The fate of nanoparticulate cerium oxide from the diesel fuel catalyst Envirox was studied from its presence in the additive to its transformations during combustion through its exposure to plants and soils using a broad range of analytical techniques. Envirox is a fuel-borne catalyst comprised of nanoparticles of cerium oxide suspended in kerosene. The particles suspended in Envirox were confirmed by synchrotron X-ray diffraction, dynamic light scattering, and electron microscopy to be 5-7 nm crystals of CeO2 present as 15 nm aggregates. Significant changes to the particles were induced by the combustion process, resulting in 50-300 nm euhedral crystals of CeO2 in the exhaust as discovered using high resolution transmission electron microscopy. Single particle electron diffraction of the emitted cerium oxide particles showed evidence of ordered oxygen vacancies, indicative of a superstructure. Variations in the engine operating load resulted in no significant differences in the emitted cerium oxide particles. The mobility through soils and impacts on the plant Brassica napus (dwarf essex rape) of the emitted cerium oxide were compared to small and large CeO2 nanoparticles as well as diesel particulate matter emissions with very low cerium. The small CeO2 nanoparticles exhibited high mobility through soils and significant uptake and translocation in the plants. The large CeO2 nanoparticles showed extremely low mobility in soils and no significant increase in cerium anywhere in the plants. Cerium emissions from a diesel engine utilizing Envirox was found to have moderate mobility through the soils as well as an increased association with the roots of the plants, though translocation of the cerium into the aboveground biomass was not statistically significant. Despite uptake and translocation of some materials by B. napus, exposure to these cerium sources at 100 ppm Ce in the topsoil showed no significant impacts on the growth or overall health of the plants when compared to unexposed control samples. This dissertation shows that CeO2 nanoparticles employed as catalysts suspended in diesel fuel are altered during their use resulting in changes to their mobility and interaction upon entering the environment. This dissertation lays the groundwork for a new approach to nanotoxicology. / Ph. D.

Nanotechnology is a rapidly growing field focused on the manipulation and control of materials with dimensions under 100 nm. The novel electronic, optical and mechanical properties observed at the nanoscale have resulted in a number of applications in catalysis, light emitting devices, solar power, self-cleaning surfaces and medicine. Medical applications of nanotechnology (“nanomedicine”) are particularly promising for rapid clinical diagnosis and targeted treatments. Understanding the interactions of nanoparticles with living matter is of fundamental importance for all application areas: manufacture, use and disposal of the growing number of nanoproducts will result in increased environmental exposure in addition to direct exposure through nanomedical applications. However, there is a lack of standard methodologies for assessing these interactions. In this work the stability of silver-based nanoparticles was established by UV- Visible (UV-Vis) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The presence of a higher valence metal or polymer on the nanoparticle surface was demonstrated to improve stability. A standard methodology was developed to study nanoparticle-cell interactions: an “atlas” of the effects of known drugs on a cell is created, and compared with the effects of a nanoparticle. Escherichia coli was selected as a model organism and the effects of a range of antibiotics were characterised through a combination of microbiological assays and AFM. Susceptibility, population cell growth and individual heights, widths, lengths and volumes of bacteria were obtained on a 2% agarose substrate in air. The methodology was applied and adjusted for silver nanoparticles due to the interactions of silver with the bacterial growth medium. 10 and 30 nm silver nanoparticles and ions were found to kill E. coli through an internal mechanism of action, with a size-specific effect on the height of bacteria. Finally, a novel AFM characterisation method is described to examine the mechanical properties of live bacterial and human cells in liquid.

