Antibacterial E ect of Chitosan–Gold Nanoparticles and Computational Modeling of the Interaction between Chitosan and a Lipid Bilayer Model

Pathogenic bacteria have the ability to develop antibiotic resistance mechanisms. Their action consists mainly in the production of bacterial enzymes that inactivate antibiotics or the appearance of modifications that prevent the arrival of the drug at the target point or the alteration of the target point itself, becoming a growing problem for health systems. Chitosan–gold nanoparticles (Cs-AuNPs) have been shown as effective bactericidal materials avoiding damage to human cells. In this work, Cs-AuNPs were synthesized using chitosan as the reducing agent, and a systematic analysis of the influence of the synthesis parameters on the size and zeta potential of the Cs-AuNPs and their UV-vis spectra was carried out. We used a simulation model to characterize the interaction of chitosan with bacterial membranes, using a symmetric charged bilayer and two different chitosan models with different degrees of the chitosan amine protonation as a function of pH, with the aim to elucidate the antibacterial mechanism involving the cell wall disruption. The Cs-AuNP antibacterial activity was evaluated to check the simulation model

Antibacterial Effect of Chitosan–Gold Nanoparticles and Computational Modeling of the Interaction between Chitosan and a Lipid Bilayer Model

Pathogenic bacteria have the ability to develop antibiotic resistance mechanisms. Their action consists mainly in the production of bacterial enzymes that inactivate antibiotics or the appearance of modifications that prevent the arrival of the drug at the target point or the alteration of the target point itself, becoming a growing problem for health systems. Chitosan–gold nanoparticles (Cs-AuNPs) have been shown as effective bactericidal materials avoiding damage to human cells. In this work, Cs-AuNPs were synthesized using chitosan as the reducing agent, and a systematic analysis of the influence of the synthesis parameters on the size and zeta potential of the Cs-AuNPs and their UV-vis spectra was carried out. We used a simulation model to characterize the interaction of chitosan with bacterial membranes, using a symmetric charged bilayer and two different chitosan models with different degrees of the chitosan amine protonation as a function of pH, with the aim to elucidate the antibacterial mechanism involving the cell wall disruption. The Cs-AuNP antibacterial activity was evaluated to check the simulation model.Fil: Fuster, M.G.. Universidad de Murcia. Facultad de Química; EspañaFil: Montalbán, M. G.. Universidad de Murcia. Facultad de Química; EspañaFil: Carissimi, G.. Universidad de Murcia. Facultad de Química; EspañaFil: Lima, Beatriz Viviana. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Feresin, Gabriela Egly. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Cano, M.. Universidad de Cordoba. Instituto Universitario de Investigación En Química Fina y Nanoquímica.; EspañaFil: Giner Casares, J. J.. Universidad de Cordoba. Instituto Universitario de Investigación En Química Fina y Nanoquímica.; EspañaFil: López Cascales, J.J.. Universidad Politécnica de Cartagena; EspañaFil: Enriz, Ricardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis; ArgentinaFil: Víllora, G.. Universidad de Murcia. Facultad de Química; Españ

Trail Making Test: Normative data for the Latin American Spanish-speaking pediatric population

OBJECTIVE: To generate normative data for the Trail Making Test (TMT) in Spanish-speaking pediatric populations. METHOD: The sample consisted of 3,337 healthy children from nine countries in Latin America (Chile, Cuba, Ecuador, Guatemala, Honduras, Mexico, Paraguay, Peru, and Puerto Rico) and Spain. Each participant was administered the TMT as part of a larger neuropsychological battery. The TMT-A and TMT-B scores were normed using multiple linear regressions and standard deviations of residual values. Age, age2, sex, and mean level of parental education (MLPE) were included as predictors in the analyses. RESULTS: The final multiple linear regression models showed main effects for age on both scores, such that as children needed less time to complete the test while they become older. TMT-A scores were affected by age2 for all countries except, Cuba, Guatemala, and Puerto. TMT-B scores were affected by age2 for all countries except, Guatemala and Puerto Rico. Models indicated that children whose parent(s) had a MLPE >12 years of education needed less time to complete the test compared to children whose parent(s) had a MLPE ≤12 years for Mexico and Paraguay in TMT-A scores; and Ecuador, Mexico, Paraguay, and Spain for TMT-B scores. Sex affected TMT-A scores for Chile, Cuba, Mexico, and Peru, in that boys needed less time to complete the test than girls. Sex did not affect TMT-B scores. CONCLUSIONS: This is the largest Spanish-speaking pediatric normative study in the world, and it will allow neuropsychologists from these countries to have a more accurate approach to interpret the TMT in pediatric populations

Spread of a SARS-CoV-2 variant through Europe in the summer of 2020.

Following its emergence in late 2019, the spread of SARS-CoV-21,2 has been tracked by phylogenetic analysis of viral genome sequences in unprecedented detail3–5. Although the virus spread globally in early 2020 before borders closed, intercontinental travel has since been greatly reduced. However, travel within Europe resumed in the summer of 2020. Here we report on a SARS-CoV-2 variant, 20E (EU1), that was identified in Spain in early summer 2020 and subsequently spread across Europe. We find no evidence that this variant has increased transmissibility, but instead demonstrate how rising incidence in Spain, resumption of travel, and lack of effective screening and containment may explain the variant’s success. Despite travel restrictions, we estimate that 20E (EU1) was introduced hundreds of times to European countries by summertime travellers, which is likely to have undermined local efforts to minimize infection with SARS-CoV-2. Our results illustrate how a variant can rapidly become dominant even in the absence of a substantial transmission advantage in favourable epidemiological settings. Genomic surveillance is critical for understanding how travel can affect transmission of SARS-CoV-2, and thus for informing future containment strategies as travel resumes. © 2021, The Author(s), under exclusive licence to Springer Nature Limited

Electrodes based on nafion and epoxy-graphene composites for improving the performance and durability of open cathode fuel cells, prepared by electrospray deposition

Embargado hasta 05/04/2024Fabrication of electrodes for polymer electrolyte fuel cells is a intriguing process in which a balance between gas transport, electrical conductivity, proton transport and water managing must be optimized. In this work four different electrodes prepared by electrospray deposition have been studied using different catalytic inks, in which Nafion and epoxy doped with Graphene-Nanoplatelets were used as binders. After studying the behavior of those electrodes in a single open cathode fuel cell proton electrolyte membrane, it is clear that the addition of epoxy as binder doped with graphene, improves the performance of the fuel cell and increase the mechanical stability of the electrode avoiding the loose of catalyst during the electrode manipulation in the fuel cell assembly process and the durability of the fuel cell. To explain this behavior, an ex-situ study was carried out, in which properties such as its surface morphology, hydrophobicity and electrical and thermal conductivity of those electrodes were studied. From the results of this study, such improvement in the performance of the fuel cell was justified on the basis of the increase in the electrical conductivity, a diminution in its thermal conductivity and an enhancement of hydrophobicity (surface morphology) of the deposited catalyst layer, when an optimum quantity of epoxy is added to the catalytic ink that makes to improve the mechanical properties of those electrodes