Synthesis and Characterization of Novel, Highly Crystalline Poly(vinyl alcohol) Microspheres for Chemoembolization Therapy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural modifications in silica sonogels prepared with additions of poly(vinyl alcohol)

Silica wet gels were prepared from acid sonohydrolysis of tetraethoxysilane (TEOS) and additions of poly(vinyl alcohol) (PVA)-water solution. Aerogels were obtained from supercritical CO(2) extraction. The samples were studied by thermal gravimetric (TG) analysis, small-angle X-ray scattering (SAXS), and nitrogen adsorption. The structure of wet gels can be described as a mass fractal with dimension D equal to 2.0 on the whole length scale experimentally probed by SAXS, from similar to 0.3 to similar to 15 nm. Pure and low-PVA-addition wet gels exhibit an upper cutoff accounting for a finite characteristic length xi of the mass fractal structure. Additions , of PVA increase without modifying D, which was attributed to a steric effect of the polymer in the structure. The pore volume fraction of the aerogels diminishes typically about 11% with respect to that of the wet gels, although nitrogen adsorption could be underestimating some porosity. The pore size distribution of the aerogels is shifted toward the mesopore region with the additions of PVA, in a straight relationship with the increase of xi in the wet gels. The thermal stability of the pore size distribution of the aerogels was studied up to 1000 degrees C.

Modifications in the correlation function in poly(vinyl alcohol)/silica hybrid wet gels

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of poly(vinyl alcohol) additions on the structure of silica xerogels

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal and photochemical stability of poly(vinyl alcohol)/modified lignin blends

A kraft lignin derivative (KLD) obtained by reaction with p-aminobenzoic acid/phthalic anhydride was blended with poly(vinyl alcohol) (PVA) by solution casting from DMSO. PVA and PVA/KLD films were exposed to ultraviolet radiation (24, 48, and 96 h) and analyzed by thermogravimetry (TG), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (H-1 NMR) spectroscopy, and scanning electron microscopy (SEM). PVA films show a loss of thermal stability due to irradiation. PVA/KLD reveals greater thermal stability than PVA and an increase in thermal stability after irradiation. These results suggest that the incorporation of KLD into PVA provides a gain in thermal and photochemical stability. FTIR, H-1 NMR, DSC, and TG results obtained for the blends suggest that intermolecular interactions between PVA and KLD chains are present. SEM micrographs revealed blend miscibility for a KLD blend content of up to 15 wt%, as observed at magnification of 1000 times. (c) 2005 Elsevier Ltd. All rights reserved.

Altering the adsorptive and electronic properties of Pt through poly(vinyl alcohol) adsorption

In the present paper we investigated the effect of adsorbed PVA on Pt electrodes on classic electrochemical processes such as hydrogen UPD, oxygen reduction and CO electro-oxidation. Upon adsorption PVA blocks roughly 50% of the hydrogen sites and can not be removed from the Pt surface through cycling in the potential range of 0.05-1.0 V vs. RHE. Potentiodynamic experiments under controlled hydrodynamic conditions provided by rotating disk electrode experiments showed a negative impact of the adsorbed PVA on the oxygen reduction reaction (ORR). Cyclic-voltammetry results revealed that not even CO was able to remove PVA from the Pt surface. Regarding the oxidation of CO, the adsorbed polymer positively shifted the CO oxidation peak potential, therefore higher potentials are required to free the Pt surface from CO poisoning. In situ Fourier transform infrared spectroscopy evidenced that the presence of PVA shifted the linearly bound CO frequency toward higher wavenumbers, a process found to be independent of the Pt surface orientation. In situ electrochemical X-ray absorption spectroscopy results showed that PVA also impacted the electronic properties of platinum by decreasing the occupancy of the Pt conducting 5d band. Our findings clearly support the efforts toward understanding the nature of the interaction between polymers and metallic surfaces as well as the impact on technological applications (e.g. in PEMFCs). © 2013 Elsevier Ltd. All rights reserved.

Photodynamic therapy for American cutaneous leishmaniasis: The efficacy of methylene blue in hamsters experimentally infected with Leishmania (Leishmania) amazonensis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Study of the interaction between cardiolipin bilayers and methylene blue in polymer-based Layer-by-Layer and Langmuir films applied as membrane mimetic systems

An increase of the reports involving mimetic systems has been observed. Briefly, these systems use biological phospholipids to exploit specific interactions between membrane-models and drugs. Here, the Layer-by-Layer (LbL) and Langmuir techniques were used to investigate the interaction between cardiolipin (CLP-negative phospholipid) and a cationic-like drug methylene blue (MB). Supported by a cationic polyelectrolyte (PAH), LbL films containing PAH/(CLP + MB) and PAH/(CLP + MB + AgNP) were grown up to 14 bilayers. The optical microscopy analysis revealed a decrease of the CLP vesicle sizes in the presence of MB as a possible consequence of the MB action onto the mechanical properties of the CLP membrane. From FTIR spectra, changes mainly related to peak position and band intensity and shape were observed in the spectra from PAH/CLP when in the presence of MB. The latter supports that the interactions between the phosphate and amine charged groups from CLP and PAH, respectively, established during the LbL film fabrication, besides the CLP hydrocarbon environment, are influenced by the presence of MB. Using the micro-Raman technique, a chemical mapping was build based on MB spectrum by resonance Raman scattering (RRS) and surface-enhanced resonance Raman scattering (SERRS). The later phenomenon was activated by Ag nanoparticles (AgNPs) trapped within the LbL film allowing collecting spectra for a single bilayer of PAH/(CLP + MB + AgNP). A rough estimation showed a SERRS amplification of 10(3) in comparison to RRS spectra. As a complementary approach, Langmuir films of CLP in the presence of co-spread MB were investigated through surface pressure vs mean molecular area (pi-A) isotherms. The results showed that for concentrations of MB below 100 mol%, the drug is expelled to water subphase for high values of surface pressure (condensed phase). For concentration at 100% and higher, the MB keeps bound to CLP floating monolayer. (C) 2010 Elsevier B.V. All rights reserved.

