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1.
Mater Today Bio ; 8: 100086, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33319188

RESUMO

Nucleic acids are relevant biopolymers in therapy and diagnosis, for which their purity and biological activity are of crucial relevance. However, these features are difficult to achieve by cost-effective methods. Herein, we report the functionalization of a macroporous chromatographic support functionalized with an ionic liquid (IL) with remarkable performance to purify nucleic acids. An initial screening with distinct IL chemical structures supported in silica was carried out, allowing to identify the IL 1-methyl-3-propylimidazolium chloride as the most promising ligand. A chromatographic macroporous matrix able to be used in preparative liquid chromatography was then functionalized and binding/elution studies were performed. The IL 1-methyl-3-propylimidazolium chloride acts as a multimodal ligand with a remarkable dynamic binding capacity. This macroporous support allows the (one-step) purification of nucleic acids, namely small RNAs, ribosomal RNA, and genomic DNA, from a bacterial lysate, and can be regenerated and reused without compromising its separation performance.

2.
Mar Pollut Bull ; 160: 111665, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33181940

RESUMO

In vitro methods have gained rising importance in ecotoxicology due to ethical concerns. The aim of this study was to assess the single and combined in vitro effects of gold, as nanoparticle (AuNPs) and ionic (Au+) form, and the pharmaceutical gemfibrozil (GEM). Sparus aurata liver organ culture was exposed to gold (4 to 7200 µg·L-1), GEM (1.5 to 15,000 µg·L-1) and combination 80 µg·L-1 gold +150 µg·L-1 GEM for 24 h. Endpoints related with antioxidant status, peroxidative/genetic damage were assessed. AuNPs caused more effects than Au+, increasing catalase and glutathione reductase activities and damaging DNA and cellular membranes. Effects were dependent on AuNPs size, coating and concentration. GEM damaged DNA at an environmentally relevant concentration, 1.5 µg·L-1. Overall, the effects of the combined exposures were higher than the predicted, based on single exposures. This study showed that liver culture can be a useful model to study contaminants effects.


Assuntos
Nanopartículas Metálicas , Dourada , Animais , Genfibrozila/toxicidade , Ouro , Fígado , Nanopartículas Metálicas/toxicidade , Técnicas de Cultura de Órgãos
3.
Aquat Toxicol ; 221: 105445, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32078886

RESUMO

Despite the widespread use of nanoparticles (NPs), there are still major gaps of knowledge regarding the impact of nanomaterials in the environment and aquatic animals. The present work aimed to study the effects of 7 and 40 nm gold nanoparticles (AuNPs) - citrate and polyvinylpyrrolidone (PVP) coated - on the liver proteome of the estuarine/marine fish gilthead seabream (Sparus aurata). After 96 h, exposure to AuNP elicited alterations on the abundance of 26 proteins, when compared to the control group. AuNPs differentially affected several metabolic pathways in S. aurata liver cells. Among the affected proteins were those related to cytoskeleton and cell structure, gluconeogenesis, amino acids metabolism and several processes related to protein activity (protein synthesis, catabolism, folding and transport). The increased abundance of proteins associated with energy metabolism (ATP synthase subunit beta), stress response (94 kDa glucose-regulated protein) and cytoskeleton structure (actins and tubulins) may represent the first signs of cellular oxidative stress induced by AuNPs. Although higher gold accumulation was found in the liver of S. aurata exposed to 7 nm PVP-AuNPs, the 7 nm cAuNPs were more bioactive, inducing more effects in liver proteome. Gold accumulated more in the spleen than in the other assessed tissues of S. aurata exposed to AuNPs, highlighting its potential role on the elimination of these NPs.


