Bakgrund: Dagens användning av antibakteriellt silver i vardagsprodukter leder till att silverförorenat avlopp hamnar i reningsverken. Ett näringsrikt slam bildas i reningsverken och används som växtnäring på jordbruksland. Ett problem som kan uppstå är att silverföroreningarna ifrån slammet överförs till mark. Eftersom silver är känt för sina antibakteriella egenskaper så är syftet med denna studien att undersöka silvrets effekt på jord och marklevande organismer. Resultat: Den lägsta koncentrationen på 0,56 mg/kg silvret NM-300K hämmade nitritproduktionen i jorden med 16%. Silvernitrat hämmade den mikrobiella massa i jord med 50% efter 7 dygn. Vid lägre silverkoncentrationer på 0,19 mg/kg gynnades nitritproduktionen i mark istället. Antalet markbakterier sjönk i den silverkontaminerade marken i jämförelse med kontrollgruppen. En PVP täckt silvernanopartikel visade sig vara mer toxisk mot nitrifikations bakterier än en silver nanopartikel otäckt yta. Slutsats: Silver har visat sig vara toxisk mot mikroorganismer i mark, dock kan ingen gemensam toxisk koncentration fastställas för alla markorganismer då olika typer av nanosilver och silverföreningar har olika effekt beroende på vilken storlek, form, yta och vad de omvandlas till i naturen.

Many consumer and medical products contain engineered nanomaterials (ENMs) due to their unique properties arising from their small size of <100 nm in at least one dimension. Although ENMs could greatly improve the quality of daily life, concerns for their health and environmental safety emerged in recent years because the same properties that make ENMs beneficial may also render them toxic. The small size allows ENMs’ entrance into the cell where they may attach to biological molecules and membranes, disrupting their function and/or leading to oxidative stress and/or damage. This thesis focused on silver nanoparticles (AgNPs). Several articles demonstrated that during washing AgNPs are released from the AgNP-impregnated fabrics and could pose a risk to aquatic species. Given that the toxicity mechanisms of AgNPs are yet to be clearly understood this thesis investigated the effects of AgNPs from ‘oxidative stress’ and ‘endocrine disruption’ points of view, using both in vivo and in vitro model fish systems. A 4 d exposure of zebrafish (Danio rerio) embryos to AgNPs increased mortality, delayed hatching, and increased oxidative stress. The silver ion (Ag+) was more effective in eliciting these effects at equivalent silver concentrations. Moreover, the Ag-chelator cysteine reduced the toxicity of both Ag-types. Despite these effects AgNPs or Ag+ did not affect the ability of zebrafish larvae or adults (raised to adulthood in Ag-free water) to increase cortisol levels, but there were differential effects on the expression of corticotropin-releasing factor (CRF)-related genes, suggesting that other physiological processes regulated by CRF may be impacted. Furthermore, a 48 h exposure of rainbow trout (Oncorhynchus mykiss) erythrocytes and hepatocytes to AgNPs or Ag+ increased oxidative stress, but Ag+ was more potent. Moreover, AgNPs elevated lipid peroxidation, while Ag+ increased DNA damage, suggesting different modes of action for the two Ag-types. Cysteine treatment reduced the toxicity of Ag+ and AgNPs, while buthionine sulfoximine, which inhibits glutathione synthesis, increased it, suggesting the importance of glutathione in silver toxicity. Finally, AgNPs increased glycogenolysis in trout hepatocytes independently of the beta-adrenoreceptor or the glucocorticoid receptor.

