Resumo em Inglês:

We developed a colorimetric and fluorescence dual-signal sensor for detecting lipase activity based on methyl thioglycolate (MT) functionalized gold nanoparticles (MT-AuNPs) and CdS quantum dots (CdS QDs). It is the first time that was developed a dual-signal sensing strategy for lipase activity based on the inner-filter effect (IFE) between MT-AuNPs and CdS QDs. This probe system (MT AuNPs + CdS QDs) is sensitive and has selective response to the concentration of the lipase, and MT-AuNPs and CdS QDs played as transducer and fluorescer, respectively. The addition of lipase triggered the accumulation and change of color in CdS QDs and MT-AuNPs solution, it also makes the fluorescence intesity of CdS QDs significantly recover. The limit of detection (LOD) was as low as 0.039 μg mL-1 for colorimetric detection as well as 0.012 μg mL-1 for the fluorescence method. This method has been successfully used in the detection of commercial lipases. We believe it would open up a new path for the sensitive and high throughput lipase assay using nanobiosensor.

Resumo em Inglês:

This work aimed to compare two different catalysts in the production of a long chain ketone, intermediate in the production of hydrocarbons, during pyrolysis of tetradecanoic acid as a model fatty acid. The studied variables were the temperature, 450 and 600 ºC, and catalysts, γ-Al2O3 and Nb2O5, the latter has never been studied under such conditions. Pyrolysis experiments were performed in a micro-pyrolyzer coupled to a gas chromatograph with mass spectrometry detector (GC-MS). In all pyrolysis conditions, 14-heptacosanone was formed in varied amounts. Under the best conditions, for pyrolysis at 600 ºC, using γ-Al2O3 as catalyst, the yield of 14-heptacosanone was 18% and the yield of hydrocarbons 24%. The major hydrocarbon product obtained was 1-dodecene. Among the partially deoxygenated compounds, the main products were the ketones 14-heptacosanone and 2-pentadecanone. The present experimental work confirmed also the possibility to obtain hydrocarbons having a chain length longer than the chain length of the original fatty acid reagent, due to a ketonization route followed by decarbonylation.

Resumo em Inglês:

Methylammonium lead iodide (MAPbI3), used as light-harvesting layer in solar cell devices, has attracted great attention from scientific community due to its excellent photovoltaic performance. In this work, we have shown a comprehensive study on the hybrid organic-inorganic MAPbI3 perovskite growth mechanism from irregular small particles to cuboid shape followed by hopper-type morphology through a systematically change on both the temperature and lead source concentration during the solution synthesis process. Indeed, we have observed very interesting hopper growth resulting in a pyramid-hollow like morphology. We have explained the morphology evolution by taking into account thermodynamics growth, which compete with kinetics growth under nonequilibrium conditions.

Resumo em Inglês:

Three new triterpenes, 3,4-seco-3,11β-epoxyfriedel-4(23)-en-3β-ol (1), friedelan-3α,11β diol (2), 7β,26-epoxyfriedelan-3a,7a-diol (3), a mixture of two new triterpenes 3α-hydroxyfriedelan-29-yl palmitate (4) and 3α-hydroxyfriedelan-29-yl stearate (5) and eleven known compounds were obtained from the hexane extract of Maytenus quadrangulata leaves. The structures and the relative stereochemistry of the new triterpenes were established through 1D/2D nuclear magnetic resonance (NMR), high resolution mass spectrometry (HRMS), and Fourier transform infrared (FTIR) spectral data. The hexane extract and isolated compounds were submitted to the cytotoxicity assays against leukemia (THP-1 and K562), ovarian (TOV-21G) and breast cancer (MDA-MB-231) cell lines. Compounds 1, 2 and 11β-hydroxyfriedelan-3-one (15) displayed high cytotoxicity and selectivity against leukemic cells when compared to positive control cytarabine (for THP-1) and imatinib (for K562). Furthermore, compound 2 showed similar cytotoxicity and an enhanced selectivity towards ovarian and breast cells in comparison to positive control etoposide.

Resumo em Inglês:

A chemical investigation of the stem of Waltheria indica (Malvaceae) yielded twelve 4-quinolone alkaloids, which were primarily waltheriones. These were waltherione A (1), waltherione B (2), waltherione C (3), waltherione G (4), waltherione H (5), waltherione J (6), waltherione L (7), waltherione P (8), chamaedrone (9), 8-deoxy-antidesmone (10), antidesmone (11), and the previously unreported alkaloid N-methoxy-waltherione A (12). These alkaloids belong to an unusual class of 4-quinolones and therefore, have chemosystematic significance for distinguishing the Waltheria and Melochia genera from the rest of the Malvaceae family. The ability of the alkaloid isolates to reverse the phenotypic expression of fluconazole-resistance was tested by using a mutant strain of Saccharomyces cerevisiae that expressed a Candida albicans transporter. Of the isolates tested, waltherione G afforded a positive result. Leishmanicidal activity and bactericidal tests were also performed using the isolated alkaloids, which showed promising results.

