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.

Synthesis of multimodal polymersomes for targeted drug delivery and MR/fluorescence imaging in metastatic breast cancer model.

The objective of the current study is to design and delivery of targeted PEG-PCL nanopolymersomes encapsulated with Gadolinium based Quantum Dots (QDs) and Doxorubicin (DOX) as magnetic resonance-florescence imaging and anti-cancer agent. Diagnostic and therapeutic efficiency of the prepared theranostic formulation was evaluated in vitro and in vivo. Hydrophobic QDs based on indium-copper-gadolinium-zinc sulfide were synthesized and characterized extensively. Hydrophobic QDs and hydrophilic DOX were loaded in PEG-PCL polymersomes through double emulsion method. Drug release pattern was studied in both citrate (pH 5.4) and phosphate (pH 7.4) buffer during 10 days. Both fluorescence and magnetic properties of bare QDs and prepared formulations were studied entirely. AS1411 DNA aptamer was covalently attached to the surface of polymersomal formulation in order to prepare targeted drug delivery system. Cellular cytotoxicity and cellular uptake analysis were performed in both nucleolin positive (MCF7 and 4T1) and nucleolin negative (CHO) cell lines. After in vitro evaluations, anti-tumor efficiency and diagnostic capability of the formulation was investigated in 4T1 tumor baring mice. Scanning emission electron microscopy (SEM) confirmed spherical shape and around 100 nm size of prepared formulations. Transmission electron microscopy (HRTEM) showed crystal shape of QDs with size of 2-3 nm. Drug release study obtained controlled release of encapsulated DOX and stability of formulation in physiologic condition. MTT and flow cytometry results demonstrated that AS1411 aptamer could enhance both toxicity and cellular uptake in nucleolin overexpressing cell lines (P < 0.05). Moreover, aptamer targeted formulation could increase survival rate and tumor inhibitory growth effect in 4T1 tumor baring mice (P < 0.05). Our results verify that aptamer targeted polymersomes loaded with non-toxic QDs as a diagnostic agent and DOX as an anti-cancer drug, could provide a theranostic platform with the purpose of optimization of treatment process and minimization of systemic side effects.

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.

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.

cRGD-functionalized reduction-sensitive shell-sheddable biodegradable micelles mediate enhanced doxorubicin delivery to human glioma xenografts in vivo.

Biodegradable micelles are one of the most studied systems for the delivery of hydrophobic anticancer drugs. Their therapeutic efficacy in vivo is, however, suboptimal, partly due to poor tumor cell uptake as well as slow intracellular drug release. Here, we show that cRGD-functionalized intracellularly shell-sheddable biodegradable PEG-SS-PCL micelles mediate enhanced doxorubicin (DOX) delivery to U87MG glioma xenografts in vivo, resulting in significantly improved tumor growth inhibition as compared to reduction-insensitive cRGD/PEG-PCL controls. cRGD/PEG-SS-PCL micelles revealed a small size of ca. 61nm, a decent DOX loading of 14.9wt%, and triggered drug release in a reductive environment (10mM glutathione). Flow cytometry, confocal microscopy, and MTT assays demonstrated that cRGD/PEG-SS-PCL micelles with a cRGD ligand density of 20% efficiently delivered and released DOX into αvß3 integrin overexpressing U87MG cells. The in vivo pharmacokinetics studies displayed that DOX-loaded cRGD20/PEG-SS-PCL micelles had a prolonged elimination half-life time of 3.51h, which was comparable to that of cRGD20/PEG-PCL counterparts, indicating that disulfide bonds in the PEG-SS-PCL micelles are stable in the circulation. Notably, in vivo imaging and biodistribution studies in U87MG glioma xenografts showed that cRGD20/PEG-SS-PCL micelles led to efficient accumulation as well as fast drug release in the tumor. The therapeutic outcomes demonstrated that DOX-loaded cRGD20/PEG-SS-PCL micelles exhibited little side effects and superior tumor growth inhibition as compared to non-targeting PEG-SS-PCL and reduction-insensitive cRGD20/PEG-PCL counterparts. The reduction-sensitive shell-sheddable biodegradable micelles have appeared as a fascinating platform for targeted tumor chemotherapy.

Challenges facing sterilization and depyrogenation of nanoparticles: effects on structural stability and biomedical applications.