Submitted by Dilene Paulo (dilene.fatima@ufcg.edu.br) on 2018-01-22T13:38:36Z No. of bitstreams: 1 ANDREIA CARLA NOVAIS DE ALMEIDA - DISSERATÇÃO PPGCMAT 2014.pdf: 1504175 bytes, checksum: df4b8e90a9d89dfe22b0388457465f25 (MD5) / Made available in DSpace on 2018-01-22T13:38:36Z (GMT). No. of bitstreams: 1 ANDREIA CARLA NOVAIS DE ALMEIDA - DISSERATÇÃO PPGCMAT 2014.pdf: 1504175 bytes, checksum: df4b8e90a9d89dfe22b0388457465f25 (MD5) Previous issue date: 2014-10-28 / Há muitos anos a prata tem sido usada em produtos de consumo em função de suas propriedades antimicrobianas. Com o advento da tecnologia para observação de átomos, vírus, se verificou a possibilidade de produzir materiais em escala nanométrica. A prata, especificamente, nesta dimensão nano, tem suas propriedades potencializadas, além de poder transpor barreiras do sistema biológico intransponíveis em escalas maiores. A preocupação, no entanto, sobre o uso deste ingrediente em produtos cosméticos é expor ao uso produtos cosméticos com nanoprata, sem antes ter a certeza da segurança quando em contato com sistemas biológicos. As autoridades têm discutido sobre nanotecnologia, mas ainda não há um consenso sobre a definição do termo nanotecnologia a ser adotada mundialmente. Desta forma, este trabalho tem como objetivo avaliar produtos cosméticos, visando identificar a composição química, estrutural e comprovar se as partículas de prata presentes nos cosméticos estão em escala nanométrica. As amostras foram separadas em triplicata e caracterizadas por meio de Difração de Raios X, Espectrometria de Infravermelho com Transformada de Fourier, Microscopia Eletrônica de Varredura, Análise Termogravimetrica, Calorimetria Exploratória Diferencial, Distribuição Granulométrica e Espectroscopia de Plasma Acoplado. As análises foram realizadas no Laboratório de Desenvolvimento e Avaliação de Biomateriais da Universidade Federal de Campina Grande (UFCG) e no Laboratório da Universidade de Brasília (UnB). Os resultados demonstram que os compostos de prata estão em baixas concentrações nos produtos desodorantes antitranspirantes analisados, chegando a partes por milhões (ppm) e em algumas amostras até partes por bilhões (ppb), isto dificultou que houvesse uma conclusão precisa, por meio das caracterizações usadas, sobre presença de nanoprata nas amostras pesquisadas. Baseado nos resultados de Distribuição Granulométrica pode-se concluir, no entanto, que considerando a média de tamanho em torno de 300nm das partículas presentes nas amostras que a prata presente não está em escala nanométrica, pois verifica-se nas literaturas que as nanopratas sintetizadas encontram-se em torno de 20nm. / For many years silver has been used in consumer products due to their antimicrobial properties. With the advent of the observation of atoms, viruses technology, there is the possibility of producing materials at the nanometer scale. Silver, specifically, this nano dimension, would have leveraged their properties, and can overcome the barriers insurmountable biological system at larger scales. The concern, however, about the use of this ingredient in cosmetic products is exposed to use cosmetic products with nanosilver, without having the assurance of safety when in contact with biological systems. Authorities have discussed about nanotechnology, but there is still no consensus on how to define the term nanotechnology and this definition be adopted worldwide. Thus, this work aims to evaluate cosmetic products in order to identify the chemical, structural composition and prove that the silver particles present in cosmetics are in the nanometer scale. The samples were separated in triplicate and characterized by means of X-ray Diffraction, Infrared Spectrometry Fourier Transform, Scanning Electron Microscopy, Thermogravimetric Analysis, Differential Scanning Calorimetry, and Grain Size Distribution Coupled Plasma Spectroscopy. The analyzes were performed at the Laboratory of Development and Evaluation of Biomaterials, Federal University of Campina Grande (UFCG) and Laboratory of the University of Brasilia (UNB). The results showed that the silver compounds are in low concentrations in antiperspirant deodorant products analyzed, reaching parts per million (ppm) and even in some samples parts per billion (ppb), so was difficult precise conclusion, through the characterizations used on presence of nanosilver in the surveyed samples. Based on the results of particle size distribution can be concluded, however, that considering the average size around 300nm particles present in the samples can be concluded that silver. this is not at the nanometer scale, because it turns out in the literature that the synthesized nanopratas are around 20nm.

