Interaction between laccase and diethylstilbestrol based on multispectral and chromatography analyses.

Diethylstilbestrol (DES) is a synthetic form of oestrogen that does not easily degrade in the environment and can be harmful to human health. Herein, the mechanism of the interaction between laccase and DES was investigated by various spectroscopic means and high-performance liquid chromatography (HPLC). The results of fluorescence experiments showed that the quenching of intrinsic fluorescence of laccase by DES was due to a static quenching, forming a binding site. According to the Förster non-radiative energy transfer theory (FRET), the action distance R0 between DES and laccase was 4.708 nm, r was 5.81 nm, and the energy transfer efficiency E was 22.08%, respectively. Both UV-Vis absorption spectra and FT-IR spectra indicated changes in the conformation and surroundings of the enzyme and changed in the secondary structure of laccase. Multispectral synthesis showed that the interaction of laccase with DES caused a change in the secondary structure of laccase. The degradation experiments showed that laccase could degrade DES, and the DES content decreased with time. This study provides a new theoretical basis and experimental method for further research on the reaction mechanism of the laccase degradation of DES. It may also provide a reference basis for human biological and environmental safety evaluations.

Diethylstilbestrol Modifies the Structure of Model Membranes and Is Localized Close to the First Carbons of the Fatty Acyl Chains.

The synthetic estrogen diethylstilbestrol (DES) is used to treat metastatic carcinomas and prostate cancer. We studied its interaction with membranes and its localization to understand its mechanism of action and side-effects. We used differential scanning calorimetry (DSC) showing that DES fluidized the membrane and has poor solubility in DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) in the fluid state. Using small-angle X-ray diffraction (SAXD), it was observed that DES increased the thickness of the water layer between phospholipid membranes, indicating effects on the membrane surface. DSC, X-ray diffraction, and 31P-NMR spectroscopy were used to study the effect of DES on the Lα-to-HII phase transition, and it was observed that negative curvature of the membrane is promoted by DES, and this effect may be significant to understand its action on membrane enzymes. Using the 1H-NOESY-NMR-MAS technique, cross-relaxation rates for different protons of DES with POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) protons were calculated, suggesting that the most likely location of DES in the membrane is with the main axis parallel to the surface and close to the first carbons of the fatty acyl chains of POPC. Molecular dynamics simulations were in close agreements with the experimental results regarding the location of DES in phospholipids bilayers.

An ultrasensitive electrochemiluminescence aptasensor for the detection of diethylstilbestrol based on the enhancing mechanism of the metal-organic framework NH2-MIL-125(Ti) in a 3,4,9,10-perylenetetracarboxylic acid/K2S2O8 system.

In this work, a sensitive and selective electrochemiluminescent aptasensor was proposed based on the enhancing mechanism of the metal-organic framework NH2-MIL-125(Ti) in a 3,4,9,10-perylenetetracarboxylic acid/K2S2O8 system for a diethylstilbestrol assay. Herein, 3,4,9,10-perylenetetracarboxylic acid was selected as the major luminophore, and the metal-organic framework NH2-MIL-125(Ti) displayed a large specific surface area to immobilize abundant PTCA molecules to facilitate electrochemiluminescence efficiency. Besides, the metal-organic framework NH2-MIL-125(Ti) was used as a novel catalyst in the 3,4,9,10-perylenetetracarboxylic acid/K2S2O8 system, which could react with the co-reactant K2S2O8 to produce more SO4˙-. In addition, we introduced the amino-aptamer of diethylstilbestrol; due to the specific binding affinity between the aptamer and diethylstilbestrol, a selective electrochemiluminescent aptasensor for diethylstilbestrol was thus developed here. Under the optimal conditions, a wide detection range from 1.0 fM to 1.0 µM with a low detection limit of 0.28 fM (S/N = 3) was obtained. More importantly, the residual diethylstilbestrol in water was detected by the developed aptasensor; this confirmed that this method has good performance and potential applications in real samples.