Assuntos
Ouro/toxicidade , Fígado/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Proteoma/metabolismo , Dourada/metabolismo , Poluentes Químicos da Água/toxicidade , Animais , Ácido Cítrico/química , Fígado/metabolismo , Redes e Vias Metabólicas/efeitos dos fármacos , Oxirredução , Estresse Oxidativo/efeitos dos fármacos , Povidona/química , Proteômica , Propriedades de Superfície
4.
Sci Total Environ ; 716: 137026, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-32036137

RESUMO

The question of whether gold (Au) is more toxic as nanoparticles or in its ionic form remains unclear and controversial. The present work aimed to clarify the effects of 96 h exposure to 4, 80 and 1600 µg·L-1 of 7 nm gold nanoparticles (AuNPs) - (citrate coated (cAuNPs) or polyvinylpyrrolidone coated (PVP-AuNPs)) - and ionic Au (iAu) on gilthead seabream (Sparus aurata). Effects at different levels of biological organization (behaviour, neurotransmission, biotransformation, oxidative stress/damage and genotoxicity) were assessed. cAuNPs induced oxidative stress and damage (lipid peroxidation increase), even at 4 µg·L-1, and reduced the ability of S. aurata to swim against a water flow at 1600 µg·L-1. Exposure to cAuNPs induced more adverse effects than exposure to PVP-AuNPs. All tested concentrations of Au (nano or ionic form) induced DNA breaks and cytogenetic damage in erythrocytes of S. aurata. Generally, iAu induced significantly more effects in fish than the nano form, probably associated with the significantly higher accumulation in the fish tissues. No fish mortality was observed following exposure to AuNPs, but mortality was observed in the group exposed to 1600 µg·L-1 of iAu.


Assuntos
Dourada , Animais , Bioacumulação , Ouro , Nanopartículas Metálicas , Estresse Oxidativo
5.
Chemosphere ; 215: 248-260, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30317096

RESUMO

Gold nanoparticles (AuNPs) are found in a wide range of applications and therefore expected to present increasing levels in the environment. There is however limited knowledge concerning the potential toxicity of AuNPs as well as their combined effects with other pollutants. Hence, the present study aimed to investigate the effects of AuNPs alone and combined with the pharmaceutical gemfibrozil (GEM) on different biological responses (behaviour, neurotransmission, biotransformation and oxidative stress) in one of the most consumed fish in southern Europe, the seabream Sparus aurata. Fish were exposed for 96 h to waterborne 40 nm AuNPs with two coatings - citrate and polyvinylpyrrolidone (PVP), alone or combined with GEM. Antioxidant defences were induced in liver and gills upon both AuNPs exposure. Decreased swimming performance (1600 µg.L-1) and oxidative damage in gills (4 and 80 µg.L-1) were observed following exposure to polyvinylpyrrolidone coated gold nanoparticles (PVP-AuNPs). Generally, accumulation of gold in fish tissues and deleterious effects in S. aurata were higher for PVP-AuNPs than for cAuNPs exposures. Although AuNPs and GEM combined effects in gills were generally low, in liver, they were higher than the predicted. The accumulation and effects of AuNPs showed to be dependent on the size, coating, surface charge and aggregation/agglomeration state of nanoparticles. Additionally, it was tissue' specific and dependent on the presence of other contaminants. Although, gold intake by humans is expected to not exceed the estimated tolerable daily intake, it is highly recommended to keep it on track due to the increasing use of AuNPs.


Assuntos
Exposição Ambiental/análise , Genfibrozila/toxicidade , Ouro/toxicidade , Nanopartículas Metálicas/toxicidade , Dourada/metabolismo , Poluentes Químicos da Água/toxicidade , Animais , Antioxidantes/metabolismo , Comportamento Animal/efeitos dos fármacos , Biotransformação/efeitos dos fármacos , Europa (Continente) , Genfibrozila/metabolismo , Genfibrozila/farmacocinética , Brânquias/efeitos dos fármacos , Brânquias/metabolismo , Ouro/metabolismo , Ouro/farmacocinética , Humanos , Fígado/efeitos dos fármacos , Fígado/metabolismo , Oxirredução , Estresse Oxidativo/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos
6.
Chemosphere ; 220: 11-19, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30576896

