Separation and identification of hormone-active compounds using a combination of chromatographic separation and yeast-based reporter assay

Enhanced Detection of Estrogen-like Compounds by Genetically Engineered Yeast Sensor Strains

The release of endocrine-disrupting compounds (EDCs) to the environment poses a health hazard to both humans and wildlife. EDCs can activate or inhibit endogenous endocrine functions by binding hormone receptors, leading to potentially adverse effects. Conventional analytical methods can detect EDCs at a high sensitivity and precision, but are blind to the biological activity of the detected compounds. To overcome this limitation, yeast-based bioassays have previously been developed as a pre-screening method, providing an effect-based overview of hormonal-disruptive activity within the sample prior to the application of analytical methods. These yeast biosensors express human endocrine-specific receptors, co-transfected with the relevant response element fused to the specific fluorescent protein reporter gene. We describe several molecular manipulations of the sensor/reporter circuit in a Saccharomyces cerevisiae bioreporter strain that have yielded an enhanced detection of estrogenic-like compounds. Improved responses were displayed both in liquid culture (96-well plate format) as well as in conjunction with sample separation using high-performance thin-layer chromatography (HPTLC). The latter approach allows for an assessment of the biological effect of individual sample components without the need for their chemical identification at the screening stage.

Screening bisphenols in complex samples via a planar Arxula adeninivorans bioluminescence bioassay

The Arxula yeast bisphenol screen (A-YBS) utilizes the bioluminescent Arxula adeninivorans yeast-based reporter cells for tailored analysis of bisphenols, one of the major endocrine-disrupting compound groups. For the first time, this bioreporter has been applied on the high-performance thin-layer chromatography (HPTLC) adsorbent surface to develop a respective planar bioluminescence bioassay (pA-YBS). The goal was to combine the advantages of HPTLC with a more selective bioassay detection for bisphenols. The performance of this pA-YBS bioluminescence bioassay was demonstrated by calculating the half-maximal effective concentration (EC50) of bisphenols compared to references. The EC50 ranged from 267 pg/band for bisphenol Z and 322 pg/band for bisphenol A (BPA) to > 1 ng/band for other bisphenols (BPC, BPE, BPF, and BPS) and references (17β-estradiol and 17α-ethinylestradiol). The EC50 value of BPA was three times more sensitive in signal detection than that of 17β-estradiol. The visual or videodensitometric limit of detection of BPA was about 200 pg/zone. The higher signal intensity and sensitivity for BPA confirmed the tailored bioassay selectivity compared to the existing estrogen screen bioassay. It worked on different types of HPTLC silica gel plates. This HPTLC-UV/Vis/FLD-pA-YBS bioluminescence bioassay method was used to analyze complex mixtures such as six tin can migrates, five thermal papers, and eleven botanicals. The detected estrogenic compound zones in the tin can migrates were successfully verified via the duplex planar yeast antagonist estrogen screen (pYAES) bioassay. The two bisphenols A and S were identified in one out of five thermal papers and confirmed with high-resolution mass spectrometry. No bisphenols were detected in the botanicals investigated via the pA-YBS bioluminescence bioassay. However, the botanicals proved to contain phytoestrogens as detected via the pYAES bioassay, which confirmed the tailored bioassay selectivity. This HPTLC-UV/Vis/FLD-pA-YBS bioluminescence bioassay is suited for cost-efficient analysis of BPA in complex samples, with no need for sterile conditions due to the fast workflow.

Methacrylic functionalized hybrid carbon nanomaterial for the selective adsorption and detection of progesterone in wastewater

