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Zn-air batteries (ZABs) are a promising technology; however, their commercialization is limited by challenges, including those occurring in the electrolyte, and thus, gel polymer electrolytes (GPEs) and hydrogels have emerged as substitutes for traditional aqueous electrolytes. In this work, PVA/PAA membranes were synthesized by the solvent casting method and soaked in 6 M KOH to act as GPEs. The thickness of the membrane was modified (50, 100, and 150 µm), and after determining the best thickness, the membrane was modified with synthesized SiO2 nanospheres and multi-walled carbon nanotubes (CNTs). SEM micrographs revealed that the CNTs displayed lengths of tens of micrometers, having a narrow diameter (95 ± 7 nm). In addition, SEM revealed that the SiO2 nanospheres had homogeneous shapes with sizes of 110 ± 10 nm. Physicochemical experiments revealed that SiO2 incorporation at 5 wt.% increased the water uptake of the PVA/PAA membrane from 465% to 525% and the ionic conductivity to 170 mS cm-1. The further addition of 0.5 wt.% CNTs did not impact the water uptake but it promoted a porous structure, increasing the power density and the stability, showing three-times-higher rechargeability than the ZAB operated with the PVA/PAA GPE.

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Objective: To evaluate 11.5% polyacrylic acid (PA) containing 0.3% methylene blue (MB) dye as a photosensitizer for photodynamic therapy (PDT) of carious dentin. Methods: One hundred twenty molars were selected and the dentin was exposed for cariogenic challenge, where the molars were placed in brain heart infusion medium containing a standard strain of Streptococcus mutans (ATCC). Samples were randomly divided into eight groups (n = 15): S: saline, PA, MB: MB 0.3%, PA+MB: PA containing 0.3% MB + LLL: irradiation with low-level laser, PDT (MB): MB 0.3% + laser, PDT (PA): PA + laser, and PDT (PA+MB): PA containing 0.3% MB + laser. Carious dentin was collected before and after exposure to S. mutans. All samples of carious dentin were homogenized, diluted, and seeded in mitis salivarius bacitracin medium, and the cultures were incubated at 37°C for 15 days in anaerobic jars. The Wilcoxon test was used for analysis. Results: The percent microbial reduction achieved with each treatment was as follows: PDT (MB), 53.62%; PDT (PA+MB), 50.47%; PDT (PA), 46.73%; PA, 38.51%; MB, 19.75%; PA+MB, 17.18%; LLL, 12.83%; S, 5.99%. The greatest reductions in S. mutans growth occurred with PDT (MB), PDT (PA+MB), and PDT (PA) when compared to the S group (p = 0.0002, 0.0023, and 0.0232, respectively). Conclusions: PA containing 0.3% MB can be used as a photosensitizer for PDT to reduce S. mutans burden in carious dentin.

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HYPOTHESIS: The development of enzymatic conjugates with industrial applications require approaches with good scalability and batch-to-batch reproducibility. Hereof, nearly monodisperse iron oxide nanoparticles can be synthesized by thermal decomposition with high yields. A mixture of gallic and polyacrylic acid is used for the direct water transfer and later immobilization of laccase (Trametes versicolor). EXPERIMENTS: Nanoparticles were synthesized by thermal decomposition (13.1 nm by TEM, 50 nm by DLS) and later transferred to water by a ligand exchange method with polyacrylic acid and a polyacrylic acid/gallic acid mixture. Laccase was immobilized on water dispersions of both nanoparticles via a carbodiimide coupling. FINDINGS: The nanoparticles exhibited superparamagnetic behavior with insignificant values of iHc. The presence of gallic acid hindered the formation of multiple polyacrylic acid layers, therefore improving the colloidal stability of the nanoparticles (100 nm by DLS) after weeks of storage. Nanoparticles containing only polyacrylic acid showed poor activity (60% loading, 4.5% activity), while nanoparticles with both polyacrylic and gallic acids showed enzymatic activity values 4.4 times higher than the free enzyme (13% loading, 57% activity). The nanoparticles improved the storage stability (8 times) of the enzyme, its thermoresistance (4 times), and its reactivity against azo dyes Camalgite and Congo Red (21 and 27% increase, respectively). In addition to some improved catalytic properties in comparison to similar works, this is the first report of the use of gallic acid for both the direct transfer to water and enzyme immobilization on highly monodisperse, batch-to-batch reproducible superparamagnetic nanoparticles.

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In this work, we synthesized chitosan grafted-polyacrylic acid (CS-g-PA) through surface-initiated atom transfer radical polymerization (SI-ATRP). We also studied the adsorption process of copper and lead ions onto the CS-g-PA surface. Adsorption equilibrium studies indicated that pH 4.0 was the best pH for the adsorption process and the maximum adsorption capacity over CS-g-PA for Pb2+ ions was 98 mg·g-1 and for Cu2+ it was 164 mg·g-1, while for chitosan alone (CS), the Pb2+ adsorption capacity was only 14.8 mg·g-1 and for Cu2+ it was 140 mg·g-1. Furthermore, the adsorption studies indicated that Langmuir model describes all the experimental data and besides, pseudo-second-order model was suitable to describe kinetic results for the adsorption process, demonstrating a larger kinetic constant of the process was larger for Pb2+ than Cu2+. Compared to other adsorbents reported, CS-g-PA had comparable or even superior adsorbent capacity and besides, all these results suggest that the new CS-g-PA polymers had potential as an adsorbent for hazardous and toxic metal ions produced by different industries.