RESUMO

Due to their diverse applications, gold nanoparticles (AuNPs) are expected to increase of in the environment, although few studies are available on their mode of action in aquatic organisms. The genotoxicity of AuNPs, alone or combined with the human pharmaceutical gemfibrozil (GEM), an environmental contaminant frequently detected in aquatic systems, including in marine ecosystems, was examined using gilthead seabream erythrocytes as a model system. Fish were exposed for 96 h to 4, 80 and 1600 µg L-1 of 40 nm AuNPs with two coatings - citrate or polyvinylpyrrolidone; GEM (150 µg L-1); and a combination of AuNPs and GEM (80 µg L-1 AuNPs + 150 µg L-1 GEM). AuNPs induced DNA damage and increased nuclear abnormalities levels, with coating showing an important role in the toxicity of AuNPs to fish. The combined exposures of AuNPs and GEM produced an antagonistic response, with observed toxic effects in the mixtures being lower than the predicted. The results raise concern about the safety of AuNPs and demonstrate interactions between them and other contaminants.


Assuntos
Dano ao DNA/efeitos dos fármacos , Genfibrozila/toxicidade , Nanopartículas Metálicas/toxicidade , Mutagênicos , Animais , Organismos Aquáticos , Interações Medicamentosas , Eritrócitos/efeitos dos fármacos , Ouro/toxicidade , Humanos , Dourada/sangue , Dourada/fisiologia
7.
Talanta ; 182: 558-566, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29501193

RESUMO

An important feature in the fabrication of surface-enhanced Raman scattering (SERS) platforms is, together with the high efficiency, to allow the rapid collection and analysis of a vestigial analyte. Conventional substrates based on rigid solid materials or metal hydrosols are not suitable for sample extraction, limiting their application in areas such as water quality monitoring. Herein, we have developed a strategy to fabricate SERS active substrates (Ag/LCP) based on liquid-crystal polymer (LCP) textile fibers decorated with Ag nanoparticles (NPs). Two distinct methods for substrate preparation envisaging the SERS detection of the pesticide thiram have been explored in this research. In a first stage, we have investigated the usefulness of both approaches using ethanolic solutions of the pesticide thiram, and after real samples spiked with thiram were used to explore the analysis in real environment. The SERS analysis of thiram dissolved in Aveiro Estuary water and in fruit juices have provided enhancement factors of 1.67 × 107 and 3.86 × 105, respectively, using the Ag/LCP composites. Noteworthy, in the latter case, the detection limit (0.024 ppm) achieved is lower than the maximal residue limit (MRL) of 5 ppm in fruit, as prescribed by European regulations (EU) 2016/1. Moreover, the selectivity of the SERS substrates for different pesticides was also evaluated, analyzing distinct pesticides such as paraquat and sodium diethyldithiocarbamate. SERS active Ag/LCP/PA filter membranes were also prepared using Ag/LCP composites supported by a polyamide (PA) filter, which can be an easy alternative to prepare simple, highly efficient and low-cost SERS active filter membranes for water analysis.


Assuntos
Ditiocarb/isolamento & purificação , Água Doce/química , Paraquat/isolamento & purificação , Praguicidas/isolamento & purificação , Extração em Fase Sólida/métodos , Tiram/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Fibra de Algodão , Sucos de Frutas e Vegetais/análise , Ouro/química , Limite de Detecção , Membranas Artificiais , Nanopartículas Metálicas/química , Nylons/química , Polímeros/química , Prata/química , Análise Espectral Raman/métodos
8.
Aquat Toxicol ; 177: 125-35, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27267391

