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PubMed2001

Predicting migration of trace amounts of styrene in poly(styrene) below the glass transition temperature.

The use of general purpose polystyrene (GPPS) as food packaging material is widespread. Therefore, the rate of migration of the styrene in GPPS is of interest in order to predict the potential exposure of consumers to styrene. Studies have shown a relatively weak dependence of the diffusion coefficient on the residual styrene content, and a strong dependence on temperature. We have compared the predictions of the free-volume theory with experimentally measured diffusivity data. The predictions and the measured values are observed to be consistent with each other. These results illustrate the capability of the free-volume theory of transport to predict the diffusivity of trace amounts of impurity in a glassy polymer.

Diffusion↗
PubMed1967

The metabolism of phenethyl bromide, styrene and styrene oxide in the rabbit and rat.

1. The chief sulphur-containing metabolite of styrene and sytrene oxide in the rabbit and rat is chromatographically identical with N-acetyl-S-(beta-hydroxyphenethyl)-l-cysteine and this compound is also formed, together with N-acetyl-S-phenethyl-l-cysteine, as a metabolite of phenethyl bromide. 2. The amounts of the phenethylmercapturic acid and its hydroxy derivative excreted in the urine of animals dosed with phenethyl bromide, styrene, styrene oxide, phenyl glycol, S-phenylethylcysteine and phenethylmercapturic acid have been determined. 3. Liver slices convert phenethylcysteine and phenethylmercapturic acid into N-acetyl-S-(beta-hydroxyphenethyl)-l-cysteine. 4. Methods for the determination by gas-liquid chromatography of mandelic acid and hippuric acid, which are metabolites of some of the compounds studied, are described.

Animals↗
PubMed1995

Styrene: from characterisation of DNA adducts to application in styrene-exposed lamination workers.

Styrene oxide, a metabolite of styrene, reacts with many centres in nucleosides but in DNA N-7-, N2- and O6-guanine are the main sites. A 32P-postlabelling method was developed for the detection of O6-styrene oxide DNA adducts from white blood cells. The method involved use of nuclease P1 and magnet transfer. The O6 adducts were detected at a fmol range with about 10% labelling efficiency. In lamination workers the O6 adducts, adjusted for adduct recovery, were detected at a level of 5 adducts/10(8) nucleotides.

DNA Adducts↗
PubMed2006

High performance poly(styrene-b-diene-b-styrene) triblock copolymers from a hydrocarbon-soluble and additive-free dicarbanionic initiator.

A new hydrocarbon-soluble (additive-free) dicarbanionic organolithium initiator, obtained by a simple halogen-lithium exchange reaction (Gilman's reaction) from a diarylhalide containing a side C15 alkyl chain, has been designed and used to initiate the anionic polymerization of butadiene and styrene. The dilithiated species formed afford well-defined poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymers with a high percentage of 1,4-microstructure polybutadiene (91%) and excellent mechanical properties, such as ultimate tensile strength higher than 30 MPa and elongation at a break of 1000%. This represents a breakthrough in the synthesis of SBS polymers, one of the most used thermoplastic elastomers.

Journal Article↗
PubMed1988

Detection of styrene oxide-DNA adducts in lymphocytes of a worker exposed to styrene.

The 32P-postlabelling procedure has been used to detect styrene oxide (SO)-DNA adducts. Reactions of SO with DNA and dGMP in vitro produced adducts that were similar, indicating that dGMP was the primary base for modification in DNA. Two SO adducts were also detected in DNA isolated from lymphocytes of a styrene-exposed worker but not in DNA from an unexposed worker. These results indicate that 32P-postlabelling can be used for quantification of DNA adducts in workers exposed to styrene.

DNA↗
PubMed1994

A physiologic pharmacokinetic model for styrene and styrene-7,8-oxide in mouse, rat and man.

