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Multidrug transporters : a study of drug interactions using a photoactive analogue of rhodamine 123Alqawi, Omar January 2003 (has links)
The emergence of multidrug resistance is a serious medical problem that has significantly affected the treatment of tumor cells and infectious diseases. This multidrug resistance phenotype is mediated by the action of a large family of membrane proteins that act as active transporters or energy driven efflux pumps in both of prokaryotic and eukaryotic cells. Most eukaryotic multidrug efflux pumps belong to the ATP binding cassette (ABC) family of transport proteins that include P-glycoprotein (P-gp1), Multidrug Resistance Associated Protein (MRP1), and Breast Cancer Resistance Protein (BCRP). In prokaryotic cells, Lactococcus lactis LmrA, a homolog of P-gp1, mediates drug resistance to antibiotics and cytotoxic drugs. The transport function of these proteins is facilitated by the hydrolysis of ATP. However, the mechanism by which these proteins bind to, and are able to transport structurally dissimilar drugs across the cell membrane remains poorly understood. In this thesis we have attempted to characterize the interactions of various ABC transporters (MRP1, BCRP, and LmrA) with structurally diverse drugs, using a well characterized photoreactive drug analogue of Rhodamine 123, [125I] iodoaryl azido-rhodamine 123 (IAARh123). In the case of MRP1 interaction with Rhodamine 123, it was of interest to determine the nature of MRP1 drug interactions. In that study, our results show that CHAPS (1-[(3-cholamidopropyl) dimethylamino]-1-propansulfate) and Brij35 inhibited the photolabeling of MRP1 with IAARh123, and this interaction occurred outside the lipid bilayer. These results were unexpected in light of previous results with another ABC transporter which also binds to Rhodamine 123. Consequently, we show that non-toxic concentrations of CHAPS and Brij35 potentiate the toxicity of two MRP1 substrates, vincristine and etoposide (VP16). In the second chapter, we have used IAARh123 to demonstrate for the first time that the BCRP mediates drug resi
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The effect of different modulators on the transport of rhodamine 123 across rat jejunum using the sweetana-grass diffusion method / C.J. LamprechtLamprecht, Christian Johannes January 2004 (has links)
P-glycoprotein (Pgp), which leads to multidrug resistance in tumour cells,
is an ATP-dependent secretory drug efflux pump. In the intestine, as well as at specific
other epithelial and endothelial sites, P-glycoprotein expression is localised to the apical
membrane, consistent with secretory detoxifying and absorption limitation functions.
The primary function of Pgp is to clear the membrane lipid bilayer of lipophilic drugs.
Results from in vitro studies with human Caco-2 cells provide direct evidence for Pgp
limiting drug absorption. Limitation has non-linear dependence of absorption on
substrate (eg. vinblastine) concentration, increased absorption upon saturation of
secretion and increased absorption upon inhibition of Pgp function, with modulators such
as verapamil. The aim of this study was to investigate the effect of a known Pgp
inhibitor (verapamil) and grapefruit juice components (naringenin, quercetin and
bergamottin) on the transport of Rhodamine 123 across rat jejunum and to compare
these results with those obtained in similar studies done in Caco-2 cells and in rat
intestine (monodirectional). Verapamil, naringenin (442 µM, 662 µM and 884
µM), quercetin (73 µM, 183 µM and 292 µM) and bergamottin (12 µM, 30 µM and 48 µM)
were evaluated as modulators of rhodamine 123 transport across rat jejunum using
Sweetana-Grass diffusion cells. This study was done bidirectionally, with three cells
measuring transport in the apical to basolateral direction (AP / BL) and three cells
measuring transport in the basolateral to apical direction (BL / AP). The rate of transport
was expressed as the apparent permeability coefficient (Papp) and the extent of active
transport was expressed by calculating the ratio of BL/AP to AP/BL.
The BL-AP/AP-BL ratio calculated for Rhodamine 123 with no modulators added was 2.31. The
known modulator verapamil decreased the BL-AP/AP-BL ratio to 1.52. This was
statistically significant and inhibition of active transport was clearly demonstrated. All
modulators inhibited active transport. Only naringenin 884 µM, quercetin 183 µM and
bergamottin 30 µM did not show a statistically significant decrease in the BL-AP/AP-BL
ratio. All three components of grapefruit juice showed inhibition of active
transport and should have an effect on the bioavailability of the substrates of Pgp and
other active transporters. The results obtained in this study are similar to the results
found in Caco-2 cells, which suggests that Sweetana-Grass diffusion method can be
used for diffusion studies. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2005.