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El objetivo de este estudio fue valorar la microfiltración del ionómero de vidrio mejorado (Ketac Molar Easymix ®) con o sin el uso de acondicionador. Para lograr éste, se seleccionaron 40 terceros molares extraídos, limpios e hidratados. Se formaron dos grupos de 20 muestras de forma aleatoria, a los cuales se les realizó profilaxis y cavidades de clase V sobre la cara vestibular. Al grupo A se le colocó un acondicionador de ácido poliacrílico como indica el fabricante, antes del ionómero, y al grupo B se le colocó el ionómero directamente. Las muestras se sometieron a un proceso de termociclado y fueron sumergidas en azul de metileno al 1%, durante 30 minutos. Cada molar fue seccionado con disco de carburo, con cortes longitudinales en el centro de la preparación. Cada sección fue examinada minuciosamente al microscopio. Se calificaron las muestras y se obtuvo que el promedio de microfiltración para el grupo A fue de 2.06% y para el grupo B fue de 1.84%, sin representar diferencias significativas. Por lo que se concluye, con que no existen diferencias significativas en colocar acondicionador en este tipo de cavidades y con este material en particular.

The aim of the present study was to assess microleakage experienced by improved glass ionomer (Ketac Molar Easymix ®) with and without use of conditioner. In order to conduct this study, 40 third molars were used. Molars had previously been extracted, cleansed and hydrated. Two 20 randomly selected sample groups were established. Samples were subjected to prophylaxis and class V cavities were created on the vestibular (labial) surface of the teeth. Before ionomer application, and according to manufacturer's instructions, group A received a polyacrylic acid conditioner, whereas group B received direct ionomer application. All samples were subjected to a thermo-cycling process and then were immersed in a 1% methylene blue solution for 30 minutes. All molars were sectioned with carbide burr executing longitudinal cuts at the preparation's center. Each section was carefully examined under the microscope. Samples were rated and the following was observed: microleakage, for group A was 2.06% and for group B 1.84% which did not represent statistically significant differences. It can therefore be concluded that application of conditioner in this type of cavities and with this particular material does not cause statistically significant differences.

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CONTEXT: Bioadhesiviness of polyacrylic acid polymers make them promising hydrogels to design topical drug delivery systems, allowing a close contact with biological substrate as well as an enhanced local concentration gradient, both factors that may improve the biological performance of the drugs. AIM: Texture and bioadhesive properties of hydrogels were assessed by using texture analyzer and they were correlated with their rheological behavior and performance as drug delivery systems. METHODS: Aqueous dispersions of both polymers were prepared at 0.5%, 1.0% and 1.5% w/v. Hardness, compressibility, adhesiveness, cohesiveness, bioadhesion, continuous flow, oscillatory dynamic test and in vitro drug release were evaluated. RESULTS: Rheological and texture parameters were dependent on polymer concentration and C974P polymer built the strongest structures. Both 1.5% hydrogels presented high bioadhesion values. About 50% of the metronidazole (MTZ) was sustained released from hydrogels within 2 h with an initial burst release at early stage. After, the release rates were decreased and 10% of the MTZ was released in the next 10 h. The drug release process was driven by Fickian diffusion and complex mechanism for PP and C974P hydrogels, respectively. CONCLUSION: The set of results demonstrated that these hydrogels are promising to be used as topical controlled drug delivery system.

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Enzyme stability is critical in biotechnology, pharmaceutical and cosmetic industries. Investigations on this subject have drawn attention because of its practical application. Bromelain is a thiol-endopeptidase, obtained from pineapple (Ananas comosus), known for its clinical and therapeutic applications, particularly to selective burn debridement and improvement of antibiotic action and anti-inflammatory activities. To date, the use of bromelain in pharmacological or industrial applications is limited, due to commercial availability, costs, and sensitivity to pH and temperature. Therefore, a better understanding of enzyme stability would be of great interest. The aim of this study was to evaluate bromelain activity and stability in several pH (2.0 to 8.0) and in polyethylene glycol and polyacrylic acid solutions. We observed that bromelain was able to maintain its stability at pH 5.0 for the temperatures studied. PEG solutions increased bromelain stability, but PAA solutions had the opposite effect.

Estabilidade de enzimas é uma questão fundamental em indústrias biotecnológicas, farmacêuticas e cosméticas. As investigações sobre o assunto têm chamado a atenção por sua aplicação prática. A bromelina é uma tiol-endopeptidase, obtida a partir do abacaxi (Ananas comosus). É conhecida por suas aplicações clínicas e terapêuticas, especialmente para desbridamento seletivo de queimaduras, melhoria de ações antibiótica e de atividades anti-inflamatórias. Até o momento, a utilização da bromelina em aplicações farmacológicas industriais é limitada, devido à disponibilidade comercial, os custos, a sensibilidade ao pH e temperatura. Portanto, a maior compreensão da estabilidade desta enzima seria de grande interesse. O objetivo deste estudo foi avaliar a estabilidade da atividade da bromelina em vários pH (2,0 a 8,0) e em soluções de polietilenoglicol e de ácido poliacrílico. Observamos que a bromelina foi capaz de manter a sua estabilidade em pH 5.0, em todas as temperaturas estudadas. Soluções de PEG aumentaram a estabilidade da bromelina, enquanto que soluções de PAA obtiveram efeito oposto.

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