RESUMEN

Poly(3-hydroxybutyrate) (PHB)-based films containing Poly(ethylene glycol) (PEG), esterified sodium alginate (ALG-e) and polymeric additives loaded with Ag nanoparticles (AgNPs) were obtained by a conventional casting method. AgNPs were produced in aqueous suspension and added to polymeric gels using a phase exchange technique. Composite formation was confirmed by finding the Ag peak in the XRD pattern of PHB. The morphological analysis showed that the inclusion of PEG polymer caused the occurrence of pores over the film surface, which were overshadowed by the addition of ALG-e polymer. The PHB functional groups were dominating the FTIR spectrum, whose bands associated with the crystalline and amorphous regions increased after the addition of PEG and ALG-e polymers. Thermal analysis of the films revealed a decrease in the degradation temperature of PHB containing PEG/AgNPs and PEG/ALG-e/AgNPs, suggesting a catalytic effect. The PHB/PEG/ALG-e/AgNPs film combined the best properties of water vapor permeability and hydrophilicity of the different polymers used. All samples showed good antimicrobial activity in vitro, with the greater inhibitory halo observed for the PEG/PEG/AgNPs against Gram positive S. aureus microorganisms. Thus, the PHB/PEG/ALG-e/AgNPs composite demonstrated here is a promising candidate for skin wound healing treatment.

RESUMEN

Kefir is a probiotic that has several health promising properties. Its grains can form microbial films on different types of substrates. In the present work, the surface characteristics of kefir biofilms associated with Maytenus rigida Mart. extract were minutely studied. Three different concentrations of plant extract were included in the biofilm forming solutions, where fresh grains of kefir were inoculated. The results showed that the plant extract was successfully incorporated into the exopolysaccharide matrix of the biofilm. The main chemical components found linked to the plant extract were triterpenes. The crystallinity of biofilms increased with the addition of the plant extract. The morphology revealed that at low concentrations of the extract there was a prevalence of lactobacilli, while at high concentrations yeasts were more observed. Adhesion and wettability were higher for biofilm with less extract. These results revealed that a combination of plant extract and kefir's exopolysaccharide could form biofilms with chemical and topographic properties of great interest in regenerative medicine.

Asunto(s)

RESUMEN

In the present study, supramolecular polyelectrolyte complexes (SPEC) based on a cyclodextrin-grafted chitosan derivative and carrageenan were prepared and evaluated for controlled drug release. Samples were characterized by FTIR, SEM, and ζ-potential measurements, which confirmed the formation of the polymeric complex. The phenolphthalein test confirmed the presence and availability of inclusion sites from the attached ßCD. Silver sulfadiazine was used as the model drug and the association with the SPEC was studied by FTIR and computational molecular modeling, using a semi-empirical method. DRS and TEM analyses have shown that Ag+ ions from the drug were reduced to form metallic silver nanostructures. In vitro tests have shown a clear bacterial activity toward Gram-positive bacteria Staphylococcus aureus and Enterococcus durans/hirae and Gram-negative bacteria Klebsiella pneumoniae and Escherichia coli. Finally, this work shows that ßCD-chitosan/carrageenan supramolecular polyelectrolyte complexes hold an expressive potential to be applied as a polymer-based system for controlled drug release.

Asunto(s)

RESUMEN

Here we report the preparation of a trimethoprim/2-hydroxypropyl-γ-cyclodextrin inclusion complex along with a physicochemical study, structural characterization, and molecular modeling of the complex. As main results, we observed from phase-solubility studies at two temperatures (20 °C and 35 °C) that the association constants decrease with increasing temperature. Values for K(1:1) constant were of the same magnitude order of those found for the parent γ-CD. The inclusion orientation as evidenced by ROESY measurements involves the inclusion of the 3,4,5-trimethoxybenzyl ring in the CD cavity from the larger rim. This is in agreement with semiempirical molecular modeling calculation.

