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Influence of the Solvent Evaporation Rate on the Crystalline Phases of Solution-Cast Poly(Vinylidene Fluoride) Films

CHINAGLIA, Dante Luis; GREGORIO JR., Rinaldo; STEFANELLO, Josiani Cristina; ALTAFIM, Ruy Alberto Pisani; WIRGES, Werner; WANG, Feipeng; GERHARD, Reimund
Fonte: JOHN WILEY & SONS INC Publicador: JOHN WILEY & SONS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.67%
The influence of the solvent-evaporation rate on the formation of of. and P crystalline phases in solution-cast poly(vinylidene fluoride) (PVDF) films was systematically investigated. Films were crystallized from PVDF/N,N-dimethylformamide solutions with concentrations of 2.5, 5.0, 10, and 20 wt % at different temperatures. During crystallization, the solvent evaporation rate was monitored in situ by means of a semianalytic balance. With this system, it was possible to determine the evaporation rate for different concentrations and temperatures of the solution under specific ambient conditions (pressure, temperature, and humidity). Fourier-Transform InfraRed spectroscopy with Attenuated Total Reflectance revealed the P-phase content in the PVDF films and its dependence on previous evaporation rates. Based on the relation between the evaporation rate and the PVDF phase composition, a consistent explanation for the different amounts of P phase observed at the upper and lower sample surfaces is achieved. Furthermore, the role of the sample thickness has also been studied. The experimental results show that not only the temperature but also the evaporation rate have to be controlled to obtain the desired crystalline phases in solution-cast PVDF films. (C) 2009 Wiley Periodicals...

Influences of surface and solvent on retention of HEMA/mixture components after evaporation

GARCIA, Fernanda C. P.; WANG, Linda; PEREIRA, Lucia C. G.; SILVA, Safira M. de Andrade e; MARQUEZINI JUNIOR, Luiz; CARRILHO, Marcela Rocha de Oliveira
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.9%
Objectives: This study examined the retention of solvents within experimental HEMA/solvent primers after two conditions for solvent evaporation: from a free surface or from dentine surface. Methods: Experimental primers were prepared by mixing 35% HEMA with 65% water, methanol, ethanol or acetone (v/v). Aliquots of each primer (50 mu l) were placed on glass wells or they were applied to the surface of acid-etched dentine cubes (2 mm x 2 mm x 2 mm) (n = 5). For both conditions (i.e. from free surface or dentine cubes), change in primers mass due to solvent evaporation was gravimetrically measured for 10 min at 51% RH and 21 degrees C. The rate of solvent evaporation was calculated as a function of loss of primers mass (%) over time. Data were analysed by two-way ANOVA and Student-Newman-Keuls (p < 0.05). Results: There were significant differences between solvent retention(%) and evaporation rate (%/min) depending on the solvent present in the primer and the condition for evaporation (from free surface or dentine cubes) (p < 0.05). For both conditions, the greatest amount of retained solvent was observed for HEMA/water primer. The rate of solvent evaporation for HEMA/acetone primer was almost 2- to 10-times higher than for HEMA/water primer depending whether evaporation occurred...

Iodeto de mercúrio (HgI2) para aplicações em detectores de radiação.; Mercuric iodide (HgI2) for applications in radiation detectors

