Preparation and characterization of ethanol-treated silk fibroin dense membranes for biomaterials application using waste silk fibers as raw material

The possibility of producing valued devices from low cost natural resources is a subject of broad interest. The present study explores the preparation and characterization of silk fibroin dense membranes using waste silk fibers from textile processing. Morphology, crystallinity, thermal resistance and cytotoxicity of membranes as well as the changes on the secondary structure of silk fibroin were analyzed after undergoing treatment with ethanol. Membranes presented amorphous patterns as determined via X-ray diffraction. The secondary structure of silk fibroin on dense membranes was either random coil (silk I) or p-sheet (silk II), before and after ethanol treatment, respectively. The sterilized membranes presented no cytotoxicity to endothelial cells during in vitro assays. This fact stresses the material potential to be used in the fabrication of biomaterials, as coatings of cardiovascular devices and as membranes for wound dressing or drug delivery systems. (C) 2010 Elsevier Ltd. All rights reserved.

Chronic ethanol intake modulates vascular levels of endothelin-1 receptor and enhances the pressor response to endothelin-1 in anaesthetized rats

Background and purpose: The contribution of endothelin-1 (ET-1) to vascular hyper-reactivity associated with chronic ethanol intake, a major risk factor in several cardiovascular diseases, remains to be investigated. Experimental approach: The biphasic haemodynamic responses to ET-1 (0.01-0.1 nmol kg(-1), i.v.) or to the selective ET(B) agonist, IRL1620 (0.001-1.0 nmol kg(-1), i.v.), with or without ET(A) or ET(B) antagonists (BQ123 (c(DTrp-Dasp-Pro-Dval-Leu)) at 1 and 2.5 mg kg(-1) and BQ788 (N-cis-2,6-dimethyl-piperidinocarbonyl-L-gamma-methylleucyl1-D-1methoxycarbonyltryptophanyl-D-norleucine) at 0.25 mg kg(-1), respectively) were tested in anaesthetized rats, after 2 weeks` chronic ethanol treatment. Hepatic parameters and ET receptor protein levels were also determined. Key results: The initial hypotensive responses to ET-1 or IRL1620 were unaffected by chronic ethanol intake, whereas the subsequent pressor effects induced by ET-1, but not by IRL1620, were potentiated. BQ123 at 2.5 but not 1 mg kg(-1) reduced the pressor responses to ET-1 in ethanol-treated rats. Conversely, BQ788 (0.25 mg kg(-1)) potentiated ET-1-induced increases in mean arterial blood pressure in control as well as in ethanol-treated rats. Interestingly, in the latter group, increases in heart rate, induced by ET-1 at a dose of 0.025 mg kg(-1) were enhanced following ET(B) receptor blockade. Finally, we observed higher levels of ET(A) receptor in the heart and mesenteric artery and a reduction of ET(B) receptor protein levels in the aorta and kidney from rats chronically treated with ethanol. Conclusions and implications: Increased vascular reactivity to ET-1 and altered protein levels of ET(A) and ET(B) receptors could play a role in the pathogenesis of cardiovascular complications associated with chronic ethanol consumption.

Ligand Reduces Galectin-1 Sensitivity to Oxidative Inactivation by Enhancing Dimer Formation

Galectin-1 (Gal-1) regulates leukocyte turnover by inducing the cell surface exposure of phosphatidylserine (PS), a ligand that targets cells for phagocytic removal, in the absence of apoptosis. Gal-1 monomer- dimer equilibrium appears to modulate Gal-1-induced PS exposure, although the mechanism underlying this regulation remains unclear. Here we show that monomer- dimer equilibrium regulates Gal-1 sensitivity to oxidation. A mutant form of Gal-1, containing C2S and V5D mutations (mGal-1), exhibits impaired dimerization and fails to induce cell surface PS exposure while retaining the ability to recognize carbohydrates and signal Ca(2+) flux in leukocytes. mGal-1 also displayed enhanced sensitivity to oxidation, whereas ligand, which partially protected Gal-1 from oxidation, enhanced Gal-1 dimerization. Continual incubation of leukocytes with Gal-1 resulted in gradual oxidative inactivation with concomitant loss of cell surface PS, whereas rapid oxidation prevented mGal-1 from inducing PS exposure. Stabilization of Gal-1 or mGal-1 with iodoacetamide fully protected Gal-1 and mGal-1 from oxidation. Alkylation-induced stabilization allowed Gal-1 to signal sustained PS exposure in leukocytes and mGal-1 to signal both Ca(2+) flux and PS exposure. Taken together, these results demonstrate that monomer-dimer equilibrium regulates Gal-1 sensitivity to oxidative inactivation and provides a mechanism whereby ligand partially protects Gal-1 from oxidation.