RESUMO

Gold nanoparticles (AuNP) are increasingly employed in a variety of applications and are likely to be increasing in the environment, posing a potential emerging environmental threat. Information on possible hazardous effects of engineered nanoparticles is urgently required to ensure human and environmental safety and promote the safe use of novel nanotechnologies. Nevertheless, there is a lack of comprehensive knowledge on AuNP effects in marine species. The present study aimed to assess AuNP effects in a marine teleost, Sparus aurata, by combining endpoints at different biological levels (molecular and biochemical). For that purpose, fish were exposed via water for 96h to 4, 80 and 1600µgL(-1) of AuNP (∼40nm) coated with citrate or polyvinylpyrrolidone (PVP). Results revealed a significant impact of AuNP-PVP in the hepatic expression of antioxidant, immune and apoptosis related genes. Total oxidative status was increased in plasma after exposure to the lowest concentration of AuNP-PVP, although without altering the total antioxidant capacity. Furthermore, AuNP did not induce significant damage in the liver since the activity of neither hepatic indicator (aspartate aminotransferase and alkaline phosphatase) increased. Overall, the present study demonstrated that AuNP, even with a biocompatible coating is able to alter oxidative status and expression of relevant target genes in marine fish. Another important finding is that effects are mainly induced by the lowest and intermediate concentrations of the PVP coated AuNP revealing the importance of different coatings.


Assuntos
Ouro/toxicidade , Nanopartículas Metálicas/toxicidade , Dourada/metabolismo , Poluentes Químicos da Água/toxicidade , Animais , Apoptose/efeitos dos fármacos , Biomarcadores/metabolismo , Relação Dose-Resposta a Droga , Ouro/química , Humanos , Sistema Imunitário/efeitos dos fármacos , Oxirredução/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Distribuição Aleatória , Testes de Toxicidade , Poluentes Químicos da Água/química
9.
Chemosphere ; 136: 86-94, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25965160

RESUMO

Release of engineered nanoparticles (ENPs) to soil is well documented but little is known on the subsequent soil-pore water distribution of ENPs once present in soil. In this study, the availability and mobility of silver (Ag) and gold (Au) ENPs added to agricultural soils were assessed in two separate pot experiments. Pore water samples collected from pots from day 1 to 45 using porous (<0.17 µm) membrane samplers suggest that both Ag and Au are retained almost completely within 24 h with less than 13% of the total added amount present in pore water on day 1. UV-Vis and TEM results showed that AuENPs in pore water were present as both homoaggregates and heteroaggregates until day 3 after which the concentration in pore water was too low to detect the presence of aggregates. A close relation between the concentration of Au and Fe in pore water suggests that the short term solubility of Au is partly controlled by natural soil colloids. Results suggest that under normal aerated soil conditions the actual availability of Ag and AuENPs is low which is relevant in view of risk assessment even though the impact of environmental conditions and soil properties on the reactivity of ENPs (and/or large ENPs aggregates) retained in the solid matrix need to be addressed further.


Assuntos
Ouro/análise , Água Subterrânea/química , Nanopartículas Metálicas/análise , Modelos Químicos , Prata/análise , Solo/química , Corantes , Meio Ambiente , Porosidade , Poluentes do Solo/análise , Água
10.
Chemosphere ; 135: 304-11, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25966049

RESUMO

To assess if the geochemical reactivity and human bioaccessibility of silver nanoparticles (AgNPs) in soils can be determined by routine soil tests commonly applied to other metals in soil, colloidal Ag was introduced to five pots containing urban soils (equivalent to 6.8 mg Ag kg(-1) soil). Following a 45 days stabilization period, the geochemical reactivity was determined by extraction using 0.43 M and 2 M HNO3. The bioaccessibility of AgNPs was evaluated using the Simplified Bioaccessibility Extraction Test (SBET) the "Unified BARGE Method" (UBM), and two simulated lung fluids (modified Gamble's solution (MGS) and artificial lysosomal fluid (ALF)). The amount of Ag extracted by 0.43 M and 2 M HNO3 soil tests was <8% and <50%, respectively of the total amount of Ag added to soils suggesting that the reactivity of Ag present in the soil can be relatively low. The bioaccessibility of Ag as determined by the four in vitro tests ranged from 17% (ALF extraction) to 99% (SBET) indicating that almost all Ag can be released from soil due to specific interactions with the organic ligands present in the simulated body fluids. This study shows that to develop sound soil risk evaluations regarding soil contamination with AgNPs, aspects of Ag biochemistry need to be considered, particularly when linking commonly applied soil tests to human risk assessment.


