433 resultados para Nanomaterials
Resumo:
RESUMO - Os nanomateriais manufaturados (NMs), isto , fabricados deliberadamente para fins especficos, apresentam propriedades fsico-qumicas nicas como a dimenso, rea superficial ou funcionalizao, que lhes conferem caratersticas mecnicas, ticas, eltricas e magnticas muito vantajosas para aplicaes industriais e biomdicas. Efetivamente, a tecnologia baseada nos NMs, ou nanotecnologia, foi identificada como uma key enabling technology, impulsionadora do crescimento econmico dos pases industrializados, devido ao seu potencial para melhorar a qualidade e desempenho de muitos tipos de produtos e de processos. Contudo, a expanso da utilizao de NMs contrasta com a insuficiente avaliao de risco para a sade humana e para o ambiente, sendo considerados como um risco emergente para a sade pblica. As incertezas sobre a segurana dos NMs para a sade pblica advm sobretudo de estudos epidemiolgicos em humanos expostos a nanomateriais produzidos como consequncia dos processos e atividades humanas e da poluio. Uma das principais preocupaes relativamente aos efeitos adversos dos NMs na sade humana o seu potencial efeito carcinognico, que sugerido por alguns estudos experimentais, como no caso dos nanomateriais de dixido de titnio ou dos nanotubos de carbono. Para avaliar em curto termo as propriedades carcinognicas de um composto, utilizam-se frequentemente ensaios de genotoxicidade em linhas celulares de mamfero ou ensaios em modelos animais, em que se analisa uma variedade de leses genticas potencialmente relacionados com o processo de carcinognese. No entanto, a investigao sobre as propriedades genotxicas dos NMs no foi, at hoje, conclusiva. O presente estudo tem por objectivo principal caracterizar os efeitos genotxicos associados exposio a nanomateriais manufaturados, de forma a contribuir para a avaliao da sua segurana. Constituram objectivos especficos deste estudo: i) avaliar a genotoxicidade dos NMs em trs tipos de clulas humanas expostas in vitro: linfcitos humanos primrios, linha celular de epitlio brnquico humano (BEAS-2B) e linha celular de adenocarcinoma epitelial de pulmo humano (A549); ii) avaliar a sua genotoxicidade num modelo de ratinho transgnico; iii) investigar alguns mecanismos de aco que podero contribuir para a genotoxicidade dos nanomateriais, como a contribuio de leses oxidativas para a genotoxicidade induzida pelos NMs in vitro, e a investigao da sua bioacumulao e localizao celular in vivo. Foram analisados os efeitos genotxicos associados exposio a duas classes de NMs, dixido de titnio e nanotubos de carbono de parede mltipla, bem como a um NM de xido de zinco, candidato a ser utlilizado como controlo positivo de dimenso nanomtrica. Os xx NMs utilizados foram previamente caracterizados com detalhe relativamente s suas caractersticas fsico-qumicas e tambm relativamente sua disperso em meio aquoso e no meio de cultura. A metodologia incluiu ensaios de citotoxicidade e de genotoxicidade in vitro, designadamente, ensaios de quebras no DNA (ensaio do cometa) e nos cromossomas (ensaio do microncleo) em clulas humanas expostas a vrias concentraes de NMs, por comparao com clulas no expostas. Tambm foram realizados ensaios in vivo de quebras no DNA, quebras cromossmicas e ainda um ensaio de mutaes em vrios rgos de grupos de ratinhos transgnicos LacZ, expostos por via intravenosa a duas doses de dixido de titnio. Foi investigada a existncia de uma relao dose-resposta aps exposio das clulas humanas ou dos animais a NMs. A contribuio de leses oxidativas para a genotoxicidade aps exposio das clulas aos NMs in vitro foi explorada atravs do ensaio do cometa modificado com enzima. Realizaram-se estudos histolgicos e citolgicos para deteo e localizao celular dos NMs nos rgos-alvo dos ratinhos expostos in vivo. Os resultados demonstraram efeitos genotxicos em alguns dos NMs analisados em clulas humanas. No entanto, os efeitos genotxicos, quando positivos, foram em nveis reduzidos, ainda que superiores aos valores dos controlos, e a sua reprodutibilidade era dependente do sistema experimental utilizado. Para outros NMs, a evidncia de genotoxicidade revelou-se equvoca, conduzindo necessidade de esclarecimento atravs de ensaios in vivo. Para esse fim, recorreu-se a uma anlise integrada de mltiplos parmetros num modelo animal, o ratinho transgnico baseado em plasmdeo contendo o gene LacZ exposto a um NM de dixido de titnio, NM-102. Embora tenha sido demonstrada a exposio e a acumulao do NM no fgado, no se observaram efeitos genotxicos nem no fgado, nem no bao nem no sangue dos ratinhos expostos a esse NM. Neste estudo concluiu-se que algumas formas de dixido de titnio e nanotubos de carbono de parede mltipla produzem efeitos genotxicos em clulas humanas, contribuindo para o conjunto de evidncias sobre o efeito genotxico desses NMs. As diferenas observadas relativamente genotoxicidade entre NMs do mesmo tipo, mas distintos em algumas das suas caractersticas fsico-quimicas, aparentemente no so negligenciveis, pelo que os resultados obtidos para um NM no devem ser generalizados ao grupo correspondente. Para