Effects of the domestic use of a disclosing solution on the denture biofilm: a preliminary study

To investigate the effect of the home use of a disclosing agent on the microbial composition of denture biofilm, by means of a cross-over randomized clinical trial. Two interventions were tested during 7 days each: (i) oral and denture hygiene instructions and (ii) instructions associated with the home use of a disclosing agent (1% neutral red). Eleven participants with visible biofilm deposits over their maxillary complete dentures were randomly assigned to one of the two sequences of interventions: (i) I followed by II, and (ii) II followed by I. A washout period of 7 days was established. After each intervention, samples of denture biofilm were evaluated by DNA checkerboard hybridization for the detection of Candida spp. and 17 bacterial species. Counts were low for all the tested species, and no significant difference was found between the tested interventions ( Wilcoxon test, P > 0.05). The home use of a disclosing agent does not remarkably change the composition of denture biofilm.

Novel colloidal materials for high-throughput screening applications in drug discovery and genomics

Tracking the reaction history is the means of choice to identify bioactive compounds in large combinatorial libraries. The authors describe two approaches to synthesis on silica beads: a) addition of a reporter dye tag during each synthesis step (see Figure), which attaches itself to the bead by colloidal forces, and b) encapsulating arrays of fluorescent dyes into the beads to encode them uniquely, for recognition with a flow cytometer after each reaction step.

Molecular Lego (R): non-centrosymmetric alignment within interdigitating layers

(E)-N-Hexadecyl-4-[2-(4-octadecyloxynaphthyl) ethenyl] quinolinium bromide, which has a wide-bodied chromophore and terminal n-alkyl groups, adopts a U-shape when spread at the air-water interface but a stretched conformation when compressed to ca. 35 mN m(-1). The high-pressure phase has a narrow stability range prior to collapse but may be extended from 40 to 60 mN m(-1) by co-spreading the dye in a 1 : 1 ratio with docosanoic acid. The mixed Langmuir-Blodgett (LB) film has a monolayer thickness of 4.6 +/- 0.2 nm which decreases to 2.5 +/- 0.1 nm layer(-1) in the bulk, the reduction arising from an interdigitating layer arrangement, both top and bottom. It is the first example of LB-Lego(R) and, in addition, represents the only fully interdigitating structure with non-centrosymmetrically aligned chromophores. They are tilted 38 degrees from the substrate normal. The second-harmonic intensity increases quadratically with the number of layers, i.e. as I-(N)(2 omega) = (I(1)N2)-N-2 omega, with a second-order susceptibility of chi ((2))(zzz) = 30 pm V-1 at 1064 nm for refractive indices of n(omega) = 1.55 and n(2 omega) = 1.73, d = 2.5 nm layer(-1) and phi = 38 degrees. Angle resolved X-ray photoelectron spectra (XPS) of these films provide no evidence of the bromide counterion, which suggests that it is replaced by OH 2 or HCO3-, which occur naturally in the aqueous subphase, or C21H43COO- from the co-deposited fatty acid. This probably applies to all cationic dyes deposited by the LB technique.

Multi-fluorescent silica colloids for encoding large combinatorial libraries

Large chemical libraries can be synthesized on solid-support beads by the combinatorial split-and-mix method. A major challenge associated with this type of library synthesis is distinguishing between the beads and their attached compounds. A new method of encoding these solid-support beads, 'colloidal bar-coding', involves attaching fluorescent silica colloids ('reporters') to the beads as they pass through the compound synthesis, thereby creating a fluorescent bar code on each bead. In order to obtain sufficient reporter varieties to bar code extremely large libraries, many of the reporters must contain multiple fluorescent dyes. We describe here the synthesis and spectroscopic analysis of various mono- and multi-fluorescent silica particles for this purpose. It was found that by increasing the amount of a single dye introduced into the particle reaction mixture, mono- fluorescent silica particles of increasing intensities could be prepared. This increase was highly reproducible and was observed for six different fluorescent dyes. Multi-fluorescent silica particles containing up to six fluorescent dyes were also prepared. The resultant emission intensity of each dye in the multi-fluorescent particles was found to be dependent upon a number of factors; the hydrolysis rate of each silane-dye conjugate, the magnitude of the inherent emission intensity of each dye within the silica matrix, and energy transfer effects between dyes. We show that by varying the relative concentration of each silane-dye conjugate in the synthesis of multi-fluorescent particles, it is possible to change and optimize the resultant emission intensity of each dye to enable viewing in a fluorescence detection instrument.

