Biblioteca Digital

A detecção e determinação de pequenas quantidades de íons cianeto é importante devido à extrema toxicidade desta espécie para a matéria viva. Os baixos limites de concentração de cianeto exigidos pelas entidades de controle ambiental para águas de superfície e subsolo, solos e efluentes industriais demandam o desenvolvimento de métodos analíticos sensíveis. O presente trabalho tem como objetivo o desenvolvimento de método analítico simples, rápido e que possibilite a determinação de cianeto a baixos limites de detecção em amostras de águas de superfície e subsolo, solos e efluentes industriais. O método utilizado se baseia em reação proposta por Guilbault e Kramer , modificada para a utilização em um sistema que permite a liberação do cianeto em forma gasosa (HCN), o qual permeia através de membrana de Teflon® antes de entrar em contato com os reagentes colorimétricos. O sistema é constituído de uma parte superior, onde é introduzida a mistura de reagentes e a membrana e uma parte inferior, onde pode ser introduzida amostra e o ácido, que provoca a liberação do HCN . Para a obtenção dos resultados semi-quantitativos foram construídas escalas de colorações, através da utilização de padrões de cianeto...

Na literatura existe muita controvérsia com respeito a quais espécies de Cr(VI) existem em solução aquosa, seus espectros, suas distribuições e as constantes de equilíbrio envolvidas. Com a finalidade de se estudar a distribuição das diferentes espécies de Cr(VI) em soluções aquosas diluídas, aplicou-se uma combinação de métodos quimiométricos ao tratamento de espectros de absorção UV/Visível de soluções de dicromato de potássio, visando a determinação do número de espécies presentes, suas concentrações relativas e seus espectros puros, em função do pH e da concentração de Cr(VI). Utilizando-se a Análise de Fatores do Modo. Q de Imbrie, seguida de Rotação Varimax e Projeção Oblíqua de Imbrie, foi possível estimar a composição dos equilíbrios sem o conhecimento anterior dos componentes puros. Combinando-se estes resultados com o Método da Matriz K, foi possível a obtenção dos espectros das espécies puras. Os resultados foram reforçados pela utilização de outros métodos quimiométricos, tais como Análise de Correspondência e Análise de Fatores Evolutiva. Inicialmente, foram estudados conjuntos de soluções em duas concentrações de Cr(VI), 3,3.10 e 3,3.10 mol/L, com uma variação de pH entre 1 e 12 (usando-se HCIO4 ou NaOH). Nesta faixa de pH os resultados indicaram a presença de dois fatores...

Neste trabalho são realizados estudos de propriedades morfológicas, estruturais e magnéticas de nanopartículas de óxidos de ferro sintetizadas por métodos químicos. Procuramos relacionar os parâmetros de síntese às características das partículas produzidas com a finalidade de melhorar sua qualidade em relação às amostras comerciais e avaliar sua aplicabilidade em biomedicina. Foram adotados os métodos de síntese por co-precipitação de sais em solução aquosa e de decomposição térmica de dois diferentes precursores organometálicos: acetilacetonato de ferro III (Fe(acac)3) e ferro pentacarbonil (Fe(CO). Para caracterização desses sistemas, foram utilizadas as técnicas de microscopia eletrônica de transmissão convencional e de alta resolução, microscopia eletrônica de varredura com canhão de emissão de campo, difração de raios-X e medidas de magnetização, além de experimentos de transfecção em células HeLa e posterior detecção por imagens de ressonância magnética. Os estudos mostraram que as partículas sintetizadas por co-precipitação não apresentam muitas vantagens em relação às amostras comerciais, pois possuem larga distribuição de tamanhos. Através da síntese por decomposição térmica de Fe(acac)3...