Many consumer and medical products contain engineered nanomaterials (ENMs) due to their unique properties arising from their small size of <100 nm in at least one dimension. Although ENMs could greatly improve the quality of daily life, concerns for their health and environmental safety emerged in recent years because the same properties that make ENMs beneficial may also render them toxic. The small size allows ENMs’ entrance into the cell where they may attach to biological molecules and membranes, disrupting their function and/or leading to oxidative stress and/or damage. This thesis focused on silver nanoparticles (AgNPs). Several articles demonstrated that during washing AgNPs are released from the AgNP-impregnated fabrics and could pose a risk to aquatic species. Given that the toxicity mechanisms of AgNPs are yet to be clearly understood this thesis investigated the effects of AgNPs from ‘oxidative stress’ and ‘endocrine disruption’ points of view, using both in vivo and in vitro model fish systems. A 4 d exposure of zebrafish (Danio rerio) embryos to AgNPs increased mortality, delayed hatching, and increased oxidative stress. The silver ion (Ag+) was more effective in eliciting these effects at equivalent silver concentrations. Moreover, the Ag-chelator cysteine reduced the toxicity of both Ag-types. Despite these effects AgNPs or Ag+ did not affect the ability of zebrafish larvae or adults (raised to adulthood in Ag-free water) to increase cortisol levels, but there were differential effects on the expression of corticotropin-releasing factor (CRF)-related genes, suggesting that other physiological processes regulated by CRF may be impacted. Furthermore, a 48 h exposure of rainbow trout (Oncorhynchus mykiss) erythrocytes and hepatocytes to AgNPs or Ag+ increased oxidative stress, but Ag+ was more potent. Moreover, AgNPs elevated lipid peroxidation, while Ag+ increased DNA damage, suggesting different modes of action for the two Ag-types. Cysteine treatment reduced the toxicity of Ag+ and AgNPs, while buthionine sulfoximine, which inhibits glutathione synthesis, increased it, suggesting the importance of glutathione in silver toxicity. Finally, AgNPs increased glycogenolysis in trout hepatocytes independently of the beta-adrenoreceptor or the glucocorticoid receptor.

Silver nanoparticles (nanosilver) are gaining significant attention from the academic and regulatory communities, not only because of their antimicrobial effects and subsequent product applications, but also because of their potential health and environmental impacts. Although some human health effects of silver nanoparticles have been reported, realistic exposure levels from the use of consumer products are still largely unknown. The objective of this work was to characterize the release of silver and silver- containing particles during the normal use of silver nanotechnology consumer products. Specific objectives were to review the environmental and human health risks of airborne, engineered nanoparticles, to characterize aerosol emissions from nanosilver spray products, and to characterize nanosilver that may be released from childrenʼs consumer products under conditions of normal use. We identified possible routes of aerosolization of nanosilver from the production, use, and disposal of consumer products and estimated that about 14% of silver nanotechnology products that have been inventoried could potentially release silver particles into the air during use. The spray products investigated emitted 0.24 – 56 ng of silver in aerosols per spray action, and the plurality of aerosols were 1 – 2.5 μm in diameter, easily inhaled, for two products. Both the products' liquid characteristics and the bottles' spraying mechanisms played roles in determining the aerosol size distributions, but the size of silver-containing aerosols was largely independent of the liquid phase size distributions. We compiled an inventory of 82 children's consumer products that claim to contain nanosilver, of which 13 products were examined for presence of silver and tested for release of silver into liquid media and air, and onto skin. All products contained some form of silver, but silver-containing particles were observed in only four products, with sizes ranging from nanoscale up to 10 μm in size. Silver leached preferably into synthetic biological media with higher chloride concentrations, such as sweat and urine. We determined that levels of silver to which children would be exposed during normal use of these products are likely to be low, and bioavailable silver is expected to be in ionic rather than particulate form. / Ph. D.

The objective of this research was the development of a novel synthetic method for preparation of silver/polymer nanocomposites containing finely dispersed silver nanoparticles. The surface of nanosilver was functionalized by amino groups, which then reacted with end acidic groups of polylactide (PLA) and its co-polymer with polyglycolide (PLGA). The condensation reaction was conducted in the presence of diisopropylcarbodiimide. Nanosilver coating with the polymers was confirmed by FT-IR and UV-vis spectroscopy. It was found that not only acid-terminated but also ester-terminated polymers can react with functionalized nanosilver. However, high dispersibility of the nanoparticles was achieved with acid-terminated polymers only. Obtained materials demonstrated X-ray contrast and bactericidal properties that makes possible their prospective application in biology and medicine.

