Relative performance of immunochemical (enzyme-linked immunosorbent assay) and gas chromatography–electron-capture detection techniques to quantify polychlorinated biphenyls in mussel tissues

A Novel Label-Free Electrochemical Immunosensor Based on a Self-Assembled Monolayer-Modified Electrode for Polychlorinated Biphenyl (PCB) in Environmental Analysis

PCBs (polychlorinated biphenyls) are a very large group of organic compounds that have between two and ten chlorine atoms attached to the biphenyl. These compounds have an acute impact as environmental pollutants, causing cancer and other adverse health effects in humans. It is therefore imperative to develop techniques for the cost-effective detection of PCBs at very low concentrations in ecosystems. In this paper, a novel label-free, indirect, competitive electrochemical immunosensor was first developed with a PCB-BSA conjugate. It is shown herein to compete with free PCBs for binding to the anti-PCB polyclonal primary antibody (IgY). Then, we used a secondary antibody to enhance the sensitivity of the sensor for the detection of PCB in a sample. It has been successfully immobilized on an 11-mercaptoundecanoic acid (11-MUA)-modified gold electrode via a carbodiimide-coupling reaction using cross-linking 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) on the electrode surface. The immunosensor was investigated by cyclic voltammetry and differential pulse voltammetry in a standard solution of [Fe(CN)6]3−/4−. A linear range of 0.011–220 ng/mL−1 and a limit of detection (LOD) of 0.11 ng/mL−1 for PCBs detection were achieved by the developed immunosensor, showing advantages over conventional assays. The novel label-free electrochemical immunosensor discussed in this paper is a solution for simple, rapid, cost-effective sample screening in a portable, disposable format. The proposed immunosensor has good sensitivity, and it can prove to be an adequate real-time monitoring solution for PCBs in soil samples or other samples.

Photoelectrochemical detection for 3,3',4,4'-tetrachlorobiphenyl in fish based on synergistic effects by Schottky junction and sensitization

In this study, a novel signal amplification strategy on photoelectrochemical (PEC) aptasensor was designed for high-sensitivity and -selectivity detection of 3,3',4,4'-tetrachlorobiphenyl (PCB77) on the basis of Schottky junction and sensitization. First, the Schottky barrier not only provided an electron-transfer irreversible passage from CuO to Au Nanoparticles (NPs) but also generated excellent local surface plasmon resonance between CuO and Au NPs, thus improving the efficiency of charge separation and light absorption. Second, to further improve the response of the PEC aptasensor under the action of the sensitization, the complementary-DNA-functionalized CdS quantum dots were introduced onto the surface of CuO/Au NPs via hybridization of the target aptamer. The PEC aptasensor exhibited a low detection limit of 17.3 pg L^-1, and a wide linear response was shown at a range of 0.2-220 ng L^-1 depending on the variation of photocurrent before and after incubation.

Development of a new polyclonal antibody for the determination of polychlorinated biphenyls in indoor air by ic-ELISA

A new polyclonal antibody (pAb) was prepared and used for the determination of polychlorinated biphenyls (PCBs) in air samples to promote the application of immunoassay technology in the determination of PCBs. Three PCB congeners immunogen mixture was used to stimulate immune responses in rabbits. The specific pAb to PCBs was obtained and used to develop an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA). A standard curve for Aroclor 1248 was prepared using concentrations ranging from 0.1 to 100 μg L(-1). The average IC50 value was 16.21 μg L(-1) and the limit of detection at 10% inhibition (IC90) was 0.069 μg L(-1). The entire procedure was then evaluated using spiked air samples. The recoveries of Aroclor 1248 at various spiking levels in the air samples ranged from 84 to 113%, with relative standard deviations of 3 to 6%. Under optimum conditions, the cross-reactivity profiles of the assays were obtained using three selected congeners, four Aroclor products, and other structurally related compounds of PCBs. The assays were found to be highly specific for PCB congeners and Aroclors 1248 and 1242. The air samples were then analyzed using gas chromatography coupled with high-resolution mass spectrometry to confirm the ic-ELISA results. The attained results demonstrated that the proposed method was an effective and inexpensive technique for the PCBs determination in air samples.

Rapid flow injection electrochemical detection of 3,3′,4,4′ tetrachlorobiphenyl using stabilized lipid membranes with incorporated sheep antibody

An electrochemical biosensor based on a supported polymerized lipid film with incorporated sheep anti-3,3′,4,4′ tetrachlorobiphenyl (PCB congener 77) antibody using flow injection analysis was developed. The polymerized lipid film contained 85% (w/w) dipalmitoylphosphatidylcholine (DPPC) and 15% (w/w) dipalmitoylphosphatidic acid (DPPA), methacrylic acid, ethylene glycol dimethacrylate, AIBN and sheep anti-congener 77 antiserum. Congener 77 was injected into flowing carrier electrolyte and the flow stopped to detect the antigen. These membranes gave only a single transient proportional to log [congener 77] from 10−8 to 10−5 M, with a detection limit of ca. 10−8 M. A membrane containing 35% (w/w) DPPA was used to examine regeneration. The maximum number of cycles was about 5.

Immunoanalysis methods for the detection of dioxins and related chemicals

With the development of biotechnology, approaches based on antibodies, such as enzyme-linked immunosorbent assay (ELISA), active aryl hydrocarbon immunoassay (Ah-I) and other multi-analyte immunoassays, have been utilized as alternatives to the conventional techniques based on gas chromatography and mass spectroscopy for the analysis of dioxin and dioxin-like compounds in environmental and biological samples. These screening methods have been verified as rapid, simple and cost-effective. This paper provides an overview on the development and application of antibody-based approaches, such as ELISA, Ah-I, and multi-analyte immunoassays, covering the sample extraction and cleanup, antigen design, antibody preparation and immunoanalysis. However, in order to meet the requirements for on-site fast detection and relative quantification of dioxins in the environment, further optimization is needed to make these immuno-analytical methods more sensitive and easy to use.