Estrogen receptor alpha (ERα)-mediated coregulator binding and gene expression discriminates the toxic ERα agonist diethylstilbestrol (DES) from the endogenous ERα agonist 17ß-estradiol (E2).

Diethylstilbestrol (DES) is a synthetic estrogen and proven human teratogen and carcinogen reported to act via the estrogen receptor α (ERα). Since the endogenous ERα ligand 17ß-estradiol (E2) does not show these adverse effects to a similar extent, we hypothesized that DES' interaction with the ERα differs from that of E2. The current study aimed to investigate possible differences between DES and E2 using in vitro assays that detect ERα-mediated effects, including ERα-mediated reporter gene expression, ERα-mediated breast cancer cell (T47D) proliferation and ERα-coregulator interactions and gene expression in T47D cells. Results obtained indicate that DES and E2 activate ERα-mediated reporter gene transcription and T47D cell proliferation in a similar way. However, significant differences between DES- and E2-induced binding of the ERα to 15 coregulator motifs and in transcriptomic signatures obtained in the T47D cells were observed. It is concluded that differences observed in binding of the ERα with several co-repressor motifs, in downregulation of genes involved in histone deacetylation and DNA methylation and in upregulation of CYP26A1 and CYP26B1 contribute to the differential effects reported for DES and E2.

The cajanine derivative LJ101019C regulates the proliferation and enhances the activity of NK cells via Kv1.3 channel-driven activation of the AKT/mTOR pathway.

BACKGROUND: Natural killer (NK) cells play important roles in immune responses and have been wildly used in immunotherapy. Nevertheless, some limitations remain. It is urgent to explore novel and safe strategies to enhance NK cell activity. PURPOSE: The aim of this study was to investigate the immuno-stimulatory effects and to reveal the molecular mechanism of LJ101019C, a derivative of a natural small-molecule compounds cajanine, on NK cells. METHODS: Cell proliferation was examined by CCK8 assay, then we used the cytotoxicity detection kit to detect the cytotoxicity of NK cells. The change of cell cycle, intracellular reactive oxygen species (ROS) level and mitochondrial mass were evaluated by FACS and Operetta high-content image analysis, respectively. Furthermore, the IFN-γ secretion of NK cells were measured by ELISA. The Kv1.3 protein expression and function were detected by western blot and patch-clamp technique, respectively. The role of Kv1.3 in AKT/mTOR pathway activation was determined by western blot. RESULTS: The results showed that LJ101019C at relatively low concentrations (0.05-0.1 µM) significantly increased the proliferation of NK cells. And 1 µM LJ101019C could elevate the proportion of NK cells in the S-phase of the cell cycle (*p < 0.1). Furthermore, the cytotoxic effects of NK cells targeting MIA PaCa-2 cells were significantly enhanced by 0.1 and 1 µM LJ101019C, and were associated with the enhanced secretion of IFN-γ by NK cells (*p < 0.1; **p < 0.05). 0.1 and 1 µM LJ101019C increased intracellular levels of ROS (**p < 0.05), and 0.1 µM LJ101019C elevated mitochondrial mass (*p < 0.1). Electrophysiological recordings indicated that LJ101019C led to a remarkably increase the Kv1.3 current density. Moreover, western blot results indicated that LJ101019C elevated Kv1.3 protein expression and activated AKT/mTOR signaling via increasing the expression of Kv1.3 in NK cells. CONCLUSION: LJ101019C increases the proliferation and the cytotoxicity of NK cells at relatively low concentrations. The mechanism is the activation of AKT/mTOR signaling pathway driven by up-regulation of Kv1.3 in NK cells. These suggest LJ101019C is a promising candidate for improving the efficacy of NK cell-based immunotherapies.

Multi-Residue Method for the Analysis of Stilbene Estrogens in Milk.

