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PubMed2005

A new method for quantifying the intensity of the C=C band of dimethacrylate dental monomers in their FTIR and Raman spectra.

The degree of conversion (DC) of methacrylate dental resins is typically determined by spectroscopically measuring the decrease of the vinyl (C=C) stretching band at 1640 cm(-1), ratioed before and after polymerization to an internal standard (aromatic ring quadrant stretching vibration (Ph)) at around 1609 cm(-1). While standard methods exist for measuring the intensity of the C=C and Ph peaks from the FTIR or Raman spectrum, these methods either fail under certain circumstances, or lack a physical basis, being purely based on spectral features. In this study, we present a rigorous method (named rotational isomerism method) for determining the intensity of the vinyl and aromatic bands from the FTIR and Raman spectra of dental monomer mixtures, and compare it to a standard baseline method (SBM) and a standard curve fitting method. Model triethyleneglycol dimethacrylate (TEGDMA)/2,2-bis(4-hydroxyphenyl)propane (Bisphenol-A) and TEGDMA/2,2-bis(4-(2-hydroxy-3-methacryloxypropoxy)phenyl)propane (Bis-GMA) mixtures with a series of known C=C/Ph molar ratios were prepared in order to simulate the effect of curing. The accuracy of the new method for measuring the DC was found to be as good as the commonly used SBM. The standard curve fitting method was shown to be inappropriate for measuring C=C/Ph ratios by FTIR spectroscopy due to its inability to realistically simulate the features of the spectra. The insight gained through the use of this new method may be useful for the characterization of other methacrylate biomaterials.

Benzhydryl Compounds↗
PubMed2002

Synthesis of 2,2'-dihydroxybisphenols and antiviral activity of some bisphenol derivatives.

New diphenylmethane-type 2,2'-dihydroxybisphenols (5a-d) were prepared regioselectively in good yields. We evaluated the antiviral activity of some bisphenol derivatives synthesized by the plaque reduction assay. Most of the compounds showed significant antiviral activity and the 4,4'-dihydroxybisphenol derivative (10) showed higher activity than 2,2'-bisphenol derivatives. This compound had EC50 value of 1.8 microg/ml.

Antiviral Agents↗
PubMed2003

Potent estrogenic metabolites of bisphenol A and bisphenol B formed by rat liver S9 fraction: their structures and estrogenic potency.

We previously demonstrated that the estrogenicity of either bisphenol A [BPA; 2,2-bis(4-hydroxyphenyl)propane] or bisphenol B [BPB; 2,2-bis(4-hydroxyphenyl)butane] was increased several times after incubation with rat liver S9 fraction (Yoshihara et al., 2001). This metabolic activation, requiring both microsomal and cytosolic fractions, was observed with not only rat liver, but also human, monkey, and mouse liver S9 fractions. To characterize the active metabolites of BPA and BPB, we investigated the structures of the isolated active metabolites by negative mode LC/MS/MS and GC/MS. The active metabolite of BPA gave a negative mass peak at [M-H](-) 267 on LC/MS and a single daughter ion at m/z 133 on MS/MS analysis, suggesting an isopropenylphenol dimer structure. Finally, this active metabolite was confirmed to be identical with authentic 4-methyl-2,4-bis(p-hydroxyphenyl)pent-1-ene (MBP) by means of various instrumental analyses. The corresponding peaks of the BPB metabolite were [M-H](-) 295 and m/z 147, respectively, suggesting an isobutenylphenol dimer structure. Further, coincubation of BPA and BPB with rat liver S9 afforded an additional active metabolite(s), which gave a negative mass peak at [M-H](-) 281 and two daughter ion peaks at m/z 133 and m/z 147 on MS/MS analysis. These results strongly suggest that the active metabolite of either BPA or BPB might be formed by recombination of a radical fragment, a one-electron oxidation product of carbon-phenyl bond cleavage. It is noteworthy that the estrogenic activity of MBP, the active metabolite of BPA, is much more potent than that of the parent BPA in several assays, including two reporter assays using a recombinant yeast expressing human estrogen receptor alpha and an MCF-7-transfected firefly luciferase plasmid.

3T3 Cells↗
PubMed2006

Biosensor recognition of thyroid-disrupting chemicals using transport proteins.

