Biodegradable polyurethane nanocomposites containing dexamethasone for ocular route

The treatment of posterior segment ocular diseases, such as uveitis, by using eye drops and oral drugs is usually not effective due to the body's natural barriers to drug penetration. In this study, ocular implants to treat uveitis were synthesized by incorporating dexamethasone acetate, an important type of corticoid used in the treatment of some uveitis, into a biodegradable polyurethane containi clay nanoparticles. Biodegradable polyurethane nanocomposites having poly(caprolactone) oligomers as soft segments were obtained by delaminating clay particles within a polyurethane aqueous dispersion. The drug was incorporated into the polymer by dispersing it in the waterborne polyurethane followed by a drying step. Nanoparticles derived from clay were demonstrated to be able to tailor the mechanical properties of polyurethanes to achieve values that can match the properties of ocular soft tissues. Infrared spectra (FTIR) showed that the presence of clay particles was able to change the microphase separation process typical of polyurethanes. X-ray diffraction and small angle x-ray scattering (SAXS) results were explored to show that the incorporation of both dexamethasone acetate and nanocomponents derived from clay led to a less defined two-phase polyurethane. The presence of clay nanoparticles increased the rate of drug release measured in vitro. Human retinal pigment epithelial cells (ARPE-19) were cultured in contact with polyurethanes and polyurethane nanocomposites, and the viability of them (evaluated by using MTT assay after 7 days) showed that no toxic components were released from polyurethanes containing no drugs during the test.     

Factors associated with adiposity in normal weight female adolescents with adequate and high percent body fat: elaborating a risk model

Factors associated with adiposity in normal weight female adolescents with adequate and high percent body fat: elaborating a risk model. This study was carried out to evaluate the factors associated with adiposity in normal weight adolescents presenting appropriate or high percent body fat, who attended the public schools in Vi?osa county-Minas Gerais/Brazil. A total of 118 female adolescents at age range from 14 to 19 years and have already presented the menarche were evaluated. The adolescents were divided into 2 groups: G1 with high percent body fat and G2 with appropriate percent body fat. The following variables were evaluated: anthropometric, body composition, lifestyle and the family history of non-communicable chronic diseases. In subsample, the basal energy consumption was determined by indirect calorimetry. The G1-grouped adolescents showed higher values for most anthropometric and body composition variables (p < 0.001). No differences were observed (p > 0.05) for basal metabolism and metabolism of lean body mass, smoking habit, total energy consumption and protein and lipid as well between groups. When comparing the physical activity level, the G1 adolescents spent more time with 1-level sedentary activities whereas the G2 ones showed higher total caloric consumption with daily activities (p < 0.001). According to risk factors under analysis, the variables related to lifestyle, as distinguishing the use of sweeteners (OR = 13.47), provided higher contribution to excessive adiposity in the normal weight adolescents. The detailed analysis of the body composition as well as the risk factors associated with excessive body fat makes possible the early diagnosis and the development of more appropriate intervention means.     

Direct electron paramagnetic resonance monitoring of the peptide synthesis coupling reaction in polymeric support

This work demonstrates, for the first time, a time-resolved electron paramagnetic resonance (EPR) monitoring of a chemical reaction occurring in a polymeric structure. The progress of the coupling of a N^α-tert-butyloxycarbonyl-2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (Boc-TOAC) spin probe to a model peptide-resin was followed through EPR spectra. Progressive line broadening of EPR peaks was observed, indicative of an increased population of immobilized spin probe molecules attached to the solid support. The time for spectral stabilization of this process coincided with that determined in a previous coupling study, thereby validating this in situ quantitative monitoring of the reaction. In addition, the influence of polymer swelling degree and solvent viscosity, as well as of the steric hindrance within beads, on the rate of coupling reaction was also addressed. A deeper evaluation of the latter effect was possible by determining unusual polymer parameters such as the average site-site distance and site-concentration within resin beads in each solvent system.     

Melt Mixing of a Styrene/Butadiene Copolymer with an Aqueous Slurry of Zirconium Phosphate as a Route for the Preparation of Nanocomposites

The preparation of functional nanocomposites by dispersion of a synthetic lamellar α‐ZrP within a styrene/butadiene random copolymer during melt compounding is described. It is shown how the physical and chemical incompatibility of filler and polymer can be overcome, and problems arising from the low viscosity ratio between slurry and polymer matrix are discussed. The aqueous phase can easily be eliminated at the end of the process. The dispersion of the ZrP requires the use of intercalants, and alkylamines were used for this purpose. XRD and TEM are used to characterize the degree of organization of ZrP in the slurries and in the matrix. DMA helps to understand the origin of the limited reinforcing effect.

     

Detoxification of Aflatoxin B1 and M1 by Lactobacillus acidophilus and prebiotics in whole cow's milk

The detoxification ability of Lactobacillus acidophilus and prebiotics was evaluated by a Plackett‐Burman Design to examine the reduction of concentration and bioaccessibility of aflatoxin B₁ (AFB₁) and M₁ (AFM₁) in artificially contaminated whole cow's milk. Six variables were evaluated: AFB₁ (3.25–6.0 μg L^?1) or AFM₁ (1.0–2.0 μg L^?1) concentration; incubation time (0–6 h); and inulin, oligofructose, β‐glucan, and polydextrose concentrations (each between 0.00 and 0.75%). All runs achieved reductions of AFB₁ (13.53–35.53%) and AFM₁ (17.65–71.52%). Comparing with the positive control, the AFB₁ bioaccessibility ranged from 23.68 to 72.67% and for AFM₁ was 0%. The probiotic, isolated or combined with prebiotics, was efficient in mycotoxin reduction, while the combination of the two reduced the mycotoxin bioaccessibility. The best experimental condition was the highest concentration of AFB₁ (6.5 μg L^?1) and AFM₁ (2.0 μg L^?1), incubation time of 0 h and the addition of probiotic and inulin (0.75%).     