Progesterone, an endocrine-disrupting chemical, has been frequently detected in wastewater for decades, posing a serious threat to ecological and human health. However, it is still a challenge to achieve the effective detection of progesterone in complex matrices water samples. In this study, a novel adsorbent CNT@CS/P(MAA) was prepared by grafting methacrylic polymers on the surface of modified carbon nanomaterials. Compared with other reported materials, the hybrid carbon nanomaterial could selectively identify the progesterone in the complex industrial pharmaceutical wastewater, and its adsorption performance is almost independent of the pH and environmental temperature. In addition, this nanomaterial could be reused with a good recovery rate. The prepared nanomaterials were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, nitrogen adsorption and desorption experiments, and thermogravimetric analysis. The results confirmed that the methacrylic polymers and chitosan layer were successfully grafted on the surface of carbon nanotubes. Adsorption isotherms, adsorption kinetics, and selectivity tests showed that CNT@CS/P(MAA) had a high adsorption capacity (44.45 mg·g-1), a fast adsorption rate and a satisfied selectivity for progesterone. Then, CNT@CS/P(MAA) was used as solid phase extraction sorbent and combined with HPLC to enrich progesterone from the wastewater samples. Under the optimum conditions, a good linearity was obtained with the correlation coefficient was 0.9998, and the limit of detection was 0.003 ng·mL-1. Therefore, this method could be used for the selective and effective detection of progesterone in industrial wastewater with complex substrates and provided a new method for the detection of progesterone in other environmental waters.

High-performance thin-layer chromatography in combination with a yeast-based multi-effect bioassay to determine endocrine effects in environmental samples

Effect-directed analysis (EDA) that combines effect-based methods (EBMs) with high-performance thin-layer chromatography (HPTLC) is a useful technique for spatial, temporal, and process-related effect evaluation and may provide a link between effect testing and responsible substance identification. In this study, a yeast multi endocrine-effect screen (YMEES) for the detection of endocrine effects is combined with HPTLC. Simultaneous detection of estrogenic, androgenic, and gestagenic effects on the HPTLC plate is achieved by mixing different genetically modified Arxula adeninivorans yeast strains, which contain either the human estrogen, androgen, or progesterone receptor. Depending on the yeast strain, different fluorescent proteins are formed when an appropriate substance binds to the specific hormone receptor. This allows to measure hormonal effects at different wavelengths. Two yeast cell application approaches, immersion and spraying, are compared. The sensitivity and reproducibility of the method are shown by dose-response investigations for reference compounds. The spraying approach indicated similar sensitivities and higher precisions for the tested hormones compared to immersion. The EC₁₀s for estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), 5α-dihydrotestosterone (DHT), and progesterone (P4) were 95, 1.4, 10, 7.4, and 15 pg/spot, respectively. Recovery rates of E1, E2, EE2, DHT, and P4 between 88 and 120% show the usability of the general method in combination with sample enrichment by solid phase extraction (SPE). The simultaneous detection of estrogenic, androgenic, and gestagenic effects in wastewater and surface water samples demonstrates the successful application of the YMEES in such matrices. This promising method allows us to identify more than one endocrine effect on the same HPTLC plate, which saves time and material. The method could be used for comparison, evaluation, and monitoring of different river sites and wastewater treatment steps and should be tested in further studies.

Yeast-Based Fluorescent Sensors for the Simultaneous Detection of Estrogenic and Androgenic Compounds, Coupled with High-Performance Thin Layer Chromatography

The persistence of endocrine disrupting compounds (EDCs) throughout wastewater treatment processes poses a significant health threat to humans and to the environment. The analysis of EDCs in wastewater remains a challenge for several reasons, including (a) the multitude of bioactive but partially unknown compounds, (b) the complexity of the wastewater matrix, and (c) the required analytical sensitivity. By coupling biological assays with high-performance thin-layer chromatography (HPTLC), different samples can be screened simultaneously, highlighting their active components; these may then be identified by chemical analysis. To allow the multiparallel detection of diverse endocrine disruption activities, we have constructed Saccharomyces cerevisiae-based bioreporter strains, responding to compounds with either estrogenic or androgenic activity, by the expression of green (EGFP), red (mRuby), or blue (mTagBFP2) fluorescent proteins. We demonstrate the analytical potential inherent in combining chromatographic compound separation with a direct fluorescent signal detection of EDC activities. The applicability of the system is further demonstrated by separating influent samples of wastewater treatment plants, and simultaneously quantifying estrogenic and androgenic activities of their components. The combination of a chemical separation technique with an optical yeast-based bioassay presents a potentially valuable addition to our arsenal of environmental pollution monitoring tools.