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Engenharia de Alimentos; O poli(3-hidroxibutirato), P(3HB), é um poliéster natural da classe dos polihidroxialcanoatos (PHAs), produzido e acumulado como reserva de energia por muitos microrganismos, com predomínio no uso da bactéria Cupriavidus necator. Esse polímero tem atraído muita atenção devido a sua biocompatibilidade, termoplasticidade, piezoeletricidade e também pela vantagem de ser degradado pela ação de microrganismos de ocorrência natural, sofrendo redução da massa molar, transformando-se em CO2 e H2O. Contudo, sua aplicação é ainda limitada devido ao custo de produção muito elevado. Para diminuir os custos de produção de P(3HB), faz-se necessário o desenvolvimento de novos processos de produção e extração do polímero a um custo mais baixo e com impacto ambiental reduzido. Atualmente, os métodos utilizados no processo de extração de P(3HB) envolvem o uso de solventes orgânicos, dispersão de hipoclorito de sódio e clorofórmio, digestão enzimática, métodos mecânicos e, recentemente, foi proposto o uso de soluções aquosas de surfactante e quelante. Neste contexto, este trabalho vem propor um método mecânico alternativo para a extração do P(3HB) usando para ruptura celular pérolas de vidro em um moinho de bolas...

Doctoral dissertation for PhD degree in Chemical and Biological Engineering; Natural organic matter (NOM) is ubiquitous in terrestrial and aquatic ecosystems; it comprises an important source of carbon for river biofilms which are major sites of carbon cycling in streams. NOM may be classified in two main categories: non-humic and humic substances (HSs). About 75 % of the dissolved organic carbon (DOC) in rivers results from HSs. The presence of HSs in water treatment plants is undesirable because they increase coagulant and disinfectant demands, and in the presence of chlorine may provoke the formation of dangerous disinfection by-products such as the carcinogenic trihalomethanes (THM). A good knowledge of HSs involvement on biofilm growth can contribute to the development of a biological alternative of HSs removal from rivers. The first step of this work consisted on characterization of HSs and comparison of two methods, combustion-infrared method and UV spectroscopy method, commonly used to HSs quantification in aqueous solution. In this study were evaluated the effect of divalent cations (calcium and magnesium) concentrations, pH and, sample filtration on HSs quantification from simulated river water. A commercial humic acid (HA) was used to simulate HSs. The experimental results demonstrate that unfiltered samples presented considerably higher total organic carbon (TOC) values than filtered ones...

Humic acids (HAs) content of raw water is an important analytical parameter in water treatment facilities because HAs in the presence of chlorine may lead to the formation of dangerous by-products (e.g., trihalomethanes). The concentration of HAs in water is not directly accessible by common analytical methods due to their heterogeneous chemical structure. The aim of this study was to compare two methods to assess humic acids (HAs) in surface water namely absorbance of ultraviolet light at 254 nm (UV254) and total organic carbon (TOC), as well as to evaluate the effects of calcium and magnesium concentrations, pH and sample filtration on the methods’ results. An aqueous solution of a commercial HA with 10 mg L1 was used in the present work. Quantification of the HA was carried out by both UV254 and TOC (combustion-infrared method) measurements. UV254 results were converted to TOC using a calibration curve. The effects of calcium (0–136.3 mg L1) and magnesium (0–34.5 mg L1) concentrations, pH (4.0, 7.0 and 9.0) and sample filtration on UV254 and TOC measurements of the HA suspension were evaluated. More accurate TOC values of HA suspensions were obtained by the combustion-infrared method than by the UV254 absorbance method. The higher differences of TOC values between unfiltered and filtered samples were detected in the presence of calcium at pH 9.0 using the spectrophotometric method.

Dissertação de mestrado em Biofísica e Bionanossistemas; The use of semiconductors for processes of self-­‐cleaning, air and water depollution as well as surface disinfection has triggered a great interest in the scientific community. One of the most used semiconductor materials is titanium dioxide (TiO2) due to their large photocatalytic effect, higher oxidation strength, chemical stability non-­‐toxicity and availability, among others. This oxide has been highly researched and was found that it is capable of decomposing various organic and inorganic compounds. Most of these studies were conducted under ultraviolet light (UV), since TiO2 has a photocatalytic activity and a relatively high chemical stability under UV radiation. The process has several advantages and one of them is the ability to combine processes involving biological decontamination methods, which makes this semiconductor capable of removing a wide range of bacteria, viruses, fungi, algae, protozoa, etc. (antimicrobial effect). Despite the advantages of this process we can notice two important limitations. Firstly...