The rapid analysis of stilbene estrogens is crucially important in the environment, food and health sectors, but quantitation of lower detection limit for stilbene estrogens persists as a severe challenge. We herein described a homologous and sensitive fluorescence polarization (FP) assay based on estrogen receptor α ligand binding domain (ER-LBD) to monitor stilbene estrogens in milk. Under optimal conditions, the half maximal inhibitory concentrations (IC50) of the FP assay were 9.27 nM, 12.94 nM, and 22.38 nM for hexestrol, dienestrol and diethylstilbestrol, respectively. And the corresponding limits of detection (LOD) values were 2.94 nM, 2.89 nM, and 3.12 nM. Finally, the assay was applied to determine the stilbenes in milk samples where the mean recoveries ranged from 95.76% to 112.78% and the coefficients of variation (CV) below 12.00%. Furtherly, we have focused our study on high cross-reactivity phenomena by using two in silico approaches, including molecular docking analysis and topology analysis. Overall, docking results show that several residues in the hydrophobic pocket produce hydrophobic interactions with the tested drug molecules, which contribute to the stability of their binding. In this paper, we conclude that the FP method is suitable for the rapid detection of stilbenes in milk samples, requiring no expensive analytical equipment or time-consuming sample preparation. This work offers a practical approach that applies bioscience technology in food safety testing and improves analytical speed and laboratory efficiency.

Polyacetal-Based Combination Therapy for the Treatment of Prostate Cancer.

The high incidence of prostate carcinogenesis has prompted the search for novel effective treatment approaches. We have employed curcumin (Curc) and diethylstilbestrol (DES) to synthesize a series of polyacetal (PA)-based combination conjugates for prostate cancer (PCa) treatment. Given their bihydroxyl functionalities, Curc and DES molecules were incorporated into a PA mainchain using a one-pot reaction between diols and divinyl ethers. The PA-conjugates released both drugs under acidic conditions, such as those found in the tumor microenvironment, endosomes, or lysosomes, while remaining stable at neutral pH 7.4. The drug ratio was optimized to achieve anticancer drug synergism with elevated cytotoxicity against LNCaP-hormone-dependent human PCa cells conferred via the induction of S phase cell cycle arrest by the upregulation of p53 and CDK inhibitors p21Waf/CIP1 and downregulation of cyclin D1. The application of rationally designed PA-Curc-DES combination conjugates represents a potentially exciting new treatment for prostate cancer.

UV photoconversion of environmental oestrogen diethylstilbestrol and its persistence in surface water under sunlight.

As one of the most oestrogenic synthetic compounds in water environment, diethylstilbestrol (DES) has been studied for decades. Some studies showed that DES can be removed by ultraviolet (UV) irradiation. However, no one has paid attention to the formation of oestrogenic disinfection by-products (DBPs) and the persistence of DES in surface water remains a mystery. In this study, UV was found to be very effective in removing oestrogenic activity regardless of water quality. Three oestrogenic DBPs were specifically isolated by oestrogen receptor-based affinity chromatography and identified as 9,10-diethylphenanthrene-3,6-diol, cis-DES and Z,Z-dienestrol. Among them, 9,10-diethylphenanthrene-3,6-diol was proved to have stronger oestrogenic activity than E2, but it can be further photodegraded. In addition, DES was also demonstrated to be a photochromic compound, whose UV-induced intermediates can be transformed back to DES under sunlight, which significantly slows down the photodegradation of DES. This study solves the question as to why UV-degradable DES is still detectable in the ambient water and provides a deep understanding of DES removal during UV disinfection.

HIF-1α inhibition by diethylstilbestrol and its polyacetal conjugate in hypoxic prostate tumour cells: insights from NMR metabolomics.