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The effect of selected methoxy flavonoids on the in vitro efflux transport of rhodamine 123 using rat jejunum / Stanley Anthony DoddDodd, Stanley Anthony January 2005 (has links)
Many orally administered drugs must overcome several barriers before
reaching their target site. The first major obstacle to cross is the intestinal epithelium.
Although lipophilic compounds may readily diffuse across the apical plasma membrane,
their subsequent passage across the basolateral membrane and into blood is by no
means guaranteed. Efflux proteins located at the apical membrane, which include P-glycoprotein
(P-gp, MDR1) and Multidrug Resistance-associated Protein (MRP2), may
drive compounds from inside the cell back into the intestinal lumen, preventing their
absorption into the blood. Intestinal P-gp is localised to the villus tip enterocytes, i.e. the
main site of absorption for orally administered compounds and in close proximity to the
lumen. P-gp is therefore ideally positioned to limit the absorption of compounds by
driving efflux back into the lumen. Drugs may also be modified by intracellular phase I
and phase II metabolizing enzymes. This process may not only render the drug
ineffective, but it may also produce metabolites that are themselves substrates for P-gp
and/or MRP2. Drugs that reach the blood are then passed to the liver, where they are
subjected to further metabolism and biliary excretion, often by a similar system of ATP binding
cassette (ABC) transporters and enzymes to that present in the intestine. Thus
a synergistic relationship exists between intestinal drug metabolizing enzymes and
apical efflux transporters, a partnership that proves to be a critical determinant of oral
bioavailability. Aim: The aim of this study was to investigate the effect of selected
methoxy flavonoids (3-methoxyflavone, 5-methoxyflavone, 6-methoxyflavone and 7-
methoxyflavone) on the mean ratio of Rhodamine123 (Rho 123) transport across rat
intestine (jejunum) and to investigate structure activity relationships (SAR) of the
selected flavonoids with reference to inhibition of P-gp. Methods: 3-Methoxyflavone, 5-
methoxyflavone, 6-methoxyflavone and 7-methoxyflavone were evaluated at a
concentration of 10μM and 20μM as modulators of Rho 123 transport across rat
jejunum. The Sweetana-Grass diffusion cells were used to determine the transport of
Rho 123. Each modulator was studied bidirectionally with two cells measuring transport
in the apical to basolateral direction (AP/BL) and two cells measuring transport in the
basolateral to apical direction (BUAP). The rate of transport was expressed as the
apparent permeability coefficient (Papp)and the extent of active transport was expressed
by calculating the ratio of BUAP to AP/BL. Each modulators Papp ratio was then
compared with that of the control. Results: 3-Methoxyflavone decreased the Papp
ratio from 3.34 (control) to 1.66 (10μM) and 1.33 (20μM) and showed statistical
significant differences. 7-Methoxyflavone decreased the Papp ratio to 1.94 (10μM) and
1.55 (20μM) but only showed a statistical significant difference at 10μM. 5-
Methoxyflavone decreased the Papp ratio to 2.41 (10μM) and 1.71 (20μM) and 6-
methoxyflavone decreased the Papp to 3.03 (10μM) and 2.49 (20μM). Both 5- and 6-
methoxyflavone showed no statistical significant differences from the control. The
structure activity relationships with reference to P-gp inhibition clearly indicated that the
C3 and C7 positioning of the methoxy-group on the A ring played a major role in the
inhibition of Rho 123 transport. Conclusion: All the selected modulators showed
inhibition of Rho 123 transport across the jejunum. This should affect the bioavailability
of the substrates of P-gp and other active transporters. In summary, this study describe
the inhibitory interaction of selected flavonoids with P-gp. Structure activity relationships
were identified describing the inhibitory potency of the flavonoids based on methoxy
groups positioning. The inhibitory potency results were 3-methoxyflavone > 7-
methoxyflavone > 5-methoxyflavone> 6-methoxyflavone / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2005.