Novel surface plasmon resonance-based biosensor assays for the bioeffect-related screening of chemicals with thyroid-disrupting activity are described. Two thyroid transport proteins (TPs), thyroxine binding globulin (TBG) and recombinant transthyretin (rTTR), were applied in an inhibition assay format in a Biacore 3000 using CM5 biosensor chips coated with l-thyroxine (T4), the main hormone of the thyroid system. Assay conditions were optimized for the natural thyroid hormones, and known thyroid disruptors and structurally related compounds were selected as model compounds to be tested in both assays for their relative potency (RP) compared to T4. The chosen compounds were halogenated phenols, halogenated bisphenols, bisphenol A, 3,5-dichlorobiphenyl, and its hydroxylated metabolite 4-hydroxy-3,5-dichlorobiphenyl (4-OH PCB 14). The TBG-based assay was highly specific for T4, and the rTTR-based assay was sensitive toward several compounds, the highest sensitivity (RP = 4.4) being obtained with 4-OH PCB 14, followed by tetrabromobisphenol A (RP = 1.5) and tetrachlorobisphenol A (RP = 0.75). For the bioeffect-related screening of known and identification of possible new thyroid disruptors, the TPs-based biosensor assays were more sensitive (IC(50) of 13.7 +/- 1.3 and 8.6 +/- 0.7 nM for the rTTR and the TBG-based assay, respectively), easier to perform, and faster alternatives (10 min/sample) than the currently used methods such as radioligand binding assays and immunoprecipitation-HPLC.

Biosensing Techniques↗
PubMed2006

Bisphenol A facilitates bypass of androgen ablation therapy in prostate cancer.

Prostatic adenocarcinomas depend on androgen for growth and survival. First line treatment of disseminated disease exploits this dependence by specifically targeting androgen receptor function. Clinical evidence has shown that androgen receptor is reactivated in recurrent tumors despite the continuance of androgen deprivation therapy. Several factors have been shown to restore androgen receptor activity under these conditions, including somatic mutation of the androgen receptor ligand-binding domain. We have shown previously that select tumor-derived mutants of the androgen receptor are receptive to activation by bisphenol A (BPA), an endocrine-disrupting compound that is leached from polycarbonate plastics and epoxy resins into the human food supply. Moreover, we have shown that BPA can promote cell cycle progression in cultured prostate cancer cells under conditions of androgen deprivation. Here, we challenged the effect of BPA on the therapeutic response in a xenograft model system of prostate cancer containing the endogenous BPA-responsive AR-T877A mutant protein. We show that after androgen deprivation, BPA enhanced both cellular proliferation rates and tumor growth. These effects were mediated, at least in part, through androgen receptor activity, as prostate-specific antigen levels rose with accelerated kinetics in BPA-exposed animals. Thus, at levels relevant to human exposure, BPA can modulate tumor cell growth and advance biochemical recurrence in tumors expressing the AR-T877A mutation.

Adenocarcinoma↗
PubMed2002

Responses of L929 mouse fibroblasts, primary and immortalized bovine dental papilla-derived cell lines to dental resin components.

OBJECTIVE: The use of adequate target cells for cytotoxicity testing of dental restorative materials has often been experimentally assessed with respect to the clinical relevance of the test results. In the present study, the responses in primary bovine dental papilla-derived cells (pulp cells) were compared with those in transformed dental papilla-derived cell lines and L929 mouse fibroblasts after exposure to various dental resin compounds. METHODS: Primary bovine dental papilla-derived cells (CPC), tCPC B (CPC cells transformed with SV40 T-antigen), tCPC E (CPC cells transformed with E6/E7 oncogen), and L929 mouse fibroblast cells were exposed to various compounds of dental resin materials for 24 h, and cytotoxicity was determined using the MTT assay. Bis-GMA, UDMA, 1,6 hexane diol dimethacrylate (HDDM), TEGDMA, HEMA, MMA, camphorquinone (CQ), bisphenol A (BPA), and glycidyl methacrylate (GMA) were tested. Concentrations leading to 50% cell survival (TC50 values) were calculated from fitted dose-response curves. RESULTS: The simple ranking of the cytotoxic effects of the dental resin compounds in the four cell types was identical, and TC50 values determined in L929 cells here were consistent with findings by other authors using continuous cell lines. However, the concentrations of the resin compounds necessary for eliciting cytotoxic responses in the various cells were clearly different. The analyses of TC50 values of the resin compounds revealed a linear correlation between cell lines, and the overall sensitivities increased as follows: CPC=tCPC B<tCPC E<L929. SIGNIFICANCE: The low sensitivities of primary cells and transformed tCPC B cells compared with the continuous L929 cell line and the transformed tCPC E cells indicates the presence of specific structural and functional properties relevant in vivo. The differences between the transformed tCPC B and tCPC E cells may indicate modifications of cellular functions caused by the different transformation processes.

