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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

Understanding the impact of engineered nanoparticles Gammarus sp. as a valuable non-vertebrate model? / Compréhension de l'impact des nanoparticules manufacturées : intérêt du gammare comme modèle invertébrés ?

Mehennaoui, Kahina 20 December 2017 (has links)
La toxicité potentielle des nanomatériaux présente un intérêt sociétal et scientifique élevé en raison de la promesse d'innovations pour de nombreuses applications techniques. Cependant, elle n’est pas forcément liée à la taille réelle, à la masse, à la surface des nanoparticules (NP) ou à leurs agglomérats. La toxicité des NPs pourrait être fortement influencée par d'autres propriétés inhérentes et encore incomprises telles que le relargage d’ions, de la particule elle-même, sa surface, ou des molécules adhérentes à la surface, qui interfèreraient avec l'absorption cellulaires des NPs. Le projet « NANOGAM» étroitement lié au projet « FNR CORE2012 NANION », vise à définir certains processus et facteurs impliqués dans l'absorption des NPs et leur toxicité. Une telle compréhension est une condition préalable au développement des nanomatériaux, fondement de la philosophie « safer-by-design ». Les objectifs de ce projet de thèse sont multiples. En tenant compte des caractéristiques des principaux paramètres physico-chimiques tels que la taille et l’aspect de la surface, l’étude a porté sur l'absorption de NPs d'argent et d'or, et leurs effets biologiques via une approche multi-biomarqueurs (mortalité, effets comportementaux, effets physiologiques, effets transcriptomiques, etc.) sur une espèce sensible, Gammarus fossarum (Crustacea Amphipoda). Le but de cette investigation est de comprendre si la toxicité des nanomatériaux est inhérente aux propriétés intrinsèques des NPs ou plutôt aux ions relargués, ce qui contribuera à la prédiction de la toxicité des NPs en rapport avec leurs propriétés physico-chimiques et ce afin de limiter le nombre d’essais répétitifs sur de nouveaux nanomatériaux. G. fossarum ont été exposés à de faibles concentrations d'AgNPs et AuNPs pendant 72h à jeun et 15 jours nourris. Les résultats obtenus ont montré que (i) la nature de l’enrobage de surface est le principal facteur responsable de l'absorption d'AgNPs et d'AuNPs par G. fossarum ; (ii) les ions libérés et les NPs elles-mêmes jouent un rôle dans la toxicité des AgNPs et AuNPs étudiées ; (iii) la composition chimique des NPs a conduit à des effets différents aux niveaux sub-individuels (transcriptomique), ainsi qu’à une distribution différente dans les tissues selon la nature métallique de la NP. Les AgNPs ont été localisées dans les branchies de G. fossarum tandis que les AuNPs ont été observées dans les caeca intestinaux. Cette étude a également révélé que Gammarus sp. est un excellent modèle pour l'étude de la toxicité et des effets des AgNPs et des AuNPs / The potential toxicity of nanomaterials is of high societal and scientific interest due to the promise of ground-breaking innovations for many technical applications. However, toxicity can often not be related to the actual size, mass or surface area of the single nanoparticles (NPs) or the NP agglomerates. Therefore, it can be proposed that the toxicity is greatly influenced by other inherent and non-understood properties of the particles to which ions dissolving from the particle, surface or molecules adhering to the surface interfering with the uptake of NPs into cells, may have important contributions. The PhD project “NANOGAM”, closely linked up to CORE2012 NANION project that aims to obtain knowledge to understand some of the processes and factors involved in NP uptake and toxicity as such understanding is a prerequisite for the development of nanomaterials following the safer-by-design philosophy. This PhD project aims to investigate, based on known characteristics of the key physico-chemical parameters; as size and surface functionalities, of a well-chosen list of silver and gold NPs, the uptake, and dependent biological effects of different complexity (mortality, behavioural effects, physiological effects, transcriptomic effects, etc.), on a sensitive species; Gammarus fossarum (Crustacea Amphipoda), in order to understand to which extent toxicity of nanomaterials is due to intrinsic material properties or ion leaching. Such understanding will contribute to the prediction of toxicity based on material properties rather than repetitive testing of an indefinite number of new nanomaterials. G. fossarum were exposed at low concentrations of AgNPs and AuNPs for 72h or 15 days in presence or absence of food. The obtained results showed that (i) surface coating is the main factor governing AgNPs and AuNPs uptake by G. fossarum, (ii) both released ions and NPs themselves play a role in the potency of the studied AgNPs and AuNPs and (iii) chemical composition led to different effects at the sub-individual levels (target genes expression) and different tissue distribution as AgNPs were found in G. fossarum gills while AuNPs were found in the intestinal caeca. Additionally, this work shows that Gammarus sp. are valuable models for the study of the effects of AgNPs and AuNPs
222