Assuntos
Recuperação e Remediação Ambiental/métodos , Nanopartículas/metabolismo , Prata/metabolismo , Poluentes do Solo/metabolismo , Solo/química , Poluição Ambiental/análise , Humanos , Nanopartículas/análise , Medição de Risco , Prata/análise , Poluentes do Solo/análise
11.
Analyst ; 140(5): 1693-701, 2015 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-25630833

RESUMO

The controlled release of pesticides using hydrogel vehicles is an important procedure to limit the amount of these compounds in the environment, providing an effective way for crop protection. A key-step in the formulation of new materials for these purposes encompasses the monitoring of available pesticides in the gel matrix under variable working conditions. In this work, we report a series of bionanocomposites made of Ag nanoparticles (NPs) and gelatine A for the surface enhanced Raman scattering (SERS) detection of sodium diethyldithiocarbamate (EtDTC) as a pesticide model. These studies demonstrate the effectiveness of these substrates for the detection of EtDTC in aqueous solutions in a concentration as low as 10(-5) M. We have monitored the Raman signal enhancement of this analyte in bionanocomposites having an increasing amount of gelatine due to their relevance in formulating hydrogels of variable gel strengths. Under these conditions, the bionanocomposites have shown an effective SERS activity using EtDTC, demonstrating their effectiveness in the qualitative detection of this analyte. Finally, experiments involving the release of EtDTC from Ag/gelatine samples have been monitored by SERS, which attest the potential of this spectroscopic method in the laboratorial monitoring of hydrogels for pesticide release.


Assuntos
Ditiocarb/análise , Gelatina/química , Nanopartículas Metálicas/química , Nanocompostos/química , Praguicidas/análise , Prata/química , Análise Espectral Raman/métodos , Quelantes/análise , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Propriedades de Superfície
12.
Physiol Res ; 63(6): 723-32, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25157653

RESUMO

The relationship between obesity and renal lesions, especially in low estrogen levels, has been less documented. The aim of this study was to assess the renal changes in diet-induced obesity in ovariectomized rats. Wistar rats were ovariectomized or sham-operated and divided into four groups: sham-operated rats fed a standard diet (SSD); ovariectomized rats fed a standard diet (OSD); sham-operated rats fed a high-fat diet (SHFD); ovariectomized rats fed a high-fat diet (OHFD). Body weight and blood pressure were measured weekly. The rats were killed 24 weeks after initiation of standard or high-fat diet treatment, the kidneys were removed for immunohistochemical and histological studies. Blood and urine samples were collected to quantify sodium, potassium and creatinine. OHFD rats presented increases in visceral adipose tissue, serum insulin levels, blood pressure and proteinuria, and a decrease in fractional excretion of sodium as well. Histological and morphometric studies showed focal alterations in the renal cortex. Expression of macrophages, lymphocytes, nuclear factor-kappa B (NF-kappaB), Proliferating Cell Nuclear Antigen (PCNA), angiotensin II (ANG II) and vimentin was greater in OHFD rats than in control rats. Thus, these results demonstrate that the high-fat diet in ovariectomized rats promoted renal function and structure changes, renal interstitial infiltration of mononuclear cells and increased expression of ANG II and NF-kappaB.