Selection of DNA aptamers against polychlorinated biphenyls as potential biorecognition elements for environmental analysis

Polychlorinated biphenyls (PCBs) have been of major concerns for decades due to their potential toxicity to human health. To trace the PCBs efficiently and sensitively, many detection methods have been developed. Aptamers, a new class of diagnostic tools, are considered to be such additional candidates for detection of pollutants. In the current study, we report the DNA aptamers, isolated by FluMag-SELEX (a modified SELEX [systematic evolution of ligands by exponential enrichment] technology), that recognize PCBs with the dissociation constants (Kd values) down to the micromolar range. Using the selected aptamers, a highly sensitive aptamer-based fluorescent assay for detection of PCBs was established using gold nanoparticles, with a widely linear range from 0.1 to 100 ng/ml. Moreover, our aptamer-based gold nanoprobe displays specificity toward 3,3',4,4'-tetrachlorobiphenyl (PCB77) compared with a few common PCB77 structural analogs. These results open the possibility of using aptamers as biorecognition elements for easy and fast environmental monitoring.

Polychlorinated biphenyls (PCBs) detection in milk samples by an electrochemical magneto-immunosensor (EMI) coupled to solid-phase extraction (SPE) and disposable low-density arrays

An electrochemical immunosensor for polychlorinated biphenyl (PCB) detection based on graphite screen-printed low-density arrays and on magnetic beads is reported. The immunological reaction for the detection of PCBs is based on a direct competitive assay using alkaline phosphatase (AP) as enzymatic label. After the immunochemical recognition, the modified magnetic beads are captured by a magnet on the surface of the graphite working electrode. The electrochemical detection is thus achieved through the addition of the AP substrate (alpha-naphthyl-phosphate). Two different antibodies (sIgG anti-PCB28 and rIgG anti-PCB77) were tested and compared in terms of sensitivity and ability to recognise different congeners. The developed electrochemical magneto-immunosensor (EMI) was successfully combined with solid-phase extraction (SPE) for the analysis of PCBs in milk samples. In spiked samples a recovery of 80% was obtained. The proposed strategy offers great promise for rapid, simple, cost-effective, and on-site analysis of clinical, food and environmental samples, considering also that low-density arrays allow the simultaneous analysis of different processed samples.

An integrated biomarker-based strategy for ecotoxicological evaluation of risk in environmental management

Environmental impacts by both natural events and man-made interventions are a fact of life; and developing the capacity to minimise these impacts and their harmful consequences for biological resources, ecosystems and human health is a daunting task for environmental legislators and regulators. A major challenge in impact and risk assessment, as part of integrated environmental management (IEM), is to link harmful effects of pollution (including toxic chemicals) in individual sentinel animals to their ecological consequences. This obstacle has resulted in a knowledge-gap for those seeking to develop effective policies for sustainable use of resources and environmental protection. Part of the solution to this problem may lie with the use of diagnostic clinical-type laboratory-based ecotoxicological tests or biomarkers, utilising sentinel animals as integrators of pollution, coupled with direct immunochemical tests for contaminants. These rapid and cost-effective ecotoxicological tools can provide information on the health status of individuals and populations based on relatively small samples of individuals. In the context of ecosystem status or health of the environment, biomarkers are also being used to link processes of molecular and cellular damage through to higher levels (i.e., prognostic capability), where they can result in pathology with reduced physiological performance and reproductive success. Complex issues are involved in evaluating environmental risk, such as the effects of the physico-chemical environment on the speciation and uptake of pollutant chemicals and inherent inter-individual and inter-species differences in vulnerability to toxicity; and the toxicity of complex mixtures. Effectively linking the impact of pollutants through the various hierarchical levels of biological organisation to ecosystem and human health requires a pragmatic integrated approach based on existing information that either links or correlates processes of pollutant uptake, detoxication and pathology with each other and higher level effects. It is further proposed here that this process will be facilitated by pursuing a holistic or whole systems approach with the development of computational simulation models of cells, organs and animals in tandem with empirical data (i.e., the middle-out approach). In conclusion, an effective integrated environmental management strategy to secure resource sustainability requires an integrated capability for risk assessment and prediction. Furthermore, if such a strategy is to influence and help in the formulation of environmental policy decisions, then it is crucial to demonstrate scientific robustness of predictions concerning the long-term consequences of pollution to politicians, industrialists and environmental managers; and also increase stakeholder awareness of environmental problems.

Ecosystem management bioindicators: the ECOMAN project--a multi-biomarker approach to ecosystem management

The ECOMAN project was initiated from an awareness of the complexity of the functioning of coastal marine systems and the clear need for more pragmatic environmental assessment techniques linking environmental degradation with its causes. The aim of the project is to develop a suite of easy to use, cost effective and environmentally valid biological responses (biomarkers) to assess the general health of coastal systems, including estuaries. To achieve this aim, various sublethal endpoints are being measured and evaluated from a range of common coastal organisms showing different feeding types (filter feeding, grazing and predation) and habitat requirements (estuary and rocky shore) and at different levels of biological response (cellular, physiological and behavioural). This holistic integrated approach is essential to identify the full impact of chemical contamination on organisms, and enables the sensitivity of organisms to be ranked and key sentinel species for specific habitats to be identified.