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The effect of selected hydroxy flavonoids on the in vitro efflux transport of rhodamine 123 using rat jejunum / S. van HuyssteenVan Huyssteen, Stephanie January 2005 (has links)
Background: Multidrug resistance (MDR) is resistance of cancer cells to multiple
classes of chemotherapeutic drugs that can be structurally unrelated. MDR involves
altered membrane transport that results in a lower cell concentration of cytotoxic drugs
which plays an important role during cancer treatment. P-glycoprotein (Pgp) is localised
at the apical surface of epithelial cell in the intestine and it functions as a biological
barrier by extruding toxic substances and xenobiotics out of cells (Lin, 2003:54). The
ATP-binding-cassette superfamily is a rapidly growing group of membrane transport
proteins and are involved in diverse physiological processes which include antigen
presentation, drug efflux from cancer cells, bacterial nutrient uptake and cystic fibrosis
(Germann, 1996:928; Kerr, 2002:47). A number of drugs have been identified which are
able to reverse the effects of Pgp, multidrug resistance protein (MRPI) and their
associated proteins on multidrug resistance. The first MDR modulators discovered and
studied during clinical trials were associated with definite pharmacological actions, but
the doses required to overcome MDR were associated with the occurrence of
unacceptable side effects. As a consequence, more attention has been given to the
development of modulators with proper potency, selectivity and pharmacokinetic
characteristics that it can be used at a lower dose. Several novel MDR reversing agents
(also known as chemosensitisers) are currently undergoing clinical evaluation for the
treatment of resistant tumours (Teodori et al., 2002:385). Aim: The aim of this study was
to investigate the effect of selected flavonoids (morin, galangin, kaempferol and
quercetin) at two different concentrations (10 μM and 20 μM) on the transport of a known
Pgp substrate, Rhodamine 123 (Rho 123) across rat intestine (jejunum) and to
investigate structure activity relationships (SAR) of the selected flavonoids with
reference to the inhibition of Pgp. Methods: Morin, galangin, kaempferol and quercetin
were evaluated as potential modulators of Rho 123 transport, each at a concentration of
10 μM and 20 μM across rat jejunum using Sweetana-Grass diffusion cells. This study
was done bidirectionally, with two cells measuring transport in the apical to basolateral
direction (AP-BL) and two cells measuring transport in the basolateral to apical direction
(BL-AP). The rate of transport was expressed as the apparent permeability coefficient
(Pap,) and the extent of active transport was expressed by calculating the ratio of BL-AP
to AP-BL. Results: The BL-AP to AP-BL ratio calculated for Rho 123 with no
modulators added was 3.29. Morin decreased the BL-AP to AP-BL ratio to 1.88 at a
concentration of 10 μM and to 1.49 at a concentration of 20 μM. Galangin decreased
the BL-AP to AP-BL ratio to 1.60 at a concentration of 20 μM. These two flavonoids
showed statistically significant results and inhibition of active transport were clearly
demonstrated. However, the other flavonoids inhibited active transport of Rho 123 but
according to statistical analysis, the results were not significantly different. The two
different concentrations (10 μM and 20 μM) indicated that galangin, kaempferol and
quercetin showed practically significant differences according to the effect sizes. Morin,
however, did not show any practically significant differences at the different
concentrations. Regarding .the SAR, it was shown by Boumendjel and co-workers
(2002:512) that the presence of a 5-hydroxyl group and a 3-hydroxyl group as well as
the C2-C3 double bond are required for high potency binding to the nucleotide binding
domain (NBD) of Pgp. All the flavonoids tested had the above-mentioned
characteristics. Conclusion: All the selected flavonoids showed inhibition of active
transport of Rho 123 and should have an effect on the bioavailability of the substrates of
Pgp and other active transporters. This study described the inhibitory interaction of
selected flavonoids on Pgp activity. Practical significant differences between the same
modulator at different concentrations were also observed. Structure activity
relationships were identified describing the inhibitory potency of the flavonoids based on
hydroxyl group positioning / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2005.