Reactive Blade Coating for Low-Cost Fabrication of Self-Assembled Metal Nanoparticles for Bio-Applications: Disinfecting SARS-CoV-2 to Limit the Spread of COVID-19 Illness

Ebrahimzadeh Asl Tabrizi, Bita 30 April 2021 (has links)
Considerable attention has been focused on nanomaterials and their extensive applications. Metallic nanoparticles, especially gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs), due to their superior physical, chemical, and optical properties, are vastly developed for numerous biomedical applications such as drug and gene delivery systems, diagnostic biosensors, imaging, and therapeutics. This study presents a low-cost method for the fabrication of self-assembled metallic nanoparticles, including gold and silver, via a reactive blade coating process, which is carried out based on in situ reduction of the metal precursors. This technique is a roll-to-roll compatible technique suitable for scalable nanomanufacturing. Oleylamine was used as a reducer agent, and gold (III) chloride hydrate and silver salts, including silver nitrate and silver perchlorate hydrate, were used as the metal precursors. Fabrication was carried out by first blade coating the reducer ink and subsequently coating the precursor ink followed by 3 hours of heat treatment. Various solvent systems were used to examine the effect of different solvents on the fabrication process. Surface morphology, crystalline phase composition, and plasmon resonance of the coated samples were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), and UV-Vis spectroscopy, respectively. Results demonstrated the synthesis of spherical self-assembled AuNPs using toluene (TOL) and isopropyl alcohol (IPA) for reducing and precursor solvents, respectively. Changing the concentration of reactants or increasing the coating layers exhibited a change in the average size of AuNPs. Self-assembled AuNPs thin films were also demonstrated to have the potential to be used as a biosensing platform based on localized surface plasmon resonance (LSPR) effect to detect the elevated levels of glucose in an aqueous solution. Recently, the world has faced a pandemic of Covid-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has threatened human health and has brought a worldwide devastating economic and social crisis. Hence, finding a solution to mitigate the current breakout of Covid-19 is vital to protect the international community from its causing harm. AgNPs as an antimicrobial agent, which has exhibited promising antiviral activity against several viruses, can offer a resolution to combat the spread of Covid-19. In this regard, AgNPs thin films were fabricated analogously via blade coating using various reducer and silver salt inks made of different solvent systems. Virucidal efficacy of reactive blade coated AgNPs on glass substrates was analyzed against human coronavirus 229E, a virus from the Coronavirus family, as a surrogate SARS-CoV-2 (according to the Level 2 Biosafety facility at uOttawa). Plaque forming assay indicated more than 99.99% reduction in infectivity of the virus when it contacts the AgNPs coated glass for 30 min before infecting cells. These results suggest the excellent potential for reactive blade coated AgNPs as an antiviral agent against coronavirus to avoid the spread of the virus.
223

