Development of an enzyme-linked immunosorbent assay for bisphenol a using chicken immunoglobulins

Advances in Chicken IgY-Based Immunoassays for the Detection of Chemical and Biological Hazards in Food Samples

As antibodies are the main biological binder for hazards in food samples, their performance directly determines the sensitivity, specificity, and reproducibility of the developed immunoassay. The overwhelmingly used mammalian-derived antibodies usually suffer from complicated preparation, high cost, frequent bleeding of animals, and sometimes low titer and affinity. Chicken yolk antibody (IgY) has recently attracted considerable attention in the bioanalytical field owing to its advantages in productivity, animal welfare, comparable affinity, and high specificity. However, a broad understanding of the application of IgY-based immunoassay for the detection of chemical and biological hazards in food samples remains limited. Here, we briefly summarized the diversity, structure, and production of IgY including polyclonal and monoclonal formats. Then, a comprehensive overview of the principles, designs, and applications of IgY-based immunoassays for these hazards was reviewed and discussed, including food-borne pathogens, food allergens, veterinary drugs, pesticides, toxins, endocrine disrupting chemicals, etc. Thus, the trend of IgY-based immunoassays is expected, and more IgY types, higher sensitivity, and diversification of recognition-to-signal manners are necessary in the future.

An Electrochemical Sensor Based on Gold Nanodendrite/Surfactant Modified Electrode for Bisphenol A Detection

In the present work, we reported the simple way to fabricate an electrochemical sensing platform to detect Bisphenol A (BPA) using galvanostatic deposition of Au on a glassy carbon electrode covered by cetyltrimethylammonium bromide (CTAB). This material (CTAB) enhances the sensitivity of electrochemical sensors with respect to the detection of BPA. The electrochemical response of the modified GCE to BPA was investigated by cyclic voltammetry and differential pulse voltammetry. The results displayed a low detection limit (22 nm) and a linear range from 0.025 to 10 µm along side with high reproducibility (RSD = 4.9% for seven independent sensors). Importantly, the prepared sensors were selective enough against interferences with other pollutants in the same electrochemical window. Notably, the presented sensors have already proven their ability in detecting BPA in real plastic water drinking bottle samples with high accuracy (recovery range = 96.60%-102.82%) and it is in good agreement with fluorescence measurements.

New Mixed Bromine/Chlorine Transformation Products of Tetrabromobisphenol A: Synthesis and Identification in Dust Samples from an E-Waste Dismantling Site

The large-scale production and usage of tetrabromobisphenol A (TBBPA) and its analogues have caused widespread contamination, raising concern about their potential endocrine disruption effects on both humans and ecosystems. In the present study, debromination and unknown mixed bromine/chlorine transformation products of TBBPA (X-BBPA) were screened in dust samples from an e-waste dismantling site. Five monochloro products (2-chloro-2',6,6'-TriBBPA, 2-chloro-2',6-DiBBPA, 2-chloro-2',6'-DiBBPA, 2-chloro-2'-MoBBPA, and 2-chloro-6-MoBBPA) and two dichloro products (2,2'-dichloro-6,6'-DiBBPA and 2,2'-dichloro-6-MoBBPA) were successfully synthesized and structurally identified. TBBPA and its transformation products were detected by comparison of their mass spectra and retention times with those of synthetic standards. The mean concentration of X-BBPA was 1.63 × 10⁴ ng/g in e-waste dismantling workshop dust samples based on dry weight, which was at a similar level to TBBPA. However, it was 1 order of magnitude lower than the concentrations of the debromination congeners. Thus, both debromination and chlorine-bromine exchange may be important reactions during the thermal processing of e-waste. The results on mixed chlorinated/brominated TBBPA transformation products provided new insights into TBBPA transformation. The elevated levels of the transformation products of TBBPA suggested that these products should be targeted to avoid underestimation of possible health risks.

Detection and Identification of Estrogen Based on Surface-Enhanced Resonance Raman Scattering (SERRS)

Many studies have shown that it is important to consider the harmful effects of phenolic hormones on the human body. Traditional UV detection has many limitations, so there is a need to develop new detection methods. We demonstrated a simple and rapid surface-enhanced resonance Raman scattering (SERRS) based detection method of trace amounts of phenolic estrogen. As a result of the coupling reaction, there is the formation of strong SERRS activity of azo compound. Therefore, the detection limits are as low as 0.2 × 10-4 for estrone (E1), estriol (E3), and bisphenol A (BPA). This method is universal because each SERRS fingerprint of the azo dyes a specific hormone. The use of this method is applicable for the testing of phenolic hormones through coupling reactions, and the investigation of other phenolic molecules. Therefore, this new method can be used for efficient detection.