Candida albicans and Candida tropicalis in Oral Candidosis: Quantitative Analysis, Exoenzyme Activity, and Antifungal Drug Sensitivity

Candida albicans and C. tropicalis obtained from whole saliva of patients presenting signs of oral candidosis were assayed for quantification of colony forming units, exoenzyme activity (phospholipase and proteinase) and antifungal drug sensitivity (amphotericin B, fluconazole and itraconazole) by the reference method of the Clinical and Laboratory Standards Institute. The number of colony forming units per milliliter varied according to the Candida species involved and whether a single or mixed infection was present. Proteinase activity was observed in both C. albicans and C. tropicalis, but phospholipase activity was noted only in C. albicans. In vitro resistance to antifungals was verified in both species, but C. tropicalis appears to be more resistant to the tested antifungals than C. albicans.

Sensitivity to cisplatin-induced mutations and elevated chromosomal aberrations in lymphocytes from sickle cell disease patients

Sickle cell disease (SCD) is an inherited disorder caused by a single nucleotide substitution in the P-globin gene. The clinical heterogeneity observed in SCD patients has been attributed to environmental and genetic factors. The patients are subjected to increased oxidative stress, particularly during vaso-occlusive crises and acute chest pain. Another possible cause of oxidative stress in SCD is the high concentration of iron in the patients` plasma. The increase in oxidative stress could be a relevant risk factor for mutagenesis and carcinogenesis. Studies on the frequency of basal chromosomal aberrations in cultured lymphocytes from SCD patients have not been reported so far. In order to contribute to the understanding of the role of the different biomarkers and their relationship with the extremely variable clinical manifestation of SCD, we investigated the frequency of chromosome damage in peripheral lymphocytes from sickle cells patients and healthy controls. We found an increased frequency of chromosome damage and percentage of aberrant metaphases in these patients when compared with control subjects, even at basal values (p < 0.05). In the cytogenetic sensitivity assay, the results showed that these patients presented a marked decrease in the mitotic index values compared with healthy controls. Cisplatin-induced chromosomal damage in lymphocytes from these patients was significantly higher than the frequency measured in healthy controls. The results obtained in the present study showed that more investigations are needed in order to elucidate the susceptibility to genomic instability of SCD patients.

Circulating Interleukin-6 and High-Sensitivity C-Reactive Protein Decrease After Periodontal Therapy in Otherwise Healthy Subjects

Background: Periodontal disease has been associated with many chronic inflammatory systemic diseases, and a common chronic inflammation pathway has been suggested for these conditions. However, few studies have evaluated whether periodontal disease, in the absence of other known inflammatory conditions and smoking, affects circulating markers of chronic inflammation. This study compared chronic inflammation markers in control individuals and patients with periodontal disease and observed whether non-surgical periodontal therapy affected inflammatory disease markers after 3 months. Methods: Plasma and serum of 20 controls and 25 patients with periodontal disease were obtained prior to and 3 months after non-surgical periodontal therapy. All patients were non-smokers, they did not use any medication, and they had no history or detectable signs and symptoms of systemic diseases. Periodontal and systemic parameters included probing depth, bleeding on probing, clinical attachment level, hematologic parameters, as well as the following inflammatory markers: interleukin (IL)-6, high-sensitivity C-reactive protein (hs-CRP), CD40 ligand, monocyte chemoattractant protein (MCP)-1, soluble P-selectin (sP-selectin), soluble vascular adhesion molecule (sVCAM)-1, and soluble intercellular adhesion molecule (sICAM)-1. Results: There were no differences in the hematologic parameters of the patients in the control and periodontal disease groups. Among the tested inflammatory markers, IL-6 concentrations were higher in the periodontal disease group at baseline compared to the controls (P=0.006). Therapy was highly effective (P<0.001 for all the analyzed clinical parameters), and a decrease in circulating IL-6 and hs-CRP concentrations was observed 3 months after therapy (P=0.001 and P=0.006, respectively). Our results also suggest that the CD40 ligand marker may have been different in the control and periodontal disease groups prior to the therapy (P=0.009). Conclusions: In apparently otherwise healthy patients, periodontal disease is associated with increased circulating concentrations of IL-6 and hs-CRP, which decreased 3 months after non-surgical periodontal therapy. With regard to the CD40 ligand, MCP-1, sP-selectin, sVCAM-1, and sICAM-1, no changes were seen in the periodontal disease group between baseline and 3 months after therapy. J Periodontol 2009;80:594-602.