Die-attachment, as the first level of electronics packaging, plays a key role for the overall performance of the power electronics packages. Nanosilver sintering has becoming an emerging solder-free, environmental friendly die-attach technology. Researchers have demonstrated the feasibility of die-attachment on silver (Ag) or gold (Au) surfaces by pressure-less or low-pressure (< 5 MPa) nanosilver sintering. This study extended the application of nanosilver sintering die-attach technique to copper (Cu) surface. The main challenge of nanosilver sintering on Cu is the formation of thick Cu oxide during processing, which may lead to weak joints. In this study, different processes were developed based on the die size: for small-area dice (< 5 * 5 mm2), different sintering atmospheres (e.g. forming gas) were applied to protect Cu surface from oxidation; for large-area dice (> 5 * 5 mm2), a double-print, low-pressure (< 5 MPa) assisted sintering process was developed. For both processes, die-shear tests demonstrated die-shear strength can reach 40 MPa. The effects of different sintering parameters of the processing were analyzed by different material characterization techniques. With forming gas as sintering atmosphere, not only Cu surface was protected from oxidation, but also the organics in the paste were degraded with nanosilver particles as catalyst. External pressure applied in the processing not only increased the density of sintered Ag, but also enhanced the contact area of sintered-Ag/Cu interface. Microstructure of Ag/Cu interface were characterized by transmission electron microscopy (TEM). Characterization results indicate that Ag/Cu metallic bonds formed at the interface, which verified the high die-shear strength of the die-attachment. Thermal performance of nanosilver sintered die-attachment on Cu was evaluated. A system was designed and constructed for measuring both transient thermal impedance (Zth) and steady-state thermal resistance (Rth) of insulated gate bipolar transistor (IGBT) packages. The coefficient of variation (CV) of Zth measurement by the system was lower than 0.5%. Lead-free solder (SAC305) was applied in comparison of thermal performance with nanosilver paste. With same sample geometry and heating power level, nanosilver sintered joints on Cu showed in average 12.6% lower Zth and 20.1% lower Rth than SAC305 soldered joints. Great thermal performances of nanosilver sintering die-attachment on Cu were mainly due to the low thermal resistivity of sintered-Ag and the good bonding quality. Both passive temperature cycling and active power cycling tests were conducted to evaluate the reliability of nanosilver sintered joints on Cu. For passive temperature cycling tests (-40 - 125 C), the die-shear strengths of mechanical samples had no significant drop over 1000 cycles, and nanosilver sintered IGBT on Cu packages showed almost no change on Zth after 800 cycles. For active power cycling test (Tj = 45 - 175 C), nanosilver sintered IGBT on Cu assembly had a lifetime over 48,000 cycles. The failure point of the assembly was the detachment of the wirebonds. Great reliability performances of nanosilver sintered die-attachment on Cu were mainly due to the low mismatch of coefficient of thermal expansion (CTE) between sintered-Ag and Cu. Meanwhile, low inter-diffusion rate between Ag and Cu prevented the interface from the reliability issue related to Kirkendall voids, which often took place in tin (Sn) -based solder joints. / Ph. D.

No description available.