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Processo de adsorção dos corantes alaranjado de metila e rodamina B por argilas esmectíticas da Paraíba, in natura e modificadas.DUARTE NETO, João Fernandes. 11 July 2018 (has links)
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Previous issue date: 2015-02-24 / Este trabalho investigou o processo de adsorção, equilibrio e cinética de argilas esmectíticas da cidade de Boa Vista (Paraíba), usadas como adsorventes de corantes com comportamentos químicos distintos - rodamina B (RB), catiônico, e alaranjado de metila (AL), aniônico - em meio aquoso. Essas argilas foram escolhidas devido às suas propriedades características do argilomineral esmectítico, que possui sítios quimicamente ativos, provocado pela substituição isomórfica e interação das arestas, tornando-o atrativo sua aplicação para fins adsortivos. As argilas utilizadas são conhecidas como bentonita chocolate e bentonita chocobofe. Esses materiais foram utilizados na forma natural e após tratamento com carbonato de sódio, ácido clorídrico e organofilização (sal quaternário de amônio PRAEPAGEN). Todos os adsorventes foram caracterizados por fluorescência de raios X, difração de raios X, análises térmicas (TG, DTG e DTA) e determinação de tamanho de partícula. Os ensaios de adsorção dos corantes foram examinados por sistema de bateladas, alterando tempo de contato, quantidade de adsorvente, concentração dos corantes e pH inicial. Para a análise do comportamento de adsorção foi utilizado espectrofotometria UV-VIS. O modelo de isoterma de Freundlich foi o que melhor se ajustou aos dados experimentais das argilas naturais e modificadas. Porém nos processos adsortivos envolvendo as argilas organofilizadas, na interação com RB, tanto o modelo de Langmuir como o de Freundlich apresentaram um bom ajuste aos dados experimentais. Os dados cinéticos de adsorção foram ajustados ao modelo de pseudo-segunda ordem (R2>0,9). Os testes de capacidades de adsorção permitiram concluir que a maior eficiência em remover a RB ocorre quando as argilas são tratadas com ácido clorídrico. A maior eficiência na remoção do AL ocorre quando as argilas estudadas foram as organofilizadas. De modo geral, as argilas esmectíticas estudadas se mostraram adsorventes adequados para a remoção do corante RB, sendo, no entanto, necessário tratamentos específicos para maximizar ou melhorar a capacidade de adsorção dos corantes RB e AL. / This study investigated the process of adsorption, equilibrium and kinetics, of smectite clays from Boa Vista of Paraíba used as chemical adsorbents of dyes with different ionic behavior in aqueous media. Smectite clays known as chocolate and chocobofe and the dyes Rhodamine B (RB) (cationic) and Methyl Orange (AL), (anionic) were used in this study. The adsorbents were characterized by X-ray fluorescence, X-ray diffraction, thermal analysis (TG, DTA and DTG) and determination of particle size. Clays have been used in natural form and after treatment with sodium carbonate, acid and organophilization (quaternary ammonium salt – PRAEPAGEN). The dye adsorption was examined by a batch system, changing: contact time, amount of adsorbent, dye concentration and initial pH. UVVIS spectrophotometry was used for the analysis of the adsorption behavior. The clays were characterized as smectite clays and the efficiency of the treatments was confirmed by X-ray fluorescence and X-ray diffraction. The model of Freundlich isotherm presented the best fit to the experimental data of natural clays. However, in the adsorptive processes involving clays organophilizated both the Langmuir model and the Freundlich model showed good fitting to the experimental data. The kinetic adsorption data were fitted to the model of pseudo-second order (R2> 0.9). The adsorption capacities test showed that the highest efficiency in removing RB occurs when the clays are treated with hydrochloric acid. The highest efficiency of the removal of AL occurs when the clays are organophilizated. In general, the smectite clays were suitable adsorbent for the removal of the dye RB. However, special treatment is necessary to maximize or improve the adsorption ability of the dyes AL and RB.
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Influência dos corantes Azul de Metileno a 2% e Rodamina B a 2% na determinação da capacidade seladora apical de diferentes cimentos endodônticosSouza, Erick Miranda [UNESP] 30 March 2004 (has links) (PDF)
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souza_em_me_arafo.pdf: 1650623 bytes, checksum: 97003cfd54c5042d5a5a6e21f97e5ffc (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Banca: Idomeo Bonetti Filho / Banca: Marco Antônio Húngaro Duarte / A proposta deste trabalho foi comparar os níveis de infiltração apical determinados pelos corantes azul de metileno a 2% e Rodamina B a 2% em canais radiculares obturados com cimentos endodônticos de diferentes composições químicas. Foi também determinada a capacidade seladora apical dos cimentos Endofill, Sealer 26, AH Plus, Sealapex, EndoREZ e um cimento experimental à base de polímero de mamona (Polifil) em cada solução corante. Foram utilizados 176 dentes unirradiculares extraídos de humanos que foram instrumentados com limas do Sistema K3 de conicidade 0,04mm/mm e obturados