Gender-specific vascular effects elicited by chronic ethanol consumption in rats: a role for inducible nitric oxide synthase

Background and purpose: Epidemiological data suggest that the risk of ethanol-associated cardiovascular disease is greater in men than in women. This study investigates the mechanisms underlying gender-specific vascular effects elicited by chronic ethanol consumption in rats. Experimental approach: Vascular reactivity experiments using standard muscle bath procedures were performed on isolated thoracic aortae from rats. mRNA and protein for inducible NO synthase (iNOS) and for endothelial NOS (eNOS) was assessed by RT-PCR or western blotting, respectively. Key results: In male rats, chronic ethanol consumption enhanced phenylephrine-induced contraction in both endothelium-intact and denuded aortic rings. However, in female rats, chronic ethanol consumption enhanced phenylephrine-induced contraction only in endothelium denuded aortic rings. After pre-incubation of endothelium-intact rings with L-NAME, both male and female ethanol-treated rats showed larger phenylephrine-induced contractions in aortic rings, compared to the control group. Acetylcholine-induced relaxation was not affected by ethanol consumption. The effects of ethanol on responses to phenylephrine were similar in ovariectomized (OVX) and intact (non-OVX) female rats. In the presence of aminoguanidine, but not 7-nitroindazole, the contractions to phenylephrine in rings from ethanol-treated female rats were greater than that found in control tissues in the presence of the inhibitors. mRNA levels for eNOS and iNOS were not altered by ethanol consumption. Ethanol intake reduced eNOS protein levels and increased iNOS protein levels in aorta from female rats. Conclusions and implications: Gender differences in the vascular effects elicited by chronic ethanol consumption were not related to ovarian hormones but seemed to involve the upregulation of iNOS.

A costs structure analysis of the Brazilian sugar and ethanol companies

The Brazil consolidated itself as the largest world producer of sugarcane, sugar and ethanol. The creation of the Programa Nacional do Alcool - PROALCOOL and the growing use of cars with flexible motors were some of the factors that helped to motivate still more the production. Evolutions in the agricultural and industrial research did the Brazilian competitiveness in sugar and ethanol globally elevated, what is evidenced when comparing the amount produced at the country and the production costs, which turned a big one differential. Therefore, the administration of costs is of great relevance to the sugar and ethanol companies, for representing a significant rationalization in the production processes, with economy of resources and the reach of better earnings, besides reducing the operational risk pertinent at the fixed costs of production. Thus, the present work has for objective to analyze the costs structure of sugar and ethanol companies of the Center-south area of the country through an empiric-analytical study based in methodologies and concepts extracted of the costs accounting. It is verified that great part of the costs and operational expenses have variable behavior, a positive factor for the sector reducing the operational risk of the activity. The main restraint of this study is the sample of five years and 10% of the number of plants in Brazil that although they represent 30% of the national production, don`t allow the generalization of the model.