Assuntos
Dieta Hiperlipídica/efeitos adversos , Rim/patologia , Obesidade/patologia , Ovariectomia , Angiotensina II/biossíntese , Animais , Pressão Sanguínea/fisiologia , Peso Corporal , Ingestão de Energia , Feminino , Insulina/sangue , Macrófagos , NF-kappa B/biossíntese , Infiltração de Neutrófilos , Ratos , Ratos Wistar , Fator de Necrose Tumoral alfa/sangue
13.
J Microencapsul ; 31(7): 627-35, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24766205

RESUMO

Natural substances derived from plants such as essential oils (EOs) are used in a variety of applications such as in the release of fragrances or active substances in cosmetics, in food industries to protect sensitive ingredients against oxidative processes and as antimicrobial agents. However, the labile and volatile nature of EOs reduces their activity during application or storage. Here, the microencapsulation of EOs in silica capsules was investigated as a mean to control the fast release of their volatile constituents. The preparation of silica capsules with oil cores was obtained by employing a sol-gel method to oil-in-water-in-oil (O/W/O) multiple emulsions. The volatile release from the SiO2 capsules was investigated by comprehensive two-dimensional gas chromatography with time of flight mass spectrometry detection (GC × GC-ToFMS). This research demonstrates that the SiO2 capsules have selectively encapsulated the different volatile species and the corresponding release profiles depend on the chemical properties of each component.


Assuntos
Óleos Voláteis/química , Óleos Voláteis/farmacocinética , Cápsulas , Preparações de Ação Retardada/química , Preparações de Ação Retardada/farmacocinética , Emulsões , Espectrometria de Massas , Dióxido de Silício
14.
Environ Sci Pollut Res Int ; 20(9): 5963-74, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23508538

RESUMO

The sorption capacity of nanoporous titanosilicate Engelhard titanosilicate number 4 (ETS-4) and silica-coated magnetite particles derivatised with dithiocarbamate groups towards Hg(II) was evaluated and compared in spiked ultra-pure and spiked surface-river water, for different batch factors. In the former, and using a batch factor of 100 m(3)/kg and an initial Hg(II) concentrations matching the maximum allowed concentration in an effluent discharge, both materials achieve Hg(II) uptake efficiencies in excess of 99 % and a residual metal concentration lower than the guideline value for drinking water quality. For the surface-river water and the same initial concentration, the Hg(II) uptake efficiency of magnetite particles is outstanding, achieving the quality criteria established by the Water Framework Directive (concerning Hg concentration in surface waters) using a batch factor of 50 m(3)/kg, while the efficiency of ETS-4 is significantly inferior. The dissimilar sorbents' Hg(II) removal efficiency is attributed to different uptake mechanisms. This study also highlights the importance of assessing the effective capacity of the sorbents under realistic conditions in order to achieve trustable results.


Assuntos
Óxido Ferroso-Férrico/química , Nanopartículas de Magnetita/química , Mercúrio/química , Tiocarbamatos/química , Poluentes Químicos da Água/química , Água/química , Monitoramento Ambiental , Cinética , Rios/química , Purificação da Água
15.
J Nanosci Nanotechnol ; 12(8): 6817-21, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22962828

RESUMO

The controlled hydrolysis of FeC2O4 in the presence of vegetable cellulose fibres was investigated to produce a pallet of cellulose/iron oxide hybrid colored materials. Distinct iron oxide phases have been deposited at the cellulose fibres surfaces by varying the relative amount of FeC2O4 and NaOH, here used as starting materials, by performing the synthesis in hydrothermal conditions. This is a new chemical strategy for the production of a number of hybrid materials whose coloristic properties have been evaluated aiming their potential use as novel pigments for polymer based products.

16.
Water Res ; 45(17): 5773-84, 2011 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-21924455

RESUMO

In order to take advantage of the high affinity between mercury and sulphur, magnetite (Fe(3)O(4)) particles functionalized with dithiocarbamate groups (CS(2)(-)), were synthesized to be used as a new type of sorbent to remove Hg (II) from synthetic and natural spiked waters. The effectiveness of this type of sorbent was studied, and its potential as cleanup agent for contaminated waters was assessed. Batch stirred tank experiments were carried out by contacting a volume of solution with known amounts of functionalized Fe(3)O(4) particles, in order to study the effect of sorbent dose, salinity, and the kinetics and the equilibrium of this unit operation. A complete Hg (II) removal (ca. 99.8%) was attained with 6 mg/L of magnetic particles for an initial metal concentration of 50 µg/L. It was confirmed that highly complex matrices, such as seawater (ca. 99%) and river water (ca. 97%), do not affect the removal capacity of the functionalized magnetic particles. Concerning isotherms, no significant differences were observed between two- and three-parameter models (P = 0.05%); however, Sips isotherm provided the lowest values of SS and S(x/y), predicting a maximum sorption capacity of 206 mg/g, in the range of experimental conditions under study. The solid loadings measured in this essay surmount the majority of the values found in literature for other type of sorbents.