NOTICE: this is the author’s version of a work that was accepted for publication in European Journal of Pharmaceutics and Biopharmaceutics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Eur J Pharm Biopharm. 2009 Feb;71(2):377-386. Epub 2008 Oct 17.; The work aims to prove the complexation of two model drugs (ibuprofen, IB and indomethacin, IN) by bcyclodextrin (bCD), and the effect of water in such a process, and makes a comparison of their complexation yields. Two methods were considered: kneading of a binary mixture of the drug, bCD, and inclusion of either IB or IN in aqueous solutions of bCD. In the latter method water was removed by air stream, spray-drying and freeze-drying. To prove the formation of complexes in final products, optical microscopy, UV spectroscopy, IR spectroscopy, DSC, X-ray and NMR were considered. Each powder was added to an acidic solution (pH = 2) to quantify the concentration of the drug inside bCD cavity. Other media (pH = 5 and 7) were used to prove the existence of drug not complexed in each powder...

This paper presents the study of the oxidation of three textile dyes (Remazol black B, Remazol Brilliant Orange 3R and Remazol Golden Yellow RNL) using electrochemical and photoelectrochemical methods. In both methods, electrolysis experiments were performed at a current density of 50 mA cm-2 in an aqueous solution of each dye (30 mg L-1), using a photoelectrochemical flow-cell. For all the dyes studied, the photoelectrochemical method was demonstrated to be more efficient than the electrochemical one. Photoelectrochemical oxidation resulted in complete decoloration after 90 min of electrolysis and total organic carbon (TOC) removal reached up to 36%. It was observed that the dyes presenting chromophores at higher wavelengths are removed the quickest, which indicates that photosensitised (photoassisted) oxidation occurs. The level of color was reduced to levels below the standards presented in the literature, which indicates the viability of the photoelectrochemical process as part of the treatment of textile effluents.

This aim of this work was to compare two methods for copper determination in insulating oils from power transformers by GFAAS. The first method was extraction induced by emulsion breaking, which determined the preconcentration of copper in an aqueous solution and exhibited a limit of quantification of 0.27 µg L-1. Also, a second method based on the direct introduction of samples into GFAAS in the form of detergent emulsions, prepared with Triton X-114 and HNO3, was investigated. In this case, the limit of quantification was 1.7 µg L-1. Seven samples of used oils were successfully analyzed by both methods.

We identified conditions under which Buffalo green monkey cells grew on the surfaces of cellulose nitrate membrane filters in such a way that they covered the entire surface of each filter and penetrated through the pores. When such conditions were used, poliovirus that had previously been adsorbed on the membranes infected the cells and replicated. A plaque assay method and a quantal method (most probable number of cytopathic units) were used to detect and count the viruses adsorbed on the membrane filters. Polioviruses in aqueous suspensions were then concentrated by adsorption to cellulose membrane filters and were subsequently counted without elution, a step which is necessary when the commonly used methods are employed. The pore size of the membrane filter, the sample contents, and the sample volume were optimized for tap water, seawater, and a 0.25 M glycine buffer solution. The numbers of viruses recovered under the optimized conditions were more than 50% greater than the numbers counted by the standard plaque assay. When ceftazidime was added to the assay medium in addition to the antibiotics which are typically used, the method could be used to study natural samples with low and intermediate levels of microbial pollution without decontamination of the samples. This methodological approach also allowed plaque hybridization either directly on cellulose nitrate membranes or on Hybond N+ membranes after the preparations were transferred.

Coxiella burnetii, phase I and II, cells cultivated in the yolk sac of chicken embryos were separated from host cell components by two cycles of isopycnic Renografin gradient centrifugation. Initial steps in the purification of viable C. burnetii involved differential centrifugation and sedimentation through an aqueous solution of 30% sucrose and 7.6% Renografin. After the first, but not the second, cycle of Renografin gradient centrifugation, the cells were passed through microfilter glass filters which facilitated the removal of host components. The integrity of morphologically different cell variants was maintained during purification procedures by suspending highly purified C. burnetii in phosphate-buffered saline-sucrose solutions. C. burnetii, phases I and II, obtained by these methods appeared to be free from host cell components by serological methods while retaining morphological integrity and infectivity for yolk sacs and experimental animals. Average yields of C. burnetii were 2.83, 1.5, and 0.84 mg (dry weight) per yolk sac of the Ohio strain (phase I), 9 Mile strain (phase I), and 9 Mile strain (phase II), respectively. Recovery of phase I cells averaged about 70%, whereas the recovery of phage II cells was approximately 40%. The temporal sequence of phase I and II antibody response was demonstrated in infected and vaccinated animals. Also...