Resumo em Inglês:

Poly(ethylene oxide-co-dimethylsiloxane) was thermally immobilized on silica particles-Si(PEO)-to separate small polar compounds with water-rich mobile phases. Poly(ethylene oxide-co-dimethylsiloxane) content on Si(PEO) stationary phase was optimized using a central composite design. Infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis morphologically and structurally characterized the optimized material. Separation of standard test mixtures showed that the Si(PEO) phase had a typical reversed-phase elution order. However, the Si(PEO) phase retained polar compounds better than C18 or aqueous C18 phases under water-rich mobile phases. Under this condition, small changes in the acetonitrile fraction resulted in a marked increase in the retention of some polar drugs on the Si(PEO) phase. A typical condition observed in per aqueous liquid chromatography separations, a more environmentally friendly liquid chromatography approach. On the other hand, hydrophobic compounds showed lower mass transfer rates due to their low solubility in the aqueous mobile phase. Thus, the Si(PEO) phase was more suitable and efficient for separating polar or hydrophilic compounds.

Resumo em Inglês:

Mercury (Hg) contamination of oceans is rapidly increasing, however Hg bioaccumulation in pinnipeds has been understudied. Here, we report for the first time Hg concentration in liver tissues of South American fur seals (Arctocephalus australis) in South and Southeast Brazil. Hg concentration was determined in twenty-five fur seals’ specimens found stranded along the coast of the Southwestern Atlantic Ocean. Samples were digested using the microwave technique and quantified by cold vapor generation atomic fluorescence spectrometry technique. The average Hg concentration was 6.37 mg kg-1 (wet weight), with a minimum concentration of 0.09 mg kg-1 and the highest concentration of 15.58 mg kg-1. No correlation between biological variables (sex, total length and weight) and Hg concentration in A. australis liver were found. The results presented here are of great importance to establish baselines for future evaluations of Hg contamination in marine mammals and the effects of this environmental problem in animal health.

Resumo em Inglês:

The main objective of this work was to develop a nanoemulsion based on linseed oil and betulinic acid, stabilized with Pluronic F127 and polyglycerol polyricinoleate, for anticancer applications. The nanoemulsions were synthesized by ultrasound and evaluated for in vitro cytotoxicity, particle size, polydispersity index, zeta potential, morphology, encapsulation efficiency, storage stability, rheology and in vitro release kinetics. In vitro cytotoxicity assays were performed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay (72 h) against HCT-116 (colorectal carcinoma), SNB-19 (glioblastoma), NCI-H460 (lung carcinoma) and L-929 (normal fibroblasts) cells. The determination of 50% inhibitory concentration (IC50) showed an increased selectivity for the emulsified betulinic acid when compared to its free form for the HCT-116 cells. The IC50 values for the synthesized nanoemulsions showed a range from 3.2 to 3.7 µM (HCT-116), 5.6 and 11.5 µM (NCI-H460), 5.8 and 7.3 µM (SNB-19) and > 16.5 µM for normal fibroblasts. In the 48 h in vitro release assays, it presented controlled release explained by the Korsmeyer-Peppas model, releasing 572.25 and 619.95 µg of betulinic acid in a controlled way, generating promising perspectives for the prolonged release of betulinic acid in anticancer applications.

Resumo em Inglês:

In this work, the influence of rolling passes on microstructure, corrosion behavior, electrochemical performance, and battery performance of AZ31 magnesium alloy was studied. The experimental results show that the grain size decreases first and then increases with rolling passes. Among them, the grain size of three passes rolled sample is the smallest, while the grain size of the four passes rolled sample is obviously refined and evenly distributed, accompanied by a small number of twins. Therefore, it exhibits more muscular discharge activity. In addition, the corrosion products of the four passes rolled samples are distributed loosely and evenly on the surface during immersion, which is easy to fall off, thus reducing the polarization. The surface of the discharged four passes rolled sample is flat, indicating that the dissolution is uniform, conducive to promoting the self-peeling of discharge products. The results show that the samples with four passes of rolling have high electrochemical activity and anode efficiency. The average cell voltage and anodic efficiency of the four passes rolled anode for Mg-air battery within 5 h at 10 mA cm-2 were 1.065 V and 56.4%, respectively. Therefore, the electrochemical performance of the four passes rolled sample is the best, and the process is more suitable for preparing magnesium alloy anode plate.

Resumo em Inglês:

A vapor-fed high temperature proton exchange ethanol electroreformer has been developed based on the use of a H3PO4-doped polybenzimidazole membrane to produce green hydrogen. As a key parameter, this article describes the influence of platinum weight percent (wt.%) in the catalyst formulation from different commercial catalysts (20, 40, 60, 80 wt.% Pt/C and Pt black) on the activity (related to the H2 production), energy consumption, and CO2 yields. The structural and morphological analysis reveal that an increase in Pt wt.% leads to the formation of bigger nanometric Pt particles, resulting in a decrease in the electrochemically active surface area. In terms of the ethanol electro-oxidation activity, the Pt wt.% impacts on the performance of the electroreformer, with the H2 flux that increase from 0.22 STP (standard pressure and temperature, 273.15 K and 105 Pa) m3 m-2 h-1 for Pt black to 1.47 STP m3 m-2 h-1 for 60 wt.% Pt/C. The Pt wt.% also impacts on the CO2 percentages, increasing from values in the range of 20-40% for the 20 wt.% Pt/C to 45-55% for the optimum 60 wt.% Pt/C and, finally, decreasing to values between 30-45% for Pt black. These values are, in overall, higher than those of low temperature (< 90 °C) ethanol electro-oxidation systems.