Enhancement of Light Emission from Metal Nanoparticles Embedded Graphene Oxide

Karna, Sanjay K. 05 1900 (has links)
A fully oxidized state of graphene behaves as a pure insulating while a pristine graphene behaves as a pure conducting. The in-between oxide state in graphene which is the controlled state of oxide behaves as a semiconducting. This is the key condition for tuning optical band gap for the better light emitting property. The controlling method of oxide in graphene structure is known as reduction which is the mixed state of sp2 and sp3 hybrid state in graphene structure. sp2 hybridized domains correspond to pure carbon-carbon bond i.e. pristine graphene while sp3 hybridized domains correspond to the oxide bond with carbon i.e. defect in graphene structure. This is the uniqueness of the graphene-base material. Graphene is a gapless material i.e. having no bandgap energy and this property prevents it from switching device applications and also from the optoelectronic devices applications. The main challenge for this material is to tune as a semiconducting which can open the optical characteristics and emit light of desired color. There may be several possibilities for the modification of graphene-base material that can tune a band gap. One way is to find semiconducting property by doping the defects into pristine graphene structure. Other way is oxides functional groups in graphene structure behaves as defects. The physical properties of graphene depend on the amount of oxides present in graphene structure. So if there are more oxides in graphene structure then this material behaves as a insulating. By any means if it can be reduced then oxides amount to achieve specific proportion of sp2 and sp3 that can emit light of desired color. Further, after achieving light emission from graphene base material, there is more possibility for the study of non-linear optical property. In this work, plasmonic effect in graphene oxide has been focused. Mainly there are two kinds of plasmon effects have been studied, one is long range (surface) and short range (localized) plasmon. For long range plasmon gold thin film was deposited on partially reduced graphene oxide and for short range plasmon silver nanoparticles have used. Results show that there are 10-fold enhancement in light emission from partial graphene oxide coated with gold thin film while 4-fold enhancement from reduced graphene oxide solution with silver nanoparticles. Chemical method and photocatalytic method have been employed for the reduction of graphene oxide for the study of surface plasmon and localized plasmon. For the characterization UV-Vis spectrometer for absorption, spectrofluorophotometer for fluorescent emission, Raman spectrometer for material characterization, photoluminescence and time resolved photoluminescence have been utilized. Silver and gold nanoparticles are spherical of average size of 80 nm and 40 nm have been used as plasmons.
224

APLIKACE NANOMATERIÁLŮ PRO VÝVOJ PÁJEK BEZ OLOVA / THE APPLICATION OF NANOMATERIALS FOR LEAD FREE SOLDERS DEVELOPMENT

Pešina, Zbyněk January 2012 (has links)
The present dissertation is motivated by the search for alternatives of lead-free soldering by nanoparticles of metals and their alloys. The research focuses on the possibility of replacing lead-free solders by nanoparticles. This issue is currently being addressed by the use of lead-free solders but their properties are not entirely equivalent to properties of lead-tin based alloys. The theoretical part of the dissertation first summarizes up-to date knowledge on the development of lead-free alloys currently used for soldering in the electronics. The work compares these lead-free solder candidates with previously used Pb-Sn alloys. The second section of the theoretical part is devoted to nanotechnology that offers possible solutions of problems associated with the use of lead-free solders. The text contains a description of the properties of nanocrystalline materials in comparison with those of compact alloys having the same chemical composition. The possibility of preparation of nanoparticles and potential problems associated with small particle sizes are also presented. Introduction of the experimental part focuses on the preparation of nanoparticles of pure metals and alloys by chemical and physical ways as well as on an instrumentation for characterisation and analysis. Attention is focused on the silver in nanoparticle form that exhibits the low temperature sintering effect, which is thermally activated by decomposition of oxide envelope covering the Ag nanoparticles. This factor is critical for low-temperature sintering and thus also for possible future applications. The thermal effects of the low sintering process were studied by methods of thermal analysis. The preparation of the Cu / Ag nano / Cu joints was carried out in-situ in inert atmosphere and under the action of atmospheric oxygen. In both cases varying conditions of thermal treatment were used. The cross sections of the prepared joints were then used for the metallographic analysis of the local mechanical properties of the resulting silver layer, for the chemical composition evaluation of the resulting layers of the joint, and for the microstructure study. Strength characteristics are represented by testing shear strength of individual joints.
225

