Mussel adhesive protein inspired coatings: a versatile method to fabricate silica films on various surfaces

A simple and versatile biomimetic strategy for the fabrication of silica films on a variety of substrates including gold, polystyrene and silicon wafers was developed using nanogram amounts per cm 2 of silicatein. The strategy exploits the adhesive property of 3,4-dihydroxyphenylalanine (DOPA) and a decapeptide (Ala-Lys-Pro-Ser-Tyr-DHP-Hyp-Thr-DOPA-Lys), important components of mussel adhesive proteins, to modify the surface of substrates. DOPA molecules polymerize to poly(DOPA) and the decapeptide forms thin films on gold substrates at pH 8.5, rendering the substrate compatible for silicatein immobilization. Nearly 50 ng cm 2 of silicatein is immobilized on poly(DOPA) and decapeptide coated surfaces where these polymer films act as "cushion" to protect the active structure and maintain the activity of the largely chemically adsorbed silicatein at ca. 95% of that experienced in solution. Uniform silica films of thickness 130-140 nm and roughness 12-14.5 nm were fabricated on coated gold surfaces. Evidence to show that this method is also applicable for the fabrication of uniform silica films on polystyrene and silicon substrates over multiple length scales in an economical way is also presented

Enhanced antibacterial activity of silver nanoparticles/halloysite nanotubes/graphene nanocomposites with sandwich-like structure

A sandwich-like antibacterial reagent (Ag/HNTs/rGO) was constructed through the direct growth of silver nanoparticles on the surface graphene-based HNTs nanosheets. Herein, various nanomaterials were combined by adhesion effect of DOPA after self-polymerization. Ag/HNTs/rGO posses enhanced antibacterial ability against E. coli and S. aureus compared with individual silver nanoparticles, rGO nanosheets or their nanocomposites

Encapsulation of lipase in mesoporous silica yolk-shell spheres with enhanced enzyme stability

Enzyme encapsulation is an attractive method among the different immobilization strategies to improve the reusability and stability of enzymes because it can separate enzymes from a hazardous external environment. However, current encapsulation methods have limitations including enzyme leakage. In this study, a new approach based on a two-step soft templating method has been proposed to encapsulate lipase within substrate permeable mesoporous silica yolk-shell spheres. In the first step, lipase was immobilized onto epoxy functionalized silica nanospheres that serve as the core materials. The core materials were mixed with a fluorocarbon surfactant, FC4, to form a core-vesicle complex. In the second step, a mesoporous silica shell was assembled surrounding the core-vesicle complex to form the yolk-shell structure with the lipase encapsulated. The mesoporous silica shell has a pore size of 2.1 nm, which is permeable to the reactant and product while isolating the enzymes from harmful external conditions. The encapsulated lipase retained 87.5% of its activity after thermal treatment at 70 °C for 2 hours while the free enzyme lost 99.5% of its activity under the same treatment. Importantly, the encapsulated lipase shows significantly enhanced resistance to degradation by proteases

Anti-bacterial activity of inorganic nanomaterials and their antimicrobial peptide conjugates against resistant and non-resistant pathogens

This review details the antimicrobial applications of inorganic nanomaterials of mostly metallic form, and the augmentation of activity by surface conjugation of peptide ligands. The review is subdivided into three main sections, of which the first describes the antimicrobial activity of inorganic nanomaterials against gram-positive, gram-negative and multidrug-resistant bacterial strains. The second section highlights the range of antimicrobial peptides and the drug resistance strategies employed by bacterial species to counter lethality. The final part discusses the role of antimicrobial peptide-decorated inorganic nanomaterials in the fight against bacterial strains that show resistance. General strategies for the preparation of antimicrobial peptides and their conjugation to nanomaterials are discussed, emphasizing the use of elemental and metallic oxide nanomaterials. Importantly, the permeation of antimicrobial peptides through the bacterial membrane is shown to aid the delivery of nanomaterials into bacterial cells. By judicious use of targeting ligands, the nanomaterial becomes able to differentiate between bacterial and mammalian cells and, thus, reduce side effects. Moreover, peptide conjugation to the surface of a nanomaterial will alter surface chemistry in ways that lead to reduction in toxicity and improvements in biocompatibility

Comparison of the Virulence Potential of Acinetobacter Strains from Clinical and Environmental Sources

Several Acinetobacter strains have utility for biotechnology applications, yet some are opportunistic pathogens. We compared strains of seven Acinetobacter species (baumannii, Ab; calcoaceticus, Ac; guillouiae, Ag; haemolyticus, Ah; lwoffii, Al; junii, Aj; and venetianus, Av-RAG-1) for their potential virulence attributes, including proliferation in mammalian cell conditions, haemolytic/cytolytic activity, ability to elicit inflammatory signals, and antibiotic susceptibility. Only Ah grew at 102 and 104 bacteria/well in mammalian cell culture medium at 37°C. However, co-culture with colonic epithelial cells (HT29) improved growth of all bacterial strains, except Av-RAG-1. Cytotoxicity of Ab and Ah toward HT29 was at least double that of other test bacteria. These effects included bacterial adherence, loss of metabolism, substrate detachment, and cytolysis. Only Ab and Ah exhibited resistance to killing by macrophage-like J774A.1 cells. Haemolytic activity of Ah and Av-RAG-1 was strong, but undetectable for other strains. When killed with an antibiotic, Ab, Ah, Aj and Av-RAG-1 induced 3 to 9-fold elevated HT29 interleukin (IL)-8 levels. However, none of the strains altered levels of J774A.1 pro-inflammatory cytokines (IL-1β, IL-6 and tumor necrosis factor-α). Antibiotic susceptibility profiling showed that Ab, Ag and Aj were viable at low concentrations of some antibiotics. All strains were positive for virulence factor genes ompA and epsA, and negative for mutations in gyrA and parC genes that convey fluoroquinolone resistance. The data demonstrate that Av-RAG-1, Ag and Al lack some potentially harmful characteristics compared to other Acinetobacter strains tested, but the biotechnology candidate Av-RAG-1 should be scrutinized further prior to widespread use