Assuntos
Ditiocarb/química , Óxido Ferroso-Férrico/química , Mercúrio/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Água/química , Adsorção , Cinética , Salinidade , Dióxido de Silício/química , Espectrofotometria Infravermelho , Propriedades de Superfície , Temperatura , Fatores de Tempo , Difração de Raios X
17.
J Hazard Mater ; 163(1): 36-42, 2009 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-18656306

RESUMO

In this work ZnO layers have been deposited by screen-printing in common ceramic tiles. These layers were characterized and tested for the photocatalytic degradation of the organic dye Orange II in aqueous solutions, using a batch photoreactor either under visible light provided by a Philips ML-160 W lamp or under direct exposure to sunlight. For sake of comparison, ZnO suspensions have also been evaluated for similar reacting conditions. The influence of experimental parameters such as (i) firing temperature of the printed layer; (ii) layer thickness; and (iii) operation time have been investigated. Screen-printed ZnO layers obtained in optimal processing conditions showed photocatalytic activity comparable to aqueous ZnO suspensions. The maximal attenuation degree is over 70% and decolourisation rate, assuming that reaction kinetics follows a pseudo-first order rate law, is over 0.015 min(-1). Thus these ZnO-layered ceramic tiles can be regarded as an alternative to photocatalytic suspensions of the same material with the advantage of avoiding the removal of the photocatalyst.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Cerâmica/química , Processos Fotoquímicos , Óxido de Zinco/química , Catálise , Cor , Microscopia Eletrônica de Varredura , Espectrofotometria , Difração de Raios X
18.
Arq. bras. med. vet. zootec ; 60(6): 1307-1314, dez. 2008. graf, tab
Artigo em Português | LILACS | ID: lil-506538

RESUMO

Identificaram-se e caracterizaram-se a resistência e a multirresistência aos principais antimicrobianos usados no tratamento de mastite bovina causada por Escherichia coli. A concentração inibitória mínima (MIC) e o sistema de efluxo foram detectados pelas curvas de crescimento, com base na densidade óptica, em diferentes concentrações da droga e na presença e na ausência do desacoplador da força próton-motora (PMF). E. coli 1 foi resistente à neomicina e à gentamicina; E. coli 3 e 4, à tetraciclina e à estreptomicina; e E. coli 2 e 6 à gentamicina. E. coli 5 apresentou modelo de sensibilidade. Observou-se que MICs de todos os antimicrobianos dos multirresistentes (E. coli 1, 3 e 4) diminuíram na presença do desacoplador, o que sugere sistema de efluxo multidrogas. Após cura, apenas E. coli 1 apresentou modelo de sensibilidade, porém não houve alterações das MICs, antes e após adição do desacoplador. Os resultados indicam possível presença de mecanismo de resistência dependente da PMF codificado, ou parte dele, em plasmídeo.


Resistance and multiresistance to main antimicrobials used for treating bovine mastitis caused by Escherichia coli were identified and characterized. The minimal inhibitory concentration (MIC) and efflux systems were detected by the use of growth curves based on optical density at different drug concentrations and both presence and absence of uncoupler of the proton-motive force (PMF). E. coli 1 was resistant to neomycin and gentamycin, E. coli 3 and 4 were resistant to tetracycline and streptomycin, whereas E. coli 2 and 6 were resistant to gentamycin. E. coli 5 showed sensibility model. MICs of all antimicrobials of the multiresistant samples (E. coli 1, 3, and 4) were decreased in presence of the uncoupler, therefore suggesting the presence of the multidrug efflux system. After healing, only E. coli 1 showed sensibility model, however no alteration occurred in MIC(s) before and after adding the uncoupler. Those data inform the possible presence of a PMF dependent resistance mechanism that is totally or partly codified in plasmid.