This review outlines and compares techniques that are currently available for the sterilization of nanoparticles and addresses the topic of endotoxin contamination. Several techniques are available for the removal of microbial contamination from nanoparticles developed for use in nanomedicine applications. These techniques include filtration, autoclaving and irradiation, as well as formaldehyde, ethylene oxide and gas plasma treatments. Of these sterilization methodologies, filtration may potentially remove microbial contamination without altering the physicochemical properties of the carrier nanoparticles, nor affecting their toxicity and functionality. However, no single process may be applied to all nanoparticle preparations and, therefore, it is recommended that each nanoparticle-drug system be validated on a case-by-case basis. From the clinical editor: This comprehensive review covers the currently available methods for removal of microbial contaminations from nanoparticles for nanomedicine applications. The review highlights the pros and cons of each available method. Authors conclude that there is no single best method and recommend a customized approach for each nanoparticle system.

Intracellular delivery mechanism and brain delivery kinetics of biodegradable cationic bovine serum albumin-conjugated polymersomes.

BACKGROUND: A novel brain drug delivery system using cationic bovine serum albumin (CBSA)-conjugated biodegradable polymersomes (CBSA-PO) was prepared, and its intracellular delivery mechanism and brain delivery kinetics were evaluated. METHODS AND RESULTS: Biodegradable poly(ethylene glycol)-poly(ɛ-caprolactone) (PEG-PCL) was used to prepare the polymersomes, and thiolated CBSA was conjugated with the surface of the polymersome. Transmission electron microscopy and dynamic light scattering showed that the CBSA-PO had a round and vesicle-like shape, with a mean diameter of around 100 nm. Coupling of CBSA with polymersomes was confirmed by X-ray photoelectron spectroscopy. Uptake of CBSA-PO by bEnd.3 cells was significantly higher than that of unconjugated polymersomes, but was inhibited by low temperature, free CBSA, and poly-L-lysine, indicating that endocytosis was energy-driven and absorptive-mediated. Cell viability assays confirmed the good safety profile of biodegradable CBSA-PO. Pharmacokinetic results demonstrated that the polymersomes had long circulation times, and CBSA conjugation on the polymersomes significantly increased the blood-brain barrier permeability surface area product by 3.6-fold and the percentage of injected dose per gram brain (% ID/g brain) by 2.1-fold. Capillary depletion experiments showed that CBSA-PO was distributed into the brain parenchyma in a time-dependent manner, with few polymersomes detected, indicating that conjugation of polymersomes with CBSA significantly improved their transcytosis across the brain-blood barrier. CONCLUSION: These results suggest that CBSA-PO is a promising drug brain delivery carrier with low toxicity.

Synthesis and evaluation of biodegradable PCL/PEG nanoparticles for neuroendocrine tumor targeted delivery of somatostatin analog.

PURPOSE: Neuroendocrine tumors often present a diagnostic and therapeutic challenge. We have aimed to synthesize and develop biodegradable nanoparticles of somatostatin analogue, octreotide for targeted therapy of human neuroendocrine pancreatic tumor. METHODS: Direct solid phase peptide synthesis of octreotide was done. Octreotide loaded PCL/PEG nanoparticles were prepared by solvent evaporation method and characterized for transmission electron microscopy, differential scanning calorimetery (DSC), Zeta potential measurement studies. The nanoparticles were evaluated in vitro for release studies and peptide content. For biological evaluations, receptor binding & cytotoxicity studies were done on BON-1 neuroendocrine tumor cell line. Biodistribution of radiolabeled peptide and nanoparticles, tumor regression studies were performed on tumor-bearing mouse models. RESULTS: We have synthesized and purified octreotide with the purity of 99.96% in our laboratory. PEG/PCL nanoparticles with an average diameter of 130-195 nm having peptide loading efficiency of 66-84% with a negative surface charge were obtained with the formulation procedure. Octreotide nanoparticles have a negative action on the proliferation of BON-1 cells. In vivo biodistribution studies exhibited major accumulation of octreotide nanoparticles in tumor as compared to plain octreotide. Octreotide nanoparticles inhibited tumor growth more efficiently than free octreotide. CONCLUSIONS: Thus, it was concluded that the PCL/PEG nanoformulation of octreotide showed high tumor uptake due to the enhanced permeation and retention (EPR) effect and then peptide ligand imparts targetability to the sst2 receptor and there by showing increase tumor growth inhibition. Selective entry of nanoparticles to the tumor also give the reduce side effects both in vivo and in vitro.

