Laser surface structuring affects polymer deposition, coating homogeneity, and degradation rate of Mg alloys

In the current work, a coating system consisted of a laser-structured surface, a thin layer primer and a polymeric coating to improve degradation behaviour of biocompatible and biodegradable Mg alloy is presented. The laser structuring allowed modification of surface topography as well as controlling the wettability of surface. The cellulose acetate primer provided protection from in-process degradation of samples during the successive layer-by-layer (LbL) coating process, where alternate layers of chitosan and carboxymethyl cellulose were applied. The results revealed that the laser structured surface plays an important role on the developed coating structure and final corrosion rate. Lowest corrosion rate among the coated samples (1.15 cm yr(-1)) was measured for the most hydrophilic laser-treated surface, corresponding to almost 16% reduction compared to the as-received samples

Antibacterial properties of chitosan-based coatings are affected by spacer-length and molecular weight

Chitosan is a biopolymer with antibacterial properties, which are dependent on its molecular weight (Mw) and its degree of deacetylation (DDA). When grafted on surfaces as a coating, chitosan antibacterial efficiency is also dependent on the polymer chain conformation on the surface, as the amine groups, responsible of the antibacterial effect, should be available for contact with bacteria. To investigate this behavior, chitosans with different Mw were grafted onto plasma aminated surfaces through three different spacers: glutaric anhydride (GA), poly(ethylene-glycol) bis(carboxymethyl) ether (PEGb), and poly (ethylene-alt-maleic anhydride) (PA). The grafting efficiency was evaluated by X-ray Photoelectron Spectroscopy (XPS), contact angle and Rose Bengal test, while morphological features were assessed by profilometry analyses. Results evidenced a clear influence of the anchor arm length and of the Mw of chitosan both on the grafting efficiency and on the antibacterial behavior. PA CHIMW surface exhibited a better antibacterial response compared to GA and PEGb, which could be correlated to a denser coating coverage as seen by XPS and profilometry results. Further, PA CHIMW coating displayed a higher amine density, thus promoting the interaction with the bacteria cell wall. Based on these results, chitosan-based coatings can then be extended to a wide range of antibacterial application

Estudos sobre a paz e cultura da paz

Segundo o autor, a cultura da paz implica uma mudança quer na forma como a “alta cultura” lida com a realidade quer no tipo de abordagem que o senso comum faz às relações sociais, sendo que a ruptura com a ideologia conservadora, ou seja, com o senso comum realista só é possível graças a estas alterações. O autor realça tanto a importância que os estudos sobre a paz têm para o surgimento de um conceito amplo de paz, desenvolvido por Johan Galtung, como o facto destes estarem estrategicamente orientados para a transformação do sistema internacional. Sequentemente, conclui que a paz é uma categoria moral e cultural que só pode ser alcançada através do comportamento quotidian

Roughness dynamic in surface growth: Layer-by-layer thin films of carboxymethyl cellulose/chitosan for biomedical applications

Surfaces are responsible for important interactions of biomaterials since they create the interface with the biological environment and affect the response that the body will have to the material. Surface roughness and morphology have great impact on the material performance, affecting cell, bacterial, and biomolecular adhesion. Thin films of chitosan and carboxymethyl cellulose were produced by layer-by-layer deposition at different pH values and had their surface growth process studied throughout roughness measurements. Both polymers are nontoxic and biocompatible to the human biological system, with biomedical applications from tissue engineering to drug delivery. Growth exponents are presented, and it is suggested that fractal-based growth models are suitable for describing surface evolution and morphology of carboxymethyl cellulose/chitosan layer-by-layer thin film growth during deposition, primarily nonlinear models124CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informação2013/05135-

Ionic liquid functionalization of chitosan beads for improving thermal stability and copper ions uptake from aqueous solution

Chitosan (CHI) beads modified with ionic liquids (ILs) were synthesized to remove copper ions from aqueous solution by adsorption. This paper presents the results of isotherm and kinetics for both pristine and ILs-modified CHI beads, comparing their adsorption capacity and evaluating the mechanisms involved in the batch adsorption process. Isotherm data for Cu(II) ions adsorption were fitted to Langmuir and Freundlich models, while adsorption kinetic was assessed by adjusting the data to pseudo-first order, pseudo-second order and intra-particle models. Characterization results indicate that IL functionalization promotes a significant modification on bead morphology, crystallinity and thermal stability. ILs lead to an increase in the adsorption capacity at lower Cu(II) concentrations (20 mg L-1), followed by the higher affinity of Cu(II) to the adsorbate. Due to the higher stability and affinity to copper ions, ILs-modified CHI beads come out as a promising strategy for developing new materials and processes with improved heavy metal uptake properties73CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO AMAZONAS - FAPEAMsem informação88882.151600/2017-012013/05135-1; 2016/10193-9sem informaçã