Activity of platinum-tin catalysts prepared by the Pechini-Adams method for the electrooxidation of ethanol

Pt-Sn electrocatalysts of different compositions were prepared and dispersed on carbon Vulcan XC-72 using the Pechini-Adams method. The catalysts were characterized by energy dispersive X-ray analysis and X-ray diffraction. The electrochemical properties of these electrode materials were also examined by cyclic voltammetry and chronoamperometric experiments in acid medium. The results showed that the presence of Sn greatly enhances the activity of Pt towards the electrooxidation of ethanol. Moreover, it contributes to reduce the amount of noble metal in the anode of direct alcohol fuel cells, which remains one of the challenges to make the technology of direct alcohol fuel cells possible. Electrolysis of ethanol solutions at 0.55 V vs. RHE allowed to determine by liquid chromatography acetaldehyde and acetic acid as the main reaction products. CO(2) was also analyzed after trapping it in a NaOH solution indicating that the cleavage of the C-C bond in the ethanol molecule did occur during the adsorption process. In situ IR reflectance spectroscopy helped to investigate in more details the reaction mechanism through the identification of the reaction products as well as the presence of some intermediate adsorbed species, such as linearly bonded carbon monoxide. (C) 2009 Elsevier B.V. All rights reserved.

Application of Ti/RuO(2)-Ta(2)O(5) electrodes in the electrooxidation of ethanol and derivants: Reactivity versus electrocatalytic efficiency

The influence of the preparation method on the performance of RuO(2)-Ta(2)O(5) electrodes was evaluated toward the ethanol oxidation reaction (EOR). Freshly prepared RuO(2)-Ta(2)O(5) thin films containing between 30 and 80 at.% Ru were prepared by two different methods: the modified Pechini-Adams method (DPP) and standard thermal decomposition (STD). Electrochemical investigation of the electrode containing RuO(2)-Ta(2)O(5) thin films was conducted as a function of electrode composition in a 0.5-mol dm(-3) H(2)SO(4) solution, in the presence and absence of ethanol and its derivants (acetaldehyde and acetic acid). At a low ethanol concentration (5 mmol dm(-3)), ethanol oxidation leads to high yields of acetic acid and CO(2). On the other hand, an increase in ethanol concentration (15-1000 mmol dm(-3)) favors acetaldehyde formation, so acetic acid and CO(2) production is hindered, in this case. Electrodes prepared by DPP provide higher current efficiency than STD electrodes for all the investigated ethanol concentrations. This may be explained by the increase in electrode area obtained with the DPP preparation method compared with STD. (c) 2008 Elsevier Ltd. All rights reserved.

Platinum nanoparticles embledded in layer-by-layer films from SnO2/polyallylamine for ethanol electrooxidation

Self-assembled films from SnO2 and polyallylamine (PAH) were deposited on gold via ionic attraction by the layer-by-layer(LbL) method. The modified electrodes were immersed into a H2PtCl6 solution, a current of 100 mu A was applied, and different electrodeposition times were used. The SnO2/PAH layers served as templates to yield metallic platinum with different particle sizes. The scanning tunnel microscopy images show that the particle size increases as a function of electrodeposition time. The potentiodynamic profile of the electrodes changes as a function of the electrodeposition time in 0.5 mol L-1 H2SO4, at a sweeping rate of 50mVs(-1). Oxygen-like species are formed at less positive potentials for the Pt-SnO2/PAH film in the case of the smallest platinum particles. Electrochemical impedance spectroscopy measurements in acid medium at 0.7 V show that the charge transfer resistance normalized by the exposed platinum area is 750 times greater for platinum electrode (300 k Omega cm(2)) compared with the Pt-SnO2/PAH film with 1 min of electrodeposition (0.4 k Omega cm(2)). According to the Langmuir-Hinshelwood bifunctional mechanism, the high degree of coverage with oxygen-like species on the platinum nanoparticles is responsible for the electrocatalytic activity of the Pt-SnO2/PAH concerning ethanol electrooxidation. With these features, this Pt-SnO2/PAH film may be grown on a proton exchange membrane (PEM) in direct ethanol fuel cells (DEFC). (c) 2008 Elsevier B.V. All rights reserved.

Electrocatalytic oxidation of ethanol on Sn((1-x))Ir((x))O(2) electrodes in acid medium

The electrochemical oxidation of ethanol at Sn((1-x))Ir (x) O(2) electrodes (with x = 0.01, 0.05, 0.1 and 0.3) was studied in 0.1 mol L(-1) HClO(4) solution. Electrolysis experiments were carried out and the reaction products were analyzed by Liquid Chromatography. It was found that the amounts of the reaction products depended on the composition of the electrode. In situ infrared reflectance spectroscopy measurements were performed to identify the adsorbed intermediates and to postulate a reaction mechanism for ethanol electrooxidation on these electrode materials. As evidence, acetaldehyde and acetic acid were formed through a successive reaction process. Carbon dioxide was also identified as the end product, showing that the cleavage of the carbon-carbon bond occurred. These results indicate that the synthesized catalysts are able to lead to the total combustion of organic compounds. Analysis of the water bending band at different potentials illustrated its role at the electrode interface.