alm disso, a genotoxicidade equvoca verificada para o NM-102 em clulas humanas expostas in vitro, no foi confirmada no modelo in vivo, pelo que o valor preditivo da utilizao dos ensaios in vitro para a identificao de NMs com efeitos genotxicos (e portanto potencialmente carcinognicos) ainda tem de ser esclarecido antes de ser possvel extrapolar as concluses para a sade humana. Por sua vez, como a informao aqui produzida pelas metodologias in vitro e in vivo no reflete os efeitos de exposio continua ou prolongada, que poder conduzir a efeitos genotxicos distintos, esta xxi dever ser complementada com outras linhas de evidncia relativamente segurana dos NMs. Perante a incerteza dos nveis de exposio real do organismo humano e do ambiente, a segurana da utilizao dos NMs no pode ser garantida a longo prazo e, tendo em conta a elevada produo e utilizao destes NMs, so prementes futuros estudos de monitorizao ambiental e humana.
Resumo:
Polymer binder modification with inorganic nanomaterials (NM) could be a potential and efficient solution to control matrix flammability of polymer concrete (PC) materials without sacrificing other important properties. Occupational exposures can occur all along the life cycle of a NM and nanoproducts from research through scale-up, product development, manufacturing, and end of life. The main objective of the present study is to analyse and compare different qualitative risk assessment methods during the production of polymer mortars (PM) with NM. The laboratory scale production process was divided in 3 main phases (pre-production, production and post-production), which allow testing the assessment methods in different situations. The risk assessment involved in the manufacturing process of PM was made by using the qualitative analyses based on: French Agency for Food, Environmental and Occupational Health & Safety method (ANSES); Control Banding Nanotool (CB Nanotool); Ecole Polytechnique Fdrale de Lausanne method (EPFL); Guidance working safely with nanomaterials and nanoproducts (GWSNN); Istituto Superiore per la Prevenzione e la Sicurezza del Lavoro, Italy method (ISPESL); Precautionary Matrix for Synthetic Nanomaterials (PMSN); and Stoffenmanager Nano. It was verified that the different methods applied also produce different final results. In phases 1 and 3 the risk assessment tends to be classified as medium-high risk, while for phase 2 the more common result is medium level. It is necessary to improve the use of qualitative methods by defining narrow criteria for the methods selection for each assessed situation, bearing in mind that the uncertainties are also a relevant factor when dealing with the risk related to nanotechnologies field.
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The production of nanotechnology-based products is increasing, along with the conscience of the possible harmful effects of some nanomaterials. The safety-by-design approaches are getting attention as helpful tools to develop safer products and production processes. The Systematic Design Analysis Approach could help to identify the solutions to control the workplace risks by defining the emission and exposure scenarios and the possible barriers to interrupt them. By applying this approach in a photocatalytic ceramic tiles development project it was possible to identify relevant nanoparticles emission scenarios and related barriers, and defining possible ways to reduce it.
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Bio-nano interactions can be defined as the study of interactions between nanoscale entities and biological systems such as, but not limited to, peptides, proteins, lipids, DNA and other biomolecules, cells and cellular receptors and organisms including humans. Studying bio-nano interactions is particularly useful for understanding engineered materials that have at least one dimension in the nanoscale. Such materials may consist of discrete particles or nanostructured surfaces. Much of biology functions at the nanoscale; therefore, our ability to manipulate materials such that they are taken up at the nanoscale, and engage biological machinery in a designed and purposeful manner, opens new vistas for more efficient diagnostics, therapeutics (treatments) and tissue regeneration, so-called nanomedicine. Additionally, this ability of nanomaterials to interact with and be taken up by cells allows nanomaterials to be used as probes and tools to advance our understanding of cellular functioning. Yet, as a new technology, assessment of the safety of nanomaterials, and the applicability of existing regulatory frameworks for nanomaterials must be investigated in parallel with development of novel applications. The Royal Society meeting 'Bio-nano interactions: new tools, insights and impacts' provided an important platform for open dialogue on the current state of knowledge on these issues, bringing together scientists, industry, regulatory and legal experts to concretize existing discourse in science law and policy. This paper summarizes these discussions and the insights that emerged.