Acrylates↗
PubMed1984

The sensitizing potential of di-(meth)acrylates based on bisphenol A or epoxy resin in the guinea pig.

Most composite materials in dentistry used today, contain resins based on dimethacrylates. BIS-GMA [2,2-bis-(4-(2-hydroxy-3-methacryloxypropoxy)phenyl)propane], the addition reaction product of bisphenol A and glycidyl methacrylate or an epoxy resin and methacrylic acid, is used most extensively. More recently, dimethacrylates based on bisphenol A, with various chain lengths have appeared on the market as a substitute for or in addition to BIS-GMA. Such compounds are BIS-MA [2,2-bis-(4-(methacryloxy)phenyl)propane], BIS-EMA [2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane] and BIS-PMA [2,2-bis-(4-(3-methacryloxypropoxy)phenyl)propane]. Increasing interest in the radiaton cure of coatings and printing inks have focused attention on these substances and on epoxy diacrylates as radiation-curable resins. The sensitizing capacity of the different acrylates based on bisphenol A or epoxy resin have been investigated with the guinea pig maximization test. The pattern of simultaneous reactivity of the compounds was also studied. Epoxy diacrylate [2,2-bis-(4-(2-hydroxy-3-acryloxy-propoxy)phenyl)propane], BIS-EMA and BIS-MA are shown to be strong sensitizers, while the linear fraction of BIS-GMA and its isomers and BIS-PMA have none or a low sensitizing capacity. The impurities in the BIS-GMA and BIS-MA batches seem to have high allergenic potential. These results stress the importance of a pure substance when discussing allergenicity and cross reactions.

Acrylates↗
PubMed2003

Identification of some plasticizers compounds in landfill leachate.

In this work it was described a simple method for extraction of plasticizer compounds (mainly phthalate esters and bisphenol A (BPA)) from landfill leachate samples. The samples were submitted to an extraction procedures based on precipitation, solid phase extraction (SPE) and ionic exchange chromatography (IEC). Firstly the landfill leachate sample was acidified by addition of HCl concentrated, in order to precipitate the organic compounds that are less soluble in water. The precipitate was washed with several solvents. The aqueous phase was then submitted to SPE with XAD-4 resin and IEC with Amberlyst A-27 resin. The instrumental analysis was performed by gas chromatography with mass spectrometer detector (GC/MSD) and the compounds were identified by the GC/MSD library (Wiley) and by using some standard substances. These methodologies allow the isolation and identification of the following compounds: dioctylphthalate, diisobutilphthalate, BPA, benzoic acid, palmitic acid and diisopentylphthalate. The methods are very simple, rapid and selective, for plasticizers extraction from landfill leachate matrices.

Brazil↗
PubMed2004

Seasonal and spatial distribution of nonylphenol in Shihwa Lake, Korea.

Alkylphenols (APs) have been known as endocrine disruptors and consequently received much environmental concern. This study focused on seasonal variation and spatial distribution of nonylphenol (NP) in various matrixes including dissolved water, particulates, surface sediment, sediment trap and sediment core taken from Shihwa Lake and its adjacent areas. A total of 11 phenolic compounds including nonylphenol, t-octylphenol (t-OP) and bisphenol A (BPA) were measured in February, June and October 2002. NP is the most abundant chemical among the phenolic compounds and its concentrations in dissolved water, particulates and surface sediments from Shihwa Lake were measured as 17.4-1533.1 ng/l, 4.3-831.2 ng/l and 10.4-5054.1 ng/g dw, respectively. NP concentration in dissolved water varied with seasons and generally showed a decreasing order of June > October > February, while the seasonal trend was hardly found in sediment. High levels of NP were measured in surrounding industrial complexes, the concentrations was decreased gradually with distance from the industrial areas. NP in core samples showed an increasing trend toward the core depth. There exists a reasonable correlation between NP in dissolved water and in particulates, whereas the correlation between NP in dissolved water and in sediments is not significant. APs concentrations in Shihwa Lake were comparable to other highly polluted areas of the world and their possible effects on various organisms in the lake are discussed.

Benzhydryl Compounds↗
PubMed2002

Disposition of a low dose of bisphenol a in male and female cynomolgus monkeys.