Effect of W on PtSn/C catalysts for ethanol electrooxidation

Binary and ternary Pt-based catalysts were prepared by the Pechini-Adams modified method on carbon Vulcan XC-72, and different nominal compositions were characterized by TEM and XRD. XRD showed that the electrocatalysts consisted of the Pt displaced phase, suggesting the formation of a solid solution between the metals Pt/W and Pt/Sn. Electrochemical investigations on these different electrode materials were carried out as a function of the electrocatalyst composition, in acid medium (0.5 mol dm(-3) H2SO4) and in the presence of ethanol. The results obtained at room temperature showed that the PtSnW/C catalyst display better catalytic activity for ethanol oxidation compared to PtW/C catalyst. The reaction products (acetaldehyde, acetic acid and carbon dioxide) were analyzed by HPLC and identified by in situ infrared reflectance spectroscopy. The latter technique also allowed identification of the intermediate and adsorbed species. The presence of linearly adsorbed CO and CO2 indicated that the cleavage of the C-C bond in the ethanol substrate occurred during the oxidation process. At 90 degrees C, the Pt85Sn8W7/C catalyst gave higher current and power performances as anode material in a direct ethanol fuel cell (DEFC).

Development of nanostructured bioanodes containing dendrimers and dehydrogenases enzymes for application in ethanol biofuel cells

This paper describes the use of the electrostatic layer-by-layer (LbL) technique for the preparation of bioanodes with potential application in ethanol/O(2) biofuel cells. More specifically, the LbL technique was employed for immobilization of dehydrogenase enzymes and polyamidoamine (PAMAM) dendrimers onto carbon paper support. Both mono (anchoring only the enzyme alcohol dehydrogenase, ADH) and bienzymatic (anchoring both ADH and aldehyde dehydrogenase, AldDH) systems were tested. The amount of ADH deposited onto the Toray (R) paper was 95 ng cm(-2) per bilayer. Kinetic studies revealed that the LbL technique enables better control of enzyme disposition on the bioanode, as compared with the results obtained with the bioanodes prepared by the passive adsorption technique. The power density values achieved for the mono-enzymatic system as a function of the enzyme load ranged from 0.02 to 0.063 mW cm(-2) for the bioanode containing 36 ADH bilayers. The bioanodes containing a gas diffusion layer (GDL) displayed enhanced performance, but their mechanical stability must be improved. The bienzymatic system generated a power density of 0.12 mW cm(-2). In conclusion, the LbL technique is a very attractive approach for enzyme immobilization onto carbon platform, since it enables strict control of enzyme disposition on the bioanode surface with very low enzyme consumption. (C) 2010 Elsevier B.V. All rights reserved.

Development of novel bioanodes for ethanol biofuel cell using PAMAM dendrimers as matrix for enzyme immobilization

This paper describes the preparation and application of a novel bioanode for use in ethanol/O(2) biofuel cells based upon immobilization of alcohol dehydrogenase (ADH) and polyamidoamine (PAMAM) dendrimers onto carbon cloth platforms. The power density measurements indicated a direct relationship between the amount of anchored ADH and the anode power values, which increased upon enzyme loading. The power density values ranged from 0.04 to 0.28 mW cm(-2), and the highest power density was achieved with the bioanode prepared with 28 U of ADH, which provided a power density of 0.28 mW cm(-2) at 0.3 V. The latter power output values were the maximum observed, even for higher enzyme concentrations. Stability of the bioanodes was quite satisfactory, since there was no appreciable reduction of enzymatic activity during the measurements. The method of bioanode preparation described here has proven to be very effective. The PAMAM dendrimer represents a friendly environment for the immobilization of enzymes, and it is stable and capable of generating high power density compared to other immobilization methods. (C) 2010 Elsevier B.V. All rights reserved.