Scientific research using nanotechnology is a relatively recent development with a variety of potential applications in many fields of science. Within this field of research, many new products, with improved performances, have been developed. Despite increased research on its toxicity to ecosystem, the knowledge about this area is still limited. To evaluate the toxicity and genotoxicity of different sizes silica nanoparticles (SiNP)to the environment, different species, on different trophic levels (Vibrio fisheri, Raphidocelissubcapitata, Daniorerio and Allium cepa) were exposed to TM40 (22 nm), HS30 (12 nm), SM30 (7 nm) with concentrations ranging from0.19 to 163.8 g/L (TM40) and 0.29 to 122.85 g/L (HS30 and SM30), and the following parameters were monitored during exposure: production of bioluminescence (V. fischeri), growth rate (R. subcapitata), embryonic development and DNA damage (D. rerio) and germination rate, growth and DNA damage (A. cepa). Within each test SiNPpresent a size dependent chronic toxicity. The bioluminescence test present a EC50 of 29.11, 32.34 and 4.58 g/L for TM40, HS30 and SM30, respectively. For the growth rate assay the EC50 was 9.32, 9.07 and 7.93 g/L for TM40, HS30 and SM30, respectively. And for the zebra fish embryonic development test for TM40, HS30 and SM30, the EC50 was 5.85, 1.13 and 2.68 g/L respectively. All particles also induce phytotoxicity in A.cepa, growth and germination reduce significatively when expose to SiNP. Futhermoregenotoxic effects were also induced by the particles for both A.cepaand D. rerio. Therefore, SiNP can cause toxicity to the environment and size can strongly influence this toxicity / Com uma variedade de aplicações potenciais, em diversos campos da ciência, as pesquisas científicas utilizando nanotecnologia são de desenvolvimento relativamente recente. Dentro deste campo de pesquisa, vários novos produtos, com desempenhos melhorados têm sido desenvolvidos. Apesar do aumento de pesquisas sobre a toxicidade dessas tecnologias à biota, o conhecimento sobre esta área ainda é limitado. Visando avaliar a toxicidade e genotoxicidade denanopartículasde sílica (SiNP) no meio ambiente diferentes espécies pertencentes a diversos níveis tróficos (Vibriofisheri, Raphidocelissubcapitata, DaniorerioandAllium cepa) foram expostos a Ludox TM40 (22 nm), Ludox HS30 (12 nm) e Ludox SM30 (7 nm). As espécies de teste foram expostas a concentrações de nanopartículas (NP) variando de 0.29 a 163.8 g/L (TM40) e 0.19 a 122.85 g/L (HS30 e SM30) e os seguintes parâmetros monitorizados durante a exposição: a produção de bioluminescência (V. fischeri), o crescimento taxa (R. subcapitata), inibição de alimentação (D. magna), desenvolvimento embrionário e dano ao DNA (D. rerio) e taxa de germinação, crescimento e danos ao DNA (A. cepa). Nos testes feitos com as SiNPfoi observado que a toxicidade é dependente do tamanho da partícula. O ensaio de bioluminescência apresentou um EC50 de 29.11, 32.34 e 4.58 g/L para TM40, HS30 e SM30, respectivamente. Para o ensaio de taxa de crescimento o EC50 foi 9.32, 9.07 e 7.93 g/Lpara TM40, HS30 e SM30, respectivamente. E para o teste de desenvolvimento embrionário com peixe zebra, para o TM40, HS30 e SM30 o EC50 foi de 5.85, 1.13 e 2.68g/L, respectivamente. Todas as partículas também induziram fitotoxicidade em A. cepa, crescimento e germinação reduziram significativamente quando o organismo foi exposto a SiNP. Efeitos genotóxicos também foram induzir pelas partículas, tanto para A. cepa quanto paraD. rerio. Portanto, as SiNP podem causar toxicidade ao ambiente e o tamanho pode influenciar fortemente a essa toxicidade

Nanopartículas possuem características físico-químicas úteis para o uso humano, com aplicação na ciência, tecnologia, medicina e produtos de uso diário. A fabricação e a variedade destes produtos vêm crescendo rapidamente, gerando uma preocupação quanto ao risco de exposição aos efeitos tóxicos da contaminação por nanopartículas. Vários efeitos adversos, derivados da exposição de nanopartículas foram descritos tanto para organismos terrestres como aquáticos, porém efeitos genotóxicos ainda são pouco conhecidos para organismos marinhos. Para avaliar a citogenotoxicidade da nanopartícula de dióxido de titânio no peixe marinho T. carolinus, foram administradas injeções intraperitoneais com dosagens de 1,5 e 3,0 ?g-nano-TiO2/grama-de-peixe. Amostras de sangue foram coletadas para realização do teste de micronúcleo (MN) e outras anormalidades nucleares eritrocitárias (ANE) e ensaio cometa (pH>13), 24, 48 e 72 horas após a injeção. Foram investigadas a viabilidade de eritrócitos e a possibilidade de acumulação da nano-TiO2 nos tecidos dos peixes injetados com a maior dosagem, após 72 horas, pelo teste de exclusão do azul de tripano e por microscopia eletrônica de transmissão. Os resultados mostraram que a nano-TiO2 é uma substância possivelmente capaz de entrar nas células e induzir efeito genotóxico e citotóxico para esta espécie, por provocar uma diminuição