCBs and PCP). Eight eggs from four different Norwegian predatory bird species were analyzed. The concentrations determined with the two different quantification methods corresponded well with each other. PCP and TBBPA were found in all samples at concentrations up to 1350 and 13 pg/g ww, respectively (GC/HRMS values). A total of 55 penta- to nonachloro-HO-PCB congeners were detected in the eight eggs, 10 of those could be structurally identified. The maximum HO-PCB congener concentration was found for 4-HO-CB 187 in a peregrine falcon egg with estimated 388 pg/g ww. Another peregrine falcon egg was highest contaminated with sum HO-PCBs (estimated 2.1 ng/g ww). This level was 1.2 per thousand of the sum PCBs value for the same egg. Furthermore, indications were found that the HO-PCB congener distribution pattern could be species specific for predatory birds.     

Toxicity equivalency factors for PCBs?

In December 1990 the U.S. Environmental Protection Agency sponsored a workshop to discuss the applicability of an interim "toxicity equivalency factor" (TEF) approach to assessing risks posed by exposures to complex mixtures of polychlorinated biphenyls (PCBs). The group concluded that application of the TEF approach to PCBs would be less straightforward than it was in the case of chlorinated dibenzo-p-dioxins and dibenzofurans (CDDs/CDFs). It appears that "dioxin"-like properties of some PCB congeners are amenable to a TEF treatment that is compatible with that used for CDDs/CDFs. Such a scheme also seems to have utility in assessing risks to wildlife. Other non-"dioxin"-like toxic endpoints (e.g., neurotoxicity) appear to have a different structure-activity-related mechanism-of-action that requires a separate TEF scheme. The workshop identified data gaps in toxicology and analytical chemistry that hinder adoption of proposed TEF schemes for PCBs at this time.     

High‐Throughput,Protein‐Targeted Biomolecular Detection Using Frequency‐Domain Faraday Rotation Spectroscopy

A clinically relevant magneto‐optical technique (fd‐FRS, frequency‐domain Faraday rotation spectroscopy) for characterizing proteins using antibody‐functionalized magnetic nanoparticles (MNPs) is demonstrated. This technique distinguishes between the Faraday rotation of the solvent, iron oxide core, and functionalization layers of polyethylene glycol polymers (spacer) and model antibody–antigen complexes (anti‐BSA/BSA, bovine serum albumin). A detection sensitivity of ≈10 pg mL^?1 and broad detection range of 10 pg mL^?1 ? c_BSA ? 100 µ g mL^?1 are observed. Combining this technique with predictive analyte binding models quantifies (within an order of magnitude) the number of active binding sites on functionalized MNPs. Comparative enzyme‐linked immunosorbent assay (ELISA) studies are conducted, reproducing the manufacturer advertised BSA ELISA detection limits from 1 ng mL^?1 ? c_BSA ? 500 ng mL^?1. In addition to the increased sensitivity, broader detection range, and similar specificity, fd‐FRS can be conducted in less than ≈30 min, compared to ≈4 h with ELISA. Thus, fd‐FRS is shown to be a sensitive optical technique with potential to become an efficient diagnostic in the chemical and biomolecular sciences.     

PCDD/F concentrations of agricultural soil in the vicinity of fluidized bed incinerators of co-firing MSW with coal in Hangzhou, China

The concentrations of 17PCDD/F congeners as well as tetra- to octa-homologues were determined in 33 soil samples collected within a radius of 7 km from a municipal solid waste (MSW) incineration plant that is equipped with three fluidized bed incinerators (FBIs) of co-firing MSW with coal in Hangzhou, China. The total PCDD/F concentrations ranged from 0.39 to 5.04 pg I-TEQ g(-1) (54-285 pg g(-1)), with an average and a median value of 1.22 and 0.84 pg I-TEQ g(-1) (105 and 86 pg g(-1)), respectively. A systematic decrease of PCDD/F levels was observed with the increasing distances and with the decreasing downwind frequencies from the plant. The comparisons of homologue and congener patterns and multivariate analysis of soil and flue gas samples strongly indicated that most of the soil samples were influenced by the FBIs. Apart from the incineration plant, historical PCDD/F emissions of hazardous waste incinerator (HWI) and motor vehicles as well as the application of 1,3,5-trichloro-2-(4-nitrophenoxy) benzene (CNP) seemed to play an important role in soil samples adjacent to these potential sources.     

