Nanofibrillated bacterial cellulose and pectin edible films added with fruit purees.

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Specificity and sensitivity comparative study between phage PVP-S1 and monoclonal antibody as receptor in polydiacetylene vesicles for Salmonella colorimetric detection

Polydiacetylene polymer (PDA) has been intensively studied because of its properties as colour change from blue to red and change from non-fluorescent to fluorescent form due to an external stimulus that lead to a reorientation of the PDA within the organized structure. External stimulus could be temperature, pH, solvent influence, bacteria presence, mechanical stresses and others (Oliveira et al., 2012). Pires et al. (2010) support the hypothesis that such phenomena occurred due to conformational changes associated with the functional group rotation around the simple carbon-carbon bond present in PDA chains. When the backbones of PDA conjugated polymer chains are perturbed, the delocalized π-network induces changes in electronic absorption and emission properties (Huo et al., 1999). For a particular colour change, it is possible to incorporate a compound in the polydiacetylene carboxyl groups that will work as a specific receptor for the bacteria detection. This technology can be used for the detection of pathogens and thus is important to avoid food contamination once the standard technology demands long time and people trained. The selection of the receptor used in the PDA is the first critical step to develop a biosensor with improved selectivity, selectivity and stability. For this reason, the aim of this study was to make a comparative study between two recognition molecules: phage PVP-S1 (Santos et al., 2011) and a monoclonal antibody in the PDA sensor for the detection of Salmonella. Antibodies lack specificity, poor separation efficiency and sensitivity. Phages are extremely specific, withstand harsh environments, are economically and easily produced, show high stability during storage and thus present potential for bacterial detection. Overall the selection of the recognition molecule that show the best features is important to develop a simple and rapid sensor for the industry and consumer’s life. The specificity of the sensor was proven by using Staphylococus aures and Escherichia coli as gram-positive and gram-negative controls, respectively

Torsion Gravity: a Reappraisal

The role played by torsion in gravitation is critically reviewed. After a description of the problems and controversies involving the physics of torsion, a comprehensive presentation of the teleparallel equivalent of general relativity is made. According to this theory, curvature and torsion are alternative ways of describing the gravitational field, and consequently related to the same degrees of freedom of gravity. However, more general gravity theories, like for example Einstein-Cartan and gauge theories for the Poincare and the affine groups, consider curvature and torsion as representing independent degrees of freedom. By using an active version of the strong equivalence principle, a possible solution to this conceptual question is reviewed. This solution favors ultimately the teleparallel point of view, and consequently the completeness of general relativity. A discussion of the consequences for gravitation is presented.Comment: RevTeX, 34 pages. Review article to be published by Int. J. Mod. Phys.

Inducible nitric oxide synthase (iNOS) expression in monocytes during acute Dengue Fever in patients and during in vitro infection

ABSTRACT: Mononuclear phagocytes are considered to be main targets for Dengue Virus (DENV) replication. These cells are activated after infection, producing proinflammatory mediators, including tumour-necrosis factor-α, which has also been detected in vivo. Nitric oxide (NO), usually produced by activated mononuclear phagocytes, has antimicrobial and antiviral activities. METHODS: The expression of DENV antigens and inducible nitric oxide synthase (iNOS) in human blood isolated monocytes were analysed by flow cytometry using cells either from patients with acute Dengue Fever or after DENV-1 in vitro infection. DENV-1 susceptibility to iNOS inhibition and NO production was investigated using N(G)-methyl L-Arginine (N(G)MLA) as an iNOS inhibitor, which was added to DENV-1 infected human monocytes, and sodium nitroprussiate (SNP), a NO donor, added to infected C6/36 mosquito cell clone. Viral antigens after treatments were detected by flow cytometry analysis. RESULTS: INOS expression in activated monocytes was observed in 10 out of 21 patients with Dengue Fever and was absent in cells from ten healthy individuals. DENV antigens detected in 25 out of 35 patients, were observed early during in vitro infection (3 days), significantly diminished with time, indicating that virus replicated, however monocytes controlled the infection. On the other hand, the iNOS expression was detected at increasing frequency in in vitro infected monocytes from three to six days, exhibiting an inverse relationship to DENV antigen expression. We demonstrated that the detection of the DENV-1 antigen was enhanced during monocyte treatment with N(G)MLA. In the mosquito cell line C6/36, virus detection was significantly reduced in the presence of SNP, when compared to that of untreated cells. CONCLUSION: This study is the first to reveal the activation of DENV infected monocytes based on induction of iNOS both in vivo and in vitro, as well as the susceptibility of DENV-1 to a NO production