The Versatile Dioctadecyldimethylammonium Bromide

Dioctadecyldimethylammonium bromide (DODAB) is a quaternary ammonium surfactant (Quat) with interesting properties and applications. In this chapter, DODAB characteristics as compared to other Quats emphasize its self-assembly in aqueous solutions and the novel applications involving this useful cationic lipid so easily combined with biomolecules and interfaces to yield a wide range of novel uses in many fields such as delivery of drugs, vaccines and genes, design of nanoparticles, modification of interfaces, and many others yet to come

Biomimetic nanoparticles: preparation, characterization and biomedical applications

Mimicking nature is a powerful approach for developing novel lipid-based devices for drug and vaccine delivery. In this review, biomimetic assemblies based on natural or synthetic lipids by themselves or associated to silica, latex or drug particles will be discussed. In water, self-assembly of lipid molecules into supramolecular structures is fairly well understood. However, their self-assembly on a solid surface or at an interface remains poorly understood. In certain cases, hydrophobic drug granules can be dispersed in aqueous solution via lipid adsorption surrounding the drug particles as nanocapsules. In other instances, hydrophobic drug molecules attach as monomers to borders of lipid bilayer fragments providing drug formulations that are effective in vivo at low drug-to-lipid-molar ratio. Cationic biomimetic particles offer suitable interfacial environment for adsorption, presentation and targeting of biomolecules in vivo. Thereby antigens can effectively be presented by tailored biomimetic particles for development of vaccines over a range of defined and controllable particle sizes. Biomolecular recognition between receptor and ligand can be reconstituted by means of receptor immobilization into supported lipidic bilayers allowing isolation and characterization of signal transduction steps

Biomimetic Nanomaterials from the Assembly of Polymers, Lipids, and Surfactants

Nanostructured materials require evaluation at a molecular level to become controllable and useful in drug and vaccine delivery. Over the years self-assembled nanomaterials such as nanoparticles and thin films have been prepared, characterized and used for biomedical applications. In this review meaningful examples of biomimetic nanomaterials and their construction based on intermolecular interactions such as the electrostatic attraction or the hydrophobic effect will be discussed. Emphasis will be placed on the interactions between polymers, lipids, surfactants and surfaces leading to bioactive supramolecular assemblies such as nanoparticles and coatings. Among the important applications of the self-assembled nanostructures and films to be reviewed are their antimicrobial effect and their adjuvant activity for vaccine delivery

Emerging Cationic Nanovaccines

Cationic vaccines of nanometric sizes can directly perform the delivery of antigen(s) and immunomodulator(s) to dendritic cells in the lymph nodes. The positively charged nanovaccines are taken up by antigen-presenting cells (APCs) of the lymphatic system often originating the cellular immunological defense required to fight intracellular microbial infections and the proliferation of cancers. Cationic molecules imparting the positive charges to nanovaccines exhibit a dose-dependent toxicity which needs to be systematically addressed. Against the coronavirus, mRNA cationic nanovaccines evolved rapidly. Nowadays cationic nanovaccines have been formulated against several infections with the advantage of cationic compounds granting protection of nucleic acids in vivo against biodegradation by nucleases. Up to the threshold concentration of cationic molecules for nanovaccine delivery, cationic nanovaccines perform well eliciting the desired Th 1 improved immune response in the absence of cytotoxicity. A second strategy in the literature involves dilution of cationic components in biocompatible polymeric matrixes. Polymeric nanoparticles incorporating cationic molecules at reduced concentrations for the cationic component often result in an absence of toxic effects. The progress in vaccinology against cancer involves in situ designs for cationic nanovaccines. The lysis of transformed cancer cells releases several tumoral antigens, which in the presence of cationic nanoadjuvants can be systemically presented for the prevention of metastatic cancer. In addition, these local cationic nanovaccines allow immunotherapeutic tumor treatment

Phylogenetic evidence based on Trypanosoma cruzi nuclear gene sequences and information entropy suggest that inter-strain intragenic recombination is a basic mechanism underlying the allele diversity of hybrid strains