na viabilidade de eritrócitos, um aumento no dano ao DNA e formação de MN e outras ANE. De acordo com nosso conhecimento, este é o único trabalho sobre a genotoxicidade de nano-TiO2 em um peixe marinho. / Nanoparticles have physicochemical characteristics useful for human use, with applications in science, technology, medicine and everyday products. The manufacture and variety of these products have been growing rapidly, creating a concern about the risk of exposure to the toxic effects of contamination by nanoparticles. Several adverse effects of exposure to nanoparticles have been reported for both terrestrial and aquatic organisms, but genotoxic effects are still poorly known for marine organisms. To evaluate the citogenotoxicity of titanium dioxide nanoparticles (nano-TiO2) in marine fish T. carolinus, the substance was administered with intraperitoneal injections at dosages of 1,5 and 3,0 ?g-nano-TiO2/gram-of-fish. Blood samples were collected for the tests of micronucleus (MN) and other erythrocytes nuclear abnormalities (ENA) and comet assay (pH> 13), 24, 48 and 72 hours after injection. We also investigated the viability of erythrocytes and the possibility of accumulation of nano-TiO2 in the tissues of fish injected with the highest dose after 72 hours using trypan blue exclusion test and transmission electron microscopy. The results showed that the nano-TiO2 is a substance that can possibly be able to enter cells and induce cytotoxic and genotoxic effect for this species, by causing a decrease in the viability of erythrocytes, an increase in DNA damage and formation of MN and other ANE. As far as we know, this is the only work done on the genotoxicity of nano-TiO2 in a marine fish

Nanopartículas possuem características físico-químicas úteis para o uso humano, com aplicação na ciência, tecnologia, medicina e produtos de uso diário. A fabricação e a variedade destes produtos vêm crescendo rapidamente, gerando uma preocupação quanto ao risco de exposição aos efeitos tóxicos da contaminação por nanopartículas. Vários efeitos adversos, derivados da exposição de nanopartículas foram descritos tanto para organismos terrestres como aquáticos, porém efeitos genotóxicos ainda são pouco conhecidos para organismos marinhos. Para avaliar a citogenotoxicidade da nanopartícula de dióxido de titânio no peixe marinho T. carolinus, foram administradas injeções intraperitoneais com dosagens de 1,5 e 3,0 ?g-nano-TiO2/grama-de-peixe. Amostras de sangue foram coletadas para realização do teste de micronúcleo (MN) e outras anormalidades nucleares eritrocitárias (ANE) e ensaio cometa (pH>13), 24, 48 e 72 horas após a injeção. Foram investigadas a viabilidade de eritrócitos e a possibilidade de acumulação da nano-TiO2 nos tecidos dos peixes injetados com a maior dosagem, após 72 horas, pelo teste de exclusão do azul de tripano e por microscopia eletrônica de transmissão. Os resultados mostraram que a nano-TiO2 é uma substância possivelmente capaz de entrar nas células e induzir efeito genotóxico e citotóxico para esta espécie, por provocar uma diminuição na viabilidade de eritrócitos, um aumento no dano ao DNA e formação de MN e outras ANE. De acordo com nosso conhecimento, este é o único trabalho sobre a genotoxicidade de nano-TiO2 em um peixe marinho. / Nanoparticles have physicochemical characteristics useful for human use, with applications in science, technology, medicine and everyday products. The manufacture and variety of these products have been growing rapidly, creating a concern about the risk of exposure to the toxic effects of contamination by nanoparticles. Several adverse effects of exposure to nanoparticles have been reported for both terrestrial and aquatic organisms, but genotoxic effects are still poorly known for marine organisms. To evaluate the citogenotoxicity of titanium dioxide nanoparticles (nano-TiO2) in marine fish T. carolinus, the substance was administered with intraperitoneal injections at dosages of 1,5 and 3,0 ?g-nano-TiO2/gram-of-fish. Blood samples were collected for the tests of micronucleus (MN) and other erythrocytes nuclear abnormalities (ENA) and comet assay (pH> 13), 24, 48 and 72 hours after injection. We also investigated the viability of erythrocytes and the possibility of accumulation of nano-TiO2 in the tissues of fish injected with the highest dose after 72 hours using trypan blue exclusion test and transmission electron microscopy. The results showed that the nano-TiO2 is a substance that can possibly be able to enter cells and induce cytotoxic and genotoxic effect for this species, by causing a decrease in the viability of erythrocytes, an increase in DNA damage and formation of MN and other ANE. As far as we know, this is the only work done on the genotoxicity of nano-TiO2 in a marine fish