Templated Oligosaccharide Synthesis: Driving Forces and Mechanistic Aspects

We previously communicated that high α-selectivity that can be achieved in intramolecular glycosylations using a rigid bisphenol A template supplemented with linkers of various lengths. Herein, we present our investigation of the mechanistic aspects of the templated synthesis that helped to design an improved template-linker combination. We demonstrate that bisphenol A as the template in combination with phthaloyl linker allows for superior stereoselectivity and yields in glycosylations. Several mechanistic studies explore origins of the enhanced stereoselectivity and yields achieved using the phthaloyl linker.

Fiber-optic based cell sensors

Different whole cell fiber optic based biosensors have been developed to detect the total effect of a wide range of environmental pollutants, providing results within a very short period. These biosensors are usually built from three major components, the biorecognition element (whole-cells) intimately attached to a transducer (optic fiber) using a variety of techniques (adsorption, covalent binding, polymer trapping, etc). Even with a great progress in the field of biosensors, there is still a serious lack of commercial applications, capable of competing with traditional analytical tools.

Analysis of estrogens and estrogen mimics in edible matrices--a review

This review provides a brief survey of the biological effects of selected endocrine-disrupting compounds that are formed after internal exposure of organisms. Further, the present analytical methods available for the determination of these compounds in foodstuffs are critically evaluated. The attention is primarily devoted to the methods for sample pretreatment, which are the main source of errors and are usually the most time-consuming step of the whole analysis. This review is focused on selected natural and synthetic estrogens, estrogen conjugates, and chemical additives used in the plastic industry that can act as estrogen mimics.

Cd-doped ZnO quantum dots-based immunoassay for the quantitative determination of bisphenol A

Bisphenol A (BPA) is a ubiquitous environmental contaminant in food products and aquatic ecosystems. Its endocrine and developmental toxicity presents a serious concern to human health and an effective high-throughput method for its detection is desirable. In this paper, water-soluble quantum dots (QDs) have been conjugated covalently with BPA antibodies and the conjugate has been utilized in a competitive fluorescence-linked immunoassay (FLISA). Cd-doped ZnO QDs were functionalized with poly(amidoamine) (PAMAM) dendrimers, as evidenced by ultraviolet absorption spectrum and fluorescence emission spectra analyses, and this led to their successful transfer into aqueous solution. Biological mass spectrometry demonstrated that the bisphenol A antibodies were successfully coupled to the water-soluble QDs, and the structures of these conjugates kept intact. The FLISA method allowed for BPA determination in a linear working range of 20.8-330.3 ng mL(-1) with the limit of detection (LOD) of 13.1 ng mL(-1). The recoveries of BPA from water samples were from 85.92% to 109.62%. In conclusion, a rapid and sensitive FLISA was developed by utilizing novel QD coupling method and validated for use in aqueous samples.

E-assay concept: detection of bisphenol A with a label-free electrochemical competitive immunoassay

A label-free electrochemical immunosensor was developed by electropolymerization of N-(3-(4-(2-(4-hydroxyphenyl)propan-2-yl)phenoxy)propyl) 3-(5-hydroxy-1,4-dihydro-1,4-dioxonaphthalen-2(3)-yl)propionamide (JugBPA). By combination with an antibody directed to bisphenol A (αBPA), this conducting polymer-based biosensor can detect BPA directly with a limit of detection of 2pgmL(-1). Square wave voltammetry shows that the polymer film presents a current decrease upon anti-BPA binding and an opposite current increase upon BPA addition in solution. This electrochemical immunosensor (E-assay) also shows high selectivity towards closely related compounds (bisphenol A dimethacrylate, and dibutyl phthalate). The E-assay concept described here could be a promising tool for simple, low-cost and reagentless on-site environmental monitoring.

