Integrative literature review: Ethylene oxide exposure signs and symptoms.

BACKGROUND: Although ethylene oxide (EtO) gas is designated as a human carcinogen, extant literature reports mixed findings on the health effects of exposure. The disparate findings may reflect industry bias as many studies were funded by a large chemical industry lobby. OBJECTIVE: To conduct an integrative review of studies free from industry bias to facilitate compilation of a comprehensive list of reported signs and symptoms of EtO exposure. METHODS: We reviewed 1887 papers of which 42 articles met inclusion criteria. The authors conducted this review in accordance with PRISMA guidelines. The presence of bias was assessed using Joanna Briggs Institute checklists. RESULTS: Non-industry biased literature confirmed serious adverse health effects associated with EtO exposure at the occupational, hospital, and community level. EtO represents a carcinogen, neurotoxin, and respiratory irritant. CONCLUSION: After removal of industry-biased studies, EtO was unequivocally found to pose a threat to human health. There remains a gap in the number of studies examining community-level exposure, which is essential to understanding the impact of EtO. Given that EtO-emitting facilities are concentrated in diverse and disadvantaged communities, further study of EtO exposure health effects is warranted to inform public policy on toxic air emissions.

Association between hemoglobin adducts of ethylene oxide levels and the risk of short sleep duration in the general population: an analysis based on the National Health and Nutrition Examination Survey.

This study aimed to evaluate the association between blood ethylene oxide (HbEtO) levels and short sleep duration (SSD). Data of 3438 participants aged 20 years or older in this study were collected from the National Health and Nutrition Examination Survey (NHANES). The ethylene oxide (EtO) biomarker (HbEtO) was quantified in blood using a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. SSD was defined as sleep time equal to or less than 6 h. The analyses utilized weighted logistic regression models and restricted cubic spline. There was a significant non-linear relationship between HbEtO levels and the risk of SSD (P for-nonlinearity = 0.035). After the full adjustment for confounders, compared with the lowest quantile, the odds ratios (ORs) with 95% confidence intervals (CIs) of SSD across the quantiles of ethylene oxide levels were 1.54(1.09-2.18), 1.15(0.87-1.53), and 1.80(1.11-2.92), respectively (P for trend < 0.05). In subgroup analysis, people who were female, who were non-Hispanic Black, who never engaged in physical activity, who consumed alcohol ≤ 14 g/day, who were normal weight or obese had a significantly higher risk of SSD when they had highest quartiles of HbEtO levels than those had lowest (p < 0.05). Our study indicated that HbEtO levels, an indicator for EtO exposure, were associated with SSD in general adult populations.

Systematic review of the scientific evidence on ethylene oxide as a human carcinogen.

Ethylene oxide is a highly reactive chemical primarily used as an intermediate in chemical production and as a sterilant of medical equipment and food products; it also is produced endogenously as a result of physiological processes. We conducted a systematic review of the potential carcinogenicity of inhaled ethylene oxide in humans using methods that adhere to PRIMSA guidelines and that incorporate aspects from the Institute of Medicine (IOM) (now the National Academy of Medicine) as well as several US Environmental Protection Agency (EPA) frameworks for systematic reviews. After a comprehensive literature search and selection process, study quality was evaluated following a method adapted from the EPA Toxic Substances Control Act (TSCA) framework. The literature screening and selection process identified 24 primary studies in animals or humans and more than 50 mechanistic studies. Integrating epidemiological, animal, and mechanistic literature on ethylene oxide and cancer according to the IOM framework yielded classifications of suggestive evidence of no association between ethylene oxide and stomach cancer, breast cancer and lymphohematopoietic malignancies at human relevant exposures. However, we acknowledge that there is additional uncertainty in the classification for lymphohematopoietic malignancies owing to a paucity of evidence for specific types of these tumors, each of which is a distinct disease entity of possibly unique etiology.

Phytochemical analysis and protective effects of Vaccinium macrocarpon (cranberry) in rats (Rattus norvegicus) following ethylene oxide-induced oxidative insult.