Deposition and characterization of BiVO4 thin films and evaluation as photoanodes for methylene blue degradation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Development of amorphous carbon protective coatings on poly(vinyl)chloride

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Glucose-6-phosphate dehydrogenase and glutathione reductase activity in methemoglobin reduction by methylene blue and cyst amine: study on glucose-6-phosphate dehydrogenase-deficient individuals, on normal subjects and on riboflavin-treated subjects

Os autores padronizaram métodos para a avaliação da atividade da glicose-6-fosfato desidrogenase e glutationa redutase. O princípio geral do primeiro método baseou-se na formação de metahemoglobina pelo nitrito de sódio, seguido da estimulação da via das pentoses pelo azul de metileno. Foram estudados 46 indivíduos adultos, sendo 23 do sexo masculino e 23 do feminino, não deficientes em glicose-6-fosfato desidrogenase (G6PD), com idades variando entre 20 e 30 anos. Os resultados revelaram que a redução da metahemoglobina pelo azul de metileno para sangue total, foram de 154.50 e 139.90 mg/min (p<0.05) respectivamente para o sexo masculino e feminino. Para hemácias lavadas os valores foram de 221.10 e 207.85 mg/min (n.s.) respectivamente. Estas observações permitiram concluir que ao se empregar hemácias lavadas e 0.7 g% de concentração de nitrito de sódio, por um lado não houve diferença entre os sexos e por outro, abreviou o tempo de leitura da quantidade residual de metahemoglobina para 90 minutos. A avaliação da atividade da glutationa redutase foi feita baseado no fato de que a cistamina (agente tiol) liga-se aos grupos SH da hemoglobina formando complexos. Estes complexos são revertidos pela ação da glutationa redutase, ocorrendo conjuntamente nesta reação a redução da metahemoglobina. Foram estudados 32 indivíduos adultos, sendo 16 do sexo masculino e 16 do feminino, não deficientes em G6PD, com idades variando entre 20 e 30 anos. Os resultados revelaram valores de redução da metahemoglobina pela cistamina de 81.27 e 91.13 mg/min (p<0.01) respectivamente para o sexo masculino e feminino. Estas observações permitiram concluir que o emprego de hemácias lavadas e 0.1 molar de concentração de cistamina torna possível a leitura da quantidade residual de metahemoglobina aos 180 minutos de incubação. A atividade da glutationa redutase avaliada por meio da redução da metahemoglobina pela cistamina, foi estudada em 14 indivíduos do sexo feminino antes e após o tratamento com 10 mg por dia de riboflavina durante 8 dias. Os resultados foram de 73.69 e 94.26 mg/min (p<0.01) antes e após o tratamento. Estas observações permitiram concluir que a oferta de riboflavina, mesmo para indivíduos normais, aumenta a atividade da glutationa redutase. Foram ainda avaliados 3 indivíduos da raça negra e deficientes em G6PD, sendo 2 do sexo masculino e 1 do feminino. Houve ativação parcial da G6PD e glutationa redutase, sendo estas alterações mais intensas nos indivíduos do sexo masculino. Considerando-se a raça e as características laboratoriais observadas, foi possível sugerir que a deficiência em G6PD verificada é do tipo Africano, bem como, permitiu considerar os indivíduos do sexo feminino coin o sendo heterozigoto para esta deficiência. Por fim, a análise dos resultados em seu conjunto permitiu concluir que os métodos propostos se mostraram eficientes para avaliar a atividade da G6PD e glutationa redutase. Esta última é dependente da via das pentoses, geradora de NADPH e da riboflavina, vitamina precursora de FAD.

Reliability of assessing dye penetration along root canal fillings using methylene blue

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Morphological Changes in Poly(Caprolactone)/Poly(Vinyl Chloride) Blends Caused by Biodegradation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and morphological changes in Poly(caprolactone)/poly(vinyl chloride) blends caused by UV irradiation

Films made from a blend of poly(epsilon-caprolactone) and poly(vinyl chloride) (PCL/PVC) retained high crystallinity in a segregated PCL phase. Structural and morphological changes produced when the films were exposed to high potency ultraviolet (UV) irradiation for 10 h were measured by UV-Vis spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). They were different to those observed with homopolymer PCL and PVC films treated under the same conditions. The FTIR spectra of the PCL/PVC blend suggest that blending decreased the susceptibility of the PCL to crystallize when irradiated. Similarly, although scanning electron micrographs of PCL showed evidence of growth of crystalline domains, particularly after UV irradiation, the images of PCL/PVC were fairly featureless. It is apparent that the degradation behavior is strongly influenced by the interaction of the two polymers in the amorphous phase.

Photodegradation of polycaprolactone/poly(vinyl chloride) blend

The photodegradation of a 1:1 w/w blend of polycaprolactone and poly(vinyl chloride) has been studied by following carbon dioxide emission during UV exposure. Similar measurements were performed for polycaprolactone and poly(vinyl chloride) homopolymers which were prepared and irradiated in the same way. It was found that the blend gave lower CO2 emission than either of the two homopolymers, indicating that the interaction of the two components in the blend provided a beneficial reduction of photodegradation. It is therefore deduced that the detailed morphological characteristics of the blend have a controlling influence over the photo-oxidation. (c) 2007 Elsevier Ltd. All rights reserved.