Microbial fuel cells: From fundamentals to applications. A review

© 2017 The Author(s) In the past 10–15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described

O ensino da leitura e da escrita no 1º ano de escolaridade: os resultados dos alunos em leitura

Tese de Doutoramento em Psicologia Aplicada, Área de especialidade Psicologia EducacionalO presente estudo teve como objetivo caracterizar as práticas de ensino da linguagem escrita em Portugal e perceber o seu impacto na aquisição da leitura no final do 1º ano de escolaridade. A primeira etapa deste estudo correspondeu a um estudo descritivo e comparativo com o realizado por Fijalkow (2003) em França. A partir da resposta a um questionário de 883 professores foi possível verificar que os professores dos dois países se aproximam no que diz respeito aos aspetos metodológicos do ensino da leitura e à avaliação da leitura e da escrita dos alunos. Contudo, os professores portugueses dizem utilizar com maior frequência do que os professores franceses, atividades a partir de livros infantis, outros materiais para além do manual e diferentes propostas de escrita. Na segunda etapa deste estudo, o questionário utilizado foi validado através da sua estrutura fatorial e foram utilizados os fatores revelados para a realização de uma análise hierárquica de clusters. Esta análise revelou três grupos de professores: a) um grupo de professores que centra as suas práticas no ensino do código da linguagem escrita (unidades curtas); b) um grupo que realça a construção de significado na interação com o material escrito (unidades longas); c) e um grupo de professores que reúne nas suas práticas características de ambos os grupos referidos anteriormente (unidades diversificadas). A terceira etapa realizada diz respeito à validação das respostas do questionário através da observação de sala de aula. Foram selecionados 5% dos professores de cada um dos três grupos constituídos (N=42). Cada professor foi observado duas vezes durante 60 minutos em situações escolhidas por si como situações privilegiadas para o ensino da linguagem escrita. Através da utilização de uma grelha de observação que divide as atividades desenvolvidas em atividades que remetem para o código ou para o significado, foi possível confirmar as respostas ao questionário para 55% dos professores participantes. No sentido de perceber o impacto das práticas dos professores na aquisição da leitura dos alunos foram selecionados os professores cujas observações foram coincidentes com as respostas ao questionário e avaliados os seus alunos com recurso a três provas de leitura: leitura de palavras isoladas, decisão lexical e compreensão. Participaram 461 alunos distribuídos pelos três grupos referidos anteriormente. Através da realização de uma MANCOVA, controlando a escolaridade das mães dos alunos, verificou-se que os alunos do grupo unidades diversificadas obtêm melhores resultados em todas as provas do que os alunos dos outros dois grupos. Foi ainda possível constatar que não existiram diferenças de desempenho entre os alunos do grupo unidades curtas e os alunos do grupo unidades longas.ABSTRACT: The present study aimed to characterize the teaching practices of written language and understand its impact on reading acquisition by the end of 1st grade. The first step of this study was a descriptive and comparative study to the one conducted by Fijalkow (2003) in France. Based on questionnaire answers of 883 teachers, we found that teachers from both countries have similar approaches regarding methodological aspects of teaching of reading and students’ assessment of reading and writing abilities. However, Portuguese teachers stated that they use more frequently activities from children's literature, other materials besides the manual and different writing proposals than French teachers. In the second step of the study, the questionnaire was validated through its factorial structure and the factors disclosed were used to perform a hierarchical cluster analysis. This analysis revealed three groups of teachers: a) a group of teachers who focus its practices in teaching the code of written language (short units), b) a group that emphasizes the construction of meaning in interaction with the written material (long units), c) and a group of teachers who gathered in their practices characteristics of both groups mentioned above (diversified units). The third step concerns the validation of the questionnaire answers through classroom observation. 5% of the teachers in each of the three groups were selected (N=42). Each teacher was observed twice during 60 minutes in situations identified by them as privileged situations for teaching written language. Using an observation grid which divides the activities conducted in code-activities or the meaning-activities it was possible to confirm questionnaire answers for 55% of the participating teachers. In order to understand the impact of teachers’ practices in students reading acquisition, teachers whose observations were coincident with the questionnaire answers were selected and their students were evaluated using three reading tests: single words reading, lexical decision task and comprehension task. Participants were 461 students distributed through the three groups previously mentioned. By conducting a MANCOVA, controlling mothers’ education level, we concluded that students in the diversified unit group obtain better results in all reading tests than students from the other groups. It was also possible to confirm that there were no differences in performance between students of the short units group and students of the long units group.Tese de Doutoramento em Psicologia Aplicada, Área de especialidade Psicologia EducacionalApoio financeiro da Fundação para a Ciência e Tecnologia (SFRH/BD/64630/2009