In this study, we have employed 1H NMR metabolomics to assess the metabolic responses of PC3 prostate tumour cells to hypoxia and to pharmacological HIF-1α inhibition by DES or its polyacetal conjugate tert-DES. Oxygen deprivation prompted a number of changes in intracellular composition and metabolic activity, mainly reflecting upregulated glycolysis, amino acid catabolism and other compensatory mechanisms used by hypoxic cells to deal with oxidative imbalance and energy deficit. Cell treatment with a non-cytotoxic concentration of DES, under hypoxia, triggered significant changes in 17 metabolites. Among these, lactate, phosphocreatine and reduced glutathione, whose levels showed opposite variations in hypoxic and drug-treated cells, emerged as possible markers of DES-induced HIF-1α inhibition. Furthermore, the free drug had a much higher impact on the cellular metabolome than tert-DES, particularly concerning polyamine and pyrimidine biosynthetic pathways, known to be tightly involved in cell proliferation and growth. This is likely due to the different cell pharmacokinetics observed between free and conjugated DES. Overall, this study has revealed a number of unanticipated metabolic changes that inform on DES and tert-DES direct cellular effects, providing further insight into their mode of action at the biochemical level.

Persulfate-assisted photodegradation of diethylstilbestrol using monoclinic BiVO4 under visible-light irradiation.

In this study, the photosynergistic performance of BiVO4 with persulfate (PS) is demonstrated under visible light irradiation for the first time. Diethylstilbestrol (DES) was selected as a reluctant compound, and factors including dosages of PS and catalyst, solution pHs, initial concertration of DES, and inorganic anions were evaluated. The morphology and chemical state of bismuth vanadate (BiVO4) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), and ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy (DRS). It was found that the degradation of DES was promoted in either acid or alkaline solutions. The increase of PS and BiVO4 dosages was beneficial to the reactions, while incremental concentration of DES showed the inhibiting effect. By scavenging hVB+, Cl- was able to make the promotion, differentiated from the exsiting HCO- 3. Moreover, the photocatalytic mechanism for the BiVO4/PS/vis-light system was proposed by using several probe compounds (isopropanol, tert-butanol, and 1,4-benzoquinone), which consists of h+ VB/e- CB generation and recombination on the surface of BiVO4 as well as free radical oxidation in the solutions. The study provides a distinctive method to treat organic contaminants using visible light in the aqueous environment.

Design and Synthesis of Cajanine Analogues against Hepatitis C Virus through Down-Regulating Host Chondroitin Sulfate N-Acetylgalactosaminyltransferase 1.

There still remains a need to develop new anti-HCV agents with distinct mechanism of action (MOA) due to the occurrence of resistance to direct-acting antiviral agents (DAAs). Cajanine, a stilbenic component isolated from Cajanus cajan L., was identified as a potent HCV inhibitor by phenotypic screening in this work (EC50 = 3.17 ± 0.75 µM). The intensive structure optimization provided significant insights into the structure-activity relationships. Furthermore, the MOA study revealed that cajanine inhibited HCV replications via down-regulating a cellular protein chondroitin sulfate N-acetylgalactosaminyltransferase 1. In consistency with this host-targeting mechanism, cajanine showed the similar magnitude of inhibitory activity against both drug-resistant and wild-type HCV and synergistically inhibited HCV replication with approved DAAs. Taken together, our study not only presented cajanine derivatives as a novel class of anti-HCV agents but also discovered a promising anti-HCV target to combat drug resistance.

Using Fenton Oxidation to Simultaneously Remove Different Estrogens from Cow Manure.

The presence of estrogens in livestock excrement has raised concerns about their potential negative influence on animals and the overall food cycle. This is the first investigation to simultaneously remove estrogens, including estriol (E3), bisphenol A (BPA), diethylstilbestrol (DES), estradiol (E2), and ethinyl estradiol (EE2), from cow manure using a Fenton oxidation technique. Based on the residual concentrations and removal efficiency of estrogens, the Fenton oxidation reaction conditions were optimized as follows: a H2O2 dosage of 2.56 mmol/g, a Fe(II) to H2O2 molar ratio of 0.125 M/M, a solid to water mass ratio of 2 g/mL, an initial pH of 3, and a reaction time of 24 h. Under these conditions, the simultaneous removal efficiencies of E3, BPA, DES, E2, and EE2, with initial concentrations in cow manure of 97.40, 96.54, 100.22, 95.01, and 72.49 mg/kg, were 84.9%, 99.5%, 99.1%, 97.8%, and 84.5%, respectively. We clarified the possible Fenton oxidation reaction mechanisms that governed the degradation of estrogens. We concluded that Fenton oxidation technique could be effective for efficient removal of estrogens in livestock excrement. Results are of great importance for cow manure reuse in agricultural management, and can be used to reduce the threat of environmental estrogens to human health and ecological safety.