Ugucioni, Julio César
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 23/02/2005 PT
Relevância na Pesquisa
46.83%
O iodeto de mercúrio(HgI2) vem sendo largamente estudado com o objetivo de utilizá-lo em detectores de radiação –X e –γ. Este material semicondutor apresenta propriedades interessantes que o tornam um grande candidato a esta aplicação em relação a outros materiais. Suas propriedades são gap óptico largo (2,13 eV), alto numero atômico (ZHg = 80; ZI = 53) e alto coeficiente de absorção para comprimentos de onda da ordem de energia do raios-X e -γ. Este, também, pode apresentar três fases quando sólido: fase vermelha (ou α-HgI2), fase amarela (ou β-HgI2) e fase laranja. Cada uma destas fases é associada com diferentes estruturas cristalinas. O α-HgI2 é tetragonal, o HgI2 laranja é também tetragonal,diferindo da fase vermelha somente na posição dos átomos de mercúrio, e β-HgI2 é ortorrômbico. Neste trabalho, estes materiais foram obtidos por duas técnicas: spray pyrolysis e evaporação de solvente. Nas duas técnicas os mais importantes parâmetros para a obtenção das diferentes estruturas são a temperatura e a taxa de evaporação do solvente. Através do método de spray pyrolysis foi possível obter filmes finos de HgI2 com duas estruturas diferentes, somente variando a temperatura do aquecedor de substratos e o solvente. Acima da temperatura de 100ºC com o solvente água foi possível obter filmes amarelados de HgI2. Por sua vez...

Iodeto de mercúrio produzido por evaporação de solvente: cristais obtidos usando etanol e tetrahidrofurano, e filmes híbridos obtidos usando polímeros isolantes; Mercuric iodide produce by solvent evaporation: crystals obtained by ethanol and tetrahydrofuran, and hybrids films obtained by isulator polymers

Ugucioni, Julio César
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/08/2009 PT
Relevância na Pesquisa
66.74%
O iodeto de mercúrio vermelho (?-HgI2 ou comumente conhecido na literatura como HgI2) vem sendo largamente estudado para utilização em detectores de radiação -X e -? por apresentar alta faixa de energia proibida (gap de energia = 2,13eV), alto número atômico (ZHg = 80; ZI = 53) e alta densidade (6,4 mg/ml), além de outras propriedades que auxiliam na absorção destes tipos de radiação. A obtenção de filmes e cristais usando uma técnica de baixo custo é abordada neste trabalho. A técnica que obtenção de cristais utilizada foi a evaporação de solvente, que consiste na evaporação de um solvente volátil de uma solução preparada com sal de HgI2. Os solventes voláteis utilizados foram etanol, tetrahidrofurano (THF) e algumas misturas de ambos. Duas principais condições de evaporação foram testadas: na presença de luz ambiente (claro) e na ausência desta (escuro) em temperatura ambiente. Somente para o etanol obteve-se cristais com controle de temperatura (temperatura de 40°C) dentro de estufa no escuro. Observou-se, como resultado geral, que os cristais apresentam um aumento da desorganização estrutural quando se adiciona THF. Como esperado, isso se refletiu nas propriedades elétricas, diminuindo a resistividade (?) e energia de ativação (Ea) destes materiais. Além disso...

Micropartículas contendo pantoprazol sódico: desenvolvimento tecnológico, produção em escala piloto e avaliação biológica; Micropartcles contaning sodium pantoprazole : technological development, scale up and biological activity

Raffin, Renata Platcheck
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
46.49%
Micropartículas contendo pantoprazol foram preparadas e caracterizadas a fim de se obter sistemas multiparticulados gastro-resistentes. O trabalho foi delineado buscando-se a melhor técnica de preparação das micropartículas, assim como o estudo do processo, aumento de escala e avaliação biológica. A metodologia analítica para quantificação do pantoprazol nas micropartículas foi desenvolvida e validada. O método mostrou-se seletivo, linear, preciso e exato. A estabilidade do pantoprazol em tampão fosfato pH 7,4 foi avaliada para verificar a viabilidade da utilização deste tampão como meio de dissolução. O pantoprazol apresentou-se estável durante 6 h e considerado adequado para estudos de dissolução. A primeira técnica utilizada na preparação de micropartículas foi a evaporação de solvente, utilizando uma emulsão O/O. O polímero utilizado foi Eudragit® S100. As micropartículas apresentaram diâmetro de 56 μm e, segundo análises de DSC e IV, o fármaco apresentou-se molecularmente disperso no polímero. As micropartículas apresentaram atividade anti-ulcerogênica em modelo de ulceração gástrica em ratos por etanol, enquanto a solução aquosa de pantoprazol não apresentou atividade. Estas micropartículas foram comprimidas e permaneceram intactas no interior dos comprimidos. Quanto à proteção do pantoprazol em meio ácido...