The diversity of Trypanosoma cruzi is categorized into six discrete typing units (DTUs) T. cruzi I to VI. Several studies indicate that T. cruzi I and II are ancestors of T. cruzi which are considered products of independent hybridization events. the individual haplotypes or alleles of these hybrids cluster in three groups, either closer to T. cruzi I or T. cruzi II or forming a midpoint clade between T. cruzi I and II in network phylogenies. To understand the origins of these different sets of haplotypes and test the hypothesis of a direct correlation between high entropy and positive selection, we analyzed four nuclear protein coding genes. We show that hybrid strains contain haplotypes that are mosaics probably originated by intragenic recombination. Accordingly, in phylogenies, the hybrid haplotypes are closer to one or both parentals (T. cruzi I and II) depending on the proportion of parental sequences composing the mosaics. in addition, Shannon entropy, used to measure sequence diversity, is highly correlated with positive selection in the four genes here analyzed. Our data on recombination patterns also support the hypothesis of two hybridization events in the hybrid structures of T. cruzi Data presented and discussed here are consistent with a scenario where TcI and TcII are phylogenetically divergent forming a hybrid zone in between (T. cruzi III-VI). We predict that because of the quasi-random nature of T. cruzi I and II hybridization more DTUs, with different haplotype combinations, will be discovered in the hybrid zone. (C) 2012 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Howard Hughes Medical InstituteUniversidade Federal de São Paulo, Dept Microbiol Imunol & Parasitol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Med, Disciplina Infectol, BR-04023900 São Paulo, BrazilUniversidade Federal de São Paulo, Lab Genom Evolut & Biocomplexidade, BR-04039032 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Microbiol Imunol & Parasitol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Med, Disciplina Infectol, BR-04023900 São Paulo, BrazilUniversidade Federal de São Paulo, Lab Genom Evolut & Biocomplexidade, BR-04039032 São Paulo, BrazilWeb of Scienc

Antimicrobial Biomimetics

A vast territory for research is open from mimicking the behaviour of microorganisms to defend themselves from competitors. Antibiotics secreted by bacteria or fungi can be copied to yield efficient molecules which are active against infectious diseases. On the other hand, nanotechnology provides novel techniques to probe and manipulate single atoms an

Identidade profissional dos professores de Matemática: processos de formação

Dissertação de mestrado em Ciências da Educação: área de Educação e DesenvolvimentoEsta dissertação é o resultado de uma investigação realizada sobre a identidade profissional dos professores de Matemática das Escolas Secundárias (esta nomenclatura é aqui usada sem ter em conta a terminologia introduzida pela Reforma do Sistema Educativo em curso) e sobre os processos de formação dessa mesma identidade, tendo como objectivo principal contribuir para a compreensão deste grupo de docentes e, consequentemente dos docentes em geral. A metodologia associada a este estudo recorreu a procedimentos quantitativos e qualitativos. No domínio do quantitativo realizaram-se dois inquéritos no Distrito de Setúbal que permitiram aí caracterizar o grupo de professores de Matemática, sendo de realçar a diversidade das habilitações académicas destes docentes. No domínio do qualitativo realizaram-se nove entrevistas, em duas escolas distintas, o que permitiu pôr em relevo a importância dos contextos na identidade profissional. De referir que uma das diferenças significativas entre as duas escolas está relacionada com a estabilidade dos professores de Matemática. Assim, os entrevistados da escola B consideraram a existência de um grande número de professores não efectivos um elemento que influencia o ensino da Matemática na sua escola enquanto os professores da escola A não manifestam tais preocupações, tão acentuadamente, já que a maioria dos docentes da sua escola é efectivo. A par de tais preocupações comuns a quase todos os professores, este estudo permitiu, também, evidenciar a singularidade de cada indivíduo, nomeadamente através da análise de conteúdo das entrevistas. Em conclusão, este estudo realçou o facto da identidade profissional estar sempre associada a um processo dinâmico onde se evidencia, simultaneamente, a singularidade dos indivíduos através da explicitação daquilo que os diferencia, e a universalidade, que transparece na comunhão daquilo que os une