Resumo:
The introduction of engineered nanostructured materials into a rapidly increasing number of industrial and consumer products will result in enhanced exposure to engineered nanoparticles. Workplace exposure has been identified as the most likely source of uncontrolled inhalation of engineered aerosolized nanoparticles, but release of engineered nanoparticles may occur at any stage of the lifecycle of (consumer) products. The dynamic development of nanomaterials with possibly unknown toxicological effects poses a challenge for the assessment of nanoparticle induced toxicity and safety.In this consensus document from a workshop on in-vitro cell systems for nanoparticle toxicity testing11Workshop on 'In-Vitro Exposure Studies for Toxicity Testing of Engineered Nanoparticles' sponsored by the Association for Aerosol Research (GAeF), 5-6 September 2009, Karlsruhe, Germany. an overview is given of the main issues concerning exposure to airborne nanoparticles, lung physiology, biological mechanisms of (adverse) action, in-vitro cell exposure systems, realistic tissue doses, risk assessment and social aspects of nanotechnology. The workshop participants recognized the large potential of in-vitro cell exposure systems for reliable, high-throughput screening of nanoparticle toxicity. For the investigation of lung toxicity, a strong preference was expressed for air-liquid interface (ALI) cell exposure systems (rather than submerged cell exposure systems) as they more closely resemble in-vivo conditions in the lungs and they allow for unaltered and dosimetrically accurate delivery of aerosolized nanoparticles to the cells. An important aspect, which is frequently overlooked, is the comparison of typically used in-vitro dose levels with realistic in-vivo nanoparticle doses in the lung. If we consider average ambient urban exposure and occupational exposure at 5mg/m3 (maximum level allowed by Occupational Safety and Health Administration (OSHA)) as the boundaries of human exposure, the corresponding upper-limit range of nanoparticle flux delivered to the lung tissue is 310-5-510-3μg/h/cm2 of lung tissue and 2-300particles/h/(epithelial) cell. This range can be easily matched and even exceeded by almost all currently available cell exposure systems.The consensus statement includes a set of recommendations for conducting in-vitro cell exposure studies with pulmonary cell systems and identifies urgent needs for future development. As these issues are crucial for the introduction of safe nanomaterials into the marketplace and the living environment, they deserve more attention and more interaction between biologists and aerosol scientists. The members of the workshop believe that further advances in in-vitro cell exposure studies would be greatly facilitated by a more active role of the aerosol scientists. The technical know-how for developing and running ALI in-vitro exposure systems is available in the aerosol community and at the same time biologists/toxicologists are required for proper assessment of the biological impact of nanoparticles.
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In the last decade, both regenerative medicine and nanotechnology have been broadly developed leading important advances in biomedical research as well as in clinical practice. The manipulation on the molecular level and the use of several functionalized nanoscaled materials has application in various fields of regenerative medicine including tissue engineering, cell therapy, diagnosis and drug and gene delivery. The themes covered in this review include nanoparticle systems for tracking transplanted stem cells, self-assembling peptides, nanoparticles for gene delivery into stem cells and biomimetic scaffolds useful for 2D and 3D tissue cell cultures, transplantation and clinical application.
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A straightforward route is proposed for the multi-gram scale synthesis of heterobifunctional poly(ethylene glycol) (PEG) oligomers containing combination of triethyloxysilane extremity for surface modification of metal oxides and amino or azido active end groups for further functionalization. The suitability of these PEG derivatives to be conjugated to nanomaterials was shown by pegylation of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles (NPs), followed by functionalization with small peptide ligands for biomedical applications.