Copper ion uptake by chitosan in the presence of amyloid-beta and histidine

Alzheimer's disease (AD) is related to the anomalous binding that occurs between amyloid-beta peptide (A beta) and copper ion, through imidazole ring of histidine (His), as stated in the literature. It is also known that high-affinity metal ion chelators can be pharmacologically used as a possible therapeutic approach. In this work, we tested the ability "in vitro" of chitosan (Chi) to reduce A beta aggregation and Thioflavin T binding assay indicated that chitosan has affinity for A beta and interferes in its aggregation. We also tested the ability of Chi to uptake copper ions in the presence of A beta or His. Equilibrium data reveals that chitosan acted as an effective chelating agent competing with A beta and histidine for copper binding. The addition of histidine or A beta in the system promotes an unfolding of chitosan chains, as verified by small-angle X-ray scattering. Extended X-ray absorption fine structure and XPS spectra show that new copper interactions with groups containing nitrogen in the presence of histidine may occur. These results can help understanding fundamental chemical interactions among species detected in AD and biopolymers, opening up possibilities for new treatment approaches for this diseaseCAPES - Coordenação de Aperfeiçoamento de Pessoal e Nível SuperiorCNPQ - Conselho Nacional de Desenvolvimento Científico e TecnológicoFAPESP – Fundação de Amparo à Pesquisa Do Estado De São Paulo88882.151600/2017-01Sem informaçãoSem informaçã

Antibacterial properties of chitosan-based coatings are affected by spacer-length and molecular weight

Chitosan is a biopolymer with antibacterial properties, which are dependent on its molecular weight (Mw) and its degree of deacetylation (DDA). When grafted on surfaces as a coating, chitosan antibacterial efficiency is also dependent on the polymer chain conformation on the surface, as the amine groups, responsible of the antibacterial effect, should be available for contact with bacteria. To investigate this behavior, chitosans with different Mw were grafted onto plasma aminated surfaces through three different spacers: glutaric anhydride (GA), poly(ethylene-glycol) bis(carboxymethyl) ether (PEGb), and poly (ethylene-alt-maleic anhydride) (PA). The grafting efficiency was evaluated by X-ray Photoelectron Spectroscopy (XPS), contact angle and Rose Bengal test, while morphological features were assessed by profilometry analyses. Results evidenced a clear influence of the anchor arm length and of the Mw of chitosan both on the grafting efficiency and on the antibacterial behavior. PA CHIMW surface exhibited a better antibacterial response compared to GA and PEGb, which could be correlated to a denser coating coverage as seen by XPS and profilometry results. Further, PA CHIMW coating displayed a higher amine density, thus promoting the interaction with the bacteria cell wall. Based on these results, chitosan-based coatings can then be extended to a wide range of antibacterial applications. (C) 2018 Elsevier B.V. All rights reserved

Laser surface structuring affects polymer deposition, coating homogeneity, and degradation rate of Mg alloys

In the current work, a coating system consisted of a laser-structured surface, a thin layer primer and a polymeric coating to improve degradation behaviour of biocompatible and biodegradable Mg alloy is presented. The laser structuring allowed modification of surface topography as well as controlling the wettability of surface. The cellulose acetate primer provided protection from in-process degradation of samples during the successive layer-by-layer (LbL) coating process, where alternate layers of chitosan and carboxymethyl cellulose were applied. The results revealed that the laser structured surface plays an important role on the developed coating structure and final corrosion rate. Lowest corrosion rate among the coated samples (1.15 cm yr−1) was measured for the most hydrophilic laser-treated surface, corresponding to almost 16% reduction compared to the as-received samples160359362CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informação2013/05135-

Antibacterial noncytotoxic chitosan coatings on polytetrafluoroethylene films by plasma grafting for medical device applications

Chitosan is an exciting alternative for the development of coating-surfaces due to its large action spectrum against pathogenic microorganisms. However, to produce a stable coating with effective antibacterial action, a compromise between deacetylation degree (DD) and molecular weight (MW) is essential. Four chitosan samples were characterized regarding Mw and DD and correlated with the minimum and bactericide concentrations against E. coli, P. aeruginosa, and S. aureus. CHI80MW (79.7% DD and 7.0 x 10(5) Da) showed the best antibacterial effect and was selected to functionalize polytetrafluoroethylene (PTFE) surfaces by plasma. CHI80MW was grafted onto the PTFE surfaces using two different spacer molecules: poly(ethylene glycol) bis (carboxymethyl) ether (PEG) and poly(ethylene-alt-maleic anhydride) (PA). PTFE-Plasma-PA-CHI80MW exhibited a coating with more attached chitosan and better antibacterial action if compared to PTFE-Plasma-PEG-CHI80MW: after 8 h, PTFE-Plasma-PEG-CHI80MW presented a bacterial reduction of 25-30% for the three bacterial strains, and PTFE-Plasma-PA-CHI80MW reduced them to 77-90%. Moreover, cytotoxicity tests showed that PTFE-Plasma-PA-CHI80MW samples were compatible with human fibroblasts