Asunto(s)

RESUMEN

A surface tension technique was used to determine the critical aggregation concentration (cac) of a yellow and a red dye in relation to the presence of the anionic surfactant sodium dodecylbenzene sulfonate (DBS) and to temperature changes in buffered aqueous solutions. The cac values of the yellow dye increase from 25 to 45 degrees C (from 41.37 to 50.32 mg L-1) and decrease from 45 to 55 degrees C (from 50.32 to 38.72 mg L-1). The cac values for the red dye/DBS aggregates decrease (from 124.52 to 88.50 mg L-1) from 25 to 55 degrees C. Adsorption of the two dyes onto a mesoporous aminopropyl silica (Sil-NH2) was also studied. The adsorption of the yellow dye increases with an increase in temperature from 25 to 55 degrees C. In the presence of DBS the adsorption on Sil-NH2 for the yellow dye decreases, and for the red dye increases from 25 to 55 degrees C. Adsorptions occurred below and above the cac of the anionic dyes/DBS aggregates. Adsorption of the dyes onto Sil-NH2 fitted well to the Langmuir, Freundlich, and Redlich-Peterson adsorption models. However, in the presence of DBS, only the Freundlich model fit the experimental adsorption data at low dye concentrations (less than 400 mg L-1). In this case, the Redlich-Peterson model was only fitted to the red dye adsorption data. The magnitude of the Dubinin-Radushkevich energetic parameters (E, from 7.00 to 15.00 kJ mol-1) indicates that the adsorption of the dyes onto Sil-NH2, in the absence and in the presence of DBS, is controlled by water adsorbed/dye in solution ion-exchange interactions. It is observed that the values of DeltaadsH are positive for both dyes and the values are quite similar to each other. The exception is the adsorption of the yellow dye in the presence of DBS, which is slightly exothermic. The DeltaadsG values are all negative. However, the interactions of the dyes with Sil-NH2 silica are more spontaneous in the presence of the surfactant. The positive adsorption entropy values (DeltaadsS) for the interaction of the dyes suggest that entropy is a driving force of the dye adsorptions. However, the entropic contribution is higher for the adsorptions in the presence of DBS. It was suggested that the chemical structures of the dyes play an important role in the formation of the dye/DBS aggregates and in dye adsorption onto the aminopropyl silica.

Asunto(s)

RESUMEN

In this work silica gels have been prepared by a sol-gel method using tetraethylorthosilicate as gel precursor. The tetraruthenated porphyrins H2(3-TRPyP), Co(3-TRPyP), and H2(4-TRPyP) were incorporated into the systems during gel formation without problems commonly found in the process, such as aggregation. Spectroscopic studies of the resulting silica gels revealed the presence of absorption bands in the range 200-400 nm associated with the transitions of the groups ruthenium-bipyridine, along with the Soret band at the same wavelengths observed in solution. The porphyrins were found to preserve fluorescence emission properties in the range 650-700 nm even after the aging period. Study of the thermal behavior and decomposition kinetics evidenced that the porphyrin H2(4-TRPyP) is the least stable of the group and that all compounds decompose according to first-order kinetics.

Asunto(s)

RESUMEN

In this study, the aminopropyl-silica (Sil-NH(2)) was used to adsorb a yellow- and a red-dye from aqueous solutions at pH 4.0. New data concerning the influence of the anionic surfactant SDS on the adsorption data was obtained. All interactions occurred below the cmc values of the Sil-NH(2)/anionic dyes aggregates. A rise of temperature accelerates the mass transfer of the red-dye into the Sil-NH(2) surface, while the yellow-dye adsorption decreased. The presence of SDS increased the adsorption quantities in relation to the temperature increasing. The exception is observed for the yellow-dye adsorption at 55 degrees C. So, it is suggested that the chemical structure of the dye, as well as the presence and position of its sulfonate groups are important factors that affect the anionic dye/SDS aggregations and the adsorption quantities. The solid-phase interactions of dyes data present good fittings to the Avrami kinetic model, where from two to four kinetic regions were found, taking into account the variations of the contact time and temperature. The presence of several values of Avrami constants, namely k(Av) and n, has been attributed to the occupation of both the surface and the internal adsorption sites of the aminopropyl-silica.

Asunto(s)

RESUMEN

Procura-se identificar os sintomas psiquiátricos mais comumente encontrados nos acadêmicos da Faculdade de Medicina da Universidade de Passo Fundo, incluindo os níveis que sao mais freqüentes. Analisou-se amostra de 75 por cento dos alunos, abservando-se que 41 por cento apresentavam sintomas sugestivos de alteraçoes psicóticas e 8.7 por cento alteraçoes neuróticas. O menor índice foi encontrado no 6§ nível com 16 por cento dos alunos com sintomas. Ressalta-se a necessidade de melhor acompanhamento dos alunos e reforma curricular.

Asunto(s)