Bisphenol A (BPA) is a weak estrogenic compound mass-produced with potential human exposure. Following a single oral or intravenous (iv) dose of 100 microg/kg [ring-14C(U)] radiolabeled bisphenol A (14C-BPA) to male and female cynomolgus monkeys, 79-86% of the administered radioactivity was excreted in urine over 7 days, and most of the urinary excretion was recovered by 24 h after dosing, a large part of this occurring within 12 h. The fecal excretion of radioactivity over 7 days was minimal (1.8-3.1%). Toxicokinetic parameters obtained from plasma 14C-BPA-derived radioactivity during 48 h were C(max) = 104-107 ng-eq/ml between 0.25 and 2 h, and AUC(oral) = 244-265 ng-eq*h/ml after oral dosing. In the case of the iv dose, AUC(iv) was 377-382 ng-eq*h/ml, and the bioavailability was 0.66-0.70. The terminal elimination half-life was larger post-iv dose (t(1/2iv) = 13.5-14.7 h) than post-oral dose (t(1/2oral) = 9.63-9.80 h). After iv dose, the fast-phase half-life (t(1/2f)) of total radioactivity was 0.61-0.67 h. The t(1/2f) of unchanged 14C-BPA for females (0.39 h) was smaller than that for males (0.57 h). These results suggested the distribution of lipophilic 14C-BPA in adipose tissue after iv dose, in contrast to first pass metabolism after oral dose. 14C-BPA-derived radioactivity was strongly bound to plasma protein (f(p) = 0.055). Radio-HPLC analysis suggested the predominant plasma and urinary metabolites were mono- and diglucuronide of 14C-BPA and unchanged 14C-BPA was very low (< or =1.5%) after oral dose. These results indicate that the intestinal absorption and metabolism of BPA was rapid and extensive, and the major metabolites, glucuronide conjugates of 14C-BPA, were rapidly excreted into urine in monkeys.

Administration, Oral↗
PubMed2002

Stability of bisphenol A, triethylene-glycol dimethacrylate, and bisphenol A dimethacrylate in whole saliva.

OBJECTIVES: This study investigated the stability of compounds of dental sealant materials in a salivary matrix. METHODS: Various amounts of bisphenol A (BPA), bisphenol A dimethacrylate (BIS-DMA) or triethylene-glycol dimethacrylate (TEGDMA) were added to whole salivary samples, and stored at -70 degrees C or -20 degrees C for up to 4 months. In other experiments, four separate whole salivary or water samples with BIS-DMA (200 ng/ml) were incubated for 0, 1, 2, 4 or 24h at 37 degrees C. Levels of analytes were determined by capillary gas chromatography/mass spectrophotometry (GC/MS) and high-performance liquid chromatography (HPLC). RESULTS: BPA was stable under all tested conditions. Samples originally containing BIS-DMA had high levels of BPA and almost no BIS-DMA after 4 months at -20 degrees C. Salivary samples incubated at 37 degrees C originally containing only BIS-DMA (200 ng/ml) demonstrated rapid decreases of BIS-DMA and increases of BPA. By 24h, the mean BIS-DMA concentration fell to 21.8 (25) ng/ml, while BPA increased to 100 (48) ng/ml. Only slight decreases in BIS-DMA and no BPA were present in the water samples incubated at 37 degrees C. BPA, BIS-DMA, and TEGDMA were stable if salivary samples were stored at -70 degrees C. Acidification of salivary samples prevented the breakdown of BIS-DMA. SIGNIFICANCE: BIS-DMA is converted rapidly to BPA in the presence of whole saliva. This could account for the findings of BPA in clinical samples collected after the placement of certain sealant products. Decreasing salivary pH and temperature can slow this process and this method should be used for clinical studies of salivary BPA leached from restorative materials.

Acids↗
PubMed2004

Identification of organic compounds and ecotoxicological assessment of sewage treatment plants (STP) effluents.