The Vaccinium genus comprises more than 126 genera of perennial flowering plants that are commonly adapted to poor and acidic soils or epiphytic environments. Their molecular and genomic characterization is a result of the recent advent in next-generation sequencing technology. In the current research, extracts were prepared in different media, such as petroleum ether, methanol and ethanol. An extract of Vaccinium macrocarpon (cranberry) was used at a dose of 200-400 mg/kg by weight (B.wt). Levels of oxidative stress markers, i.e., superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), advanced oxidation protein products (AOPPs) and malondialdehyde (MDA), were measured. A histopathological study of six vital organs in rats was also conducted. The results indicated that the antioxidant levels were lower in the group given only ethylene oxide (EtO) but higher in the groups receiving cranberry extract as a treatment. Major improvements were also observed in stress markers such as advanced oxidation protein products (AOPPs) and MDA following cranberry treatment. Histopathological changes induced by EtO were observed in the heart, kidney, liver, lung, stomach and testis and were reversed following cranberry treatment. The major toxic effects of EtO were oxidative stress and organ degeneration, as observed from various stress markers and histopathological changes. Our study showed that this extract contains strong antioxidant properties, which may contribute to the amelioration of the observed toxic effects.

Ethylene Oxide Exposure in U.S. Populations Residing Near Sterilization and Other Industrial Facilities: Context Based on Endogenous and Total Equivalent Concentration Exposures.

Given ubiquitous human exposure to ethylene oxide (EO), regardless of occupation or geography, the current risk-specific concentrations (RSCs: 0.0001-0.01 ppb) from the U.S. Environmental Protection Agency (EPA) cancer risk assessment for EO are not useful metrics for managing EO exposures to the general U.S. population. The magnitude of the RSCs for EO are so low, relative to typical endogenous equivalent metabolic concentrations (1.1-5.5 ppb) that contribute ~93% of total exposure, that the RSCs provide little utility in identifying excess environmental exposures that might increase cancer risk. EO monitoring data collected in the vicinity of eight EO-emitting facilities and corresponding background locations were used to characterize potential excess exogenous concentrations. Both 50th and 90th percentile exogenous exposure concentrations were combined with the 50th percentile endogenous exposure concentration for the nonsmoking population, and then compared to percentiles of total equivalent concentration for this population. No potential total exposure concentration for these local populations exceeded the normal total equivalent concentration 95th percentile, indicating that excess facility-related exposures are unlikely to require additional management to protect public health.

Genotoxicity as a toxicologically relevant endpoint to inform risk assessment: A case study with ethylene oxide.

The purpose of the present investigation is to analyze the in vivo genotoxicity dose-response data of ethylene oxide (EO) and the applicability of the derived point-of-departure (PoD) values when estimating permitted daily exposure (PDE) values. A total of 40 data sets were identified from the literature, and benchmark dose analyses were conducted using PROAST software to identify a PoD value. Studies employing the inhalation route of exposure and assessing gene or chromosomal mutations and chromosomal damage in various tissues were considered the most relevant for assessing risk from EO, since these effects are likely to contribute to adverse health consequences in exposed individuals. The PoD estimates were screened for precision and the values were divided by data-derived adjustment factors. For gene mutations, the lowest PDE was 285 parts per trillion (ppt) based on the induction of lacI mutations in the testes of mice following 48 weeks of exposure to EO. The corresponding lowest PDE value for chromosomal mutations was 1,175 ppt for heritable translocations in mice following 8.5 weeks of EO exposure. The lowest PDE for chromosomal aberrations was 238 ppt in the mouse peripheral blood lymphocytes following 48 weeks of inhalation exposure. The diverse dose-response data for EO-induced genotoxicity enabled the derivation of PoDs for various endpoints, tissues, and species and identified 238 ppt as the lowest PDE in this retrospective analysis.

Analysis of DNA Adducts and Mutagenic Potency and Specificity in Rats Exposed to Acrylonitrile.

