Binding of dipyridamole to phospholipid vesicles: a fluorescence study

AbstractBinding and localization of the vasodilator and antitumor drug coactivator dipyridamole (DIP) and one of its derivatives, RA25, to phospholipid vesicles of DMPC (dimyristoylphosphatidylcholine) and DPPC (dipalmitoylphosphatidylcholine) was studied using fluorescence spectroscopy as well as quenching of fluorescence. The analysis of fluorescence data indicates that neutral dipyridamole binds to the phospholipids in their liquid crystalline phase with an association constant of 950 M−1 and 1150 M−1 to DMPC and DPPC, respectively. Protonation of DIP leads to a 3-fold reduction of the association constant. For the gel phospholipid phase, the binding is smaller (a factor of 2), independently of pH, suggesting that the more flexible lipid packing in the liquid crystalline phase facilitates the binding of the drug. The association constant of RA25 neutral form is considerably lower than for DIP, being around 295 M−1. Fluorescence quenching with nitroxides TEMPO and stearic acid doxyl derivatives suggests the localization of DIP to be closer to the 5th carbon of alkyl chain. The quenching effect of 5-DSA below the lipid phase transition suggests that a strong static quenching may be operative. The quenching effect of 16-DSA is almost as great as that for 5-DSA below the phase transition, being even higher above the phase transition. This effect is probably due to the trans-gauche isomerization of the stearic acid nitroxide, making the encounter of its paramagnetic fragment with the DIP chromophore possible. Our data are consistent with DIP location close to the bilayer surface in the border of hydrophobic-polar heads interface which is similar to the data in micellar systems. In the case of RA25, the drug is in the outer part of the head group interface being much exposed to the aqueous phase and being significantly less accessible to the membrane nitroxide quenchers

Propuesta no convencional de un sistema de producción de cabras lecheras, bajo un enfoque sustentable en el rancho El Capulín en Mesas de Dolores, Valle de Bravo.

En el trabajo de tesis se realiza la propuesta de producción sustentable en un rebaño de cabras lecheras, basadas en el uso de pastoreo y la suplementación estratégica. Se realizó un análisis de la sustentabilidad del rancho considerando la metodología de MESMIS

Two-dimensional low resolution raman spectroscopy applied to fast discrimination of clinically relevant microorganisms: a whole-organism fingerprinting approach

The discrimination of the bacteria that cause gastroenteritis through classical microbiological methods is very efficient in the great majority of the cases. However, the high cost of chemicals and the time spent for such identifications, about four days, could generate serious consequences for the patients. Thus, the search for low cost spectroscopic methods which would allow a fast and reagentless discrimination of these microorganisms is extremely relevant. In this work the main microorganisms that cause gastroenteritis: E. coli, S. chroleraesuis, S. flexneri were studied. For each of the microorganisms sixty different dispersions were prepared using physiological solution as solvent and its Raman spectra recorded. The 1D spectra obtained were similar, making it very difficult to differentiate the microorganisms. However, applying the 2D correlation method, it was possible to identify the microorganisms evaluated using the synchronous spectrum as whole-organism fingerprinting in a reduced time interval (~10 h).A diferenciação de bactérias causadoras de gastrenterites através de métodos microbiológicos clássicos é muito eficiente, na maior parte dos casos. Todavia, o elevado custo dos reagentes e o tempo necessário para tais determinações, cerca de 4 dias, podem causar sérias conseqüências, quando os pacientes são crianças, idosos ou adultos com baixa resistência imunológica. Assim, a pesquisa por métodos espectroscópicos de baixo custo, que permitam tais determinações com pouco uso de reagentes e em curtos intervalos de tempo é extremamente relevante. Neste trabalho os principais microrganismos causadores de gastrenterites, E. coli, S. chroleraesuis, S. flexneri foram avaliados. Foram preparadas sessenta dispersões para cada um dos microrganismos, usando solução fisiológica como solvente, e seus espectros adquiridos. Os espectros obtidos foram muito similares, tornando muito difícil a diferenciação dos microrganismos. Entretanto, aplicando a teoria de correlação generalizada em 2D, foi possível diferenciar os microrganismos avaliados usando o espectro síncrono como impressão digital do organismo em um curto intervalo de tempo (~10h).7378Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Aminoiron(III)–porphyrin–alumina catalyst obtained by non-hydrolytic sol-gel process for heterogeneous oxidation of hydrocarbons

An aminoiron(III) porphyrin immobilized on an alumina matrix was prepared and used as catalyst for the oxidation of organic substrates. Powder alumina had been prepared by a non-hydrolytic sol-gel method through condensation of aluminum chloride with anhydrous ethanol. Then, iron(III) [5,10,15,20-tetrakis(2,6-dichloro-3-aminophenyl)-porphyrin] was immobilized on the alumina powder under magnetic stirring, reflux, and inert atmosphere. Ultraviolet–visible and infrared spectroscopies, powder X-ray diffraction, scanning electron microscopy and thermal analysis were applied for characterizing the resulting material, confirming that the ironporphyrin was immobilized on the alumina support. The catalytic activity of ironporphyrin/alumina was evaluated in the oxidation of (Z)-cyclooctene and cyclohexane and in the Baeyer-Villiger oxidation of cyclohexanone using iodosylbenzene or hydrogen peroxide as oxygen donors. The novel immobilized catalyst proved to be a promising system for the efficient and selective oxidation of the organic substrates with 85–92% selectivity to the epoxide in the oxidation of alkenes and 25–41% to the ketone in the oxidation of cyclohexane. As for the Baeyer-Villiger oxidation of cyclohexanone, good conversion to ԑ-caprolactone was observed as well. The material is a reusable heterogeneous catalyst, which makes it more economically feasible than its homogeneous counterpar