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Aquest projecte de doctorat s un treball interdisciplinari adreat a lobtenci de nous nanocompsits (NCs) funcionals sintetitzats a partir de materials polimrics bescanviadors dions que sn modificats amb nanopartcules metlliques (NPMs) de diferent composici. Els materials desenvolupats savaluen en funci de dues possibles aplicacions: 1) com a catalitzadors de reaccions orgniques dinters actual (NCs basats en palladi) i, 2) la seva dedicaci a aplicacions bactericides en el tractament daiges domstiques o industrials (NCs basats en plata). El desenvolupament de nanomaterials s de gran inters a lactualitat donades les seves especials propietats, laprofitament de les quals s la fora impulsora per a la fabricaci de nous NCs. Les nanopartcules metlliques estabilitzades en polmer (Polymer Stabilized Metal Nanoparticles, PSNPM) shan preparat mitjanant la tcnica in-situ de sntesi intermatricial (Inter-matrix synthesis, IMS) que consisteix en la crrega seqencial dels grups funcionals de les matrius polimriques amb ions metllics, i la seva posterior reducci qumica dins de la matriu polimrica de bescanvi inic. Lestabilitzaci en matrius polimriques evita lagregaci entre elles (self-aggreagtion), un dels principals problemes coneguts de les NPs. Pel desenvolupament daquesta metodologia, shan emprat diferents tipus de matrius polimriques de bescanvi inic: membrana Sulfonated PolyEtherEtherKetone, SPEEK, aix com fibres sinttiques basades en polypropil amb diferents tipus de grups funcionals, que ens permeten el seu s com a filtres en la desinfecci de solucions aquoses o com a material catalitzador. Durant el projecte sha anat avanant en loptimitzaci del material nanocomposite final per a les aplicacions dinters, en quant activitat i funcionalitat de les nanopartcules i estabilitat del nanocomposite. Aix, sha optimitzat la sntesi de NPs estabilitzades en resines de bescanvi inic, realitzant un screening de diferents tipus de resines i la seva avaluaci en aplicacions industrials dinters.
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Les nanopartcules metlliques sn catalitzadors molt efectius degut a la seva elevada rea superficial especfica. No obstant, degut a la seva gran tendncia a lagregaci, sovint s necessria la seva immobilitzaci sobre suports per tal de dur a terme aplicacions especfiques. La immobilitzaci de les nanopartcules dins duna matriu polimrica ha demostrat ser una bona metodologia per a aquest propsit, doncs permet lestabilitzaci i protecci de les partcules, aix com la recuperaci del catalitzador. Mitjanant la incorporaci de nanopartcules metlliques a membranes polimriques es poden obtenir materials nanocomposites molt efectius, que podrien combinar la capacitat cataltica dels nanomaterials amb lefectivitat dels processos de membrana en un sol pas. Lobjectiu a llarg termini s lobtenci de membranes cataltiques actives capaces de realitzar simultniament la separaci i la destrucci de contaminants presents en soluci. Concretament, en aquest treball shan desenvolupat membranes polimriques de Politersulfona amb grup Cardo modificada amb grups sulfnics per tal de sintetitzar nanopartcules de Pd mitjanant la tcnica de la Sntesi Intermatricial. Tant el polmer modificat com les membranes i el nanocomposite obtingut han estat caracteritzats i leficincia cataltica sha avaluat monitoritzant la reducci cataltica del 4-nitrofenol en presncia de NaBH4.
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Nonlinear optical nanocrystals have been recently introduced as a promising alternative to fluorescent probes for multiphoton microscopy. We present for the first time a complete survey of the properties of five nanomaterials (KNbO(3), LiNbO(3), BaTiO(3), KTP, and ZnO), describing their preparation and stabilization and providing quantitative estimations of their nonlinear optical response. In the light of their prospective use as biological and clinical markers, we assess their biocompatibility on human healthy and cancerous cell lines. Finally, we demonstrate the great potential for cell imaging of these inherently nonlinear probes in terms of optical contrast, wavelength flexibility, and signal photostability.
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Hydrophilic nanocarriers formed by electrostatic interaction of chitosan with oppositely charged macromolecules have a high potential as vectors in biomedical and pharmaceutical applications. However, comprehensive information about the fate of such nanomaterials in biological environment is lacking. We used chitosan from both animal and fungal sources to form well-characterized chitosan-pentasodium triphosphate (TPP)//alginate nanogels suitable for comparative studies. Upon exposure of human colon cancer cells (HT29 and CaCo2), breast cancer cells (MDA-MB-231 and MCF-7), glioblastoma cells (LN229), lung cancer cells (A549), and brain-derived endothelial cells (HCEC) to chitosan-(TPP)//alginate nanogels, cell type-, nanogel dosage-, and exposure time-dependent responses are observed. Comparing chitosan-TPP//alginate nanogels prepared from either animal or fungal source in terms of nanogel formation, cell uptake, reactive oxygen species production, and metabolic cell activity, no significant differences become obvious. The results identify fungal chitosan as an alternative to animal chitosan in particular if biomedical/pharmaceutical applications are intended.