Physicochemical characterization of a hydrophilic model drug-loaded PHBV microparticles obtained by the double emulsion/solvent evaporation technique

Farago, Paulo Vitor; Raffin, Renata Platcheck; Pohlmann, Adriana Raffin; Sílvia Stanisçuaski Guterres; Zawadzki, Sônia Faria
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
66.49%
Micropartículas de poli(3-hidroxibutirato-co-3-hidroxivalerato) (PHBV) contendo um fármaco modelo hidrofílico, o cloridrato de metformina (MH), foram obtidas pela técnica de emulsão múltipla/evaporação do solvente. Diversas formulações foram preparadas, com o objetivo de investigar a influência de cada composição sobre a eficiência de encapsulação (EE). O resultado mais elevado de EE (9,76%) foi verificado quando da simultânea alcalinização e adição de NaCl na fase aquosa externa da formulação. O estudo por MEV das micropartículas revelou morfologia esférica e superfície rugosa. As intensidades de difração cristalina para as micropartículas contendo o MH foram menores do que aquelas observadas para a mistura física. Os resultados obtidos por IVTF sugerem que nenhuma ligação química foi formada entre o polímero e o fármaco. A avaliação por análise térmica indica o surgimento de interações favoráveis entre MH e PHBV. O estudo de liberação in vitro demonstrou a influência do PHBV no perfil de dissolução do MH.; Poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) microparticles containing a water-soluble model drug, metformin hydrochloride (MH), were obtained by a double emulsion/solvent evaporation technique. Several formulations were prepared in order to investigate the influence of each composition on the encapsulation efficiency (EE). The highest value of EE (9.76%) was obtained using simultaneously pH alkalinization and NaCl addition in the external water phase of the formulation. SEM study revealed a spherical morphology and a rough surface. The crystalline diffraction intensities for the MH-loaded microparticles were lower than that verified for the physical mixture. FTIR results suggested that no chemical bond between the polymer and the drug was formed. Also thermal analyses indicated a favorable interaction between MH and PHBV. In vitro drug release demonstrated the influence of the PHBV on the dissolution profile of MH.

Influence of the Solvent Evaporation Rate on the Crystalline Phases of Solution-Cast Poly(Vinylidene Fluoride) Films

Chinaglia, Dante Luis; Gregorio, Rinaldo; Stefanello, Josiani Cristina; Pisani Altafim, Ruy Alberto; Wirges, Werner; Wang, Feipeng; Gerhard, Reimund
Fonte: John Wiley & Sons Inc Publicador: John Wiley & Sons Inc
Tipo: Artigo de Revista Científica Formato: 785-791
ENG
Relevância na Pesquisa
56.67%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); The influence of the solvent-evaporation rate on the formation of of. and P crystalline phases in solution-cast poly(vinylidene fluoride) (PVDF) films was systematically investigated. Films were crystallized from PVDF/N,N-dimethylformamide solutions with concentrations of 2.5, 5.0, 10, and 20 wt % at different temperatures. During crystallization, the solvent evaporation rate was monitored in situ by means of a semianalytic balance. With this system, it was possible to determine the evaporation rate for different concentrations and temperatures of the solution under specific ambient conditions (pressure, temperature, and humidity). Fourier-Transform InfraRed spectroscopy with Attenuated Total Reflectance revealed the P-phase content in the PVDF films and its dependence on previous evaporation rates. Based on the relation between the evaporation rate and the PVDF phase composition, a consistent explanation for the different amounts of P phase observed at the upper and lower sample surfaces is achieved. Furthermore, the role of the sample thickness has also been studied. The experimental results show that not only the temperature but also the evaporation rate have to be controlled to obtain the desired crystalline phases in solution-cast PVDF films. (C) 2009 Wiley Periodicals...