Concern about the carcinogenic potential of styrene (ST) is due to its reactive metabolite, styrene-7,8-oxide (SO). To estimate the body burden of SO resulting from various scenarios, a physiologically based pharmacokinetic (PBPK) model for ST and its metabolite SO was developed. This PBPK model describes the distribution and metabolism of ST and SO in the rat, mouse and man following inhalation, intravenous (i.v.), oral (p.o.) and intraperitoneal (i.p.) administration of ST or i.v., p.o. and i.p. administration of SO. Its structure includes the oxidation of ST to SO, the intracellular first-pass hydrolysis of SO catalyzed by epoxide hydrolase and the conjugation of SO with glutathione. This conjugation is described by an ordered sequential ping-pong mechanism between glutathione, SO and glutathione S-transferase. The model was based on a PBPK model constructed previously to describe the pharmacokinetics of butadiene with its metabolite butadiene monoxide. The equations of the original model were revised to refer to the actual tissue concentration of chemicals instead of their air equivalents used originally. Blood:air and tissue:blood partition coefficients for ST and SO were determined experimentally and have been published previously. Metabolic parameters were taken from in vitro or in vivo measurements. The model was validated using various data sets of different laboratories describing pharmacokinetics of ST and SO in rodents and man. In addition, the influences of the biochemical parameters, alveolar ventilation and blood:air ventilation and blood:air partition coefficient for ST on the pharmacokinetics of ST and SO were investigated by sensitivity analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1994

Expoxidation of styrene and substituted styrenes by whole cells of Mycobacterium sp. M156.

Whole cells of the propene utilizing Mycobacterium sp. M156 (NCIMB 40156) oxidised styrene, 2-,3- and 4-fluorostyrene, 3- and 4-chlorostyrene and 3- and 4-methylstyrenes to their respective epoxides. Rates of oxidation were comparable to that of styrene. alpha-Methylstyrene was also epoxidised at a lower rate, while trans-beta-methylstyrene and 1,2-dihydronaphthalene were poor substrates. In those cases that were investigated, epoxidation occurred with a high degree of stereospecificity.

Biotransformation↗
PubMed2006

A newly designed glaucoma drainage implant made of poly(styrene-b-isobutylene-b-styrene): biocompatibility and function in normal rabbit eyes.

OBJECTIVE: To report clinical evaluation, flow patency, and histopathological findings of a novel glaucoma drainage implant (GDI) made of poly(styrene-b-isobutylene-b-styrene) (SIBS) in rabbits. METHODS: In 16 normal eyes, the proximal end of the SIBS GDI was inserted into the anterior chamber while the distal end was placed in the subconjunctival space. A control group underwent implantation of a similarly designed silicone GDI. Slitlamp follow-up and intraocular pressure measurements were recorded. Flow patency was evaluated by injecting 0.01% fluorescein into the anterior chamber. Immunostaining against collagen IV, macrophages, and alpha smooth muscle actin was performed. RESULTS: Slitlamp examination suggested adequate biocompatibility. A low and diffuse bleb was observed in the SIBS group. All SIBS tubes were patent 6 months after insertion. Immunostaining demonstrated noncontinuous collagen deposition. No macrophages or myofibroblasts were visible around the SIBS tubes. In contrast, silicone induced collagen deposition and myofibroblast differentiation. CONCLUSION: This new GDI is clinically biocompatible in the rabbit and maintained 100% patency at 6 months. A remarkable difference was the absence of myofibroblasts in the surrounding tissue in the SIBS group. CLINICAL RELEVANCE: This novel GDI made of SIBS would prevent the feared complication of hypotony and will decrease the amount of subconjunctival fibrosis.

Actins↗
PubMed1979

Heparinized styrene-butadiene-styrene elastomers.

A heparinized high-strength elastomer has been developed which is potentially useful as a nonthrombogenic vascular prosthesis. A surface hydroxylated styrene-butadiene-styrene (SBS) block copolymer with at least 40% extent of reaction after glow-discharge cleaning was coated with a 20% acetylated polyvinyl alcohol/heparin mixture containing glutaraldehyde and magnesium chloride. After curing at 80 degrees C for 100 min, the polyvinyl alcohol, heparin, and hydroxylated SBS were covalently bound to each other by acetal bridges. The effects of the various substrate and coating parameters were optimized to achieve very strong adhesion between the coating layer and the surface hydroxylated SBS. Heparin was not leached from the surface of the new material using 3M saline at pH 7.4 despite a detection limit of 10(-5) micrograms heparin/cm2 min. Prolonged partial thromboplastin times of greater than 1200 sec were observed (control: PTT = 120 sec). Preliminary ex vivo testing using a simple arteriovenous shunt in the leg of a rabbit showed good thromboresistance. The heparinized SBS shunt chamber remained patent for more than two hours without desorption of heparin. It was concluded that surface hydroxylated SBS heparinized by acetal coupling owed its thromboresistance to the heparin covalently bound to the surface and not to a microenvironment of heparin in solution at the blood/material interface.