Silver Nanoparticles: An effective antibacterial agent against Gram-negative bacteria

Wilcox, Ashley M. 19 December 2019 (has links)
No description available.
226

Analyse qualitative et quantitative des nanoparticules d’argent dans des matrices alimentaires à l’aide de l’ICP-MS en mode particule unique

Amiri, Nesrine 11 1900 (has links)
Les nanoparticules d’argent (Ag NPs) sont considérablement utilisées dans l’industrie alimentaire. Elles sont fortement appliquées comme enrobages d’emballages alimentaires afin d’assurer une meilleure qualité des aliments et une plus longue durée de conservation sur les étagères des supermarchés. En revanche, les risques associés aux Ag NPs sont inquiétants. Leurs effets potentiels sur les humains et sur l’environnement suscitent un grand intérêt scientifique. C’est pourquoi il est important de valider des méthodes analytiques pour détecter, caractériser et quantifier les Ag NPs dans la nourriture mise en contact avec ce type de contenant. Les méthodes permettront de mieux comprendre la migration de l'argent vers les aliments directement ingérés par l’humain. La spectrométrie de masse à plasma à couplage inductif en mode particule unique (SP-ICP-MS) est une technique prometteuse pour caractériser et quantifier de petites particules (de quelques nanomètres) à de faibles concentrations (dans l'ordre du ng L-1). Contrairement aux techniques analytiques conventionnelles, telles que les techniques de microscopie et de diffusion de la lumière, le SP-ICP-MS distingue la forme ionique de la forme particulaire de l'analyte. Cette présente étude valide une méthode pour la caractérisation et la quantification des Ag NPs et de l’argent ionique dans deux boissons et trois simulants: jus d'orange, préparation en poudre pour nourrissons, eau Milli-Q, acide acétique à 3% et éthanol à 10%. De plus, une meilleure compréhension du devenir et de la migration de l’argent provenant d'emballages alimentaires nano-activés a pu être obtenue. En effet, les milieux acides et les traitements thermiques ont engendré de plus grands relargages d’argent, sous forme ionique, contrairement aux milieux dits « lipophiles » tels que la préparation pour nourrissons et l’éthanol. En conclusion, ce mémoire nous démontre que les voies de libération des NPs des contenants nano-activés ne sont pas encore très bien comprises. De plus amples études doivent être entreprises afin de pouvoir établir des modèles de migration clairs et afin de mieux comprendre les risques associés à leurs utilisations. / Silver nanoparticles (Ag NPs) are increasingly used in the food industry. They are integrated into coatings of various food packaging to help ensure longer product shelf life. However, the risks associated with Ag NPs are currently not well known and their potential effects on humans are causing growing concern. Furthermore, it is not clear whether NPs have greater or lesser risk than dissolved silver ions or bulk phase Ag. Consequently, it is necessary to detect and to characterize the release of silver from silver-enhanced containers into real food matrices using sensitive analytical techniques that allow one to distinguish between silver ions and nanoparticles. Single particle ICP-MS is a promising technique to count and size small particles at low concentrations. Compared to other conventional instrumentation, it can distinguish between ionic and particulate forms of the analyte. This thesis focused firstly on the validation of an analytical method for the analysis of Ag NPs and ionic silver in three different food simulants (Milli-Q water, 10% ethanol and 3% acetic acid) and in two drinks (orange juice and infant milk formula). A better understanding of the aging and of the migration of silver has been reached in these matrices. Essentially, acidic media caused significant NP oxidation whereas organic macromolecules like lipids, proteins and polysaccharides appeared to increase the stability of the NPs. Subsequently, a migration study from silver-enhanced containers showed significant release of dissolved Ag in 3% acetic acid and a lower release in milk formula. Also, heating led to a considerable release of silver from the container. To conclude, further studies are needed to obtain clear release models to better understand the risk on humans and on the environment.
227

Evaluation of Silver Nanoparticle Acute and Chronic Effects on Freshwater Amphipod (Hyalella Azteca)