Resumo:
L' valuation quantitative des dangers et des expositions aux nanomatriaux se heurte de nombreuses incertitudes qui ne seront leves qu' mesure de la progression des connaissances scientifiques de leurs proprits. L' une des consquences de ces incertitudes est que les valeurs limites d'exposition professionnelle dfinies actuellement pour les poussires ne sont pas ncessairement pertinentes aux nanomatriaux. En l'absence de rfrentiel quantitatif et, la demande de la DGS pour clairer les rflexions de l' AFNOR et de l'ISO sur le sujet, une dmarche de gestion gradue des risques (control banding) a t labore au sein de l' Anses. Ce dveloppement a t ralis l'aide d'un groupe d'experts rapporteurs rattach au Comit d'experts spcialiss valuation des risques lis aux agents physiques, aux nouvelles technologies et aux grands amnagements. La mise en oeuvre de la dmarche de gestion gradue des risques propose repose sur quatre grandes tapes: 1. Le recueil des informations. Cette tape consiste runir les informations disponibles sur les dangers du nanomatriau manufactur considr ; ainsi que sur l'exposition potentielle des personnes aux postes de travail (observation sur le terrain, mesures, etc.). 2. L'attribution d'une bande de danger. Le danger potentiel du nanomatriau manufactur prsent, qu'il soit brut o incorpor dans une matrice (liquide ou solide) est valu dans cette tape. La bande danger attribue tient compte de la dangerosit du produit bulk ou de sa substance analogue l'chelle non-nanomtrique, de la bio-persistance du matriau (pour les matriaux fibreux), de sa solubilit et de son ventuelle ractivit. 3. Attribution d'une bande d'exposition. La bande d'exposition du nanomatriau manufactur considr ou du produit en contenant est dfinie par le niveau de potentiel d'mission du produit. Elle tient compte de sa forme physique (solide, liquide, poudre arosol), de sa pulvrulence et de sa volatilit. Le nombre de travailleurs, la frquence, la dure d'exposition ainsi que la quantit mise en oeuvre ne sont pas pris en compte, contrairement une valuation classique des risques chimiques. 4. Obtention d'une bande de matrise des risques. Le croisement des bandes de dangers et d'exposition pralablement attribues permet de dfi nir le niveau de matrise du risque. Il fait correspondre les moyens techniques et organisationnels mettre en oeuvre pour maintenir le risque au niveau le plus faible possible. Un plan d'action est ensuite dfi ni pour garantir l'effi cacit de la prvention recommande par le niveau de matrise dtermin. Il tient compte des mesures de prvention dj existantes et les renforce si ncessaire. Si les mesures indiques par le niveau de matrise de risque ne sont pas ralisables, par exemple, pour des raisons techniques ou budgtaires, une valuation de risque approfondie devra tre ralise par un expert. La gestion gradue des risques est une mthode alternative pour raliser une valuation qualitative de risques et mettre en place des moyens de prvention sans recourir une valuation quantitative des risques. Son utilisation semble particulirement adapte au contexte des nanomatriaux manufacturs, pour lequel les choix de valeurs de rfrence (Valeurs limites d'exposition en milieu professionnel) et des techniques de mesurage appropries souffrent d'une grande incertitude. La dmarche propose repose sur des critres simples, accessibles dans la littrature scientifi que ou via les donnes techniques relatives aux produits utiliss. Pour autant, sa mise en oeuvre requiert des comptences minimales dans les domaines de la prvention des risques chimiques (chimie, toxicologie, etc.), des nanosciences et des nanotechnologies.
The effects of electron-hole separation on the photoconductivity of individual metal oxide nanowires
Resumo:
The responses of individual ZnO nanowires to UV light demonstrate that the persistent photoconductivity (PPC) state is directly related to the electronhole separation near the surface. Our results demonstrate that the electrical transport in these nanomaterials is influenced by the surface in two different ways. On the one hand, the effective mobility and the density of free carriers are determined by recombination mechanisms assisted by the oxidizing molecules in air. This phenomenon can also be blocked by surface passivation. On the other hand, the surface built-in potential separates the photogenerated electronhole pairs and accumulates holes at the surface. After illumination, the charge separation makes the electronhole recombination difficult and originates PPC. This effect is quickly reverted after increasing either the probing current (self-heating by Joule dissipation) or the oxygen content in air (favouring the surface recombination mechanisms). The model for PPC in individual nanowires presented here illustrates the intrinsic potential of metal oxide nanowires to develop optoelectronic devices or optochemical sensors with better and new performances.