Purification of egg yolk immunoglobulin (IgY) by ultrafiltration: effect of pH, ionic strength, and membrane properties

Immunoglobulin Y (IgY) was purified from hen egg yolk water-soluble protein fraction by ultrafiltration-diafiltration with different membranes. The effect of changing solution properties (pH and ionic strength) on purification factor (P), process selectivity (Psi), and IgY recovery (RIgY) was studied. Salt presence (150 and 1500 mM) decreased the selectivity and purity factor. This effect was more evident at pH values closer to or higher than the IgY's isoelectric point. The best results were obtained in the absence of salt at pH values of 5.7 and 6.7 using poliethersulfone (PES) and modified PES (MPES), respectively. Process selectivity was doubled, and IgY's purification factors were increased in more than 1 order of magnitude when diafiltration was used. Results from this work show the potential of membrane technology for the purification of IgY from hen's egg yolk.

Rapid method for qualitative detection of in environmental samples

A gel-based immunoassay that can be used for the detection of 2,4,6-trinitrotoluene (TNT) in water samples was developed. Four polyclonal antibodies were generated in chickens using TNT derivatives. The assay was based on the immunoaffinity preconcentration and immuno-enzyme analysis of TNT in the gel. The results of the assay, assessed by color development, were evaluated visually and also by using a flatbed scanner and subsequent digital processing of the scanned gel. The most sensitive color mode, parameter S (saturation, HSB mode), was used for the immunoassay optimization and evaluation of the results. The immunoassays with the best parameters were optimized and characterized. A cut-off level of 5 µg TNT L-1 was reached for water samples. It was shown that tap and environmental water samples could be analyzed directly, without sample preparation and dilution. The developed test is acceptable for use in an on-site field test to provide rapid (about 15 min for six samples), qualitative and reliable results for making environmental decisions such as identifying "hot spots", monitoring of military and terrorist activities, and selecting of site samples for laboratory analysis.

Spreeta-based biosensor assays for endocrine disruptors

The construction and performance of an automated low-cost Spreeta-based prototype biosensor system for the detection of endocrine disrupting chemicals (EDCs) is described. The system consists primarily of a Spreeta miniature liquid sensor incorporated into an aluminum flow cell holder, dedicated to support a Biacore chip frame, in combination with a simple pressurized air-driven fluid system. During the optimization, a monoclonal antibody (MAb)-based immunoassay for the estrogenic compound bisphenol A (BPA) was used as a model. After the optimization two thyroxine transport protein inhibition assays for thyroid endocrine disruptors were implemented. The average noise of the system for 1 min of baseline was 1.1 microRIU (refractive index units) and it could be operated in the range of 18-22 degrees C with a minimum baseline drift (5-10 microRIU/100 min). Optimum signal to noise ratio (S/N R) was obtained using a flow cell height of 100 microm and a flow rate of 180 microl/min. The sensitivity of the Spreeta-based biosensor inhibition assays implemented (50% inhibition concentration (IC50) of 30.2 nM for BPA using MAb12 and 12.3 and 11.6 nM for thyroxine (T4) using thyroxine-binding globulin (TBG) and recombinant transthyretin (rTTR), respectively) was comparable to the sensitivity previously obtained using a Biacore 3000 (IC50 of 39.9 nM for BPA and 8.6 and 13.7 nM, respectively, for T4). The results indicate that the alternative prototype system can be used in combination with ready-to-use biosensor chip surfaces and it is potentially a useful tool for the bioeffect-related screening of EDCs.

Analysis of bisphenol A in natural waters by means of an optical immunosensor

This work describes a very simple, fast and sensitive method based on the use of the optical immunosensor "RIver ANAlyser" (RIANA) to the determination of bisphenol A in a waters. RIANA is based on a rapid solid-phase indirect inhibition immunoassay that takes place at an optical transducer chip chemically modified with an analyte derivative. Fluorescence produced by labelled antibodies bound to the transducer is detected by photodiodes and can be correlated with the analyte concentration. The sensor surface can be regenerated thus allowing the performance of several measurements (around 300) with the same transducer. Each test cycle, including one regeneration step, is accomplished in 15 min. The detection limit achieved in the direct determination of bisphenol A in water with this system was 0.014 microg/L. Satisfactory repeatability, with relative standard deviations (RSD) ranging between 1.48% and 6.93% were obtained. The immunosensor method developed was applied to the monitoring of bisphenol A in various types of water collected in a waterworks (from the river water source to the finished drinking water) and validated against the results obtained in the same approach by a more traditional method, based on solid-phase extraction followed by liquid chromatography-mass spectrometry. Results obtained by both techniques were in general good agreement (considering the typical overestimation bias of immunoassays), and served to prove the satisfactory removal efficiency of the overall purification process applied in the waterworks and, in particular, of the sand filtration step.