Two different methods were used to determine the relative permeability and the voltage-dependent conductance of several different cations in excitability-inducing material (EIM)-doped lipid bilayers. In one method, the conductances of individual channels were measured for Li, Na, K, Cs, NH4, and Ca, and in the other method biionic potentials of a membrane with many channels were measured for Li, Na, K, Cs, and Rb. The experimental results for the two methods are in agreement. The relative permeabilities are proportional to the ionic mobilities in free aqueous solution. The voltage dependence of the conductance is the same for all cations measured.

The aim of this study is to confirm the formation of inclusion complexes between miconazole (MCZ) and two derivatives of beta-cyclodextrin, methyl-beta-cyclodextrin (MβCD) and 2-hydroxypropyl-beta-cyclodextrin (HPβCD) in aqueous solution by phase solubility studies. Inclusion complexes with MβCD in the solid state were then prepared by different methods, i.e., kneading, coevaporation (COE), spray-drying (SD), and lyophilization (LPh). The physicochemical properties of these complexes were subsequently studied by means of differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction techniques. Phase solubility diagrams with MβCD and HPβCD were classified as AP type, indicating the formation of 1:1 and 1:2 stoichiometric inclusion complexes. The apparent stability constants (KS) calculated from the phase solubility diagram were 145.69 M−1 (K1:1) and 11.11 M−1 (K1:2) for MβCD and 126.94 M−1 (K1:1) and 2.20 M−1 (K1:2) for HPβCD. The method of preparation of the inclusion complexes in the solid state was shown to greatly affect the properties of the formed complex. Hence, the LPh, SD, and COE methods produce true inclusion complexes between MCZ and MβCD. In contrast...

There has been growing interest in the use of rapid and selective separation methods such as high-performance affinity chromatography (HPAC) or affinity capillary electrophoresis (ACE) for the characterization of drug-protein interactions. L-Tryptophan is commonly used in these and other methods as a site-selective probe for examining the binding of small solutes and drugs at Sudlow site II on the protein human serum albumin (HSA). However, solutions of L-tryptophan can be unstable and are generally prepared fresh daily for these studies. In this report, HPAC was used to examine other indole compounds as possible replacements for L-tryptophan as a site-selective probe for use in the high-throughput screening of drug binding to HSA; the implications of these results in the use of such compounds in ACE were also considered. The probe candidates that were tested included indole-3-acetic acid, indole-3-carboxylic acid, indole-3-butyric acid, indole-3-propionic acid, indole-3-methanol, 3-acetylindole, and 3-methylindole. All of these compounds were found by 1H NMR spectroscopy and UV/vis spectroscopy to be stable for up to three weeks at room temperature when in pH 7.4, 0.067 M phosphate buffer. The binding of these compounds was examined by using columns that contained immobilized HSA. 3-Acetylindole was found to be the best candidate in this group for use as an alternative probe to L-tryptophan for Sudlow site II. This probe had the same binding site and a similar affinity to L-tryptophan but was more stable in aqueous solution...

This paper describes two SlipChip-based approaches to protein crystallization: a SlipChip-based free interface diffusion (FID) method and a SlipChip-based composite method that simultaneously performs microbatch and FID crystallization methods in a single device. The FID SlipChip was designed to screen multiple reagents, each at multiple diffusion equilibration times, and was validated by screening conditions for crystallization of two proteins, enoyl-CoA hydratase from Mycobacterium tuberculosis and dihydrofolate reductase/thymidylate synthase from Babesia bovis against 48 different reagents at 5 different equilibration times each, consuming 12 μL of each protein for a total of 480 experiments using three SlipChips. The composite SlipChip was designed to screen multiple reagents, each at multiple mixing ratios and multiple equilibration times, and was validated by screening conditions for crystallization of two proteins, enoyl-CoA hydratase from Mycobacterium tuberculosis and dihydrofolate reductase/thymidylate synthase from Babesia bovis. To prevent cross-contamination while keeping the solution in the neck channels for FID stable, the plates of the SlipChip were etched with a pattern of nanowells. This nanopattern was used to increase the contact angle of aqueous solutions on the surface of the silanized glass. The composite SlipChip increased the number of successful crystallization conditions and identified more conditions for crystallization than separate FID and microbatch screenings. Crystallization experiments were scaled up in well plates using conditions identified during the SlipChip screenings...