An integrated approach combining chemistry and biological methods was conducted to assess the toxicity of seven sewage treatment plant effluents. Solid phase concentration procedures were applied to facilitate the study of organic micro pollutants. A chemical analysis was performed by GC/MS. Organic fraction toxicity was determined by using bioassays such as Daphnia magna and Chlorella vulgaris tests and sub-lethal effects were also evaluated by using Salmonella typhimurium Test (mutagenicity), recombinant yeast screen (estrogenicity), and Oryzias latipes embryo-larval test. More than 49 compounds were detected in the organic fraction due to the various inputs of each effluents. The most frequently detected compounds in the effluents were bisphenol A (BPA), octylphenol (OP), 1,2-benzenedicarboxylic acid, bis(2-ethylhexyl) ester (DEHP) and 1,2-benzenedicarboxylic acid, bis(methylpropyl) ester (DBP). Biological assays showed toxicity effects on D. magna tests in all samples, whereas toxicity on C. vulgaris or S. typhimurium tests were not observed. Estrogenicity and teratogenicity were observed in several samples. The cause-effect relationship could not be established given the high chemical complexity of the effluents and the lack of information available on 70% of the detected compounds subsequent to reviewing various data bases. Nevertheless, due to the high chemical variability revealed by STP effluents, bioassay sets may provide a very useful amount of information for detecting potential toxicity risks.

Animals↗
PubMed2004

Transient inhibition of synergistically insulin-like growth factor-1- and bisphenol A-induced poliferation of estrogen receptor alpha (ERalpha)-positive human breast cancer MCF-7 cells by melatonin.

There are many subclones of human breast cancer MCF-7 cells that respond to different levels of estrogen and that have been used for evaluating the estrogenic potential of environmental chemicals such as bisphenol A. In this study, I examined the effects of melatonin, an endogenous growth-inhibitory hormone, on the bisphenol A-induced proliferation of an MCF-7 subclone, designated as MCF-7-EMF cells. MCF-7-EMF cell growth was extremely slow in the presence of either estrogen at 10(-7) M or bisphenol A at 10(-7) M in a phenol-red-free medium and 10% charcoal-stripped fetal bovine serum. It was difficult to detect the increment of BrdU incorporation in MCF-7-EMF cells (2x10(4) cells) upon exposure to 10(-7) M bisphenol A alone for up to 50 h. The same result was obtained with cells exposed to 10 ng/ml insulin-like growth factor-1 (IGF-1) alone for up to 50 h. However, in the presence of 10 ng/ml IGF-1, bisphenol A markedly increased cell proliferation. The synergistic response was transiently inhibited by 10(-10) M melatonin (p<0.05). Thus, melatonin caused a transient inhibition of cell growth of estrogen receptor alpha (ERalpha)-positive MCF-7-EMF cells induced synergistically by both IGF-1 and bisphenol A.

Antioxidants↗
PubMed2004

Polymer-based adsorption medium prepared using a fragment imprinting technique for homologues of chlorinated bisphenol A produced in the environment.

A polymer-based adsorption medium having molecular recognition ability for homologues of chlorinated bisphenol A produced in environment was prepared using a fragment imprinting technique. 2,6-Dimethyl phenol was utilized as a pseudo-template molecule and the adsorption media prepared was evaluated by high performance liquid chromatography (HPLC) and solid-phase extraction (SPE). As results, the adsorption medium showed preferable chromatographic retention and specific adsorption ability for the chlorinated bisphenol As having chlorine substituents at 3,5-positions through fragment imprinting effect.

Adsorption↗
PubMed2003

Identification and quantification of bisphenol A by gas chromatography and mass spectrometry in a lab-scale dual membrane system.

Endocrine disruptor contamination is an emerging issue of concern in the field of water quality engineering. In this study, a lab-scale microfiltration (MF) and reverse osmosis (RO) based water reclamation system was set up to monitor and evaluate the removal of bisphenol A (BPA), which is a known oestrogenic compound. The identification and quantification of BPA were performed by using gas chromatography coupled with mass spectrometry. It was noted that the detection method used in this study was able to achieve an average recovery ranging from 88.2 to 94.1% of BPA with standard deviations of less than 10% in different spiked samples. The detection limit of the analytical protocol was determined at 20 ng L(-1). Based on the analytical protocol, it was noted that a low level of BPA (1.18-3.04 microg L(-1)) could be detected in feed water (effluent of an activated sludge treatment system) to the dual membrane water reclamation system. The results obtained suggested that BPA could be easily chlorinated by sodium hypochlorite with a dosage of 4 to 5 mg L(-1) and a contact time of 1 to 2 min. In this lab-scale study, a satisfactory removal of BPA was readily obtained by RO and BPA was abated to an undetectable level in the product water. It was noted that the RO rejection characteristic of BPA was not sensitive to the variations in raw feed water characteristics experienced in this study. In addition, it was noted that BPA concentration present in raw feed water did not exert any significant impact on RO performance in terms of BPA rejection. The results of this study demonstrated that membrane technology could be effectively used for BPA removal.

Benzhydryl Compounds↗