Eficacia de diferentes metodos empregados na evaporação de olventes presentes em resinas experimentais; Solvent elimination from experimental dental adhesives with different hydrophilic features

Michele Bail
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 29/06/2007 PT
Relevância na Pesquisa
46.65%
O objetivo deste estudo foi avaliar a eficácia de diferentes métodos empregados na eliminação dos solventes incorporados a sistemas de união com características hidrofílicas diferentes. As hipóteses avaliadas consideraram que a eliminação/retenção dos solventes seria dependente: 1) da característica hidrofílica da resina; 2) da técnica e intervalo de tempo empregados na eliminação desses solventes; 3) do tipo de solvente empregado. Três resinas experimentais, R2, R3 e R5, foram formuladas de modo a exibirem características hidrofílicas distintas, dadas pela seleção e proporcionamento de monômeros, comumente empregados na odontologia. A resina R2 era a menos hidrofílica e R5 a mais hidrofílica. Acetona ou etanol foram adicionados a cada resina numa proporção de 50% (em peso). A eliminação dos solventes foi verificada por método gravimétrico, aplicado antes e após a realização dos seguintes tratamentos: 1) jato de ar à temperatura ambiente (JAAmb) por 15s; 2) JAAmb por 30s; 3) JAAmb por 60s; 4) jato de ar aquecido (JAAq) por 15s; 5) JAAq por 30s ou 6) JAAq por 60s. Os dados foram analisados por análise de variância e teste de Bonferroni (α =0,05). Nenhum tratamento eliminou completamente o solvente incorporado às resinas. Maior eliminação do solvente foi verificada para a resina menos hidrofílica R2...

Tailoring porous structure of ferroelectric poly(vinylidene fluoride-trifluoroethylene) by controlling solvent/polymer ratio and solvent evaporation rate

California, A.; Cardoso, V. F.; Costa, Carlos M.; Sencadas, V.; Botelho, Gabriela; Gómez Ribelles, J. L.; Lanceros-Méndez, S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2011 ENG
Relevância na Pesquisa
66.54%
Ferroelectric macroporous poly(vinylidene fluoride-trifuoroethylene) membranes have been produced by isothermal crystallization from the solution at different temperatures starting from different diluted solutions of the co-polymer in dimethylformamide. In this way pore architecture, consisting in interconnected spherical pores can be obtained. The mechanism and kinetics of solvent evaporation was investigated and related to the evolution of the polymer microstructure. The mechanism underlying the pattern formation has been discussed on the light of the Flory-Huggins (FH) lattice teory, grain boundary effects and the Cahn-Hilliard equation for mass conservation systems. It was also observed that the temperature or initial concentration of the crystallization process does not affect the phase, ferroelectric transition temperature or the melting temperature of the polymer.; Fundação para a Ciência e a Tecnologia (FCT) - PTDC/CTM-NAN/112574/2009, PTDC/CTM/73030/2006, PTDC/CTM/69316/2006, NANO/NMed-SD/0156/2007, SFRH/BD/44289/2008, SFRH/BD/68499/2010, SFRH/BPD/63148/2009; Universidad Politécnica de Valencia - Programa de Apoyo a la Investigación y Desarrollo (PAID-00-09); Spanish Ministry of Science - MAT2010-21611-C03-01; Conselleria de Sanidad (Generalitat Valenciana); Instituto de Salud Carlos III

Effect of drug properties on the release from CAP microspheres prepared by a solvent evaporation method