Combination of yeast-based in vitro screens with high-performance thin-layer chromatography as a novel tool for the detection of hormonal and dioxin-like compounds

The combination of classic in vitro bioassays with high-performance thin-layer chromatography (HPTLC) is a promising technique to directly link chemical analysis of contaminants to their potential adverse biological effects. With respect to endocrine disruption, much work is focused on estrogenicity. While a direct combination of HPTLC and the yeast estrogen screen is already developed, it is well accepted that further endocrine effects are relevant for monitoring environmental wellbeing. Here we show that non-estrogenic specific biological endpoints, (partly) related to the endocrine system, can also be addressed by combining respective yeast reporter gene assays with HPTLC to support effect-directed analysis (EDA). These are: androgenicity (YAS), thyroidogenicity (YTS), dioxin-like effects (YDS), effects on the vitamin D (YVS) and the retinoic acid receptor (YRaS). A proof of principle is demonstrated within this study by the characterization of dose-dependent responses to different model compounds for the respective receptors with and without chromatographic development of the HPTLC-plate. Limits of quantification (LOQ) for several model compounds were determined, e.g. 37 pg for testosterone (p-YAS), 0.476 ng for β-naphthoflavone (p-YDS) and 1.02 ng for calcipotriol hydrate (p-YVS) with chromatographic development. The LOQ for p-YTS and p-YRaS were 10.16 pg for 3,3',5-triiodothyroacetic acid (p-YTS) and 0.41 pg for tamibarotene (p-YRaS), without chromatographic separation. Furthermore, we challenged the developed methodology using environmental samples, demonstrating an elimination efficiency of androgenic activity from municipal wastewater by a wastewater treatment plant between 99.4 and 100%. We anticipate our methodology to substantially broaden the spectrum of specific endpoints combined with HPTLC for an efficient and robust screening of environmental samples to guide a subsequent in-depth EDA.

Coupling High-Performance Thin-Layer Chromatography with Bacterial Genotoxicity Bioreporters

We present an innovative technological platform for monitoring the direct genotoxicity of individual components in complex environmental samples, based on bioluminescent Escherichia coli genotoxicity bioreporters, sprayed onto the surface of a high-performance thin-layer chromatography (HPTLC) plate. These sensor strains harbor plasmid-borne fusions of selected gene promoters of the E. coli SOS DNA repair system to the Photorhabdus luminescens luxABCDE gene cassette, and mark by increased luminescence the presence of potentially DNA-damaging sample components separated on the plate. We demonstrate an "on plate" quantifiable dose-dependent response to several model genotoxicants (without metabolic activation). We further demonstrate the applicability of the system by identifying as genotoxic specific components of HPTLC-separated influent and effluent samples of wastewater treatment plants, thereby alleviating the need for a comprehensive chemical analysis of the sample.

Validation of Arxula Yeast Estrogen Screen assay for detection of estrogenic activity in water samples: Results of an international interlaboratory study

Endocrine-active substances can adversely impact the aquatic ecosystems. A special emphasis is laid, among others, on the effects of estrogens and estrogen mimicking compounds. Effect-based screening methods like in vitro bioassays are suitable tools to detect and quantify endocrine activities of known and unknown mixtures. This study describes the validation of the Arxula-Yeast Estrogen Screen (A-YES®) assay, an effect-based method for the detection of the estrogenic potential of water and waste water. This reporter gene assay, provided in ready to use format, is based on the activation of the human estrogen receptor alpha. The user-friendly A-YES® enables inexperienced operators to rapidly become competent with the assay. Fourteen laboratories from four countries with different training levels analyzed 17β-estradiol equivalent concentrations (EEQ) in spiked and unspiked waste water effluent and surface water samples, in waste water influent and spiked salt water samples and in a mixture of three bisphenols. The limit of detection (LOD) for untreated samples was 1.8ng/L 17β-estradiol (E2). Relative repeatability and reproducibility standard deviation for samples with EEQ above the LOD (mean EEQ values between 6.3 and 20.4ng/L) ranged from 7.5 to 21.4% and 16.6 to 28.0%, respectively. Precision results are comparable to other frequently used analytical methods for estrogens. The A-YES® has been demonstrated to be an accurate, precise and robust bioassay. The results have been included in the ISO draft standard. The assay was shown to be applicable for testing of typical waste water influent, effluent and saline water. Other studies have shown that the assay can be used with enriched samples, which lower the LOD to the pg/L range. The validation of the A-YES® and the development of a corresponding international standard constitute a step further towards harmonized and reliable bioassays for the effect-based analysis of estrogens and estrogen-like compounds in water samples.