pela técnica da condensação lateral modificada utilizando-se um cone principal de conicidade 0,04mm/mm e dois cones auxiliares. As raízes foram divididas em grupos de acordo com o cimento obturador utilizado e estes novamente divididos em subgrupos de 14 dentes cada de acordo com a solução corante a ser utilizada como traçador da infiltração. Oito dentes foram utilizados como controle sendo 4 controles positivo e 4 controles negativo. As raízes foram impermeabilizadas em toda superfície radicular externa com exceção do forame apical e submetidas à infiltração nas duas soluções corantes, em um ambiente de vácuo por 24 horas. Foram mensuradas as infiltrações apicais por meio do programa ImageTool for Windows versão 3.0 e os resultados submetidos à análise estatística pelos testes ANOVA, t-Student e Newman-Kells. Verificou-se que os níveis de infiltração determinados pelas soluções corantes dependem de qual cimento é avaliado. A solução de azul de metileno a 2% determinou nos cimentos Endofill, Sealer 26 e Sealapex menores níveis de infiltração que os determinados pela Rodamina B nos mesmos cimentos, sugerindo uma incapacidade da solução de azul de metileno a 2% em revelar a totalidade da falha da obturação realizada com estes cimentos... . / The purpose of this study was to compare the levels of apical leakage determined by the 2% methylene blue and 2% Rhodamine B dyes in root canals filled with endodontic sealers of different chemical compositions. It was also determined the apical sealing ability of the sealers Endofill, Sealer 26, AH Plus, Sealapex, EndoREZ and an experimental sealer based on castor oil polymer (Polifil) in each dyeing solution. It was used 176 single root teeth extracted from humans that were instrumented with K3 system files taper .04 and filled by the modified lateral condensation technique using a main cone taper .04 and two auxiliary cones. The roots were divided in groups according to the filling sealers that were used and these ones were divided again in subgroups of 14 teeth each one according to the dyeing solution used as infiltration tracer. Eight teeth were used as control group, four positive controls and 4 negative controls. The roots were impermeabilized on all external root surface, excepting for the apical foramen, and subjected to the infiltration into the two dye solutions in a vacuum environment for 24 hours. The apical leakage were measured by means of the software ImageTool® for Windows version 3.0 and the results were subjected to statistical analysis by the tests ANOVA, t-Student and Newman-Kells. It was noticed that the levels of leakage determined by the dye solutions depend on which sealer is evaluated. The 2%methylene blue solution in the sealers Endofill, Sealer 26 and Sealapex presented lower levels of leakage compared to the ones determined by 2% Rhodamine B in the same sealers, suggesting that 2% methylene blue dye is unable to determine the total extension of the leakage in those sealers. The other sealers did not present significant differences in the apical leakage levels determined by both dye solutions. In relation to the apical sealing... (Complete abstract, click electronic address below).
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Influência dos corantes Azul de Metileno a 2% e Rodamina B a 2% na determinação da capacidade seladora apical de diferentes cimentos endodônticos /Souza, Erick Miranda. January 2004 (has links)
Orientador: Roberto Miranda Esberard / Banca: Idomeo Bonetti Filho / Banca: Marco Antônio Húngaro Duarte / Resumo: A proposta deste trabalho foi comparar os níveis de infiltração apical determinados pelos corantes azul de metileno a 2% e Rodamina B a 2% em canais radiculares obturados com cimentos endodônticos de diferentes composições químicas. Foi também determinada a capacidade seladora apical dos cimentos Endofill, Sealer 26, AH Plus, Sealapex, EndoREZ e um cimento experimental à base de polímero de mamona (Polifil) em cada solução corante. Foram utilizados 176 dentes unirradiculares extraídos de humanos que foram instrumentados com limas do Sistema K3 de conicidade 0,04mm/mm e obturados pela técnica da condensação lateral modificada utilizando-se um cone principal de conicidade 0,04mm/mm e dois cones auxiliares. As raízes foram divididas em grupos de acordo com o cimento obturador utilizado e estes novamente divididos em subgrupos de 14 dentes cada de acordo com a solução corante a ser utilizada como traçador da infiltração. Oito dentes foram utilizados como controle sendo 4 controles positivo e 4 controles negativo. As raízes foram impermeabilizadas em toda superfície radicular externa com exceção do forame apical e submetidas à infiltração nas duas soluções corantes, em um ambiente de vácuo por 24 horas. Foram mensuradas as infiltrações apicais por meio do programa ImageTool for Windows versão 3.0 e os resultados submetidos à análise estatística pelos testes ANOVA, t-Student e Newman-Kells. Verificou-se que os níveis de infiltração determinados pelas soluções corantes dependem de qual cimento é avaliado. A solução de azul de metileno a 2% determinou nos cimentos Endofill, Sealer 26 e Sealapex menores níveis de infiltração que os determinados pela Rodamina B nos mesmos cimentos, sugerindo uma incapacidade da solução de azul de metileno a 2% em revelar a totalidade da falha da obturação realizada com estes cimentos... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: The purpose of this study was to compare the levels of apical leakage determined by the 2% methylene blue and 2% Rhodamine B dyes in root canals filled with endodontic sealers of different chemical compositions. It was also determined the apical sealing ability of the sealers Endofill, Sealer 26, AH Plus, Sealapex, EndoREZ and an experimental sealer based on castor oil polymer (Polifil) in each dyeing solution. It was used 176 single root teeth extracted from humans that were instrumented with K3 system files taper .04 and filled by the modified lateral condensation technique using a main cone taper .04 and two auxiliary cones. The roots were divided in groups according to the filling sealers that were used and these ones were divided again in subgroups of 14 teeth each one according to the dyeing solution used as infiltration tracer. Eight teeth were used as control group, four positive controls and 4 negative controls. The roots were impermeabilized on all external root surface, excepting for the apical foramen, and subjected to the infiltration into the two dye solutions in a vacuum environment for 24 hours. The apical leakage were measured by means of the software ImageTool® for Windows version 3.0 and the results were subjected to statistical analysis by the tests ANOVA, t-Student and Newman-Kells. It was noticed that the levels of leakage determined by the dye solutions depend on which sealer is evaluated. The 2%methylene blue solution in the sealers Endofill, Sealer 26 and Sealapex presented lower levels of leakage compared to the ones determined by 2% Rhodamine B in the same sealers, suggesting that 2% methylene blue dye is unable to determine the total extension of the leakage in those sealers. The other sealers did not present significant differences in the apical leakage levels determined by both dye solutions. In relation to the apical sealing... (Complete abstract, click electronic address below). / Mestre
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Estudo da fotodegradação por pulsos de femtossegundos em Rodamina B na presença de TiO2 / Study of femtosecond pulses induced photodegradation of Rhodamine B in the presence of TiO2Tarcísio Rocha Figueredo 14 February 2014 (has links)
Este trabalho investigou a fotodegradação do corante Rodamina-B com o auxílio do catalisador semicondutor Dióxido de Titânio, utilizando como fonte de irradiação pulsos de 40 fs gerados por um sistema laser de Titânio - Safira. Os pulsos laser foram formatados espectralmente (modulação senoidal), gerando trens de pulsos cuja separação foi escolhida para ser ressonante com um modo Raman intenso do catalisador. A fotodegradação da Rodamina-B foi monitorada através de medidas de fluorescência excitada via absorção de dois fótons. Não observamos fotodegradação do corante mediante a irradiação com pulsos ultracurtos, mesmo na presença do catalisador, tanto para o pulso de menor duração alcançada quanto para os trens de pulsos com diferentes separações temporais. Contudo, observamos uma diminuição no espalhamento da luz de excitação devido às nanopartículas de Dióxido de Titânio. Este processo foi estudado com mais detalhes, tendo sido analisada a influência da formatação espectral senoidal no resultado da medida. A relação entre a irradiação com pulsos de femtossegundos e a quebra de aglomerados de nanopartículas foi intuída a partir dos resultados obtidos, sendo fortalecida por medidas de microscopia eletrônica de varredura de um filme das amostras. / This work investigated the photodegradation of Rhodamine-B assisted by Titanium Dioxide semiconductor catalyst, using as irradiation source a Ti:Sapphire laser system delivering 40 fs pulses. The laser pulses were spectrally shaped (sinusoidal modulation), generating pulse trains whose separation was chosen to be resonant with an intense catalysts Raman mode. The Rh-B photodegradation was monitored by two photon excited fluorescence measurements. We have not observed dye photodegradation by the ultrashort pulses irradiation, in the absence of the catalyst, neither with the shortest pulse obtained, nor with pulse trains. Nevertheless, we observed a decrease in the excitation light scattering due to the Titanium Dioxide nanoparticles. Such process was studied by analyzing the influence of sinusoidal spectral phase mask in the signal. The results indicate a relationship between femtosecond pulse irradiation and the breaking of nanoparticles clusters, which was also corroborated by scanning electron microscopy measurements.
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Materiais Micro e Nanoestruturados para Aplicações FotônicasSILVA, Renato Barbosa da 27 August 2015 (has links)
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Previous issue date: 2015-08-27 / CAPES / Diferentes tipos de materiais foram abordados nesta tese visando sua possível aplicação na
fotônica. Por isso, o texto foi dividido em duas partes. A Parte 1 trata da preparação de materiais
para a aplicação em laser aleatório. O primeiro material sintetizado foram as nanocascas
metálicas, cuja estrutura é formada por um caroço de sílica com uma casca metálica ao seu redor.