The purpose of this work was to investigate the potential of functionalized magnetite nanoparticles to improve the antibiofilm properties of textile dressing, tested in vitro against monospecific Candida albicans biofilms. Functionalized magnetite (Fe3O4/C18), with an average size not exceeding 20 nm, has been synthesized by precipitation of ferric and ferrous salts in aqueous solution of oleic acid (C18) and NaOH. Transmission electron microscopy, X-ray diffraction analysis, and differential thermal analysis coupled with thermo gravimetric analysis were used as characterization methods for the synthesized Fe3O4/C18. Scanning electron microscopy was used to study the architecture of the fungal biofilm developed on the functionalized textile dressing samples and culture-based methods for the quantitative assay of the biofilm-embedded yeast cells. The optimized textile dressing samples proved to be more resistant to C. albicans colonization, as compared to the uncoated ones; these functionalized surfaces-based approaches are very useful in the prevention of wound microbial contamination and subsequent biofilm development on viable tissues or implanted devices.

The delivery of therapeutic proteins has gained momentum with development of biotechnology. However, large molecular weight, hydrophilic nature and susceptibility to harsh environment of gastrointestinal tract (GIT) resulted in low absorption. The main objective of this work was the design of a particulate system for oral delivery of recombinant human growth hormone (rhGH) on the basis of particle uptake mechanism in GIT. Biodegradable protein-loaded microspheres were prepared using Resomers (RG207, RG756 and RG505) by double emulsion methods. Aqueous solution of protein and freshly prepared rhGH-zinc complex were used for loading process. Various analytical methods, including fluorescence spectroscopy, SDS-PAGE electrophoresis and reversed-phase chromatography, were set up for the quantification and qualification of rhGH before and after the formulation and fabrication procedures. At the optimum conditions, microspheres were mostly below 10 μm with relatively high protein loading (> 50%). Obtained data showed that the stability of protein did not change during the formulation and microencapsulation processes. Results also showed that the encapsulation process in the presence of zinc caused no detectable change in the protein chemical stability. In-vitro stability study of microspheres in different simulated GI media indicated that the entrapped protein was physically stable. Less than 20% of rhGH was released from the microspheres incubated in both simulated stomach and intestine fluids for 3 and 6 h...

Microfluidic platforms provide several advantages for liquid-liquid extraction (LLE) processes over conventional methods, for example with respect to lower consumption of solvents and enhanced extraction efficiencies due to the inherent shorter diffusional distances. Here, we report the development of polymer-based parallel-flow microfluidic platforms for LLE. To date, parallel-flow microfluidic platforms have predominantly been made out of silicon or glass due to their compatibility with most organic solvents used for LLE. Fabrication of silicon and glass-based LLE platforms typically requires extensive use of photolithography, plasma or laser-based etching, high temperature (anodic) bonding, and/or wet etching with KOH or HF solutions. In contrast, polymeric microfluidic platforms can be fabricated using less involved processes, typically photolithography in combination with replica molding, hot embossing, and/or bonding at much lower temperatures. Here we report the fabrication and testing of microfluidic LLE platforms comprised of thiolene or a perfluoropolyether-based material, SIFEL, where the choice of materials was mainly guided by the need for solvent compatibility and fabrication amenability. Suitable designs for polymer-based LLE platforms that maximize extraction efficiencies within the constraints of the fabrication methods and feasible operational conditions were obtained using analytical modeling. To optimize the performance of the polymer-based LLE platforms...

IRMM-304 is a new nanoparticle reference material (RM) consisting of silica nanoparticles suspended in an aqueous solution, of which the particle size was characterized by dynamic light scattering (DLS) and centrifugal liquid sedimentation (CLS). The homogeneity and stability of IRMM-304 were confirmed and three method-specific mean particle sizes around a nominal particle size of 40nm were assigned to the material. The characterization tests have revealed a systematic deviation between the measurement results obtained with DLS and CLS. The availability of IRMM-304 makes it possible to study this difference between methods. Several possible causes for differences between the DLS and CLS results are suggested and preliminarily investigated, such as the interaction between particle and suspending medium, the particle shape and the effect of polydispersity on the size averaging procedure. These investigations are one illustration of the potential role of IRMM-304 and other nanoparticle RMs in the development, comparison, improved understanding, and quality assurance of nanoparticle sizing methods.; JRC.D.2-Reference materials