Functional heterogeneity within rhodamine123(lo) Hoechst33342(lo/sp) primitive hemopoietic stem cells revealed by pyronin Y

Objective. The aim of this study was to determine the function of primitive hematopoietic stem cells (PHSC) at phases G(0) and G(1) of the cell cycle. Materials and Methods. A combination of supravital dyes rhodamine123 (Rh), Hoechst33342 (Ho), and pyronin (PY) was used to isolate the G(0) and G(1) subsets of PHSC. A competitive repopulation assay was used to evaluate their in vivo function. Results. We confirmed that the Rh(lo)Lin(-)Kit(+)Sca-1(+) PHSC were relatively quiescent when compared with the more mature Rh(hi)Lin(-)Kit(+)Sca-1 HSC and Rh(hi)Lin(-)Kit(+)Sca-1(-) progenitors. In addition, cells with Rh(lo)Lin(-)Kit(+)Sca-1(+), Rh(lo)Ho(lo)Lin(-)Sca-1(+), or Rh(lo)Ho(sp)Lin(-)Sca-1(+) phenotypes identified the same cell population. We further subfractionated the Rh(lo)Ho(lo/sp)Lin(-)Sca-1(+) PHSC using PY into PYlo and PYhi subsets. Limiting dilution analysis revealed that the frequency of long-term in vivo competitive repopulating units (CRU) of the (PYRhHolo/sp)-Rh-lo-Ho-lo PHSC was 1 in 10 cells, whereas there was at least a three-fold lower frequency in those isolated at the G(1) phase (PYhi) We found a dose-dependent PY-mediated cytotoxicity that at moderate concentration affected most of the murine hematopoietic compartment but spared the early HSC compartment. Conclusion. Our data confirm that the HSC compartment is hierarchically ordered on the basis of quiescence and further extend this concept to PY-mediated cytotoxicity. PY supravital dye can be used to reveal functional heterogeneity within the (RhHolosp)-Ho-lo PHSC population but is of limited use in dissecting the relatively more mature hematopoietic stem/progenitor cell population. (C) 2001 International Society for Experimental Hematology. Published by Elsevier Science Inc.

Comparative analysis of genetic diversity in the mangrove species Avicennia marina (Forsk.) Vierh. (Avicenniaceae) detected by AFLPs and SSRs

Avicennia marina is an important mangrove species with a wide geographical and climatic distribution which suggests that large amounts of genetic diversity are available for conservation and breeding programs. In this study we compare the informativeness of AFLPs and SSRs for assessing genetic diversity within and among individuals, populations and subspecies of A. marina in Australia. Our comparison utilized three SSR loci and three AFLP primer sets that were known to be polymorphic, and could be run in a single analysis on a capillary electrophoresis system, using different-colored fluorescent dyes. A total of 120 individuals representing six populations and three subspecies were samplcd. At the locus level, SSRs were considerably more variable than AFLPs, with a total of 52 alleles and an average heterozygosity of 0.78. Average heterozygosity for AFLPs was 0.193, but all of the 918 bands scored were polymorphic. Thus, AFLPs were considerably more efficient at revealing polymorphic loci than SSRs despite lower average heterozygosities. SSRs detected more genetic differentiation between populations (19 vs 9%) and subspecies (35 vs 11%) than AFLPs. Principal co-ordinate analysis revealed congruent patterns of genetic relationships at the individual, population and subspecific levels for both data sets. Mantel testing confirmed congruence between AFLP and SSR genetic distances among, but not within, population comparisons, indicating that the markers were segregating inde- pendently but that evolutionary groups (populations and subspecies) were similar. Three genetic criteria of importance for defining priorities for ex situ collections or in situ conservation programs (number of alleles, number of locally common alleles and number of private alleles) were correlated between the AFLP and SSR data sets. The congruence between AFLP and SSR data sets suggest that either method, or a combination, is applicable to expanded genetic studies of mangroves. The codominant nature of SSRs makes them ideal for further population-based investigations, such as mating-system analyses, for which the dominant AFLP markers are less well suited. AFLPs may be particularly useful for monitoring propagation programs and identifying duplicates within collections, since a single PCR assay can reveal many loci at once.

Solubility of selected esters in supercritical carbon dioxide

The solubility of ethyl propionate, ethyl butyrate, and ethyl isovalerate in supercritical carbon dioxide was measured at temperature ranging from 308.15 to 333.15 K and pressure ranging from 85 to 195 bar. At the same temperature, the solubility of these compounds increases with pressure. The crossover pressure region was also observed in this study. The experimental data were correlated by the semi-empirical Chrastil equation and Peng-Robinson equation of state (EOS) using several mixing rules. The Peng-Robinson EOS gives better solubility prediction than the empirical Chrastil equation. (C) 2002 Elsevier Science B.V. All rights reserved.