Silva, J. P. S.; Ferreira, J. P. M.
Fonte: Informa Healthcare Publicador: Informa Healthcare
Tipo: Artigo de Revista Científica
Publicado em //1999 ENG
Relevância na Pesquisa
66.49%
Drugs with different water-solubility and molecular weights were microencapsulated in cellulose acetate phthalate, using an emulsion-solvent evaporation technique with a continuous oil-phase. The mean size of the particles was approximately 600mum, and they were non-porous. The capacity of the microspheres to retain the drugs was evaluated by in vitro release studies in acidic medium. For low molecular weight compounds the release rates increased with solubility: for thiamin hydrochloride and phenacetin, a highly and a poorly soluble compound respectively, the percentages released at 60 min were 90 and 10%. Drugs with molecular weights above approximately 700 Da were retained in the microspheres. The above dependence on solubility was corroborated by release studies in ethanol, and by modelling the release of phenacetin in acidic media. Microspheres with a different polymer matrix, Eudragit RS PO, were also prepared by a similar technique, and these particles prolonged the release of thiamin for over 6h, under simulated GI conditions.

Physicochemical characterization of a hydrophilic model drug-loaded PHBV microparticles obtained by the double emulsion/solvent evaporation technique

Farago,Paulo V.; Raffin,Renata P.; Pohlmann,Adriana R.; Guterres,Sílvia S.; Zawadzki,Sônia F.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
Relevância na Pesquisa
66.49%
Poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) microparticles containing a water-soluble model drug, metformin hydrochloride (MH), were obtained by a double emulsion/solvent evaporation technique. Several formulations were prepared in order to investigate the influence of each composition on the encapsulation efficiency (EE). The highest value of EE (9.76%) was obtained using simultaneously pH alkalinization and NaCl addition in the external water phase of the formulation. SEM study revealed a spherical morphology and a rough surface. The crystalline diffraction intensities for the MH-loaded microparticles were lower than that verified for the physical mixture. FTIR results suggested that no chemical bond between the polymer and the drug was formed. Also thermal analyses indicated a favorable interaction between MH and PHBV. In vitro drug release demonstrated the influence of the PHBV on the dissolution profile of MH.

The effect of some processing conditions on the characteristics of biodegradable microspheres obtained by an emulsion solvent evaporation process

Maia,J. L.; Santana,M. H. A.; Ré,M. I.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2004 EN
Relevância na Pesquisa
56.54%
Unloaded microspheres were prepared from polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHB-HV) polymers using an oil-in-water emulsion solvent evaporation method. The study was conducted to evaluate how the polymer and some process parameters affect properties of the final microspheres such as particle size, superficial area, zeta potential, surface morphology and microsphere degradation. The variables included surfactant concentration in the emulsion water phase and solvent composition. From the results, it was found that the parameters affecting microsphere size the most were surfactant concentration in the emulsion water phase and solvent composition. Properties such as zeta potential, surface area and surface morphology remained pratically unchanged over the range of the processing conditions studied here.

Co-solvent Evaporation Method for Enhancement of Solubility and Dissolution Rate of Poorly Aqueous Soluble Drug Simvastatin: In vitro–In vivo Evaluation

Pandya, Priyanka; Gattani, Surendra; Jain, Pankaj; Khirwal, Lokesh; Surana, Sanjay
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em 31/12/2008 EN
Relevância na Pesquisa
46.7%
A number of synthesized chemical molecules suffer from low aqueous solubility problems. Enhancement of aqueous solubility, dissolution rate, and bioavailability of drug is a very challenging task in drug development. In the present study, solubility and dissolution of poorly aqueous soluble drug simvastatin (SIM) was enhanced using hydrophilic, low viscosity grade polymer hydroxypropyl methylcellulose (HPMC K3LV). The co-solvent evaporation method was developed for efficient encapsulation of hydrophobic drug in polymer micelles of HPMC K3LV. Spray drying and rotaevaporation method were applied for solvent evaporation. Co-solvent-evaporated mixture in solid state was determined by differential scanning calorimetry (DSC), X-ray diffraction studies (XRD), scanning electron microscopy, and Fourier-transform infrared spectroscopy. In vitro–in vivo studies were performed on co-solvent-evaporated mixture and compared with SIM. In vivo study was conducted on healthy albino rats (Wister strain), and formulations were administered by oral route. Results of the study show the conversion of crystalline form of SIM into amorphous form. The dissolution rate was remarkably increased in co-solvent-evaporated mixtures compared to SIM. co-solvent-evaporated mixtures showed better reduction in total cholesterol and triglyceride levels than the SIM. The low-viscosity grade HPMC acts as a surfactant...

