Seasonal changes of α-tocopherol in green marine algae (Caulerpa genus)

Abstract: Marine algae are a promising source of beneficial compounds for human use. Among these, pro‐vitamin A carotenoids and vitamins B, C, and E stand out. The objective of this study was to investigate seasonal variation of α‐tocopherol levels in 5 species of green marine algae of the Caulerpa genus. This research was carried out with both fresh and dry specimens; and, in addition, differences arising as a result of the drying process were examined. Analyses were carried out by high‐performance liquid chromatography (HPLC) using an isocratic system and a reversed‐phase C‐18 column. The distribution of α‐tocopherol throughout the year in Caulerpa genus was variable. All samples of both fresh and dried algae contained α‐tocopherol, except for the dried C. racemosa from March 2006. The drying process was responsible for losses of α‐tocopherol ranging from 21% to 93%.     

Thermal stability of polycaprolactone/Nafion blends prepared in the presence of 3‐aminopropyltriethoxysilane

Polycaprolactone (PCL) and Nafion blends were prepared in the presence of 3‐aminopropyltriethoxysilane (3‐APTEOS) by a sol–gel reaction. The presence of 3‐APTEOS allowed the preparation of macroscopically homogeneous self‐supported films of PCL/Nafion blends in a wider composition range. The thermal properties of the blends were evaluated by thermogravimetric analysis and differential scanning calorimetry. The thermal stability of the blends decreased as the Nafion content increased. The reduction of the thermal stability of PCL in the presence of Nafion was confirmed with Fourier transform infrared/photoacoustic spectroscopy, and it was attributed to the possible hydrolysis of PCL caused by the reaction with the SO₃H acid groups of Nafion. An opposite effect on the thermal stability of the blends was caused by the addition of 3‐APTEOS. The increase in the thermal stability of the blends with the increase in the 3‐APTEOS content was assigned to the neutralization of the acid groups of Nafion by the formation of an ionic complex. The differential scanning calorimetry results showed that PCL and Nafion were immiscible. The degree of crystallinity of PCL slightly increased with an increase in the Nafion content, whereas the melting temperature remained basically unchanged. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3701–3709, 2004     

Bactericidal Activity of a Self-Biodegradable Lysine-Containing Dendrimer against Clinical Isolates of Acinetobacter Genus

The genus Acinetobacter consists of Gram-negative obligate aerobic pathogens, including clinically relevant species, such as A. baumannii, which frequently cause hospital infections, affecting debilitated patients. The growing resistance to antimicrobial therapies shown by A. baumannii is reaching unacceptable levels in clinical practice, and there is growing concern that the serious conditions it causes may soon become incurable. New therapeutic possibilities are, therefore, urgently needed to circumvent this important problem. Synthetic cationic macromolecules, such as cationic antimicrobial peptides (AMPs), which act as membrane disrupters, could find application in these conditions. A lysine-modified cationic polyester-based dendrimer (G5-PDK), capable of electrostatically interacting with bacterial surfaces as AMPs do, has been synthesized and characterized here. Given its chemical structure, similar to that of a fifth-generation lysine containing dendrimer (G5K) with a different core, and previously found inactive against Gram-positive bacterial species and Enterobacteriaceae, the new G5-PDK was also ineffective on the species mentioned above. In contrast, it showed minimum inhibitory concentration values (MICs) lower than reported for several AMPs and other synthetic cationic compounds on Acinetobacter genus (3.2–12.7 µM). Time-kill experiments on A. baumannii, A. pittii, and A. ursingii ascertained the rapid bactericidal effects of G5-PDK, while subsequent bacterial regrowth supported its self-biodegradability.     

Novel hydrogels based on a high‐molar‐mass water‐soluble dimethacrylate monomer

This report describes the preparation and swelling behaviour of novel hydrogels based on a water‐soluble dimethacrylate monomer (EBisEMA), which is characterized by a relatively high molar mass (M_n ～ 1700 g mol^?1) and contains a high proportion of aliphatic ether bonds in its structure. This feature results in moderately crosslinked and flexible polymer networks. Significant differences were observed in degree of swelling, depending on the synthesis method employed to obtain the hydrogels. The equilibrium water sorption of EBisEMA photopolymerized in bulk was 68 wt% while that of EBisEMA photopolymerized in aqueous solution (0.5 g mL^?1) was 104 wt%. Thiol–methacrylate hydrogels were prepared by visible light photopolymerization of EBisEMA with a tetrafunctional thiol (PETMP) at various EBisEMA‐to‐PETMP molar ratios. These hydrogels contained unreacted thiol groups because of a faster homopolymerization reaction of EBisEMA. Hydrogels were also prepared in bulk by propylamine‐catalysed Michael addition reaction. No significant differences in swelling were observed between EBisEMA homopolymer and photocured EBisEMA–PETMP copolymer. Conversely, a marked increase in water uptake (110 wt%) was observed in the EBisEMA–PETMP hydrogels prepared by the Michael addition reaction catalysed by propylamine. These trends are explained in terms of a balance between the mass fraction of hydrophilic groups and the crosslinking density of the network. EBisEMA–PETMP hydrogels formulated with thiol in excess showed a noticeable tendency to adhere to diverse substrates, including paper, metals, glass and skin. This feature makes them especially attractive in applications for which adhesion is particularly critical such as dermatological patches. © 2018 Society of Chemical Industry     