Enthalpies of Solution of 1-Butyl-3-methylimidazolium Tetrafluoroborate in 15 Solvents at 298.15 K

Enthalpies of solution of 1-butyl-3-methylimidazolium tetra fluoroborate, [BMIm]BF4, are reported at 298.15 K in a set of 15 hydrogen bond donor and hydrogen bond acceptor solvents, chosen by their diversity, namely, water, methanol, ethanol, 1,2-ethanediol, 2-choroethanol, 2-methoxyethanol, formamide, propylene carbonate, nitromethane, acetonitrile, dimethyl sulfoxide, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, and aniline. These values are shown to be largely independent of [BMIm]BF4 concentration. The obtained enthalpies of solution vary from very endothermic to quite exothermic, thus showing a very high sensitivity of the enthalpies of solution of [BMIm]BF4 to solvent properties. Solvent effects on the solution process of this IL are analyzed by a quantitative structure-property relationship methodology, using the TAKA equation and a modified equation, which significantly improves the model's predictive ability. The observed differences in the enthalpies of solution are rationalized in terms of the solvent properties found to be relevant, that is, pi* and E-T(N).

Solubility of red 153 and blue 1 in supercritical carbon dioxide

Solubilities of red 153, (3-[[4-[[5,6(or 6,7)-dichloro-2-benzothiazolyl]azo]phenyl]ethylamino]propanenitrile), an azo compound, and disperse blue1 (1,4,5,8-tetraaminoantraquinone) in supercritical carbon dioxide (SC CO(2)) were measured at T = (333.2 to 393.2) K over the pressure range (12.0 to 40.0) MPa by a flow type apparatus. The solubility of red 153 (0.985. 10(-6) to 37.2. 10(-6)) in the overall region of measurements is found to be significantly higher than that of disperse blue 1 (1.12.10(-7) to 4.89.10(-7)). The solubility behavior of disperse red 153 follows the general solubility trend displayed by disperse dyes with a crossover pressure at about 20 MPa. On the other hand, blue 1, which is a disperse anthraquinone dye, exhibits unexpected behavior not recorded previously there is no crossover pressure at the temperature and pressure ranges studied, and the dye's solubility at T = 333.2 K practically does not increase with pressure. To the best of our knowledge, there are no previous measurements of blue 1 solubility in SC CO(2) reported in the literature. The experimental data were correlated by using the Soave Redlich Kwong equation of state (EoS) with the one-fluid van der Waals mixing rule, and an acceptable correlation of the solubility data for both dyes was obtained.

A novel flow cytometric protocol for assessment of yeast cell adhesion

Microbial adhesion is a field of recognized relevance and, as such, an impressive array of tools has been developed to understand its molecular mechanisms and ultimately for its quantification. Some of the major limitations found within these methodologies concern the incubation time, the small number of cells analyzed, and the operator's subjectivity. To overcome these aspects, we have developed a quantitative method to measure yeast cells' adhesion through flow cytometry. In this methodology, a suspension of yeast cells is mixed with green fluorescent polystyrene microspheres (uncoated or coated with host proteins). Within 2 h, an adhesion profile is obtained based on two parameters: percentage and cells-microsphere population's distribution pattern. This flow cytometry protocol represents a useful tool to quantify yeast adhesion to different substrata in a large scale, providing manifold data in a speedy and informative manner.

Molecular imaging agents for detection of β-amyloid plaques in Alzheimer’s disease

The formation of amyloid structures is a neuropathological feature that characterizes several neurodegenerative disorders, such as Alzheimer´s and Parkinson´s disease. Up to now, the definitive diagnosis of these diseases can only be accomplished by immunostaining of post mortem brain tissues with dyes such Thioflavin T and congo red. Aiming at early in vivo diagnosis of Alzheimer´s disease (AD), several amyloid-avid radioprobes have been developed for b-amyloid imaging by positron emission tomography (PET) and single-photon emission computed tomography (SPECT). The aim of this paper is to present a perspective of the available amyloid imaging agents, special those that have been selected for clinical trials and are at the different stages of the US Food and Drugs Administration (FDA) approval.