Kusi, Joseph, Maier, Kurt J. 01 January 2022 (has links)
Silver nanoparticles (AgNPs) are known to cause ecotoxic effects, but there are no existing derived ambient water quality criteria (AWQC) for these nanomaterials to protect freshwater aquatic life due to insufficient toxicological data. We exposed Hyalella azteca to silver nitrate, citrate-coated AgNPs (citrate-AgNPs), and polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs) in a 10-day and 28-day water-only static renewal system with clean sand as a substrate for the amphipods and compared their point estimates with the United States Environmental Protection Agency (USEPA) AWQC for silver. We observed that all treatments decreased the survival, growth, and biomass of H. azteca, and the order of toxicity was AgNO > citrate-AgNPs > PVP-AgNPs. The LC50s of AgNO, citrate-AgNPs, and PVP-AgNPs were 3.0, 9.6, and 296.0 µg total Ag L, respectively, for the acute exposure and 2.4, 3.2, and 61.4 µg total Ag L, respectively, for the chronic exposure. Acute and chronic EC20s of citrate-AgNPs ranged from 0.5 to 3.5 µg total Ag L while that of PVP-AgNPs ranged from 31.2 to 175 µg total Ag L for growth and biomass. Both Ag released from AgNPs and the nanoparticles contributed to the observed toxicity. The dissolution and toxicity of AgNPs were influenced by surface coating agents, particle size, and surface charge. Most point estimates for AgNPs were above AWQC for silver (4.1 µg L) and the lowest concentration (0.12 µg/L) at which Ag is expected to cause chronic adverse effects to freshwater aquatic life. Our study demonstrates that the current AWQC for silver, in general, is protective of freshwater aquatic life against AgNPs tested in the present study.
228

Incorporation of silver nanoparticles and eucalyptus oil onto electrospun hemp/PVA nanofibres and their antibacterial activity

Mogole, Lebogang January 2021 (has links)
M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / The world is continuously losing the battle against superbugs (resistant bacteria towards commonly used antibiotics), hence there is an urgent need to develop novel antibacterial agents. In this study, green synthesized silver nanoparticles (AgNPs) and eucalyptus oil, were incorporated into the polymer blend fibres of polyvinyl alcohol (PVA) and cellulose nanocrystals (CNC’s). Various techniques were used to characterize the AgNPs, PVA/CNC polymer fibres, and PVA/CNC incorporated with AgNPs/eucalyptus oil. The morphology of AgNPs synthesized using an increasing concentration of the Citrus sinensis peels (CSP) extract was obtained from transmission electron microscopy (TEM). AgNPs synthesized using 1 and 2 % m/v (CSP) were agglomerated and whereas those synthesized using 3 % m/v of the extract were spherical with an average particle size 10 ± 1.2 nm. UV/Visible absorption spectra for all the synthesized AgNPs exhibited a surface plasmon resonance (SPR) peak at around 400 nm which is a characteristic peak of silver. Significant shifts in the absorption peaks or maxima were observed to signify changes in the shape and size of the nanoparticles. Scanning electron microscopy (SEM) was used to study the morphology of the fabricated polymer fibres. The Addition of CNC’s to PVA resulted in an increase in fibre diameter due to an increase in viscosity of the solution. An increase in the concentration of silver nanoparticles and the eucalyptus oil in the PVA/CNC resulted in a decrease in fibre diameter due to an increase in conductivity of the material. The fibres with AgNPs were smooth while the ones with the eucalyptus oil were beaded. X-ray diffraction (XRD) showed the presence of the AgNPs in the polymer fibres and Fourier transform infrared (FTIR) showed the presence of the functional groups that are available in the eucalyptus oil. The antibacterial efficiency of the PVA/CNC incorporated with AgNPs, eucalyptus oil, and the mixture of AgNPs and the eucalyptus oil was investigated using S. aureus and K. pneumoniae. All the materials showed significant inhibition of the growth of the selected bacterial strains. PVA/CNC polymer fibres incorporated with AgNPs showed higher antibacterial activity compared to PVA/CNC polymer fibres incorporated with eucalyptus oil.
229