Acrylonitrile (ACN), which is a widely used industrial chemical, induces cancers in multiple organs/tissues of rats by unresolved mechanisms. For this report, evidence for ACN-induced direct/indirect DNA damage and mutagenesis was investigated by assessing the ability of ACN, or its reactive metabolite, 2-cyanoethylene oxide (CEO), to bind to DNA in vitro, to form select DNA adducts [N7-(2'-oxoethyl)guanine, N2,3-ethenoguanine, 1,N6-ethenodeoxyadenosine, and 3,N4-ethenodeoxycytidine] in vitro and/or in vivo, and to perturb the frequency and spectra of mutations in the hypoxanthine-guanine phosphoribosyltransferase (Hprt) gene in rats exposed to ACN in drinking water. Adducts and frequencies and spectra of Hprt mutations were analyzed using published methods. Treatment of DNA from human TK6 lymphoblastoid cells with [2,3-14C]-CEO produced dose-dependent binding of 14C-CEO equivalents, and treatment of DNA from control rat brain/liver with CEO induced dose-related formation of N7-(2'-oxoethyl)guanine. No etheno-DNA adducts were detected in target tissues (brain and forestomach) or nontarget tissues (liver and spleen) in rats exposed to 0, 3, 10, 33, 100, or 300 ppm ACN for up to 105 days or to 0 or 500 ppm ACN for ∼15 months; whereas N7-(2'-oxoethyl)guanine was consistently measured at nonsignificant concentrations near the assay detection limit only in liver of animals exposed to 300 or 500 ppm ACN for ≥2 weeks. Significant dose-related increases in Hprt mutant frequencies occurred in T-lymphocytes from spleens of rats exposed to 33-500 ppm ACN for 4 weeks. Comparisons of "mutagenic potency estimates" for control rats versus rats exposed to 500 ppm ACN for 4 weeks to analogous data from rats/mice treated at a similar age with N-ethyl-N-nitrosourea or 1,3-butadiene suggest that ACN has relatively limited mutagenic effects in rats. Considerable overlap between the sites and types of mutations in ACN-exposed rats and butadiene-exposed rats/mice, but not controls, provides evidence that the carcinogenicity of these epoxide-forming chemicals involves corresponding mutagenic mechanisms.

Associations between exposure to ethylene oxide, job termination, and cause-specific mortality risk.

BACKGROUND: Previous analyses of mortality were conducted in a large cohort of ethylene oxide (EtO) exposed workers employed at 13 sterilization facilities throughout the U.S. and followed from the start of operation through 1998. Statistically significant elevated mortality was reported from hematopoietic cancer in men and breast cancer in women compared to the general population. Possible healthy worker survivor bias was not addressed. METHODS: To examine survivor bias in this cohort, employment termination was analyzed with statistical models stratified on sex and race that included age, employment duration, and cumulative EtO exposure. To reduce survivor bias employment duration was included in Poisson regression model specifications for estimating standardized mortality ratios for several cancer outcomes. RESULTS: Strong statistically significant effects of unlagged cumulative EtO exposure were observed on rate of employment termination, indicating potential healthy worker survivor effect bias. Adjustment for employment duration in analyses of mortality resulted in statistically significant and stronger associations between cumulative EtO exposure and lung cancer, female breast cancer and hematopoietic cancer. There was a striking reduction in nonmalignant respiratory disease mortality risk with increasing employment duration with a further (nonsignificant) reduction with cumulative EtO, suggesting that EtO itself is driving termination of workers with respiratory morbidity even though the average EtO exposures in this population were generally far below odor and acute irritancy thresholds. CONCLUSIONS: Important survivor bias was present in this EtO cohort and may be present in many occupational settings involving irritant exposures.

Enzyme responsive copolymer micelles enhance the anti-biofilm efficacy of the antiseptic chlorhexidine.