Effect of physical state and particle size distribution on dissolution enhancement of nimodipine/PEG solid dispersions prepared by melt mixing and solvent evaporation

Papageorgiou, George Z.; Bikiaris, Dimitrios; Karavas, Evagelos; Politis, Stavros; Docoslis, Aristides; Park, Yong; Stergiou, Anagnostis; Georgarakis, Emmanouel
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Publicado em 06/10/2006 EN
Relevância na Pesquisa
46.54%
The physical structure and polymorphism of nimodipine were studied by means of micro-Raman, WAXD, DSC, and SEM for cases of the pure drug and its solid dispersions in PEG 4000, prepared by both the hot-melt and solvent evaporation methods. The dissolution rates of nimodipine/PEG 4000 solid dispersions were also measured and discussed in terms of their physicochemical characteristics. Micro-Raman and WAXD revealed a significant amorphous portion of the drug in the samples prepared by the hot-melt method, and that saturation resulted in local crystallization of nimodipine forming, almost exclusively, modification I crystals (racemic compound). On the other hand, mainly modification II crystals (conglomerate) were observed in the solid dispersions prepared by the solvent evaporation method. However, in general, both drug forms may appear in the solid dispersions. SEM and HSM microscopy studies indicated that the drug particle size increased with drug content. The dissolution rates were substantially improved for nimodipine from its solid dispersions compared with the pure drug or physical mixtures. Among solid dispersions, those resulting from solvent coevaporation exhibited a little faster drug release at drug concentrations lower than 20 wt%. Drug amorphization is the main reason for this behavior. At higher drug content the dissolution rates became lower compared with the samples from melt...

Comparison of Spray Freeze Drying and the Solvent Evaporation Method for Preparing Solid Dispersions of Baicalein with Pluronic F68 to Improve Dissolution and Oral Bioavailability

He, Xiuqiong; Pei, Lixia; Tong, Henry H. Y.; Zheng, Ying
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em 23/12/2010 EN
Relevância na Pesquisa
46.61%
The objective of this study was to prepare solid dispersions consisting of baicalein and a carrier with a low glass transition/melting point (Pluronic F68) by spray freeze drying (SFD). We compared these powders to those produced from the conventional solvent evaporation method. In the SFD process, a feeding solution was atomized above the surface of liquid nitrogen following lyophilization, which resulted in instantaneously frozen microparticles. However, solid dispersions prepared by the solvent evaporation method formed a sticky layer on the glass flask with crystalline baicalein separated out from the carrier. The powder samples were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), surface area measurement, differential scanning calorimetry, and Fourier transform infrared spectrometry. SEM and PXRD results suggested that the majority of baicalein in the SFD-processed solid dispersion was in the amorphous state, which has a higher specific surface area than pure baicalein. However, the majority of baicalein was recrystallized in the solid dispersion at the same composition prepared by the solvent evaporation method, which showed a similar dissolution rate to the physical mixture. SFD product was physically and chemically stable after being stored at 40°C with low humidity for 6 months. After enzyme hydrolysis...