Ni based catalysts promoted with cerium used in the steam reforming of toluene for hydrogen production

Ni_xMg_6?xAl_1.8Ce_0.2 (with 0 ≤ x ≤ 6) mixed oxides catalysts were prepared by hydrotalcite route. All the oxides were calcined at 800 °C and characterized by different physico-chemical methods. The catalysts are then reduced before their use in the steam reforming of toluene. The XRD and TG/DTA confirmed the formation of the hydrotalcite structure for the non-calcined samples. The N₂ adsorption/desorption results revealed that all catalysts correspond to mesoporous materials. The study by temperature programmed reduction (H₂-TPR) showed that the reducibility of the catalysts is influenced by the nickel content. The CO₂-TPD results showed that the catalyst with high magnesium content present the highest basicity. The Ni₂Mg₄Al_1.8Ce_0.2 shows the best toluene conversion among all the catalysts and it was then compared to a non-promoted catalyst. The spent catalysts were characterized by TPO, TG/DTA and XRD and they didn't reveal any coke formation.     

Using PA11 and 12 as curing agents for epoxy networks: Influence of reactivity on miscibility and properties

The Rilsan PA11 prepolymer was evaluated as a curing agent of a diepoxy prepolymer (DGEBA). The miscibility, the glass transition temperature, and the melting of the blend were studied as a function of time at 200°C. A gelation phenomenon was evidenced by dynamic mechanical analysis and the gel time was determined at 200°C. The participation of amide groups to the reaction process at this temperature was confirmed by the study of the PA12 Orgasol®/DGEBA system and a reaction mechanism was elucidated by the study of a model system composed of ethylacetamide/phenyl glycidyl ether. The mechanical properties of DGEBA/Rilsan networks cured 7 h at 200°C were evaluated and indicate very high Young's modulus and critical stress intensity factor. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 857–865, 2000     

Characterization of the "viable but nonculturable" (VBNC) state in the wine spoilage yeast Brettanomyces

Although the viable but not culturable (VBNC) state has been studied in detail in bacteria, it has been suggested that maintenance of viability with loss of culturability also exists in eukaryotic cells, such as in the wine spoilage yeast Brettanomyces. To provide conclusive evidence for the existence of a VBNC state in this yeast, we investigated its capacity to become viable and nonculturable after sulfite stress, and its ability to recover culturability after stressor removal. Sulfite addition induced loss of culturability but maintenance of viability. Increasing the medium pH to decrease the concentration of toxic SO(2) allowed yeast cells to become culturable again, thus demonstrating the occurrence of a VBNC state in Brettanomyces upon SO(2) exposure. Relative to culturable Brettanomyces, VBNC yeast cells were found to display a 22% decrease in size on the basis of laser granulometry. Assays for 4-ethylguaiacol and 4-ethylphenol, volatile phenols produced by Brettanomyces, indicated that spoilage compound production could persist in VBNC cells. These morphological and physiological changes in VBNC Brettanomyces were coupled to extensive protein pattern modifications, as inferred by comparative two-dimensional electrophoresis and mass spectrometric analyses. Upon identification of 53 proteins out of the 168 spots whose abundance was significantly modified in treated cells relative to control, we propose that the SO(2)-induced VBNC state in Brettanomyces is characterized by a reduced glycolytic flux coupled to changes in redox homeostatis/protein turnover-related processes. This study points out the existence of common mechanisms between yeast and bacteria upon entry to the VBNC state.     

Changes in bioactive compounds and antioxidant capacity of fresh-cut cashew apple

In this study, ascorbic acid, total polyphenols and proanthocyanidins of fresh-cut cashew apple were quantified. Antioxidant capacity was determined in whole juice and in polyphenols extracts by three methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and ??-carotene bleaching. Effect of cutting and storage for 24 h at 2 °C, 27 °C and 40 °C on these compounds were also evaluated. Cashew apple presented 163 mg of ascorbic acid per 100 g of fresh weight (FW). Soluble and hydrolysable polyphenols contents were 12.79 mg GAE/100 g FW and 18.53 mg GAE/100 g FW and proanthocyanidins were 9.27 mg/100 g FW. Antioxidant capacity of juice and polyphenols extract was high for DPPH method. Storage temperatures affected bioactive compounds on cut cashew apple. The content of ascorbic acid decreased in all temperatures. Proanthocyanidins were more sensitive to 40 °C than to other temperatures. The content of polyphenols and antioxidant capacity of juice by DPPH assay did not change. However, the reducing power was lower in samples kept at high temperatures. A strong positive correlation between ascorbic acid and FRAP (r = 0.99) and a negative correlation between DPPH and FRAP (r = − 0.79) were observed. No correlations were found between polyphenols and antioxidant capacity indicating the importance of phenolic composition in the extracts. The results confirm the importance of temperature and injury on the quality of cashew apple.