Staphylococcal biofilms cause many infectious diseases and are highly tolerant to the effects of antimicrobials; this is partly due to the biofilm matrix, which acts as a physical barrier retarding the penetration and reducing susceptibility to antimicrobials, thereby decreasing successful treatment outcomes. In this study, both single and mixed micellar systems based on poly vinyl caprolactam (PCL)-polyethylene glycol (PEG) copolymers were optimised for delivery of chlorhexidine (CHX) to S. aureus, MRSA and S. epidermidis biofilms and evaluated for their toxicity using Caenorhabditis elegans. The respective polyethylene glycol (PEG) and poly vinyl caprolactam (PCL) structural components promoted stealth properties and enzymatic responsive release of CHX inside biofilms, leading to significantly enhanced penetration (56%) compared with free CHX and improving the efficacy against Staphylococcus aureus biofilms grown on an artificial dermis (2.4 log reduction of CFU). Mixing Soluplus-based micelles with Solutol further enhanced the CHX penetration (71%) and promoted maximum reduction in biofilm biomass (>60%). Nematodes-based toxicity assay showed micelles with no lethal effects as indicated by their high survival rate (100%) after 72 h exposure. This study thus demonstrated that bio-responsive carriers can be designed to deliver a poorly water-soluble antimicrobial agent and advance the control of biofilm associated infections.

N-(2-Hydroxyethyl)-L-valyl-L-leucine in rat urine as a hydrolytic cleavage product of ethylene oxide adduct with globin.

Ethylene oxide (EO), a genotoxic industrial chemical and sterilant, forms covalent adducts with DNA and also with nucleophilic amino acids in proteins. The adduct with N-terminal valine in globin [N-(2-hydroxyethyl)valine (HEV)] has been used in biomonitoring of cumulative exposures to EO. Here we studied in rats the fate of EO-adducted N-termini of globin after life termination of the erythrocytes. Rat erythrocytes were incubated with EO to produce the HEV levels in globin at 0.4-13.2 µmol/g as determined after acidic hydrolysis. Alternative hydrolysis of the isolated globin with enzyme pronase afforded N-(2-hydroxyethyl)-L-valyl-L-leucine (HEVL) and N-(2-hydroxyethyl)-L-valyl-L-histidine (HEVH), the EO-adducted N-terminal dipeptides of rat globin α- and ß-chains, respectively. The ratio of HEVL/HEVH (1:3) reflected higher reactivity of EO with the ß-chain. The EO-modified erythrocytes were then given intravenously to the recipient rats. HEVL and HEVH were found to be the ultimate cleavage products excreted in the rat urine. Finally, rats were dosed intraperitoneally with EO, 50 mg/kg. Herein, the initial level of globin-bound HEVL (11.7 ± 1.3 nmol/g) decreased almost linearly over 60 days corresponding to the life span of rat erythrocytes. Daily urinary excretion of HEVL was almost constant for 30-40 days, decreasing faster in the subsequent phase of elimination. Recoveries of the total urinary HEVL from its globin-bound form were 84 ± 6% and 101 ± 17% after administrations of EO and the EO-modified erythrocytes, respectively. In conclusion, urinary HEVL appears to be a promising novel non-invasive biomarker of human exposures to EO.

Understanding the importance of low-molecular weight (ethylene oxide- and propylene oxide-induced) DNA adducts and mutations in risk assessment: Insights from 15 years of research and collaborative discussions.

The interpretation and significance of DNA adduct data, their causal relationship to mutations, and their role in risk assessment have been debated for many years. An extended effort to identify key questions and collect relevant data to address them was focused on the ubiquitous low MW N7-alkyl/hydroxyalkylguanine adducts. Several academic, governmental, and industrial laboratories collaborated to gather new data aimed at better understanding the role and potential impact of these adducts in quantifiable genotoxic events (gene mutations/micronucleus). This review summarizes and evaluates the status of dose-response data for DNA adducts and mutations from recent experimental work with standard mutagenic agents and ethylene oxide and propylene oxide, and the importance for risk assessment. This body of evidence demonstrates that small N7-alkyl/hydroxyalkylguanine adducts are not pro-mutagenic and, therefore, adduct formation alone is not adequate evidence to support a mutagenic mode of action. Quantitative methods for dose-response analysis and derivation of thresholds, benchmark dose (BMD), or other points-of-departure (POD) for genotoxic events are now available. Integration of such analyses of genetox data is necessary to properly assess any role for DNA adducts in risk assessment. Regulatory acceptance and application of these insights remain key challenges that only the regulatory community can address by applying the many learnings from recent research. The necessary tools, such as BMDs and PODs, and the example datasets, are now available and sufficiently mature for use by the regulatory community. Environ. Mol. Mutagen. 60: 100-121, 2019. © 2018 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.