Investigation on design of stable etoposide-loaded PEG-PCL micelles: effect of molecular weight of PEG-PCL diblock copolymer on the in vitro and in vivo performance of micelles.

In the present study, six different molecular weight diblock copolymer of methoxy poly (ethylene glycol)-b-poly (ε-caprolactone) (MPEG-PCL) were synthesized and characterized and was used for fabrication of etoposide-loaded micelles by nanoprecipitation technique. The particle size and percentage drug entrapment of prepared micelles were found to be dependent on the molecular weight of PCL block and drug to polymer ratio. The maximum drug loading of 5.32% was found in micellar formulation MPEG5000-PCL10000, while MPEG2000-PCL2000 exhibited 2.73% of maximum drug loading. A variation in the fixed aqueous layer thickness and PEG surface density of micellar formulations was attributed to difference in MPEG molecular weight and interaction of PEG and PCL block of copolymer. The MPEG2000-PCL2000 micelles demonstrated poor in vitro stability among other micellar formulations, due to its interaction with bovine serum albumin and immediate release of drug from micelles. Furthermore, plain etoposide and MPEG2000-PCL2000 micelles exhibited greater extent of hemolysis, due to presence of surfactants and faster release of drug from micelles, respectively. The biodistribution studies carried out on Ehrlich ascites tumor-bearing Balb/C mice confirmed higher accumulation of etoposide-loaded micellar formulation at tumor site compared to plain etoposide due to enhanced permeability and retention effect.

Hydrogel-electrospun fiber composite materials for hydrophilic protein release.

Although hydrogels are widely used in controlled-release systems, obtaining extended, uniform drug release with little initial burst has been challenging. However, recently researchers have shown that combining hydrogels with another drug delivery material can dramatically improve release kinetics. Here we describe a novel hydrogel-based composite material that exhibits stable, near-linear, sustained release of a model hydrophilic protein (e.g., bovine albumin serum, BSA) for over two months with a significant reduction in initial burst release (7% vs. 20%). The composite is comprised of poly(ε-caprolactone) (PCL) electrospun fiber mats coupled with poly(ethylene glycol)-poly(ε-caprolactone) diacrylate (PEGPCL) hydrogels through photo-polymerization. It is believed that the additional diffusion barrier provided by hydrophobic electrospun fiber mats reduces hydrogel swelling and water penetration rates and increases the diffusion path length, resulting in delayed, more uniform drug release. Further, released proteins remain bioactive as demonstrated by PC12 cell neurite extension in response to released nerve growth factor (NGF). The use of electrospun fiber mats to modulate hydrogel drug release provides a new method to control release kinetics of hydrophilic proteins, reducing burst release and extending the release duration.

Anticoagulación del circuito extracorpóreo esterilizado con óxido de etileno y rayos gamma: ¿necesitan las mismas dosis de heparina? / Anticoagulation of the extracorporeal circuit sterilized with ethylene oxide and gamma irradiation: is the same dose of heparin needed?

Introducción: En los últimos años se han ido sustituyendo las líneas de hemodiálisis esterilizadas con óxido de etileno por las esterilizadas con rayos gamma, dado que numerosos autores han demostrado que es un método más biocompatible. Al utilizar líneas esterilizadas con rayos gamma observamos que se formaban más coágulos que con las esterilizadas con óxido de etileno. Objetivos: Observar si hay diferencia en las dosis de heparina utilizadas y en la formación de coágulos en los circuitos extracorpóreos esterilizados con rayos gamma y óxido de etileno. Material y método: Hemos realizado un estudio cuasi-experimental, longitudinal y prospectivo, utilizando en el mismo paciente líneas de hemodiálisis esterilizadas con rayos gamma y con óxido de etileno. Se realizaron en cada paciente 12 sesiones de hemodiálisis consecutivas con cada tipo de línea. Después de cada sesión se valoraron las pérdidas hemáticas en las cámaras arteriales y venosas, así como las necesidades de heparina. Resultado: Los resultados obtenidos demuestran que la formación de coágulos es mayor en las líneas esterilizadas con rayos gamma y que sí se modificó la dosis de heparina aunque no fue estadísticamente significativa. Discusión: Mantener una buena anticoagulación del circuito extracorpóreo durante la diálisis permite: realizar un tratamiento clínicamente satisfactorio durante el tiempo requerido, evitar pérdidas estimadas altas y minimizar la heparina circulante disminuyendo los efectos secundarios (AU)