Development, characterization and solubility study of solid dispersions of Cefuroxime Axetil by the solvent evaporation method

Arora, S. C.; Sharma, P. K.; Irchhaiya, Raghuveer; Khatkar, Anurag; Singh, Neeraj; Gagoria, Jagbir
Fonte: Medknow Publications & Media Pvt Ltd Publicador: Medknow Publications & Media Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
46.49%
Cefuroxime Axetil (Poorly water soluble drug), when prepared as solid dispersion showed improved solubility and dissolution. Therefore, the main purpose of this investigation was to increase the solubility and dissolution rate of Cefuroxime Axetil by the preparation of its solid dispersion with urea, using the solvent evaporation method. Physical mixtures and solid dispersions of Cefuroxime Axetil were prepared by using urea as a water-soluble carrier in various proportions (1:1, 1:2, 1:3, 1:4, 1:5, 1:6, and 1:7 by weight), by employing the solvent evaporation method. The drug release profile was studied and it was found that the dissolution rate and the dissolution parameters of the drug from the physical mixture as well as solid dispersion were higher than those of the intact drug. The Fourier Transform Infrared (FTIR) spectra revealed no chemical incompatibility between the drug and urea. Drug-polymer interactions were investigated using differential scanning calorimetry (DSC) and Powder X-Ray Diffraction (PXRD).

Nanoprecipitation is more efficient than emulsion solvent evaporation method to encapsulate cucurbitacin I in PLGA nanoparticles

Alshamsan, Aws
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.54%
Cucurbitacin I is a hydrophobic molecule that exerts a degree of polarity, which is expected to complicate its loading in PLGA nanoparticles by the classical emulsion solvent evaporation technique. In the current study, variants of emulsion solvent evaporation method were used to prepare PLGA nanoparticles of cucurbitacin: CI-NP1 (single emulsion starting with 1000 μg drug), CI-NP2 (double emulsion starting with 250 μg drug), and CI-NP3 (double emulsion starting with 500 μg drug). On the other hand, CI-NP4 was prepared by nanoprecipitation (starting with 1000 μg drug). In CI-NP1, cucurbitacin I encapsulation efficiency (EE) was 1.29%. The employment of double emulsion, in CI-NP2 and CI-NP3, increased cucurbitacin I EE to 4.8% and 7.96%, respectively. Nanoprecipitation significantly increased the EE of cucurbitacin I to 48.79% in CI-NP4. It is likely that cucurbitacin I escapes with the organic solvent after the emulsification step to the aqueous phase leading to ineffective entrapment in the polymeric matrix. Avoiding emulsification seems efficient in increasing cucurbitacin I disposition in the instantly-precipitating NPs. Therefore, nanoprecipitation method increases cucurbitacin I entrapment in PLGA NPs and possibly other water-insoluble polar drugs.

In vitro assessment of solvent evaporation from commercial adhesive systems compared to experimental systems

NIHI, Fabio Mitugui; FABRE, Hebert Samuel Carafa; GARCIA, Georges; FERNANDES, Karen Barros Parron; FERREIRA, Flaviana Bombarda de Andrade; WANG, Linda
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.67%
Solvents should be properly evaporated after application to dental substrates. The aim of this study was to assess the evaporation of commercial, experimental and neat solvents. The tested null hypotheses were that there are no differences in solvent evaporation regardless of its formulation and over time. Evaporation from commercial adhesive systems (Scotchbond Multipurpose Primer, Scotchbond Multipurpose Adhesive, Prime & Bond NT, Multi Bond, Excite, Single Bond 2, Adhese Primer, Adhese Bond, Xeno III A and Xeno III B) and experimental primers (35% HEMA plus 65% acetone or ethanol or water v/v) were compared to neat solvents (acetone, ethanol and water). Samples (10 µL) of these products were dripped into glass containers placed on a digital precision balance. Evaporation was assessed at 0, 5, 10, 15, 30, 60, 120, 300 and 600 s times to calculate mass loss. Data were analyzed statistically by ANOVA and Bonferroni's correction (a=0.05). Acetone-based products exhibited a remarkable capacity to evaporate spontaneously over time. Neat acetone evaporated significantly more than the HEMA-mixtures and the commercial formulations (p<0.05). The incorporation of monomers and other ingredients in the commercial formulations seem to reduce the evaporation capacity. Solvent evaporation was time and material-dependent.; O solvente deve ser adequadamente evaporado após aplicação ao substratos dentários. O objetivo deste estudo foi avaliar a evaporação de formulações comerciais...