Biocompatible Materials↗
PubMed2004

In situ-formed, tissue-adhesive co-gel composed of styrenated gelatin and styrenated antibody: potential use for local anti-cytokine antibody therapy on surgically resected tissues.

Styrenated antibody (ST-Ab) and styrenated gelatin (ST-gelatin) were prepared by condensation reaction of antibody or gelatin with 4-vinylbenzoic acid, respectively. The affinity loss of ST-Ab to its antigen was minimal. ST-Ab and ST-gelatin were copolymerized with by visible-light irradiation in the presence of a water-soluble camphorquinone as a photoinitiator to produce a tissue-adhesive, in situ-formed co-gel of ST-gelatin and ST-Ab. The amount of non-reacted ST-Ab released from the co-gel of ST-gelatin and ST-Ab into the medium was minimal. The confocal laser scanning microscopy observation showed that local accumulation of rhodamine-labeled bovine serum albumin (BSA) as a model antigen was noticed in the surface-to-subsurface region of the co-gel of ST-gelatin and anti-BSA ST-Ab, indicating that the gel prevented the permeation of BSA into the gel. In invasion double chamber assay using anti-hepatocyte growth factor (HGF) antibody, the co-gel prevented HGF-dependent invasion of pancreatic cancer cells. The discussion was made for potential application of an in situ-formed tissue-adhesive co-gel of ST-gelatin and ST-Ab, developed in this study, as a cytokine-barrier on a surgically resected tissue where cancer cells might still remain after resection of cancerous tissue.

Antibodies↗
PubMed2005

NMR characterization of paclitaxel/poly (styrene-isobutylene-styrene) formulations.

TAXUStrade mark is a coronary drug-eluting stent system utilizing a formulation consisting of cellular-target drug paclitaxel and poly (styrene-isobutylene-styrene) (SIBS). The present study investigates the interaction and interfacial dynamics of paclitaxel incorporated in a nano-polymeric matrix system. Solution and solid-state CP/MAS NMR experiments were designed to characterize the microstructure of heterogeneous drug-polymer mixtures in terms of its composition, molecular mobility, molecular order, paclitaxel-SIBS molecular interactions, and molecular mobility of the drug in the polymer matrix. The NMR spectra demonstrated unchanged chemical shifts between the neat and incorporated paclitaxel, and suggested that the level of the interactions between paclitaxel and SIBS is limited to non-bonding interactions or physical interactions between paclitaxel and SIBS when mixed in solution under NMR detection. Carbon spin-lattice relaxation time and proton spin-lattice relaxation time in the rotating frame offer further confirmation that the mobility of paclitaxel is increased in the paclitaxel-SIBS mixture. The results also indicate that a change occurs from crystalline packing to amorphous packing in paclitaxel due to its intermolecular interaction with SIBS. Our studies were used in understanding the detailed structure, morphology, and molecular motion of paclitaxel in the paclitaxel-SIBS system and to probe chemical and physical heterogeneity down to the nanometer scale.

Antineoplastic Agents, Phytogenic↗
PubMed2003

A toxicokinetic model for styrene and its metabolite styrene-7,8-oxide in mouse, rat and human with special emphasis on the lung.