Synthesis of haptens for development of antibodies to alkylphenols and evaluation and optimization of a selected antibody for ELISA development

The development of an enzyme-linked immunosorbent assay (ELISA) based on polyclonal antibodies for a class of endocrine disrupting compounds, 4-nonylphenol, is described. The parent molecule was derivatized at the ortho position of the free phenolic hydroxyl group to obtain the hapten, NP1, and it was conjugated with keyhole limpet hemocyanin, which was used as an immunogen. Four antisera were generated and screened against three coating antigens. The most sensitive ELISA from the screening tests (antiserum NP03As, 1/1000, and coating antigen NP1-BSA, 1 microg/mL) was further optimized and characterized. The influence of various physicochemical factors (organic solvent, pH, ion strength) was investigated. Methanol as the additive organic solvent was found to be the best organic solvent for the ELISA, with optimal sensitivity observed at a concentration of 5%. The ELISA parameters were changed at more acidic or basic pH values, whereas higher ionic strengths strongly suppressed the I(50) value and the maximum absorbance. The most sensitive ELISA for 4-nonylphenol exhibited an I(50) value of 38.6 +/- 5.5 microg/L, with a dynamic range from 12 to 350 microg/L, and the lower limit of detection was 7.7 +/- 1.3 microg/L. The optimized ELISA displayed no significant cross-reaction against the parent compounds, nonylphenol ethoxylates, degradation products, carboxylates, and bisphenol A, except in 4-octylphenol.

Development of an indirect competitive ELISA for flumequine residues in raw milk using chicken egg yolk antibodies

To detect flumequine in raw milk, an indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed. By carbodiimide conjugation, flumequine was conjugated to cationized bovine serum albumin (cBSA-flumequine) and to cationized ovalbumin (cOVA-flumequine). For the immunization of chickens, cBSA-flumequine was used, which allowed the isolation of specific chicken egg yolk immunoglobulins (IgY) for flumequine. As the coating antigen in the immunoassay, cOVA-flumequine was used. In the indirect competitive assay, standard flumequine was incubated together with the anti-flumequine antibodies. The antibody by which the lowest concentration of free flumequine that gives 50% inhibition of binding (IC50) was found in aqueous dilution was further tested for the applicability to detect flumequine in raw milk. An IC50 level in milk was reached that was about 5 times lower than in aqueous solution. So flumequine can be detected directly in raw milk at maximum residue level (50 microg/kg). No cross-reactivity was noticed with various related quinolones.

Express detection of nonylphenol in water samples by fluorescence polarization immunoassay

The development of express method for detection of endocrine-disrupting chemicals (EDC) such as alkylphenols is required for ecological monitoring. Several attempts have been made to produce antibodies against 4-nonylphenol (NP) in recent years. This work describes the production of new antibodies against NP and also summarizes the characterization of antibodies obtained earlier. Three approaches used to produce alkylphenol-specific antibodies are compared; these are based on: 1. omega-(4-hydroxyphenyl)nonanoic or omega-(4-hydroxyphenyl)heptanoic acid NP derivatives designed to mimic the linear NP isomer; 2. 4-aminophenol, which potentially mimics various substituted phenolic compounds with different side-chain structures at position 4 of the benzene ring; and 3. a mixture of branched NP isomers, conjugated to the carrier protein via a benzene ring by the Mannich reaction, and expected to be the closest mimic of NP structure by preserving its natural alkyl moiety.Fluorescence polarization immunoassays based on different combinations of antibody and labeled antigen for screening detection of NP were developed and structural aspects of assay sensitivity and specificity were investigated. The assays based on the antisera raised against omega-(4-hydroxyphenyl)nonanoic acid and NP conjugate via Mannich reaction are capable of express detection of NP with detection limit of 7 microg mL(-1 )and assay dynamic range of 18-300 microg mL(-1).