Introduction: In recent years, haemodialysis lines sterilized using ethylene oxide have been replaced with lines sterilized using gamma irradiation, as several authors have proven that it is a more biocompatible method. On using lines sterilized by gamma irradiation, we observed that more clots were formed than with lines sterilized with ethylene oxide. Aims: To observe whether there is a difference in the heparin doses used and in the formation of clots in the extracorporeal circuits sterilized using gamma irradiation and ethylene oxide. Material and method: We carried out a quasiexperimental, longitudinal and prospective study using haemodialysis lines sterilized by gamma irradiation and by ethylene oxide on the same patient. On each patient, 12 consecutive haemodialysis sessions with each type of line were carried out. After each session, the blood loss in the arterial and venous chambers was evaluated, together with the heparin needs. Results: The results obtained show that clot formation is higher in the lines sterilized using gamma irradiation and that the heparin dose was indeed modified, although it was not statistically significant. Discussion: Maintaining good anticoagulation of the extracorporeal circuit during dialysis makes it possible to: carry out a clinically satisfactory treatment during the time required, prevent estimated high losses and minimize the circulating heparin, reducing the side effects (AU)

Quantitative cancer risk assessment for ethylene oxide inhalation in occupational settings.

The estimated occupational ethylene oxide (EO) exposure concentrations corresponding to specified extra risks are calculated for lymphoid mortality as the most appropriate endpoint, despite the lack of a statistically significant exposure-response relationship. These estimated concentrations are for occupational exposures--40 years of occupational inhalation exposure to EO from age 20 to age 60 years. The estimated occupational inhalation exposure concentrations (ppm) corresponding to specified extra risks of lymphoid mortality to age 70 years in a population of male and female EO workers are based on Cox proportional hazards models of the most recent updated epidemiology cohort mortality studies of EO workers and a standard life-table calculation. An occupational exposure at an inhalation concentration of 2.77 ppm EO is estimated to result in an extra risk of lymphoid mortality of 4 in 10,000 (0.0004) in the combined worker population of men and women from the two studies. The corresponding estimated concentration decreases slightly to 2.27 ppm when based on only the men in the updated cohorts combined. The difference in these estimates reflects the difference between combining all of the available data or focusing on only the men and excluding the women who did not show an increase in lymphoid mortality with EO inhalation exposure. The results of sensitivity analyses using other mortality endpoints (all lymphohematopoietic tissue cancers, leukemia) support the choice of lymphoid tumor mortality for estimation of extra risk.

Micronucleus assay for mouse alveolar Type II and Clara cells.

The objective of our study was to develop a micronucleus (MN) assay for detecting genotoxic damage after inhalation exposure in mouse alveolar Type II and Clara cells, potential target cells for lung carcinogens. Ten male C57BL/6J mice were exposed to ethylene oxide (630 mg/m(3)) for 4 hr via inhalation; 10 unexposed mice serving as controls. 72 hr after the exposure, Clara cells and alveolar Type II cells were isolated using two different methods. Method 1 included a 15-min trypsin lavage and a 2-hr incubation of cell suspension. Method 2 involved a 30-min trypsin lavage, Percoll gradient centrifugation, and a 48-hr incubation for cell attachment. Nitro blue tetrazolium (NBT) -staining was applied to distinguish Clara cells. The frequency of micronuclei (MNi) was scored in NBT-negative cells (defined as Type II cells in Method 2) and NBT-positive cells (Clara cells). To detect possible differences between the techniques, MNi in Clara cells were analyzed from samples prepared by both methods. With Method 2, a clear increase in the mean frequency of micronucleated cells was seen in the exposed mice as compared with the controls, for both alveolar Type II and Clara cells. However, no significant increase in MN frequency was seen in Clara cells analyzed from samples prepared by Method 1. Based on our findings, mouse alveolar Type II and Clara cells seem to be suitable for MN analysis in studies aimed at identifying genotoxic lung carcinogens. Both alveolar Type II and Clara cells can be isolated using Method 2.

Reciprocal translocations in somatic and germ cells of mice chronically exposed by inhalation to ethylene oxide: implications for risk assessment.