A physiologically based toxicokinetic model for inhaled ethylene and ethylene oxide in mouse, rat, and human.

Ethylene (ET) is the largest volume organic chemical. Mammals metabolize the olefin to ethylene oxide (EO), another important industrial chemical. The epoxide alkylates macromolecules and has mutagenic and carcinogenic properties. In order to estimate the EO burden in mice, rats, and humans resulting from inhalation exposure to gaseous ET or EO, a physiological toxicokinetic model was developed. It consists of the compartments lung, richly perfused tissues, kidneys, muscle, fat, arterial blood, venous blood, and liver containing the sub-compartment endoplasmic reticulum. Modeled ET metabolism is mediated by hepatic cytochrome P450 2E1, EO metabolism by hepatic microsomal epoxide hydrolase or cytosolic glutathione S-transferase in various tissues. EO is also spontaneously hydrolyzed or conjugated with glutathione. The model was validated on experimental data collected in mice, rats, and humans. Modeled were uptake by inhalation, wash-in-wash-out effect in the upper respiratory airways, distribution into tissues and organs, elimination via exhalation and metabolism, and formation of 2-hydroxyethyl adducts with hemoglobin and DNA. Simulated concentration-time courses of ET or EO in inhaled (gas uptake studies) or exhaled air, and of EO in blood during exposures to ET or EO agreed excellently with measured data. Predicted levels of adducts with DNA and hemoglobin, induced by ET or EO, agreed with reported levels. Exposures to 10000 ppm ET were predicted to induce the same adduct levels as EO exposures to 3.95 (mice), 5.67 (rats), or 0.313 ppm (humans). The model is concluded to be applicable for assessing health risks from inhalation exposure to ET or EO.

The Effect of Sterilization Methods of Endoscopic Instruments on the Body: A Study on Rat Model.

PURPOSE: Laparoscopy is widely used in many surgical areas for diagnosis and treatment. The need for sterilization of reusable instruments is an important issue. Ensuring patient safety, preventing infection, and protecting the functionality of the instruments are the most important points to be considered. We aimed to investigate two sterilization methods and their effects generated by their distribution into intra-abdominal tissues during insufflation. MATERIALS AND METHODS: 21 rats were used in the study. The Control Group (Group 1) received anesthesia for 1 hour; Group 2 (Glutaraldehyde (GA)-Pneumoperitoneum Group) received anesthesia for 1 hour; Group 3 (Ethylene Oxide (EO)-Pneumoperitoneum Group) received anesthesia for 1 hour. After 24 hours, the animals were sacrificed, and the kidneys and omentum of the animals were analyzed in a histopathological manner. Blood samples were analyzed at preoperative 24th hour and at postoperative 24th hour. RESULTS: There was a statistically significant difference in omentum, endothelium, and glomerular scores between the groups (p < 0.001 for all groups). Endothelial and glomerular scores were different at a statistically significant level in the EO and GA groups compared to the Control Group. The total score was higher at a statistically significant level in the EO and GA groups compared to the Control Group (p < 0.001 for both groups). CONCLUSION: It was determined in our study that sterilization methods such as EO and GA cause damage in intra-abdominal tissues. In the light of these results, we consider that the most ideal laparoscopic surgery set is the single-use laparoscopy set. However, this does not seem possible especially in developing countries in practice.

Carcinogenicity of ethylene oxide: key findings and scientific issues.