Basic dyestuffs removal from textile effluents using feathers: equilibrium, kinetic and column studies

This research work has been focused in the study of gallinaceous feathers, a waste that may be valorised as sorbent, to remove the Dark Blue Astrazon 2RN (DBA) from Dystar. This study was focused on the following aspects: optimization of experimental conditions through factorial design methodology, kinetic studies into a continuous stirred tank adsorber (at pH 7 and 20ºC), equilibrium isotherms (at pH 5, 7 and 9 at 20 and 45ºC) and column studies (at 20ºC, at pH 5, 7 and 9). In order to evaluate the influence of the presence of other components in the sorption of the dyestuff, all experiments were performed both for the dyestuff in aqueous solution and in real textile effluent. The pseudo-first and pseudo-second order kinetic models were fitted to the experimental data, being the latter the best fit for the aqueous solution of dyestuff. For the real effluent both models fit the experimental results and there is no statistical difference between them. The Central Composite Design (CCD) was used to evaluate the effects of temperature (15 - 45ºC) and pH (5 - 9) over the sorption in aqueous solution. The influence of pH was more significant than temperature. The optimal conditions selected were 45ºC and pH 9. Both Langmuir and Freundlich models could fit the equilibrium data. In the concentration range studied, the highest sorbent capacity was obtained for the optimal conditions in aqueous solution, which corresponds to a maximum capacity of 47± 4 mg g-1. The Yoon-Nelson, Thomas and Yan’s models fitted well the column experimental data. The highest breakthrough time for 50% removal, 170 min, was obtained at pH 9 in aqueous solution. The presence of the dyeing agents in the real wastewater decreased the sorption of the dyestuff mostly for pH 9, which is the optimal pH. The effect of pH is less pronounced in the real effluent than in aqueous solution. This work shows that feathers can be used as sorbent in the treatment of textile wastewaters containing DBA.

Selecção do melhor descolorante para a eliminação da cor residual num efluente têxtil

Mestrado em Engenharia Química

Reutilização das águas de tingimento utilizando a Nanofiltração

Este trabalho na área dos processos físicos de separação por membranas, nomeadamente, a nanofiltração (NF), tem como objectivo principal a recuperação dos efluentes resultantes das águas da 3ª lavagem utilizadas na operação de tingimento de fibras de algodão, com corantes reactivos. Estão inerentes as problemáticas: da escassez da água como matéria-prima na vertente de água potável; da diminuição de efluentes que necessitam de tratamentos devido à sua carga poluente; da recuperação sempre que seja viável dos produtos químicos adicionados nesta fase de tratamento das fibras de algodão e por último e não menos importante, da energia contida nestes efluentes que vão para o esgoto a temperaturas na ordem dos 50 ºC. A metodologia adoptada na realização deste trabalho consistiu, inicialmente num estudo sobre os trabalhos realizados até hoje nesta área, seguindo-se a recolha dos efluentes na empresa ―Estamparia Têxtil Adalberto Pinto da Silva, S.A.‖ (ETAPS) e posterior estudo da recuperação dos efluentes em causa pelo processo de NF utilizando a membrana NF270-2540 da empresa FILMTEC. Os efluentes estudados no presente trabalho continham corantes reactivos sendo um corante azul-claro (CAC) de composição (Amarelo Bril Remazol GL 150% + Azul Brilhante Remazol BB 133% + Azul Turqueza Remazol G) e o outro corante azul-marinho (CAM) de composição (Preto Remazol B 133% + Vermelho Remazol RGB + Amarelo Ouro Remazol RGB). Estes estudos de recuperação compreenderam basicamente 3 fases: caracterização do efluente recolhido na empresa; tratamento desse efluente utilizando uma instalação piloto de NF de fluxo cruzado ou também conhecido por membrana de fluxo tangencial instalado no Laboratório de Tecnologia (LT) do Instituto Superior de Engenharia do Porto (ISEP), e caracterização dos permeados e dos rejeitados obtidos. A análise de resultados do presente trabalho permitiu concluir ser possível a recuperação e reutilização das 3ª águas de lavagem do processo de tingimento quando tratadas pelo processo de NF a pressões de operação de 6 bar. Nestas circunstâncias os permeados obtidos (tanto no efluente com corante azul-claro como no efluente com corante azul-marinho) apresentam valores, em todos os parâmetros estudados, significativamente abaixo dos valores limites recomendáveis para uma água de abastecimento na Industria Têxtil (IT). Salienta-se reduções mais expressivas nos permeados do corante CAM, com vários parâmetros a sofrerem reduções no intervalo de 98 a 100%, nomeadamente, na cor, turvação, CQO, dureza total, alumínio e manganês. Os resultados obtidos para as pressões de operação de 4 e 8 bar mostram alguns parâmetros com valores acima dos recomendados para uma água de abastecimento na Indústria Têxtil, nomeadamente a cor no corante CAC quando se opera a 4 bar e no corante CAM quando se opera a 8 bar e os sulfatos e ferro no CAM à pressão de 4 bar. Estes resultados mostram ser possível a reutilização da água na própria instalação industrial, trazendo um benefício económico e ambiental, pela redução no consumo de água fresca e energia, além da redução do volume de efluentes que necessitam ser tratados, estando na mesma linha de pensamento de Gross et al (1999), que refere que o uso de membranas para o tratamento de efluentes do processo de tingimento tem como principal objectivo a viabilidade económica, a redução no consumo de água, de sais, de corantes e energia, bem como, a redução do volume de efluentes a ser tratado.