Groups of male B6C3F1 mice were exposed by inhalation to 0, 25, 50, 100 or 200 p.p.m. ethylene oxide (EO) for up to 48 weeks (6 hours/day, 5 days/week). Animals were sacrificed at 6, 12, 24 and 48 weeks after the start of the exposure for analyses of reciprocal translocations in peripheral blood lymphocytes and germ cells. The frequency of the total chromosomal aberrations in the peripheral blood lymphocytes was significantly increased at the 100 and 200 p.p.m. exposure concentrations at the 12-week time point, at 50, 100 and 200 p.p.m. at the 24-week time point and at all EO concentrations at the 48-week time point. The frequency of stable reciprocal translocations, which can be used as biomarkers, was increased (P < 0.05) at 100 and 200 p.p.m. at the 12-week time point, at 100 and 200 p.p.m. at the 24-week time point and at 50, 100 and 200 p.p.m. at the 48-week time point. No statistically significant increase could be observed in translocation frequencies at the 6-week time point in the peripheral blood lymphocytes. The exposure-response curves were non-linear when the frequencies of translocations were plotted against EO exposure durations or against EO exposure concentrations. There was no effect of exposure concentration rate on reciprocal translocation frequency. Reciprocal translocations induced in spermatogonial stem cells (observed at the sprematocyte stage) showed significant increases in translocation frequencies over controls at all EO concentrations at 48 weeks. However, increases were small and they did not occur in a dose-responsive manner. The statistically significant increase observed at 12 weeks in the spermatocytes was equivocal. This study provides low-level chronic exposure somatic cytogenetic data generated in mice that can be used to support the shape of the tumour dose-response in rodents and humans The germ cell cytogenetic data are discussed in terms of its relevance for a threshold response for genetic effects at low exposures.

Dose-response relationships for N7-(2-hydroxyethyl)guanine induced by low-dose [14C]ethylene oxide: evidence for a novel mechanism of endogenous adduct formation.

Ethylene oxide (EO) is widely used in the chemical industry and is also formed in humans through the metabolic oxidation of ethylene, generated during physiologic processes. EO is classified as a human carcinogen and is a direct acting alkylating agent, primarily forming N7-(2-hydroxyethyl)guanine (N7-HEG). To conduct accurate human risk assessments, it is vital to ascertain the relative contribution of endogenously versus exogenously derived DNA damage and identify the sources of background lesions. We have therefore defined in vivo dose-response relationships over a concentration range relevant to human EO exposures using a dual-isotope approach. By combining liquid chromatography-tandem mass spectrometry and high-performance liquid chromatography-accelerator mass spectrometry analysis, both the endogenous and exogenous N7-HEG adducts were quantified in tissues of [(14)C]EO-treated rats. Levels of [(14)C]N7-HEG induced in spleen, liver, and stomach DNA increased in a linear manner from 0.002 to 4 adducts/10(8) nucleotides. More importantly, the extent of damage arising through this route was insignificant compared with the background abundance of N7-HEG naturally present. However, at the two highest doses, [(14)C]EO exposure caused a significant increase in endogenous N7-HEG formation in liver and spleen, suggesting that EO can induce physiologic pathways responsible for ethylene generation in vivo and thereby indirectly promote N7-HEG production. We present evidence for a novel mechanism of adduct formation to explain this phenomenon, involving oxidative stress and 1-aminocyclopropane-1-carboxylic acid as a potential biosynthetic precursor to ethylene in mammalian cells. Based on the proposed pathway, N7-HEG may have potential as a biomarker of cellular oxidative stress.

Évaluation de solutions de rechange à l'oxyde d'éthylène en stérilisation: plasma de peroxyde d'hydrogène et ozone / Evaluation of alternatives to ethylene oxide in sterilization: hydrogen peroxide and ozone plasma