Possible relationship between endocrine disrupting chemicals and hormone dependent gynecologic cancers.

The effects of the natural and synthetic estrogens have been studied for a long time but the data regarding estrogen related chemicals (endocrine disrupting chemicals, EDCs) and their effects on reproductive system are scarce. EDCs are hormone like agents that are readily present in the environment, which may alter the endocrine system of humans and animals. Approximately 800 chemicals are known or suspected to have the potential to function as EDC. Potential role of EDCs on reproductive disease has gained attention in medical literature in recent years. We hypothesize that exposure to low doses of EDCs in a chronic manner could cause hormone dependent genital cancers including ovarian and endometrial cancer. Long term exposure to low concentrations of EDCs may exert potentiation effect with each other and even with endogenous estrogens and could inhibit enzymes responsible for estrogen metabolism. Exposure time to these EDCs is essential as we have seen from Diethylstilbestrol experience. Dose-response curves of EDCs are also unpredictable. Hence mode of action of EDCs are more complex than previously thought. In the light of these controversies lower doses of EDCs in long term exposure is not harmless. Possibility of this relationship and this hypothesis merit further investigation especially through in vivo studies that could better show the realistic environmental exposure. With the confirmation of our hypothesis, possible EDCs could be identified and eliminated from general use as a public health measure.

Occurrence and removal of phenolic endocrine disrupting chemicals in the water treatment processes.

This paper evaluated the occurrence and removal efficiency of four selected phenolic endocrine disrupting chemicals (bisphenol A (BPA), octylphenol (OP), nonylphenol (NP) and diethylstilbestrol (DES)) in two drinking waterworks in Jiangsu province which take source water from Taihu Lake. The recombined yeast estrogen screen (YES) and liquid chromatography tandem mass spectrometry (LC-MS/MS) were applied to assess the estrogenicity and detect the estrogens in the samples. The estrogen equivalents (EEQs) ranged from nd (not detected) to 2.96 ng/L, and the estrogenic activities decreased along the processes. Among the 32 samples, DES prevailed in all samples, with concentrations ranging 1.46-12.0 ng/L, BPA, OP and NP were partially detected, with concentrations ranging from nd to 17.73 ng/L, nd to 0.49 ng/L and nd to 3.27 ng/L, respectively. DES was found to be the main contributor to the estrogenicity (99.06%), followed by NP (0.62%), OP (0.23%) and BPA (0.09%). From the observation of treatment efficiency, the advanced treatment processes presented much higher removal ratio in reducing DES, the biodegradation played an important role in removing BPA, ozonation and pre-oxidation showed an effective removal on all the four estrogens; while the conventional ones can also reduce all the four estrogens.

Synthetic cajanin stilbene acid derivatives inhibit c-MYC in breast cancer cells.