Vers une meilleure évaluation des risques liés à une exposition aux nanoparticules d'argent : inhalation et toxicocinétique

Andriamasinoro, Sandra Nirina 09 1900 (has links)
Les nanoparticules (NP) figurent aux premiers rangs des contaminants émergents prioritaires dans le champ de surveillance des grands organismes de santé et sécurité du travail. Parmi les NP les plus utilisées, on peut citer les NP d’argent (Ag). L’exposition humaine aux NP d’Ag augmente alors inévitablement avec l’accroissement de leur production et leur utilisation généralisée ce qui suscite des préoccupations sur les risques à la santé. L'objectif du projet est de mieux documenter le devenir des NP d’Ag dans l’organisme, à partir d’études expérimentales chez l’animal exposé sous différentes conditions par inhalation, la principale voie d’exposition des travailleurs. Ces informations sont nécessaires pour le développement sécuritaire de ces nouvelles technologies. Dans un premier temps, le profil toxicocinétique des NP d’Ag inhalées a été documenté. Les rats ont été exposés « nez seulement » à des NP de 20 nm pendant 6 h à une concentration cible de 15 mg/m3. L'évolution temporelle de l'élément Ag dans les poumons, le sang, les tissus et les excrétas a été déterminée pendant 14 jours après le début de l'inhalation. La cinétique des NP d’Ag inhalées a été ensuite comparée avec la cinétique d’une forme soluble de l’élément Ag suite à l’exposition au nitrate d’argent (AgNO3) dans de mêmes conditions expérimentales pour mieux comprendre leur comportement, principalement, en raison de leur dissolution et leur capacité à libérer progressivement des ions Ag+ en milieu biologique. Ainsi, dans un dernier temps, dans le but de déterminer la meilleure métrique à utiliser pour mieux évaluer les risques associés à ces NP d’Ag, nous avons étudié l’impact de la cinétique entre un nombre plus faible et un nombre plus élevé de particules. Les profils cinétiques des NP d’Ag inhalées ont montré que la fraction de la dose inhalée qui a atteint les poumons est rapidement éliminée au cours des 72 premières heures suivant l'inhalation, puis la fraction restante de la dose est lentement éliminée par la suite. La dose inhalée éliminée des poumons semble être transférée dans la circulation systémique et atteint un maximum entre 48 et 72 h après l'inhalation. Cependant, les niveaux d'Ag dans le sang étaient faibles, ce qui suggère une biodistribution rapide dans les tissus tels que le foie, l’organe cible des NP d’Ag chez le rat après inhalation. Une translocation vers le bulbe olfactif et les ganglions lymphatiques était évidente durant l'exposition par inhalation de 6 h jusqu'à 6 h après la fin de l'exposition, démontrant l’occurrence d’un transport direct des NP d’Ag via le nerf nasal par le transport axonal et via la circulation lymphatique après la clairance pulmonaire, respectivement. Les profils d'excrétion ont également révélé que l'excrétion fécale est la voie d'excrétion dominante pour les NP d’Ag. Les résultats obtenus après l'inhalation d'AgNO3 ont montré des différences dans la cinétique de l’Ag sous la forme soluble par rapport à la forme insoluble (nanoparticulaire) avec des niveaux plus élevés dans le sang, le tractus GI et les tissus extrapulmonaires, mais des niveaux plus faibles dans les poumons. En plus de ces observations, l'évolution temporelle de l’Ag dans le tube digestif et les fèces après l'exposition à la forme soluble était associée à une réabsorption intestinale de l'Ag. Une fraction plus élevée de la dose a été également récupérée dans les reins et l'urine pour les formes solubles d’Ag; en effet, la filtration glomérulaire des agrégats de NP d’Ag peut être limitée alors que le cation monovalent dissous peut plus facilement passer dans le filtrat du sang. Notre étude a également révélé des différences significatives dans les profils temporels de l'Ag dans les poumons, le sang, les ganglions lymphatiques et le tractus gastro-intestinal entre les rats exposés à des aérosols de NP d'Ag avec un nombre faible et un nombre élevé de particules, mais dont la concentration massique est identique. Certaines similitudes entre les deux conditions ont également été notées, telles que la distribution tissulaire relative, le