Mass spectrometric immunoassay for parathyroid hormone-related protein

This paper describes a novel two-site peptide immunoassay using the isotope 14C as the label and accelerator mass spectrometry as the detection system. A mouse monoclonal antibody (1A5) against the amino terminal region of human parathyroid hormone-related protein (PTHrP) was labeled with 14C by growing the hybridoma cells in a miniPERM bioreactor in the presence of [U-14C]L-leucine and [U-14C]D-glucose. The antibody was purified from the culture media using protein G affinity chromatography. The purified 14C-labeled antibody (14C-1A5) fractions showed excellent correlation between the levels of radioactivity and binding activity for PTHrP. Using 14C-1A5 as the detection antibody in a two-site immunoassay format for PTHrP1-141, a 16-kDa polypeptide, an analytic sensitivity of 10 pmol/L was achieved with a linear measurement range up to 1.3 nmol/L. Only approximately 17 pCi/ well (or 1.6 nCi/96-well microtiter plate) 14C-1A5 was used, which is far below the limit (50 nCi/g) for disposal as nonradioactive waste. This study may serve as a model for the development of sensitive and "nonradioactive" immunoassays for peptides, including polypeptide tumor markers.     

Cell-free bioassay for measurement of dioxins based on fluorescence enhancement of fluorescein isothiocyanate-labeled DNA probe

This study aims to develop a rapid and sensitive cell-free bioassay of dioxins. It is known that dioxin ligand can bind heterodimeric aryl hydrocarbon receptor (AhR) and triggers the formation of the complex of dioxin-AhR, AhR nuclear translocator (ARNT), and dioxin-responsive element (DRE) region of the DNA. The hypothesis of the proposed method is that if FITC were labeled at the DRE sequence, its fluorescence intensity would be enhanced when the complex forms because the interaction interface of the binding components (AhR, ARNT, and DRE) creates a rather hydrophobic condition that is in favor of FITC emission. Effects of modification site of FITC on the DNA probes on binding efficiency between the complex components and fluorescence emission enhancement were evaluated by surface plasmon resonance and fluorescence analysis, respectively. Results showed that the labeling site at the second base at the 5' end apart from the core region (5'-TNGCGTG-3') of DRE did not obviously interfere with the binding between the DNA probe and dioxin-AhR/ARNT hybrid but presented significant fluorescence emission enhancement. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) was used as the typical toxin in this study. The method had a linear range of 1-100 pM, with detection limit of 0.1 pM (0.64 fg/assay) and coefficient of variation of 5.6% (n = 10, 50 pM TCDD in transformed cytosol). The whole detection cycle was approximately 4 h. The method was also used to estimate the toxic equivalents (TEQ) of 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD) and 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (HxCDD). Measurement of TEQs of the mixture of TCDD, PeCDD, and HxCDD were highly consistent with the predicted data. The average recovery using fly ash extract was approximately 93%.     

Persistent pollutants emission abatement in waste-to-energy systems

The paper is focused on analyzing methods, which enable a substantial reduction of persistent organic pollutants (POP) emissions to meet the environmental limits. Technologies based on adsorption of harmful compounds using activated carbon, technologies DeNOx/DeDiox as well as technology of catalytic filtration using a special material REMEDIA D/F are considered and compared. The latter technology consists in using a bag-house with bags manufactured from a special material (two layers—membrane from expanded PTFE and felt with bound in catalyst) called REMEDIA, which has successfully been used for the removal of PCDD/F during recent period. An optimum design is based on the computational support concerning the bag-house. It is illustrated through an industrial application of the municipal solid waste (MSW) incinerator with capacity of 15 t/h (96.000 t/year) of waste treated which is operated as a waste-to-energy system. Based on the experience from operating this incineration plant it has been proved that even after more than 3 years operation the activity of filtration material was not decreased and efficiency of dioxins removal from flue gas ranges from 97 to 99%. These facts come from complex measurements where concentration of PCDD/F toxic congeners in both flue gas and separated flying ash was measured. We arrived at confirming expected assumptions that various congeners are not decomposed uniformly in the dioxin filter and the stage of their decomposition depends on their representation in the gas phase. It is strongly influenced by their molecular weight. Their results and experience contribute to further improving the system.