In support of the Integrated Risk Information System (IRIS), the U.S. Environmental Protection Agency (EPA) completed an evaluation of the inhalation carcinogenicity of ethylene oxide (EtO) in December 2016. This article reviews key findings and scientific issues regarding the carcinogenicity of EtO in EPA's Carcinogenicity Assessment. EPA's assessment critically reviewed and characterized epidemiologic, laboratory animal, and mechanistic studies pertaining to the human carcinogenicity of EtO, and addressed some key scientific issues such as the analysis of mechanistic data as part of the cancer hazard evaluation and to inform the quantitative risk assessment. The weight of evidence from the epidemiologic, laboratory animal, and mechanistic studies supports a conclusion that EtO is carcinogenic in humans, with the strongest human evidence linking EtO exposure to lymphoid and breast cancers. Analyses of the mechanistic data establish a key role for genotoxicity and mutagenicity in EtO-induced carcinogenicity and reveal little evidence supporting other mode-of-action hypotheses. In conclusion, EtO was found to be carcinogenic to humans by inhalation, posing a potential human health hazard for lymphoid and breast cancers.

Derivation of endogenous equivalent values to support risk assessment and risk management decisions for an endogenous carcinogen: Ethylene oxide.

An approach is presented for ethylene oxide (EO) to derive endogenous equivalent (EE) values, which are endogenous levels normally found within the body expressed in terms of exogenous exposures. EE values can be used to support risk assessment and risk management decisions for chemicals such as EO that have both endogenous and exogenous exposure pathways. EE values were derived using a meta-analysis of data from the published literature characterizing the distribution for an EO biomarker of exposure, hemoglobin N-(2-hydroxyethyl)-valine (HEV), in unexposed populations. These levels are compared to the those reported in exposed populations (smokers, workers). Correlation between the biomarker of exposure and external exposures of EO were applied to this distribution to determine corresponding EE values, which range from 0.13 to 6.9 ppb for EO in air. These values are orders of magnitude higher than risk-based concentration values derived for EO using default methods, and are provided as a pragmatic, data-driven alternative approach to managing the potential risks from exogenous exposures to EO.

Dose and temporal evaluation of ethylene oxide-induced mutagenicity in the lungs of male big blue mice following inhalation exposure to carcinogenic concentrations.

Ethylene oxide (EO) is a direct acting alkylating agent; in vitro and in vivo studies indicate that it is both a mutagen and a carcinogen. However, it remains unclear whether the mode of action (MOA) for cancer for EO is a mutagenic MOA, specifically via point mutation. To investigate the MOA for EO-induced mouse lung tumors, male Big Blue (BB) B6C3F1 mice (10/group) were exposed to EO by inhalation, 6 hr/day, 5 days/week for 4 (0, 10, 50, 100, or 200 ppm EO), 8, or 12 weeks (0, 100, or 200 ppm EO). Lung DNA samples were analyzed for cII mutant frequency (MF) at 4, 8 and 12 weeks of exposure; the mutation spectrum was analyzed for mutants from control and 200 ppm EO treatments. Although EO-induced cII MFs were 1.5- to 2.7-fold higher than the concurrent controls at 4 weeks, statistically significant increases in the cII MF were found only after 8 and 12 weeks of exposure and only at 200 ppm EO (P ≤ 0.05), which is twice the highest concentration used in the cancer bioassay. Consistent with the positive response, DNA sequencing of cII mutants showed a significant shift in the mutational spectra between control and 200 ppm EO following 8 and 12 week exposures (P ≤ 0.035), but not at 4 weeks. Thus, EO mutagenic activity in vivo was relatively weak and required higher than tumorigenic concentrations and longer than 4 weeks exposure durations. These data do not follow the classical patterns for a MOA mediated by point mutations. Environ. Mol. Mutagen. 58:122-134, 2017. © 2017 Wiley Periodicals, Inc.

Genotoxicity of ethylene oxide: A review of micronucleus assay results in human population.