temps jusqu'aux niveaux de pointe (Tmax) et les profils d'excrétion. Cependant, pour confirmer si le modèle de biodistribution des NPs d'Ag est conditionné par le nombre de particules, des investigations supplémentaires sont nécessaires. / Nanoparticles (NPs) are among the top priority emerging contaminants in the monitoring field of the major occupational health and safety organizations. Among the most widely used nanoparticles, we can cite silver nanoparticles (Ag). Human exposure to Ag NPs inevitably increases with the increase in their production and their widespread use which raises concerns about the health risks. The objective of the project is to better document the fate of Ag nanoparticles in the body, based on experimental studies in animals exposed under different conditions by inhalation, the main route of exposure for workers. This information is necessary for the safe development of these new technologies. First, the toxicokinetic profile of inhaled Ag NPs was documented. Rats were exposed "nose only" to 20 nm NPs for 6 h at a target concentration of 15 mg/m3. The temporal evolution of the Ag element in the lungs, blood, tissues and excreta was determined for 14 days after the start of inhalation. Thus, to better understand their behavior, mainly because of their dissolution and their capacity to progressively release Ag+ ions in the biological medium, the kinetics of inhaled Ag NPs were compared with the kinetics of a soluble form of the element Ag following exposure to silver nitrate (AgNO3) under the same experimental conditions. Thus, as a last step, in order to determine the best metric to use to better assess the risks associated with these Ag NPs, we studied their kinetic from inhalation studies by comparing the effect of a lower -number with a higher- number of particles. The kinetic profiles of inhaled Ag nanoparticles showed that the fraction of the inhaled dose that reached the lungs is rapidly eliminated during the first 72 hours after inhalation, and the remaining fraction of the dose is slowly eliminated thereafter. The inhaled dose cleared from the lungs appears to be transferred to the systemic circulation and reaches a maximum between 48 and 72 hours after inhalation. However, Ag levels in the blood were low, suggesting rapid biodistribution to tissues such as the liver, the target organ of Ag nanoparticles in rats after inhalation. A translocation of Ag NPs in olfactory bulbs and lymph nodes was apparent, demonstrating the occurrence of direct transport of Ag NPs through nasal nerve by axonal transport and via lymphatic circulation after lung clearance, respectively. The excretion profiles also revealed that fecal excretion is the dominant excretion route for Ag nanoparticles. The results obtained after inhalation of AgNO3 showed differences in the kinetics of soluble AgNO3 compared to insoluble Ag NPs, with higher levels in blood, GI tract and extrapulmonary tissues, but lower levels in lungs. In addition to these observations, the time courses of Ag elements in the GI tract and feces following ionic form exposure were compatible with an intestinal reabsorption of Ag. A higher fraction of the dose was further recovered in kidneys and urine after AgNO3 inhalation compared to Ag NP inhalation. Indeed, filtration of Ag NP aggregates may be restricted while the dissolved Ag+ monovalent ion can more easily pass into the filtrate from blood. Our study also revealed significant differences in the time profiles of Ag element in lungs, blood, lymphatic nodes and GI tract between rats exposed to Ag NPs aerosols of lower- and higher-total particle number counts, but with the same mass concentration. Some similarities between the two conditions were also noted, such as the relative tissue distribution, time-to-peak levels (Tmax) and excretion profiles. However, to confirm if the biodistribution pattern of Ag NPs is conditioned by the particle number, further investigations are needed.
230

Toxicity Of Silver Nanoparticles In Mouse Embryonic Stem Cells And Chemical Based Reprogramming Of Somatic Cells To Sphere Cells

Rajanahalli Krishnamurthy, Pavan January 2011 (has links)
No description available.

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