R. Benavides

Acute and chronic administration of gold nanoparticles cause DNA damage in the cerebral cortex of adult rats.

The use of gold nanoparticles is increasing in medicine; however, their toxic effects remain to be elucidated. Studies show that gold nanoparticles can cross the blood-brain barrier, as well as accumulate in the brain. Therefore, this study was undertaken to better understand the effects of gold nanoparticles on rat brains. DNA damage parameters were evaluated in the cerebral cortex of adult rats submitted to acute and chronic administration of gold nanoparticles of two different diameters: 10 and 30nm. During acute administration, adult rats received a single intraperitoneal injection of either gold nanoparticles or saline solution. During chronic administration, adult rats received a daily single injection for 28 days of the same gold nanoparticles or saline solution. Twenty-four hours after either single (acute) or last injection (chronic), the rats were euthanized by decapitation, their brains removed, and the cerebral cortices isolated for evaluation of DNA damage parameters. Our study showed that acute administration of gold nanoparticles in adult rats presented higher levels of damage frequency and damage index in their DNA compared to the control group. It was also observed that gold nanoparticles of 30nm presented higher levels of damage frequency and damage index in the DNA compared to the 10nm ones. When comparing the effects of chronic administration of gold nanoparticles of 10 and 30nm, we observed that occurred significant different index and frequency damage, comparing with control group. However, there is no difference between the 10 and 30nm groups in the levels of DNA damage for both parameters of the Comet assay. Results suggest that gold nanoparticles for both sizes cause DNA damage for chronic as well as acute treatments, although a higher damage was observed for the chronic one.

Effect of acute and long-term administration of gold nanoparticles on biochemical parameters in rat brain

The present study investigated stress oxidative parameters and activities of enzymes of the energy metabolism in various brain structures. Rats were subjected to acute and long-term administration of gold nanoparticles (GNPs) with mean diameters of 10nm and 30nm. Adult (60days old) male Wistar rats received a single intraperitoneal injection (acute administration; 70μg·kg-1) or repeated injections once daily for 28days (long-term administration; 70μg·kg-1) of saline solution or GNPs (10nm or 30nm). Twenty-four hours after administration of the final dose, the animals were killed and the cerebral structures were isolated for enzyme analysis. In this study, we observed that the thiobarbituric acid-reactive species and carbonyl protein levels were decreased after acute administration of GNPs, whereas the superoxide dismutase activity was increased after acute and long-term of GNPs. The catalase activity was affected by the administration of GNPs. Furthermore, we have not found change in the citrate synthase activity. The succinate dehydrogenase, malate dehydrogenase, complexes I, II, II-III and IV, and creatine kinase activities were altered. These results indicate that inhibition energy metabolism can be caused by oxidative stress.

Synthesis and Evaluation of Amides as Slip Additives in Polypropylene

Abstract In this study, we describe the synthesis of amides and evaluate their use as slip additive agents in polypropylene films. The additives N-isopropyl-stearamide and N,N-diisopropyl-stearamide were synthesized and characterized and then used to prepare masterbatches. Erucamide, a commercial masterbatch, was used as the reference standard. A 32 factorial experimental design was used to create the different compositions of slip additives in polymer films. The films were processed via flat-die extrusion and stored in an oven at a constant temperature of 40 °C for seven days. The following are the properties evaluated in the study: thermal decomposition temperature, fusion temperature, fusion enthalpy, coefficient of friction, surface energy, contact angle, and seal initiation temperature. The results were evaluated by analysis of variance (ANOVA) at a 90 % confidence interval. The analysis of the results showed that N-isopropyl stearamide and N,N-diisopropyl stearamide do not provide an adequate surface slip for polypropylene films at the conditions used in the study. In turn, at the same conditions, erucamide, the commercial amide, also does not provide the required surface energy for printing and lamination processes required for polypropylene films.

Effect of the scaling-up the reactions synthesis of the poly(styrene-co-acrylic acid) polyelectrolyte at laboratory level

Sulfonated styrene-acrylic acid copolymers have been used as an alternative polyelectrolyte membrane for applications in fuel cells. In this work, the raw copolymer has been prepared by a well studied solution copolymerization reaction method, but at two different capacity reactor conditions: 100 mL and 3 L. The main idea was to scale up the copolymer production for having enough material for future sulfonation reactions. The reaction conditions consisted of styrene/acrylic acid in a 94/6 % mol, BPO as radical initiator in a 0.045 % mol, divinyl benzene (DVB) as crosslinking agent at 0.25 %mol and the solvent diethyl benzene (DEB) in a 50/50 volume ratio with monomers. Temperature was kept at 90 °C and the system stirred at 200 rpm during 2 hours, for both reactors. Molecular weight of copolymers was obtained by means of GPC, glass transition (Tg) by DSC and decomposition temperature (Td) through TGA analysis.