Ethylene oxide (EtO) has been categorized as "carcinogenic to humans (Group 1)" by the IARC. While several epidemiological studies have reported carcinogenicity and EtO-Hb formation; information from cytogenetic endpoints are rather inconclusive. In the present review, we focus on the results of eleven studies which have reported the results of micronucleus assay in EtO exposed workers. We have critically reviewed these studies based on the exposure assessment, concentration and duration, and compared the sensitivity of micronucleus assay to other reported endpoints like EtO-Hb, CA, SCE. The levels of EtO and EtO-Hb adducts in all the studies were strongly correlated to the results of SCE, but not to MN. MN were only observed in a limited number of studies with high EtO exposure (2-28ppm 8h-TWA) and not below the recommended concentration of <1ppm. To further understand the effect of exposure of EtO on MN assay outcome, we propose studies with more harmonized protocol for exposure assessment and MN analysis, determination of suitable sample size and use of multiple target tissues to understand the effect of metabolite.

Quantification of the mutagenic potency and repair of glycidol-induced DNA lesions.

Glycidol (Gly) is an electrophilic low-molecular weight epoxide that is classified by IARC as probably carcinogenic to humans. Humans might be exposed to Gly from food, e.g. refined vegetable oils, where Gly has been found as a food process contaminant. It is therefore important to investigate and quantify the genotoxicity of Gly as a primary step towards cancer risk assessment of the human exposure. Here, quantification of the mutagenic potency expressed per dose (AUC: area under the concentration-time curve) of Gly has been performed in Chinese hamster ovary (CHO) cells, using the HPRT assay. The dose of Gly was estimated in the cell exposure medium by trapping Gly with a strong nucleophile, cob(I)alamin, to form stable cobalamin adducts for analysis by LC-MS/MS. Gly was stable in the exposure medium during the time for cell treatment, and thus the dose in vitro is the initial concentration×cell treatment time. Gly induced mutations in the hprt-gene at a rate of 0.08±0.01 mutations/10(5) cells/mMh. Through comparison with the effect of ionizing radiation in the same system a relative mutagenic potency of 9.5rad-eq./mMh was obtained, which could be used for comparison of genotoxicity of chemicals and between test systems and also in procedures for quantitative cancer risk assessment. Gly was shown to induce strand breaks, that were repaired by base excision repair. Furthermore, Gly-induced lesions, present during replication, were found to delay the replication fork elongation. From experiments with repair deficient cells, homologous recombination repair and the ERCC1-XPF complex were indicated to be recruited to support in the repair of the damage related to the stalled replication elongation. The type of DNA damage responsible for the mutagenic effect of Gly could not be concluded from the present study.

Effect of Sterilization Methods on Electrospun Poly(lactic acid) (PLA) Fiber Alignment for Biomedical Applications.

Medically approved sterility methods should be a major concern when developing a polymeric scaffold, mainly when commercialization is envisaged. In the present work, poly(lactic acid) (PLA) fiber membranes were processed by electrospinning with random and aligned fiber alignment and sterilized under UV, ethylene oxide (EO), and γ-radiation, the most common ones for clinical applications. It was observed that UV light and γ-radiation do not influence fiber morphology or alignment, while electrospun samples treated with EO lead to fiber orientation loss and morphology changing from cylindrical fibers to ribbon-like structures, accompanied to an increase of polymer crystallinity up to 28%. UV light and γ-radiation sterilization methods showed to be less harmful to polymer morphology, without significant changes in polymer thermal and mechanical properties, but a slight increase of polymer wettability was detected, especially for the samples treated with UV radiation. In vitro results indicate that both UV and γ-radiation treatments of PLA membranes allow the adhesion and proliferation of MG 63 osteoblastic cells in a close interaction with the fiber meshes and with a growth pattern highly sensitive to the underlying random or aligned fiber orientation. These results are suggestive of the potential of both γ-radiation sterilized PLA membranes for clinical applications in regenerative medicine, especially those where customized membrane morphology and fiber alignment is an important issue.