Assim, foi descrito um procedimento experimental melhorado com o intuito de se obter
nanocascas de ouro e de prata de maneira mais reprodutível no menor tempo possível. Neste
experimento, foi demostrado que a taxa de agitação no final da síntese tem importante influência
na formação ou não das nanocascas metálicas. O crescimento de nanocascas de ouro e prata
ocorria para taxas de 190 rpm e 1500 rpm respectivamente.
O segundo material consistiu de partículas sub-micrométricas de sílica com corante
rodamina 640 encapsulado. O encapsulamento ocorreu pela simples adição de uma solução do
corante durante a síntese das partículas de sílica. Assim, para uma concentração de corante de
10-2 M, foi descrito um experimento de laser aleatório bicromático. Ao contrário de outros
trabalhos na literatura foi possível controlar a emissão do laser aleatório apenas mudando a
intensidade de excitação. Durante estes experimentos também foi verificada a existência de
frequency-pulling entre dímeros e monômeros nos experimentos.
Finalmente na Parte 2 é discutida a síntese e caracterização de nanocristais de silício
(ncSi). Os ncSi apresentam luminescência cujo comprimento de onda pode ser controlado
variando o tamanho dos nanocristais. A síntese foi baseada no processamento termal em altas
temperaturas do hidrossilicato HSiO1.5, derivado do triclorossilano (HSiCl3). Em seguida, os
vidros são finamente macerados num almofariz e pistilo de ágata antes dos ncSi serem extraídos
via extração ácida. Neste experimento o objetivo foi obter nanocristais de silício monodispersos
sem a utilização de etapas pós-síntese como a ultracentrifugação. O objetivo foi alcançado
adicionando cloreto de sódio (NaCl) durante a etapa maceração, com o intuito de diminuir o
tamanho dos grãos e garantir uma extração uniforme dos mesmos / Different materials were reported in this thesis aiming their possible photonic applications.
Therefore the content of this thesis was distributed in two parts. Part 1 is related to the synthesis
of materials for applications in random laser. The first material synthesized were the metallic
nanoshells, which structure is based in a silica core and a metallic shell around it. An improved
experimental method was reported for synthesize gold and silver nanoshells in order to guarantee
the reproducibility and decrease the time necessary for synthesis. It was shown that the stirring
rate at the end of synthesis plays an important role on the growth of metallic nanoshells. The
growth of gold nanoshells was performed using a stirring rate of 190 rpm, on the other hand, the
growth of silver nanoshells was performed using a stirring rate of 1500 rpm.
The second material consisted of sub-micrometer silica particles whith encapsulated
rhodamine 640. The encapsulation was made by the simple addition of a dye solution to do
during a Synthesis of silica particles. An bichromatic random laser was operated using a
concentration of 10-2 M of laser dye. Unlike other works in the literature it was possible to
control the emission of the random laser only changing the intensity of the excitation source.
These experiments were also revealed the possibility of frequency-pulling between dimers and
monomers of rhodamine through the shift of the laser emission.
Finally, in Part 2 it is discussed the synthesis and characterization of silicon nanocrystals
(ncSi). The ncSi present luminescence that can be tunable by changing the ncSi sizes The
synthesis was based on the thermal processing at high temperatures of HSiO1.5 hydrosilicate
derivative of trichlorosilane (HSiCl3). Then, the glasses are finely grounded in a agate mortar and
pestle before been extracted via an acid etching. In this experiment the objective was to obtain
monodisperse nanocrystals of silicon without the use of post-synthesis steps such as
ultracentrifugation. The objective was reached added sodium chloride (NaCl) during the ground
step in order to decrease the size of grain for to obtain a uniform etching.