Assuntos
Antibacterianos/farmacologia , Escherichia coli/imunologia , Escherichia coli/isolamento & purificação , Farmacorresistência Bacteriana Múltipla , Leite/microbiologia , Mastite Bovina/microbiologia , Testes de Sensibilidade Microbiana/métodos , Bovinos
19.
J Colloid Interface Sci ; 320(2): 575-81, 2008 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-18279881

RESUMO

The rheological behavior of silica/kappa-carrageenan nanocomposites has been investigated as a function of silica particle size and load. The addition of silica nanoparticles was observed to invariably impair the gelation process, as viewed by the reduction of gel strength and decrease of gelation and melting temperatures. This weakening effect is seen, for the lowest particle size, to become slightly more marked as silica concentration (or load) is increased and at the lowest load as particle size is increased. These results suggest that, under these conditions, the particles act as physical barriers to polysaccharide chain aggregation and, hence, gelation. However, for larger particle sizes and higher loads, gel strength does not weaken with size or concentration but, rather, becomes relatively stronger for intermediate particles sizes, or remains unchanged for the largest particles, as a function of load. This indicates that larger particles in higher number do not seem to increasingly disrupt the gel, as expected, but rather promote the formation of stable gel network of intermediate strength. The possibility of this being caused by the larger negative surface charge found for the larger particles is discussed. This may impede further approximation of neighboring particles thus leaving enough inter-particle space for gel formation, taking advantage of a high local polysaccharide concentration due to the higher total space occupied by large particles at higher loads.


Assuntos
Carragenina/química , Nanocompostos/química , Dióxido de Silício/química , Géis , Tamanho da Partícula , Temperatura de Transição
20.
J Am Chem Soc ; 130(1): 150-67, 2008 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-18076163

RESUMO

Isostructural modular microporous Na2[Y(hedp)(H2O)0.67] and Na4[Ln2(hedp)2(H2O)2].nH2O (Ln = La, Ce, Nd, Eu, Gd, Tb, Er) framework-type, and layered orthorhombic [Eu(H2hedp)(H2O)2].H2O and Na0.9[Nd0.9Ge0.10(Hhedp)(H2O)2], monoclinic [Ln(H2hedp)(H2O)].3H2O (Ln = Y, Tb), and triclinic [Yb(H2hedp)].H2O coordination polymers based on etidronic acid (H5hedp) have been prepared by hydrothermal synthesis and characterized structurally by (among others) single-crystal and powder X-ray diffraction and solid-state NMR. The structure of the framework materials comprises eight-membered ring channels filled with Na+ and both free and lanthanide-coordinated water molecules, which are removed reversibly by calcination at 300 degrees C (structural integrity is preserved up to ca. 475 degrees C), denoting a clear zeolite-type behavior. Interesting photoluminescence properties, sensitive to the hydration degree, are reported for Na4[Eu2(hedp)2(H2O)2].H2O and its fully dehydrated form. The 3D framework and layered materials are, to a certain extent, interconvertable during the hydrothermal synthesis stage via the addition of HCl or NaCl: of the 3D framework Na4[Tb2(hedp)2(H2O)2].nH2O, affords layered [Tb(H2hedp) (H2O)].3H2O, whereas layered [Tb(H2hedp)(H2O)2].H2O reacts with sodium chloride yielding a material similar to Na4[Tb2(hedp)2(H2O)2].nH2O. In layered [Y(H2hedp)(H2O)].3H2O, noncoordinated water molecules are engaged in cooperative water-to-water hydrogen-bonding interactions, leading to the formation of a (H2O)13 cluster, which is the basis of an unprecedented two-dimensional water network present in the interlayer space.

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