Cavitation Clusters in Lipid Systems: The Generation of a Bifurcated Streamer and the Dual Collapse of a Bubble Cluster

Several studies have reported the use of high-intensity ultrasound (HIU) to induce the crystallization of lipids. The effect that HIU has on lipid crystallization is usually attributed to the generation of cavities but acoustic cavitation has never been fully explored in lipids. The dynamics of a particular cavitation cluster next to a piston like emitter (PLE) in an oil was investigated in this study. The lipid systems, which are important in food processing, are studied with high-speed camera imaging, laser scattering, and acoustic pressure measurements. A sequence of stable clusters was noted. In addition, a bifurcated streamer was detected, which exists within a sequence of clusters. This is shown to originate from two clusters on the PLE tip oscillating with a 180° phase shift in time with respect to one another. Finally, the collapse phase of the cluster is shown to involve a rapid (~10 μs) two-stage process. These results show that the dynamics of cluster formation and collapse is driven by HIU power levels and might have implications in lipid sonocrystallization.     

Nano/microfibers of EVA copolymer obtained by solution blow spinning: Processing,solution properties,and pheromone release application

Pheromones have been used for monitoring and control of insect pests in crops, reducing the use of pesticides. However, among obstacles for this technology to be more useful, is the control and time to release. In this way, this work aims the evaluation of the release of pheromones using micro/nanofibers of ethylene–vinyl acetate (EVA) produced by blow spinning. Solutions with 0.5–15 wt % EVA were prepared based on the solubility parameter of the copolymer. Fibers were obtained from solutions in the semidiluted concentration regime. Synthetic sex pheromones from the oriental fruit moth, Grapholita molesta and citrus leafminer Phyllocnistis citrella were incorporated into the micro/nanofibers. The morphology and structure of these fibers were evaluated employing field emission scanning electron microscopy and wide-angle X-ray diffraction. The fibers sizes (95–426 nm) were dependent on the feed rate of the solution. As a result, pheromone release has occurred linearly over 10 weeks, as determined by thermogravimetry analysis. The solubility parameter influences the amount incorporated in the fiber and the rate of pheromone release. The proposed fiber/pheromone system is interesting since it reduces the use of actives and can be used in several planting cycles and reused. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47647.     

Sunflower Protein Concentrates and Isolates Prepared from Oil Cakes Have High Water Solubility and Antioxidant Capacity

Increasing the applications of industrial by-products is of great interest. Therefore, in the present study, sunflower oil cake from a local oil manufacturing company was used to obtain soluble protein concentrates and isolates with different content of phenolic compounds. All the extraction procedures evaluated resulted in concentrates and isolates with water solubility higher than 75% but with different chemical composition, color and physicochemical properties (i.e. surface hydrophobicity, thermal stability, and polypeptide composition). Since no extraction process led to a complete extraction of phenolic compounds, all the products exhibited antioxidant activity, which depended on the concentration of such compounds. Phenolic compounds give a dark color to sunflower protein concentrates and isolates; nevertheless their final color tone was more dependent on the conditions used in the preparation process than on the amount of phenolic compounds in the product. The results demonstrate the value of sunflower industrial oil cake as a source of proteins with high water solubility, good physicochemical properties and antioxidant activity.     

Approximate calculation of conversion with kinetic normalization for finite reaction rates in wall‐coated microchannels

We consider the problem of mass transfer in a channel with wall reaction and present approximate results to describe the conversion profile. We report analytical solutions in both Graetz's and Lévêque's regime in cases where only (semi)numerical studies have been presented before. In particular, for first‐order kinetics under conditions of a fully developed concentration profile, an approximate procedure for conversion calculation is proposed for finite reaction rates. When the profile is developing, asymptotic limits are used to formulate accurate approximations in intermediate parametric ranges. Moreover, the effect of finite reaction rates in the corrections due to curvature or velocity profile nonlinearities are reported. Finally, we extend the previous results to an mth order “power‐law” wall reaction, so that kinetic normalization is achieved in suitable limits. These results are of relevance for the modeling and simulation of processes involving catalytic monoliths or microreactors. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

Hybrid organic–inorganic macromolecular photoinitiator system for visible-light photopolymerization

Hybrid organic–inorganic macrophotoinitiator bearing pendant tertiary amine groups (OI-AH) was prepared by hydrolytic condensation of a silane containing amino groups. The macromolecular amino-functionalized photoinitiator was used in combination with camphorquinone (CQ) for visible-light photo-polymerization. The OI-AH was incorporated into methacrylate resins at loadings between 1 and 10 wt.%. The photodecomposition of the CQ/OI-AH in methacrylate monomers under visible light irradiation (λ = 470 nm) was examined. The photolysis products of CQ/OI-AH were transparent at the irradiating wavelengths; consequently, the consumption of the CQ is accompanied by increased light intensity in the underlying lays. The clean and rapid photobleaching of CQ in combination with OI-AH makes this photoinitiator system very attractive for polymerization of thick sections. The evolution of monomer conversion versus irradiation time showed that the OI-AH is an efficient co-initiator of CQ because a fast reaction and high conversion of methacrylate groups result after 60 s irradiation with a LED source of 140 mW.