In the present study, we investigated the activity and modes of action of cajanin stilbene acid (CSA) and its derivatives in terms of cytotoxicity, gene expression profile, and transcription factor activity. XTT assays on MCF7 cells were performed upon treatment with CSA or derivatives. After the determination of IC50 values, gene expression profiling was performed with Agilent microarray experiments. Deregulated genes were determined with Chipster software, pathway and functional analyses were performed with Ingenuity pathway software. In order to identify the potential upstream regulators, MatInspector software was used to perform transcription factor binding motif search in the promoter regions of the deregulated genes. Molecular docking on MYC/MAX complex and reporter cell line experiments were performed to validate the MYC inhibitory activity of CSA and its derivatives. Two known MYC inhibitors: 10058-F4 and 10074-G5 were used as positive control. All compounds showed cytotoxicities in the micromolar range. Microarray analyses pointed to cell cycle, DNA damage, and DNA repair as mainly affected cellular functions. Promoter motif analysis of the deregulated genes further supported the microarray gene expression analysis results emphasizing the relevance of transcription factors regulating cell cycle and proliferation, with MYC as being the most pronounced one. Luciferase-based reporter cell line experiments and molecular docking studies yielded supportive results emphasizing the inhibitory activity of CSA and its derivatives on MYC. CSA and its derivatives are shown to be promising anticancer compounds with low toxicity. They inhibit MYC activity comparable to 10058-F4 and 10074-G5. Further studies are warranted to analyze the therapeutic applicability of these compounds in more detail.

Determination of diethylstilbestrol in seawater by molecularly imprinted solid-phase extraction coupled with high-performance liquid chromatography.

An effective and highly selective molecularly imprinted material was prepared by suspension polymerization for the isolation and pre-concentration of synthetic estrogen diethylstilbestrol (DES) in seawater. The obtained MIPMs were proved to have more uniform size and porous structure, with maximum adsorption capacity of 8.43 mg g(-1) almost two times more than NIPMs (4.43 mg g(-1)). The MIPMs showed no significant deterioration of the adsorption capacity after five rounds of regeneration. An off-line molecularly imprinted solid phase extraction (MISPE) method followed by HPLC-DAD was proposed for the detection of DES in seawater, and recoveries were satisfactorily higher than 77%. Four seawater samples in aquaculture area were analyzed and 0.61 ng mL(-1) DES was detected in one sample. The result demonstrated that this method can be used for the rapid separation and clean up of trace residual of DES in seawater.

Picogram-level quantification of some growth hormones in bovine urine using mixed-solvent bubble-in-drop single drop micro-extraction.

Growth hormones are important biologically active compounds. However, they can cause deleterious effects if not used with care and their use in farmed animals is banned in the European Union. This study presents the development and application of a mixed-solvent "bubble-in-drop single drop micro-extraction" (BID-SDME) method for enrichment of stilbene hormones in bovine urine samples. The hormones are quantified using GC-MS showing good linearity with the coefficient of determination (R(2)) of 0.999 and 0.999 for hexestrol and diethylstilbestrol, respectively, in the concentration range 0.05-10 ng mL(-1). Excellent precision (RSD<10%) and accuracy (using a bovine urine certified reference material) were obtained. The observed detection capability (CCα, or LOD) values were 0.01 ng mL(-1) (hexestrol), 0.03 ng mL(-1) (cis-diethylstilbestrol) and 0.02 ng mL(-1) (trans-diethylstilbestrol), respectively, while the decision limit (CCß, or LOQ) values were 0.03 ng mL(-1), 0.08 ng mL(-1) and 0.07 ng mL(-1), which are comparable to or better than those reported in literature. Importantly, sample handling is significantly simplified by our method and enrichment values are greatly enhanced. The results show that a 3:1 chloroform/toluene mixture gave the highest extraction efficiency with a drop-bubble ratio of 2:1. We highlight the importance of solvent density on the success of the BID-SDME method.

Diethylstilbestrol-scaffold-based pregnane X receptor modulators.