Styrene (ST) occurs ubiquitously in the environment and it is an important industrial chemical. After its uptake by the exposed mammalian organism, ST is oxidized to styrene-7,8-oxide (SO) by cytochrome P450 dependent monooxygenases. This reactive intermediate is further metabolized by epoxide hydrolase (EH) and glutathione S-transferase (GST). In long-term animal studies, ST induced lung tumors in mice but not in rats. Considering the lung to be the relevant target organ for ST induced carcinogenicity in mice, we extended a previously developed physiological toxicokinetic model in order to simulate the lung burden with ST and SO in the ST exposed mouse, rat and human. The new model describes oral and pulmonary uptake of ST, its distribution into various tissues, its exhalation and its metabolism to SO in lung and liver. It also simulates the distribution of the produced SO into the tissues and its EH and GST mediated metabolism in liver and in lung. In both organs the ST induced GSH consumption is described together with the formation of adducts to hemoglobin and to DNA of lymphocytes in ST exposed mice, rats and humans. The model includes compartments for arterial, venous and pulmonary blood, liver, muscle, fat, richly perfused tissues and lung. The latter organ is represented by two compartments, namely by the conducting and the alveolar zone. The physiological description of the pulmonary compartments relies on measured alveolar retentions, literature values of surface area of capillary endothelium, of the thickness of the tissue 'air-to-plasma', of the partition coefficient lung:blood and of metabolic parameters of ST and SO measured in pulmonary cell fractions of rodents and humans. Simulations of average pulmonary GSH levels in ST exposed rodents agree with measured data. The model predicts a significant GSH depletion (40%) in the conducting zone of mice exposed for 6 h to a ST concentration of only 20 ppm. In the conducting zone of rats, exposure to 200 ppm ST results in a loss of GSH of about 15% only. In humans, a pulmonary GSH reduction does not occur. The highest average pulmonary SO concentrations are predicted for mice, somewhat lower values for rats and by far the lowest ones for humans. Following steady state exposure to 20 ppm ST, the average SO concentration in mouse lungs is expected to be only three times higher than in rats. This difference diminishes to a factor of less than two at 70 ppm. In humans exposed to 20 ppm ST for 8 h, the average pulmonary SO burden of 0.016 micromol/kg is predicted to be about 17 and 50 times smaller than the corresponding values for rat and mouse. In agreement with reported values, pulmonary DNA adduct levels in rodents exposed to 160 ppm ST were simulated to be similar in rats and mice. In summary, there was no dramatic difference in the calculated average pulmonary SO burden between both animal species. However, pulmonary GSH loss was by far more expressed in ST exposed mice than rats. Since the model was validated on all available ST/SO data in mice, rats and humans, we consider it to be useful for estimating the risk resulting from exposure to ST.

Administration, Inhalation↗
PubMed1996

Molded monolithic rod of macroporous poly(styrene-co-divinylbenzene) as a separation medium for HPLC of synthetic polymers: on-column precipitation--redissolution chromatography as an alternative to size exclusion chromatography of styrene oligomers and polymers.

A process for the separation of styrene oligomers and polymers by size and composition using a novel separation medium has been demonstrated. The process involves precipitation of the macromolecules on the molded macroporous rod columns, followed by progressive elution utilizing a simple gradient of the mobile phase. Molded macroporous rod columns are ideally suited for this technique because convection through the large pores of the rod enhances the mass transport of large analyte molecules and accelerates the separation process. Styrene oligomers and polymers are separated in a 50-mm x 8-mm-i.d. column using a solvent gradient composed of a poor solvent such as water, methanol, or acetonitrile and increasing amounts of a good solvent, tetrahydrofuran. Excellent separations are obtained, demonstrating that precipitation-redissolution can be a suitable alternate to size exclusion chromatography (SEC) of some polymers. Compared to SEC, the gradient elution separation can be achieved at higher flow rates in a much shorter time. Precipitation-redissolution with gradient elution can also be used for the separation of copolymers, for which the process is controlled not only by molecular weight but also by the composition of the copolymers.

Chromatography, Gel↗
PubMed2002

Physiologically based pharmacokinetic modeling of styrene and styrene oxide respiratory-tract dosimetry in rodents and humans.