Although there are over 1,600 Engineered Nanomaterials (ENMs)-containing consumer products available, our understanding of ENM safety is still limited. Airborne ENMs can readily enter the human body through inhalation potentially leading to many adverse health effects such as cardiovascular and pulmonary diseases. The conventional in vitro submerged cell culture method was developed decades ago and has been widely used as a fast screening method to elucidate cellular toxicity upon exposure to hazardous materials; however, it has many limitations compared with the in vivo models. Our group has previously utilized and validated an integrated low flow system capable of generating and depositing airborne nanoparticles (NPs) directly onto cells at an air-liquid interface (ALI) condition, and our results confirmed that this exposure system produced reproducible toxicological data for ENMs including gold (Au), 16% silver coated onto silica (16% Ag-SiO2), and copper oxide (CuO). To further improve this ALI method for an even closer representation of the in vivo model, a co-culture model containing three cell lines (A549, THP-1 differentiated macrophages, and EA.hy 926) was established and validated for testing ENMs toxicity. The co-culture model was exposed to 16% Ag-SiO2 and CuO NPs under the same protocol (4 h ALI exposure with a concentration of 3.5 mg/m3) as monoculture (A549 only) for comparison. Toxicity was assessed by measuring cell viability, reactive oxygen species (ROS) production, lactate dehydrogenase (LDH) release, and interleukin (IL) 8 level. Results showed that 16% Ag-SiO2 NPs induced higher ROS generation, and CuO NPs produced a significant level of proinflammatory response compared with monoculture. In addition, the co-culture model exhibited a similar response with the primary human bronchial epithelia cell line (HBEC) in terms of ROS and IL-8 responses after CuO NPs exposure, suggesting a more advanced refinement of the conventional model for in vitro inhalation study.

Manufactured CeO2 nanomaterials (CeO2-MNMs) are used for a wide variety of applications including diesel fuel additives and chemical/mechanical planarization media. To test the effects of CeO2-MNM surface coating charge on to model organism Caenorhabditis elegans, we synthesized 4 nm CeO2 with cationic (DEAE-), anionic (CM-), and neutral (DEX) coatings. In L3 nematodes exposed for 24 hours, DEAE-CeO2 induced lethality at lower concentrations than CM- or DEX-CeO2. Feeding slightly decreased CeO2 toxicity, regardless of coating. In L2 nematodes exposed for 48 hours with feeding, DEAE-CeO2 caused lethality at the lower concentrations as compared to CM- and DEX-CeO2. Sublethal effects were measured by observing reproduction and oxidative/nitrosative protein damage. Low concentrations of DEAE-CeO2 induced similar reductions as CM- and DEX-CeO2 that were two orders of magnitude higher. Using immunochemical slot blots to explore oxidative/nitrosative stress, no treatments produced significant changes in protein carbonyl or 3-nitrotyrosine formation; however, the statistical power of our assay was low. All treatments caused large but not statistically significant increases in protein carbonyl levels. DEAE-CeO2 exposure caused a significant reduction in 4-hydroxy-2-nonenol levels. This research suggests that cationic coatings render CeO2 significantly more toxic to C. elegans than neutral or anionic coatings.

Nanotoxicology is a nascent field of study concerned with the potential for nanotechnology to adversely impact human health or result in ecological damage. Nanomaterials can display unique physicochemical properties not present in the parent bulk material and it is these properties that may be a potential source of toxicity. There are a growing number of examples of nanomaterials functioning differently in biosystems compared to the parent bulk material. With the rapid growth of nanotechnology and increasing exposure of people to novel nanomaterials there is an urgent need to evaluate the toxicity of nanomaterials. In this study the toxicities of silver and zinc oxide nanoparticles were assessed. The effects of size and surface coating on the cytotoxicity and immunogenicity of silver nanoparticles were investigated, with cytotoxicity found to be inversely proportional to nanoparticle size. The subcutaneous penetration of zinc oxide nanoparticles was assessed to determine whether this material can be safely used as a UV filter in sunscreens and cosmetics. No dermal penetration was detected using a porcine in vitro model. Zinc oxide nanoparticles were also used as a model material to investigate nano-specific toxicity by comparing cytotoxicity and changes to gene expression with bulk scale zinc oxide. In both cases cytotoxicity and changes to gene expression were greater for zinc oxide nanoparticles. Methods and techniques to test the toxicity of nanomaterials in vitro and the implication for in vivo toxicity are only beginning to be elucidated. The methods and techniques used in this study, particularly nanomaterial stabilization in biofluids and toxicity testing using blood cell cultures, may assist the establishment of standard in vitro testing protocols for nanomaterials.

Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T14:00:18Z No. of bitstreams: 1 DissRCG.pdf: 1738048 bytes, checksum: 5fe499e8468dd911a3576a5aaf9afff3 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T14:00:27Z (GMT) No. of bitstreams: 1 DissRCG.pdf: 1738048 bytes, checksum: 5fe499e8468dd911a3576a5aaf9afff3 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T14:00:33Z (GMT) No. of bitstreams: 1 DissRCG.pdf: 1738048 bytes, checksum: 5fe499e8468dd911a3576a5aaf9afff3 (MD5) / Made available in DSpace on 2017-08-22T14:00:38Z (GMT). No. of bitstreams: 1 DissRCG.pdf: 1738048 bytes, checksum: 5fe499e8468dd911a3576a5aaf9afff3 (MD5) Previous issue date: 2017-03-02 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Nanoparticles (NPs) have been produced on a large scale worldwide for various consumer purposes such as the production of cosmetics, sunscreen, biosensors, human prosthetics and cancer therapy. However, due to its large production, NPs can have water bodies as final destination, where current studies addressing these compounds are not sufficient to estimate the threat that these substances could cause to aquatic organisms. Chronic studies with nano-Fe3O4 are scarce and, to the best of our knowledge, inexistent regarding tropical zooplankton species, although chronic studies are of great importance to predict the effects of the substances because they analyses great part of this organisms life cycle. At present study, we investigated nanoparticles of Fe3O4, to the tropical cladoceran Ceriodaphnia silvestrii using acute toxicity tests (0.00; 0.01; 0.10; 1.00; 10.00 and 100.00 mg L-1) during 48h, and chronic toxicity tests (0.00; 3.125; 6.25; 12.50; 25.00 and 50.00 mg L-1) during 14 days. Characterization of NPs in the exposure medium revealed that they experienced agglomeration and aggregation on a micrometer scale. Results showed non-toxicity of nano-Fe3O4 after 48h of acute exposure (EC5048h > 100.00 mg L-1). ). In chronic tests, treatment of 50 mg L-1 caused significant inhibition of growth and reproduction, affecting the maximum length (inhibited 12.71%), accumulated number of eggs (reduction of 51.99%) and neonates (decrease of 61.37%) per female (Dunnett’s test, p < 0.05). We concluded that nano-Fe3O4, in the 14th day, was toxic to C. silvestrii only at the highest concentration tested (50.00 mg L-1) during this chronic exposure.. The use of nano-Fe3O4 in aquatic environments could be considered safe to this species in concentrations up to 25.00 mg L-1, according to the parameters evaluated. / As nanopartículas (NPs) têm sido amplamente produzidas em larga escala para vários propósitos tais como: produção de cosméticos, protetores solares, biosensores, próteses humanas e tratamento do câncer. No entanto, devido à ampla produção, eventualmente as NPs podem encontrar seu destino final nos corpos d’água, onde os estudos relativos à presença dessas substâncias muitas vezes não são suficientes para estimar os efeitos que as mesmas poderiam causar nos organismos aquáticos. Estudos de toxicidade crônica com nanopartículas de óxido de ferro (nano-Fe3O4) são escassos e, até onde sabemos, inexistentes para cladóceros tropicais, embora avaliações crônicas sejam de grande importância para predição dos efeitos de substâncias, pois abrangem grande parte do ciclo de vida dos organismos. No presente estudo, foram estudadas nanopartículas de Fe3O4 para cladócero neotropical Ceriodaphnia silvestrii, por meio de testes de toxicidade aguda (0,00; 0,01; 0,10; 1,00; 10,00 e 100,00 mg L-1), durante 48 horas, e crônica (0,00; 3,125; 6,25; 12,50; 25,00 e 50,00 mg L-1), durante 14 dias. A caracterização das NPs nos meios de exposição revelou que elas sofreram aglomeração e agregação em escalas micrométricas. Os resultados obtidos apontaram ausência de toxicidade aguda para as nano-Fe3O4 (CE(I)5048h > 100,00 mg L-1). Nos testes de toxicidade crônica, no tratamento de 50,00 mg L-1, houve inibição significativa no crescimento e reprodução, afetando o comprimento máximo (inibição de 12,71%) e o número acumulado de ovos (diminuição de 51,99%) e de neonatas (diminuição de 61,37%) produzidos por fêmea (teste de Dunnett p < 0.05). Concluiu-se que as nano-Fe3O4 apresentaram efeitos crônicos, no 14º dia, para o cladócero C. silvestrii somente na maior concentração avaliada (50,00 mg L-1). O uso de nano-Fe3O4 em ambientes aquáticos pode ser considerado seguro para esta espécie de cladócero tropical, com base nos parâmetros avaliados, até concentrações de 25,00 mg L-1. / CNPq: 132379/2015-5 / FAPESP: 2014/14139-3 / FAPESP: 2016/00753-7