Avaliação do desempenho de adsorventes obtidos a partir de resíduos da indústria de curtumes na adsorção de poluentes

Na procura por uma solução de valorização dos resíduos gerados pela indústria de curtumes, o presente trabalho tem como principais objectivos a preparação de adsorventes a partir de resíduos desta actividade e a avaliação do seu desempenho na adsorção de poluentes. Para atingir este objectivo, inicialmente procedeu-se à carbonização das aparas de couro wet-white à temperatura de 800 ºC. Seguidamente, os carbonizados foram activados por activação química, tendo sido o hidróxido de potássio o agente activante escolhido. As razões mássicas hidróxido de potássio:precursor usadas na impregnação, foram iguais a 0,5:1 e 1:1. Para a razão 0,5:1, as temperaturas de activação escolhidas foram 700 e 800 ºC. Para a razão de impregnação 1:1, as temperaturas de activação usadas foram 700, 800 e 900 ºC. Para uma avaliação preliminar da capacidade de adsorção dos carvões activados produzidos, efectuou-se a determinação do número de azul de metileno. Este teste provou serem as amostras activadas a 900 ºC as que apresentaram melhores resultados (número de azul de metileno: 24g/100g) e as amostras activadas a 700 ºC, as que apresentaram menor capacidade de adsorção (1g/100g, para a razão de 0,5:1 e 7g/100g, para a razão de 1:1). Verificou-se também que amostras preparadas com iguais condições de activação (temperatura de activação e razão de impregnação), mas produzidas a partir de carbonizado de diferentes granulometrias, apresentaram diferentes desempenhos na adsorção de azul de metileno. As propriedades texturais dos carvões activados produzidos foram obtidas pela determinação das isotérmicas de adsorção de azoto a 77 K. Para tal, selecionaram-se quatro amostras: dois carvões activados a 800 ºC, com uma razão de impregnação de 1:1 e dois carvões activados a 900 ºC, com a mesma razão de impregnação, obtidos a partir de carbonizados com diferentes granulometrias. As isotérmicas obtidas são características de materiais essencialmente microporosos, com mesoporos e macroporos. Verificou-se também que a granulometria do precursor carbonizado influencia as propriedades texturais dos carvões activados produzidos. Para as temperaturas de activação usadas, 800 e 900 ºC, os carvões activados preparados a partir de carbonizado de menor granulometria apresentam melhores propriedades texturais. O carvão activado que apresentou maior área superficial específica foi obtido a 900 ºC, a partir de carbonizado finamente moído (SBET = 1475 m2/g). Determinadas as propriedades texturais dos carvões activados produzidos, realizaram-se ensaios de adsorção do corante CORIACIDE DARK BROWN VR, usado na indústria de curtumes com um carvão activado produzido no âmbito deste trabalho e com um carvão activado comercial NORIT ROW 0,8. A amostra de carvão activado produzida a partir de resíduos de wet-white escolhida para estes ensaios foi o carvão activado a 800 ºC, à razão de 1:1, a partir de carbonizado finamente moído (ww_800_1:1_carb.moído). Verificou-se que as quantidades adsorvidas pela amostra ww_800_1:1_carb.moído variaram entre os valores 7,47 e 32,07 mgcorante/gcarvão activado. Quanto ao carvão activado comercial, as quantidades adsorvidas situaram-se entre 8,95 e 69,13 mgcorante/gcarvão activado. Assim, conclui-se que o carvão activado comercial apresentou melhor desempenho na adsorção do corante da indústria de curtumes. Os carvões activados obtidos revelaram-se materiais essencialmente microporosos, com capacidade de adsorção de poluentes, como por exemplo corantes, no entanto o seu desempenho seria mais eficaz na adsorção de pequenas moléculas devido ao elevado volume de microporos que apresentaram.