Effects of solvent evaporation on water sorption/solubility and nanoleakage of adhesive systems

CHIMELI,Talita Baumgratz Cachapuz; D'ALPINO,Paulo Henrique Perlatti; PEREIRA,Patrícia Nóbrega; HILGERT,Leandro Augusto; DI HIPÓLITO,Vinicius; GARCIA,Fernanda Cristina Pimentel
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2014 EN
Relevância na Pesquisa
46.61%
Objective: To evaluate the influence of solvent evaporation in the kinetics of water diffusion (water sorption-WS, solubility-SL, and net water uptake) and nanoleakage of adhesive systems. Material and Methods: Disk-shaped specimens (5.0 mm in diameter x 0.8 mm in thickness) were produced (N=48) using the adhesives: Clearfil S3 Bond (CS3)/Kuraray, Clearfil SE Bond - control group (CSE)/Kuraray, Optibond Solo Plus (OS)/Kerr and Scotchbond Universal Adhesive (SBU)/3M ESPE. The solvents were either evaporated for 30 s or not evaporated (N=24/per group), and then photoactivated for 80 s (550 mW/cm2). After desiccation, the specimens were weighed and stored in distilled water (N=12) or mineral oil (N=12) to evaluate the water diffusion over a 7-day period. Net water uptake (%) was also calculated as the sum of WS and SL. Data were submitted to 3-way ANOVA/Tukey's test (α=5%). The nanoleakage expression in three additional specimens per group was also evaluated after ammoniacal silver impregnation after 7 days of water storage under SEM. Results: Statistical analysis revealed that only the factor "adhesive" was significant (p<0.05). Solvent evaporation had no influence in the WS and SL of the adhesives. CSE (control) presented significantly lower net uptake (5.4%). The nanoleakage was enhanced by the presence of solvent in the adhesives. Conclusions: Although the evaporation has no effect in the kinetics of water diffusion...

In vitro assessment of solvent evaporation from commercial adhesive systems compared to experimental systems

Nihi,Fabio Mitugui; Fabre,Hebert Samuel Carafa; Garcia,Georges; Fernandes,Karen Barros Parron; Ferreira,Flaviana Bombarda de Andrade; Wang,Linda
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
56.67%
Solvents should be properly evaporated after application to dental substrates. The aim of this study was to assess the evaporation of commercial, experimental and neat solvents. The tested null hypotheses were that there are no differences in solvent evaporation regardless of its formulation and over time. Evaporation from commercial adhesive systems (Scotchbond Multipurpose Primer, Scotchbond Multipurpose Adhesive, Prime & Bond NT, Multi Bond, Excite, Single Bond 2, Adhese Primer, Adhese Bond, Xeno III A and Xeno III B) and experimental primers (35% HEMA plus 65% acetone or ethanol or water v/v) were compared to neat solvents (acetone, ethanol and water). Samples (10 µL) of these products were dripped into glass containers placed on a digital precision balance. Evaporation was assessed at 0, 5, 10, 15, 30, 60, 120, 300 and 600 s times to calculate mass loss. Data were analyzed statistically by ANOVA and Bonferroni's correction (a=0.05). Acetone-based products exhibited a remarkable capacity to evaporate spontaneously over time. Neat acetone evaporated significantly more than the HEMA-mixtures and the commercial formulations (p<0.05). The incorporation of monomers and other ingredients in the commercial formulations seem to reduce the evaporation capacity. Solvent evaporation was time and material-dependent.