Le dioxyde de titane (TiO2) compte parmi les nanoparticules (NP) les plus produites dans le monde. Ce constat soulève la question de sa toxicité, en particulier par inhalation, voie d'exposition la plus probable en milieu professionnel. Il a été montré précédemment in vitro que ces NP induisent des dommages à l'ADN et réduisent l'activité de réparation de l'ADN. L'objectif est ici d'étudier les mécanismes de toxicité sous-jacents à l'aide de cellules épithéliales alvéolaires humaines A549 exposées à 1-100 µg/mL de NP de TiO2 pendant 4-48 h. L'expression de 40 gènes et de 6 protéines de réparation de l'ADN a été étudiée par RT-qPCR et western-blot. L'impact des NP de TiO2 sur des régulateurs amont comme la méthylation des promoteurs de certains de ces gènes, l'activité du protéasome et la signalisation cellulaire par phosphorylation a également été investigué. De plus les profils de cyto-/géno-toxicité et d'expression des gènes de réparation de l'ADN ont été comparés avec ceux des cellules épithéliales bronchiques BEAS-2B. Les résultats montrent une répression globale des gènes et des protéines dans l'ensemble des voies de réparation de l'ADN. Cette répression pourrait être due en partie à la répression de régulateurs transcriptionnels et à l'augmentation de la méthylation de certains promoteurs et de l'activité caspase du protéasome. Les NP de TiO2 engendrent par ailleurs une perturbation du phosphoprotéome. Invisible à l'échelle du phosphoprotéome entier, celle-ci impacte de nombreuses protéines impliquées dans divers processus cellulaires, reflétant les effets toxiques connus de ces NP. On note en particulier un impact sur le cycle cellulaire, mais pas sur la prolifération, ainsi que la dérégulation du niveau de phosphorylation de quelques protéines liées à la réparation de l'ADN. Enfin on relève des profils de cyto-/géno-toxicité et d'expression des gènes de réparation de l'ADN similaires dans les cellules A549 et BEAS-2B, ce qui renforce la pertinence de ces modèles dans le cadre de l'étude de la génotoxicité des nanomatériaux. Dans l'ensemble, ces données apportent de nouvelles pistes d'explication des mécanismes de toxicité des NP de TiO2, qui pourraient notamment expliquer la chute précédemment observée des capacités cellulaires de réparation de l'ADN. / Titanium dioxide (TiO2) belongs to the top nanoparticles (NPs) most produced worldwide. This raises the question of their impact on human health, especially through inhalation, which is the main exposure route in occupational settings. It was previously shown in vitro that these NPs induce DNA damage and impair DNA repair activity. The aim here is to study the underlying toxicity mechanisms, in human A549 epithelial alveolar cells exposed to 1-100 µg/ml TiO2 NPs during 4-48 h. The expression of 40 genes and 6 proteins involved in DNA repair was investigated by RT-qPCR and western-blotting. The impact of TiO2 NPs on upstream regulators such as the methylation rate of some corresponding gene promoters, proteasome activity and cellular signaling through phosphorylation was assayed as well. Moreover cyto-/geno-toxicity and DNA repair gene expression patterns were compared with those of BEAS-2B bronchial epithelial cells. Results show a global down-regulation of genes and proteins in all DNA repair pathways. This could be partly explained by the down-regulation of transcriptional regulators and increased gene promoter methylation and caspase-like proteasome activity. TiO2 NPs also scramble the phosphoproteome. While invisible on a global scale, this dysregulation affects numerous proteins involved in diverse cellular processes, which reflect the toxicity pathways reported for these NPs. Although cell proliferation is unaffected, a significant impact is observed on cell cycle, as well as on a few proteins involved in DNA repair. Finally cyto-/geno-toxicity and DNA repair gene expression profiles are similar in both A549 and BEAS-2B cells, thereby strengthening the relevance of using any of these cell lines in nanomaterial genotoxicity studies. On the whole these data bring novel insights into TiO2-NP toxicity mechanisms, which could especially explain the previously observed impairment of DNA repair activity.