INTRODUCTION: La stérilisation des instruments médicaux constitue un des maillons essentiels de l'hygiène et de la salubrité dans les établissements de santé et concourt à la lutte contre les infections nosocomiales. Pour être efficace, la stérilisation doit être organisée de façon fiable et faire appel à des techniques dont on maîtrise bien les bases scientifiques et l'utilisation. Les instruments médicaux thermosensibles sont stérilisés efficacement à l'oxyde d'éthylène (OE) dans de nombreux établissements de santé de par le monde depuis les années 1950. Toutefois, depuis le début des années 1990, de nouveaux procédés de retraitement des dispositifs médicaux réutilisables apparaissent sur le marché, dont certains semblent d'un grand intérêt en lien avec les préoccupations que génère la stérilisation à l'oxyde d'éthylène. Diverses raisons conjuguées sont à l'origine de la demande de nouvelles technologies pour remplacer ce procédé de stérilisation. MÉTHODE DE RECHERCHE: Stratégie de Recherche Documentaire: Une revue exhaustive de la littérature, portant sur toute publication en langues anglaise, française, italienne, espagnole et portugaise, a été menée dans les bases de données MEDLINE à l'aide du portail PubMed, CINAHL, et sur la Cochrane Library. Les termes utilisés pour cette recherche documentaire, « sterilization ¼, « plasma ¼, « plasmas ¼ et « ozone ¼, ont été employés seuls ou reliés par les opérateurs booléens « AND ¼ et « OR ¼. Une recherche sur le thème de la stérilisation en milieu médical a été réalisée dans diverses bibliothèques nationales et universitaires. La littérature grise a été explorée au moyen d'Internet. La recherche s'est plus spécialement concentrée sur la base de données Nosobase, spécialisée en hygiène hospitalière et infections nosocomiales, et sur d'autres bases semblables (catalogue et index des sites médicaux francophones, CISMeF, Banque française de données en santé publique, BDSP). L'ensemble a été complété par une recherche manuelle de publications à partir des documents repérés et par la consultation des sites Web des deux principaux fabricants de stérilisateurs à basse température qui ont recours à la technologie au plasma de H2O2 ou à l'ozone2. Toutes les publications affichant dans leur résumé des termes tels que « stérilisation à basse température ¼, « coût ¼, « efficacité microbicide ¼, « activité sporicide ¼, « sécurité ¼, «comparaison ¼, « altération de surface ¼, et dont la lecture du sommaire a confirmé la pertinence relativement à notre thème de travail, ont été sélectionnées. Méthode d'Évaluation: Toute étude repérée, réalisée sur les matériaux constitutifs des instruments, sur les instruments eux-mêmes, sur des porte-germes, en conditions simulées d'utilisation, en conditions réelles d'utilisation, ou toute étude comparative des techniques ont été évaluées au regard de leur conformité avec les normes et standards scientifiques communément admis pour les études de stérilisation. Ont été également retenus les guides de recommandation et fiches techniques rédigés à la suite du travail de groupes d'experts. La documentation extraite des sites commerciaux de Advanced Sterilization Products (ASP) (procédé Sterrad® au plasma de peroxyde d'hydrogène) et de TSO3 inc. (procédé TSO3 125L, à l'ozone) a servi à recueillir les caractéristiques des appareils disponibles et à vérifier l'origine des revendications d'efficacité et d'innocuité fournies par les fabricants. Il est à noter que peu d'études québécoises ont été trouvées. CONCLUSION: La stérilisation à l'oxyde d'éthylène des instruments médicaux thermosensibles est un procédé très efficace et longuement éprouvé. Toutefois, les besoins actuels de restérilisation en établissements de soins, la toxicité environnementale de l'oxyde d'éthylène, celle de ses sous-produits et les lignes directrices d'Environnement Canada conduisent le ministère de la Santé et des Services sociaux du Québec à s'interroger sur la pertinence ou non de remplacer le procédé de stérilisation à l'oxyde d'éthylène par de nouvelles techniques de stérilisation à basse température, efficaces, sécuritaires, rentables, et répondant donc aux critères habituels d'un procédé de stérilisation idéal. À la lumière de la littérature pertinente, il ressort que s'il est facile de trouver des arguments en faveur de l'abandon de la stérilisation à l'oxyde d'éthylène, il n'est pas toujours aisé de s'en séparer totalement. En effet, aucun des trois procédés à basse température ne répond en totalité aux critères d'un procédé idéal de stérilisation, les deux plus récents (plasma de peroxyde d'hydrogène et ozone) faisant l'objet de certaines limitations. De nombreux établissements de soins de par le monde ont opté depuis plusieurs années pour l'une ou l'autre des deux techniques émergentes, en remplacement du procédé à l'oxyde d'éthylène, trop toxique et trop long. Ces deux récents procédés, à l'opposé de la technologie à l'oxyde d'éthylène, présentent les avantages d'être plus rapides, respectueux de l'environnement et sans danger majeur pour le personnel de stérilisation et les patients. Ce sont des méthodes de rechange qui ont démontré leur efficacité et leur innocuité lorsque les indications et les limitations sont respectées, et lorsque le personnel de stérilisation observe les instructions d'utilisation des manufacturiers. Des recherches se poursuivent sur la stérilisation au plasma avec d'autres gaz que le peroxyde d'hydrogène. Celles -ci pourraient déboucher sur l'arrivée sur le marché de nouveaux appareils. D'autres recherches sur la stérilisation des instruments médicaux à l'ozone sont aussi en cours. Les études en collaboration avec les manufacturiers de matériels médicaux réutilisables continuent également, ce qui permet d'espérer une évolution positive régulière de la liste des instruments compatibles avec l'un ou l'autre des deux procédés émergents. Le choix de permutation éventuelle du procédé à l'oxyde d'éthylène vers l'un ou l'autre des procédés émergents de stérilisation à basse température résultera du travail collégial que mèneront les différents professionnels concernés. Ce travail comprend une analyse de toutes les difficultés rencontrées et même une exploration de la possibilité de remplacer les instruments thermosensibles par du matériel métallique pouvant être stérilisé à la vapeur chaude sous pression; enfin, il exige la mise en balance de l'efficacité microbicide du procédé avec ses effets sur la santé humaine et la toxicité environnementale de ses déchets, ainsi qu'avec son coût financier.