Styrene (ST) is widely used to manufacture resins, glass-reinforced plastics, and a number of commercially important polymers (Miller et al., 1994). Chronic ST inhalation studies in rodents have demonstrated unique species specificity in the resulting pulmonary toxicity and carcinogenicity. Increased incidences of pulmonary bronchioloalveolar tumors have been observed in mice, but not in rats. No other tumor type was increased significantly in either species. Clara cells lining the respiratory epithelium metabolize ST to styrene 7,8-oxide (SO), which is cytotoxic and weakly genotoxic. Rodent species show marked differences in the distribution and regional density of Clara cells within the respiratory tract, as well as in their capacity to produce and eliminate SO. A mode of action-based physiologically based pharmacokinetic (PBPK) model was developed to predict the concentration of ST and SO in blood, liver, and the respiratory-tract tissues, particularly in terminal bronchioles (target tisue), in order to conduct interspecies extrapolations and determine the extent to which there is a pharmacokinetic basis for the observed species specificity. This PBPK model has a multicompartment description of the respiratory tract and incorporates species-specific quantitative information on respiratory-tract physiology, cellular composition, and metabolic capacity. The model is validated against multiple data sets, including blood, liver, and whole lung tissue concentration of ST and SO following multiple routes of exposure. The trend in neoplastic incidences in mice correlated well with model-estimated SO concentration in the terminal bronchioles. The PBPK model predicts a 10-fold lower SO concentration in the terminal bronchioles in rats compared to mice, which is consistent with the observed species sensitivity to the development of respiratory-tract neoplasms. The model-based analysis suggests that humans would be expected to be 100-fold less sensitive to ST-inducted lung tumors than mice, based on pharmacokinetic differences. Pharmacodynamic factors are also expected to contribute to species sensitivity, potentially augmenting pharmacokinetics-based differences.

Animals↗
PubMed1978

Exposure of rabbits to styrene. Electronystagmographic findings correlated to the styrene level in blood and cerebrospinal fluid.

Objective methods for critically evaluating the toxic effect of industrial solvents are highly desirable. As many of these solvents are suspected to cause vertigo, an animal experimental model was set up for studying the effects of solvents on the vestibular systems. The vestibular function was studied by registration of involuntary eye movements--nystagmus--which are elicited via central vestibulo-oculomotor connections. During exposure to styrene a so-called positional nystagmus was demonstrated that indicated vestibular disturbances. Nystagmus is normally elicited by rotatory acceleration. During exposure to styrene the direction of this rotatory nystagmus was reversed. The incidence of the positional nystagmus correlated well with the blood level of the solvent, measured by gas chromatography. Kinetic studies also demonstrated a rapid equilibration between the level of the solvent in arterial blood and cerebrospinal fluid, and therefore suggested that estimation of the arterial level reliably indicates the level in the central nervous system.

Animals↗
PubMed1978

Arene oxides in styrene metabolism, a new perspective in styrene toxicity?

The metabolism of styrene was studied in the rat after intraperitoneal administration of the cold and the 14C-labeled compound. In addition to phenylethylene glycol, mandelic acid, benzoic acid and hippuric acid, phenolic metabolites, namely, 4-vinylphenol, p-hydroxymandelic acid, p-hydroxybenzoic acid, and p-hydroxyhippuric acid, were identified in the urine of the treated animals. These biotransformation products were characterized by mass spectrometry and by comparative thin layer chromatography with standard compounds. Results of covalent binding studies of 14C-phenylethylene glycol to rat liver microsomal proteins suggest that these phenolic compounds may be formed as a result of chemical rearrangements of unstable arene oxides, reactive intermediates possibly implicated in styrene toxicity.

Animals↗
PubMed1982

Mutagenicity of (R) and (S) styrene 7,8-oxide and the intermediary mercapturic acid metabolites formed from styrene 7,8-oxide.

We have tested the two enantiomers of styrene 7,8-oxide and various thioether metabolites of racemic styrene 7,8-oxide for their direct mutagenicity in Salmonella typhimurium TA100. The mutagenicity data suggests that the (R) enantiomer is more mutagenic than the (S) enantiomer, with the racemic mixture intermediate between the two. The thioether metabolites were not mutagenic. The difference in the mutagenicities of enantiomers probably resulted from a stereoselective process in the Salmonella tester strain. At the present time it is not clear whether the rate-limiting reaction is the interaction of the enantiomers with DNA or some other cellular component.

DNA, Bacterial↗