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Estratégias para adição de rodamina B em sistemas adesivos / Strategies for adding rhodamine B to bonding agentsOdair Bim Junior 01 April 2013 (has links)
A rodamina B e outros marcadores fluorescentes vêm sendo empregados na avaliação morfológica da interface de adesão com o auxílio de microscopia confocal de varredura a laser. Acrescentando-se rodamina B a sistemas adesivos, é possível observar as características de espessura da camada de adesivo, micromorfologia da camada híbrida, extensão e quantidade de tags, bem como diagnosticar defeitos ou alterações na interface de adesão. A literatura revela, entretanto, uma falta de precedentes sobre as quantidades de marcadores nos componentes resinosos. Além disso, ainda não se avaliou o efeito da concentração de rodamina B sobre a qualidade da análise da interface de adesão, bem como sobre o comportamento fotofísico dos marcadores nos sistemas adesivos. Este estudo foi realizado com o propósito de sistematizar um método de adição de rodamina B a sistemas adesivos, incluindo-se estratégias para a determinação de concentrações mínimas de rodamina nos componentes resinosos, porém, ainda viáveis para a realização da análise morfológica da interface de adesão através de microscopia confocal de varredura a laser. Para tal, os sistemas adesivos não simplificados e considerados padrão-ouro em suas categorias Adper™ Scotchbond™ Multi-Purpose (convencional de três passos) e Clearfil™ SE Bond (auto-condicionante de dois passos) foram modificados com rodamina B em cinco diferentes concentrações: C1 (0,5 mg/mL), C2 (0,10 mg/mL), C3 (0,02 mg/mL), C4 (0,004 mg/mL) e C5 (0,0008mg/mL) e o comportamento fluorescente da rodamina nos adesivos foi avaliado tanto no âmbito espectroscópico (espectroscopia de fotoluminescência), como no âmbito microscópico (microscopia confocal de varredura a laser). Para a modificação dos adesivos, utilizou-se uma técnica precisa de proporcionamento na qual o marcador fluorescente foi incorporado às resinas fluidas a partir de soluções de rodamina B em etanol. Os espectros de fluorescência mostraram diferenças nos máximos das bandas de emissão e de excitação, de acordo com as concentrações de rodamina B em cada material dispersante. A análise microscópica dos espécimes em dentina confirmou que é possível utilizar sistemas adesivos contendo rodamina B em concentrações muitas vezes menores do que as mencionadas na literatura. Ambos os sistemas avaliados puderam ser visualizados, microscopicamente, quando marcados com rodamina B nas três concentrações pré-selecionadas para a avaliação da interface de adesão: C2 (0,10 mg/mL), C3 (0,02 mg/mL) e C4 (0,004 mg/mL), sendo que C3 forneceu os melhores resultados em relação ao contraste e à saturação nas fotomicrografias. Concluiu-se que o comportamento fotofísico da rodamina B é influenciado tanto pela concentração, como pelo sistema adesivo no qual o marcador está dissolvido. A concentração de rodamina B também interfere na qualidade da análise morfológica da interface de adesão, sendo que o excesso do marcador pode dificultar a distinção de detalhes micromorfológicos. / Rhodamine B and other fluorescent markers have been used for the assessment of the bonding interface via confocal laser scanning microscopy. By adding rhodamine into adhesive systems, it is possible to study morphological characteristics of the hybrid layer, the extent and amount of resin tags and the adhesive layer thickness, as well as detecting potential defects or alterations at bonding interface. Meantime the literature reveals lack of standards among the quantities of fluorescent markers in resin-based polymers. The effects of rhodamine B concentration on the quality of the microscopic analysis, as well as on the photophysics of labeled adhesive systems were not assessed up to now. This study aimed to systematize methodologies for adding rhodamine B into adhesive systems, including suitable strategies for determining the minimum serviceable rhodamine concentrations to perform the morphological analysis of the bonding interface. Two non-simplified adhesive system considered gold standard categories Adper™ Scotchbond™ Multi-Purpose (3 steps conventional) and Clearfil™ SE Bond (2 steps self-etching) were modified with rhodamine B at five concentrations: C1 (0.5 mg/ml), C2 (0.10 mg/ml), C3 (0.02 mg/ml), C4 (0.004 mg/ml) and C5 (0.0008 mg/ml ) and the fluorescent behavior of the labeled resins was assessed both by photoluminescence spectroscopy and by confocal laser microscopy The preparation of the labeled resins was proceed by means of a precise proportioning technique in which the fluorescent marker was incorporated into the bonding agents from solutions of rhodamine B in ethanol. The fluorescence spectra showed differences in the intensity and wavelength fluorescence according to the rhodamine B concentration. Microscopic analysis of the dentin specimens confirmed adhesive systems can be modified with rhodamine B at far lower concentrations than those mentioned in the literature. Both evaluated systems were microscopically visualized while labeled with Rhodamine B at three pre-selected concentrations: C2 (0.10 mg/mL), C3 (0.02 mg/ml) and C4 (0.004 mg/ml), and C3 offered the best outcome with respect to contrast and saturation in photomicrographs. It was concluded that the photophysical behavior of rhodamine B depends on both the concentration and labeled adhesive system. The rhodamine B concentration also interferes with the quality of morphological analysis of the bonding interface, and the excess of the fluorescent marker may jeopardize the discrimination of morphological details.
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