Due to its function as a regulator of drug-metabolizing enzymes and transporters, pregnane X receptor (PXR) represents an important factor involved in drug metabolism. In this work, we describe the discovery of diethylstilbestrol-based PXR modulators, which were designed from marine sulfated steroids with PXR agonistic activity, solomonsterols A and B, and our recently reported bazedoxifene scaffold-derived PXR antagonists. The methylated diethylstilbestrol derivative 1 displayed potent PXR agonistic activity with an EC50 value of 10.5 µM, whereas compounds 3, 4 and 6 (IC50 for 6 = 27.4 µM) and diethylstilbestrol (2) itself (IC50 = 14.6 µM) exhibited PXR antagonistic effects in HepG2 cells. The PXR modulatory effects of the synthesized diethylstilbestrol derivatives were further confirmed by the induction of PXR-regulated CYP3A4 expression with compound 1, as well as by the inhibition of the rifaximin-promoted up-regulation of CYP3A4 expression with 2 and its derivative 6.

Performance of metal-organic framework MIL-101 after surfactant modification in the extraction of endocrine disrupting chemicals from environmental water samples.

The research presented in this paper explored the modification and application of a metal-organic framework, MIL-101, with nonionic surfactant-Triton X-114 in dispersive solid-phase extraction for the preconcentration of four endocrine disrupting chemicals (estrone, 17α-ethynylestradiol, estriol and diethylstilbestrol) from environmental water samples. Triton X-114 molecules could be adsorbed by the hydrophobic surface of the MIL-101 crystals, and thus improved the dispersibility of MIL-101 in aqueous solution by serving as a hydrophilic coating. Cloud point phase separation from Triton X-114 accelerated the separation of extracts from the aqueous matrix. The proposed method combines the favorable attributes of strong adsorption capacity resulting from the porous structure of MIL-101 and self-assembly of Triton X-114 molecules. Post-extraction derivatization using N-methyl-N-(trimethylsilyl)trifluoroacetamide was employed to facilitate the quantitative determination of the extracts by gas chromatography-mass spectrometry. The main factors affecting the preparation of modified MIL-101, and extraction of the analytes, such as the amount of surfactant, the ultrasonic and vortex durations, solution pH and desorption conditions, were investigated in detail. Under the optimized conditions, the present method yielded low limits of detection (0.006-0.023 ng/mL), good linearity from 0.09 to 45 ng/mL (coefficients of determination higher than 0.9980) and acceptable precision (relative standard deviations of 2.2-13%). The surface modified MIL-101 was demonstrated to be effective for the extraction of the selected estrogens from aqueous samples, giving rise to markedly improved extraction performance compared to the unmodified MIL-101.

Novel molecularly imprinted stir bar sorptive extraction based on an 8-electrode array for preconcentration of trace exogenous estrogens in meat.

A novel 8-electrode array as stir bar was designed for selective extraction of trace level exogenous estrogens from food samples, followed by liquid desorption and HPLC-photodiode array detection. The array consisted of 8 screen-printed electrodes and each electrode was modified with Fe3O4@meso-/macroporous TiO2 microspheres and molecularly imprinted film (m-TiMIF). The fabrication of the imprinted film coating was very simple without organic solvents and chemical grafting. Both bisphenol A (BPA) and diethylstilbestrol (DES) were employed as templates in m-TiMIF fabrication in order to enrich both targets simultaneously. Interestingly, the imprinted stir bar array showed higher extraction capacity and selectivity for BPA and DES than the non-imprinted counterpart. Meanwhile, it exhibited fast adsorption and desorption kinetics due to increased mass transport in the ultra-thin film. Importantly, the m-TiMIF coating was robust enough for at least 20 uses without obvious alteration in extraction performance. The main parameters affecting the extraction efficiency, including stir speeding, sample pH, ionic strength, extraction time, desorption solvent and time, were optimized. Under optimal experimental conditions, the limits of detection (S/N=3) of the developed method were 0.28 and 0.47 µg L(-1) for BPA and DES respectively, with enrichment factors of 32.6 and 52.8-fold. The linear ranges were 3.0-1500 µg L(-1) and 4.0-1500 µg L(-1) for BPA and DES, respectively. The m-TiMIF-coating conferred better recovery and selectivity, compared with the commercial stir bar coating. The new method was successfully applied to assess BPA and DES in pork and chicken samples with satisfactory recovery.