Modulation of intracellular ceramide using polymeric nanoparticles to overcome multidrug resistance in cancer.

Although multidrug resistance (MDR) is known to develop through a variety of molecular mechanisms within the tumor cell, many tend to converge toward the alteration of apoptotic signaling. The enzyme glucosylceramide synthase (GCS), responsible for bioactivation of the proapoptotic mediator ceramide to a nonfunctional moiety glucosylceramide, is overexpressed in many MDR tumor types and has been implicated in cell survival in the presence of chemotherapy. The purpose of this study was to investigate the therapeutic strategy of coadministering ceramide with paclitaxel, a commonly used chemotherapeutic agent, in an attempt to restore apoptotic signaling and overcome MDR in the human ovarian cancer cell line SKOV3. Poly(ethylene oxide)-modified poly(epsilon-caprolactone) (PEO-PCL) nanoparticles were used to encapsulate and deliver the therapeutic agents for enhanced efficacy. Results show that indeed the cotherapy eradicates the complete population of MDR cancer cells when they are treated at their IC(50) dose of paclitaxel. More interestingly, when the cotherapy was combined with the properties of nanoparticle drug delivery, the MDR cells can be resensitized to a dose of paclitaxel near the IC(50) of non-MDR (drug sensitive) cells, indicating a 100-fold increase in chemosensitization via this approach. Molecular analysis of activity verified the hypothesis that the efficacy of this therapeutic approach is indeed due to a restoration in apoptotic signaling, although the beneficial properties of PEO-PCL nanoparticle delivery seemed to enhance the therapeutic success even further, showing the promising potential for the clinical use of this therapeutic strategy to overcome MDR.

Determination of endogenous and exogenously derived N7-(2-hydroxyethyl)guanine adducts in ethylene oxide-treated rats.

Ethylene oxide (EO) is one of the most widely used intermediates in the chemical industry. It is also formed endogenously as a result of cytochrome P450-mediated metabolism of ethylene, which is ubiquitous in the environment. Additionally, ethylene is generated in vivo during normal physiological processes such as methionine oxidation and lipid peroxidation; therefore, humans are continually exposed to EO. EO is classed by the IARC as carcinogenic to humans and reacts with DNA, primarily forming N7-(2-hydroxyethyl)guanine adducts (N7-HEG), which can be used as biomarkers of exposure and potential cancer risk. To assess the risks to humans associated with occupational exposure to low EO concentrations, it is necessary to establish the relative contribution of DNA damage arising from endogenous and exogenously derived EO. Using a newly developed highly sensitive LC-MS/MS assay with selected reaction monitoring that offers a limit of detection of 0.1 fmol of N7-HEG on column, we have established background levels of N7-HEG (1.1-3.5 adducts/10(8) nucleotides) in tissues of rats. Following intraperitoneal administration of a single dose or three daily doses of EO (0.01-1.0 mg/kg), N7-HEG adducts generally increased with dose, except at the lowest concentration where total N7-HEG levels were no different to that detected in control animals, indicating that any increase was negligible as compared to the endogenous damage already present. In the 3 day study, the kinetics of adduct removal were also investigated and in comparing N7-HEG formation in the two studies, DNA damage did not appear to accumulate with repeated administration.