<p>The antimicrobial properties of silver have been taken advantage of by societies for thousands of years. Its use has come back in favor in the form of silver nanoparticles, which are highly efficacious antimicrobial agents. Silver nanoparticles are incorporated into a myriad of products specifically designed for clinical use, but also for general use by consumers. Silver nanoparticles can be found in textiles such as clothing and stuffed toys, and in home appliances including washing machines and curling irons. A large number of products specifically marketed for use by children are also available to consumers, including pacifiers, sippy cups, and even breast milk storage bags. The hazards and toxicities associated with silver nanoparticles are not well understood, however modes of toxicity have been reported for ionic silver. It is assumed that the main mechanism of toxicity of silver nanoparticles relates to the release of ionic silver, however studies have indicated an additional nano-effect, likely due to nanoparticle size, differential coatings, and means of sustained dosing of ionic silver. However we are sure that these silver nanoparticles will accumulate in the waste stream, likely arriving during different stages of a product’s lifespan. A main sink of these nanoparticles travelling through both natural and engineered environments is wastewater treatment plants. As a society we rely on the biological removal of nutrients, which takes place primarily in the activated sludge of secondary treatment. Studies have already indicated possible, temporary decreases in removal efficiencies as well as changes in microbial communities, including losses of diversity, following exposure to silver nanoparticles. Therefore, it is of paramount importance to examine the effects of both silver nanoparticles and ionic silver on the community and function of wastewater bacteria. </p><p> Sequencing batch reactors were operated to mimic wastewater treatment. They were fed synthetic wastewater and after reaching acclimation, were dosed over time with varying concentrations of both ionic and nanosilver. Cell samples were collected periodically to assess the presence and identity of cultivable silver resistant bacteria and to map the microbial community changes taking place under different treatments using Next Generation Sequencing. Isolates were tested for the presence of known silver resistance (sil) genes as were activated sludge samples from a collection of domestic wastewater treatment plants, by designing TaqMan probe assays and performing quantitative PCR. The silver resistant isolates were also used to test the growth implications, as well as sil gene expression changes, following treatment with ionic silver and a variety of silver nanoparticles with various coatings, all at multiple concentrations. This was accomplished by performing multiple batch experiments and then using the TaqMan assays and reverse transcription-quantitative PCR.</p><p>Overall, microbial community changes were observed in the sequencing batch reactors, and there were differences noted based on treatment, including ionic silver versus nanosilver and between the two silver nanoparticle coatings. Most notably, the possibility of nitrification in wastewater treatment being particularly susceptible was strongly indicated. Individual wastewater bacteria isolates all contained sil genes, as did the majority of the wastewater treatment plant activated sludge, however the levels of actual sil gene expression were inconsistent. This particular finding supports a current body of work indicating that there are alternate modes of bacterial silver resistance in play that we are just becoming aware of.</p> / Dissertation

This dissertation focuses on the versatility and integrity of a novel, ultrasoft polycarbonate polyurethane (PCPU) by the introduction of nanoparticles and lithium salts. Additionally, the research takes into account the use of electrospinning as a technique to create PCPU and polyimide (PI) fibers. These polymers are of interest as they offer a wide range of properties and uses within the medical and industrial fields. An industrial batch of an ultrasoft thermoplastic polyurethane (TPU) was synthesized using a two-step process. The first was to create an end capped pre-polymer from methylene bis (4-cyclohexylisocyanate), and a polycarbonate polyol made up of 1,6- hexanediol and 3-methyl-1,5-pentanediol. The second step was done by reacting the pre-polymer with an excess of the polycarbonate polyol with a chain extender, 1,4-butanediol. Biocompatibility testing such as USP Class VI, MEM Elution Cytotoxicity and Hemolysis toxicology reported that PCPU showed no toxicity. This novel type of polyurethane material targets growing markets of biocompatible polymers and has been used for peristaltic pump tubing, but also can be utilized as balloon catheters, enteral feeding tubes and medical equipment gaskets and seals. This material is ideal for replacing materials such as soft plastisols containing diethylhexyl phthalate for use in biomedical and industrial applications. After extensive characterization of this polymer system another dimension was added to this research. The addition of nanoparticles and nanofillers to polyurethane can express enhanced mechanical, thermal and adhesion properties. The incorporation of nanoparticles such as nanosilica, nanosilver and carbon black into polyurethane materials showed improved tensile strength, thermal performance and adhesion properties of the PCPU. Samples were characterized using contact angle measurements, Fourier transform spectroscopy (FTIR), differential scanning calorimetry (DSC), parallel plate rheology and tensile testing. The second chapter entails the fabrication and characterization of PCPU nanofibers and nanomembranes through a process known as electrospinning. The resulting PCPU nanomembranes showed a crystalline peak from the WAXS profile which is due to electrospun and solution strain induced crystallinity. The PCPU nanocomposite nanomembranes displayed increased thermal stability and an increase in tensile performance at higher weight percent. The nanomembranes were investigated using contact angle measurements, thermogravimetric analysis (TGA), DSC, WAXS, SAXS and tensile testing. The final chapter focuses on investigating the rheological properties of PCPU/lithium electrolytes as well as transforming an unprocessable polyimide powder into a nanomembrane. The PCPU/ lithium composite electrolyte showed an increase in the activation energy and conductivity, while the PI/lithium showed increased conductivity over time. Dynamic mechanical analysis and four-point probe was used to investigate the samples.