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In this work four different commercially available enzyme-linked immunosorbent assays (ELISA) (from Japan EnviroChemicals, Ltd., Tokyo, Japan) were evaluated in terms of performance for the rapid screening of estrogens in different water matrices, including natural and spiked samples from urban wastewater, river water and ground water. All four test kits are based on monoclonal antibodies. The compounds detected by these immunoassays are (1) 17-beta-estradiol, (2) estrone, (3) 17-alpha-ethynyl estradiol and (4) estrogens in general, with high recognition properties for 17-beta-estradiol, estrone and estriol. Standards were prepared in water containing 10% (v/v) methanol. The IC50 (corresponding to the 50% of the effective concentration) values, the dynamic ranges, and the limits of detection of the ELISA kits were 0.060-0.304 microg/L, 0.05-5 microg/L and 0.05 microg/L, respectively. All samples were extracted by solid-phase extraction (SPE) beforehand, and the evaluation was carried out by comparing the results obtained by ELISA with those obtained by HPLC-MS/MS using a triple quadrupole (QqQ) instrument. In addition, two different solid-phase extraction procedures were carried out and compared. Except for moderate overestimation in the results observed with the ELISA kits in the analysis of complex wastewater samples, the results obtained using all of the tested techniques were generally in very good agreement.

Six kinds of enzyme-linked immunosorbent assay (ELISA) systems were developed for the quantitative analysis of hormone-disrupting chemicals (HDCs), such as estrogen (ES: the total amount of estrone (E1), 17 β-estra (E2) and estriol (E3)), E2, bisphenol A (BPA), alkylphenol (AP), phthalate esters (PE) and chlorophenols (CP). To generate specific monoclonal antibodies against BPA, AP, PE, CP, hybridoma cells were produced by the fusion of mouse myeloma cells and spleen cells from mice immunized with carboxylated derivatives, while anti E2 monoclonal antibody was selected from those available on the market, and anti ES monoclonal antibody was purchased from Teikoku Hormone Mfg Co. Ltd. The detection limits of ES, E2, BPA, AP, PE and CP ELISAs were 0.1, 0.1, 5, 10, 200, 10 μg/L, when E2, E2, BPA, Nonylphenol (NP), Dibutylphthalate (DBP), 2,4-CP were used as standard, respectively, and the specificity of each ELISA was confirmed with the cross-reaction test using several compounds which have structural resemblance to the compounds of interest.

An immunoassay in which BPA competed with a BPA-horseradish peroxidase conjugate for binding to anti-BPA antibodies, coupled to a piezoelectric (PZ) immunosensor, was able to detect 0.1 ng mL(-1) BPA. To enhance the sensitivity of the assay, we tested nanoparticles approximately 200 nm in diameter, coupled to anti-BPA antibodies, to increase the mass change on the surface of the immunosensor and thereby increase the frequency shift detected. This second step, using nanoparticles coated with anti-BPA antibodies, improved the sensitivity of the assay by approximately eight times at BPA concentrations below 10 ng mL(-1). Field emission-scanning electron microscopy (FE-SEM) showed that polymeric 2-methacrolyloxyethyl phosphorylcholine (MPC) nanoparticles coupled to antibodies remained monodisperse on the surface of the immunosensor and therefore produced stable signals in the immunosensors. Since the frequency shift detected in the assay mainly originated from the mass change on the surface of the PZ crystal, the colloidal stability of the antibody-conjugated particles used in the enhancement step played an extremely important role in achieving a stable and highly sensitive signal.