Synthesis of indium tin oxide nanoparticles by a nonhydrolytic sol-gel method

Indium tin oxide nanoparticles were synthesized in two different sizes by a nonhydrolytic sol-gel method. These powders were then transformed into ITO via an intermediate metastable state at between 300 and 600 ºC. The presence of characteristic O-In-O and O-Sn-O bands at 480 and 670 cm-1 confirmed the formation of ITO. The X-ray diffraction patterns indicated the preferential formation of metastable hexagonal phase ITO (corundum type) as opposed to cubic phase ITO when the reflux time was less than 3 h and the heat treatment temperature was below 600 ºC. Particle morphology and crystal size were examined by scanning electron microscopy

Polylactic acid scaffolds obtained by 3D printing and modified by oxygen plasma

The purpose of tissue engineering is to repair, replace, and regenerate tissues and organs. For this aim, materials supports, as polylactic acid (PLA) are used. PLA is a thermoplastic polymer that presents biodegradability, biocompatibility and good processability. PLA scaffolds can accurately constructed by 3D printing. Then, the objectives of this work were to modify the hydrophobic surface of PLA scaffolds using oxygen plasma and to study the cell viability and proliferation. The characterization was done by AFM, contact angle, FTIR and studies of proliferation and cell viability. Results showed that the material acquired hydrophilic properties by the presence of oxygen reactive species and by contact angle decrease. It was also observed an increase in the surface roughness. We can conclude that although the surface modifications were effective and the PLA scaffolds were not cytotoxic, there were no improvements in the proliferation process with the studied osteo-1 lineage cells.

Synthesis and biocompatibility of an experimental glass ionomer cement prepared by a non-hydrolytic sol-gel method

The aims of this study were to demonstrate the synthesis of an experimental glass ionomer cement (GIC) by the non-hydrolytic sol-gel method and to evaluate its biocompatibility in comparison to a conventional glass ionomer cement (Vidrion R). Four polyethylene tubes containing the tested cements were implanted in the dorsal region of 15 rats, as follows: GI - experimental GIC and GII - conventional GIC. The external tube walls was considered the control group (CG). The rats were sacrificed 7, 21 and 42 days after implant placement for histopathological analysis. A four-point (I-IV) scoring system was used to graduate the inflammatory reaction. Regarding the experimental GIC sintherization, thermogravimetric and x-ray diffraction analysis demonstrated vitreous material formation at 110oC by the sol-gel method. For biocompatibility test, results showed a moderate chronic inflammatory reaction for GI (III), severe for GII (IV) and mild for CG (II) at 7 days. After 21 days, GI presented a mild reaction (II); GII, moderate (III) and CG, mild (II). At 42 days, GI showed a mild/absent inflammatory reaction (II to I), similar to GII (II to I). CG presented absence of chronic inflammatory reaction (I). It was concluded that the experimental GIC presented mild/absent tissue reaction after 42 days, being biocompatible when tested in the connective tissue of rats.O objetivo deste estudo foi demonstrar a sinterização pelo método sol-gel não-hidrolítico de um cimento de ionômero de vidro experimental (CIV) e avaliar sua biocompatibilidade em relação a um cimento de ionômero de vidro convencional (Vidrion R). Quatro tubos de polietileno contendo os cimentos testados foram implantados no dorso de 15 ratos, da seguinte maneira: GI - CIV Experimental e GII - CIV Convencional. A lateral do tubo foi considerada Grupo Controle. Os ratos foram sacrificados em 7, 21 e 42 dias pós-implantação para análise histopatológica. Uma escala de I a IV foi utilizada como sistema de score para graduar a reação inflamatória. Em relação à sinterização do CIV experimental, as análises termogravométrica e por difração de raio-x demonstraram a formação de material vítreo aos 110oC pelo método sol-gel. Para o teste de biocompatibilidade, os resultados mostraram uma reação inflamatória moderada para o GI (III), severa para o GII (IV) e branda para o Grupo Controle (II) aos 7 dias. Após 21 dias, GI apresentou uma reação branda (II); GII, moderada (III) e Grupo Controle, branda (II). Aos 42 dias, GI apresentou uma reação inflamatória branda/ausente (II a I), similar ao GII (II a I). O Grupo Controle demonstrou ausência de reação inflamatória (I). Concluiu-se que o CIV Experimental apresentou reação tecidual branda/ausente após 42 dias, sendo biocompatível quando testado em tecido conjuntivo de ratos