Association of albumin or protamine to lipoplexes: enhancement of transfection and resistance to serum

The successful application of gene therapy depends on the availability of carriers to efficiently deliver genetic material into target cells. Such efficacy is strongly related to key parameters including serum resistance and protection of DNA.The complexes were tested in terms of their biological activity, in the absence or presence of serum, by following transfection activity. Interaction with plasma proteins was evaluated by immunoblotting, while cytotoxicity was assessed by the Alamar Blue assay. Extent of DNA protection was determined both by using ethidium bromide intercalation and DNase I digestion assays.Our results show that, depending on the charge ratio and on the lipid composition, albumin and protamine can be used (either individually or co-associated) to generate cationic liposome/DNA complexes fulfilling in vivo requirements, while exhibiting high levels of transfection activity. In the present work a novel cationic lipid was tested. It was demonstrated that 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (EPOPC):cholesterol (Chol) liposomes constitute a very promising carrier for gene delivery as illustrated by their enhancing effect on transfection, as compared with DOTAP-containing liposomes. Moreover, the biological activity of EPOPC-containing complexes is significantly improved upon association of albumin, even in the presence of 60% serum (namely for the 4/1 lipid/DNA charge ratio). Nevertheless, our studies also show that transfection activity mediated by DOTAP-containing complexes can be significantly enhanced upon pre-condensation of DNA with protamine.Co-association of HSA and protamine to lipoplexes ensures a high degree of DNA protection and results in high levels of transfection activity even in the presence of serum. Copyright © 2004 John Wiley & Sons, Ltd

A plasmonic route towards the energy scaling of on-chip integrated all-photonic phase-change memories

This is the author accepted manuscript.Phase-change photonic memory devices, conventionally implemented as a thin layer of phase-change material deposited on the top of an integrated Si or SiN waveguide, have the flexibility to be applied in a widely diverse context, as a pure memory device, a logic gate, an arithmetic processing unit and for biologically inspired computing. In all such applications increasing the speed, and reducing the power consumption, of the phase-switching process is most desirable. In this work, therefore, we investigate, via simulation, a novel integrated photonic device architecture that exploits plasmonic effects to enhance the light-matter interaction. Our device comprises a dimer nanoantenna fabricated on top of a SiN waveguide and with a phase-change material deposited into the gap between the two nanoantenna halves. We observed very considerably increased device speeds and reduced energy requirements, of up to two orders of magnitude, when compared to the conventional structure.Engineering and Physical Sciences Research Council (EPSRC

Accepter n’est pas intégrer: Les langues et cultures d’origine vues par les enseignants au Portugal

Cet article présente les premiers résultats d’une vaste recherche réalisée en milieu scolaire portugais et dont les objectifs sont, d’une part, de comprendre la façon dont les enseignants, en milieu scolaire du centre du Portugal facilitent la mise en place de relations positives qui valorisent et reconnaissent la diversité linguistique et culturelle des élèves de minorités linguistiques et culturelles et, d’autre part, de savoir s’ils mobilisent les langues et cultures d’origine (LCO) dans leurs planifications, activités et discours en salle de classe.This article presents a first set of results of a broader research carried out in Portuguese schools and whose objectives are on the one hand to understand the form as the teachers interviewed, teaching in schools in central Portugal, facilitate or not the establishment of teaching-learning strategies that value and recognize the linguistic and cultural diversity of students of linguistic and cultural minorities, and on the other hand whether they mobilize heritage languages and cultures (HLC) in their planning, activities and discourses in the classroom.publishe

Heritage languages of young people from linguistic and cultural minorities in Portuguese schools: monolingual temptation versus multilingual realities

The main purpose of this poster is to present a case study aimed at researching the multilingual repertoires of young people from a linguistic and cultural minority. Further, it analyzes the role of and the place given to heritage languages (HL) in the development of a multilingual and intercultural competence in schools. In the scope of this study, a survey was conducted using two online questionnaires distributed to students from a migrant background and teachers. These students and teachers attended two primary and secondary schools in the central region of Portugal during the academic year 2013–2014. The results show that the students value their HL and perceive them as an instrument of social interaction as well as identity construction and affirmation. Additionally, the results show that both school and teachers recognize and respect the students’ linguistic and cultural capital as well as their composite and plural identities. However, they do not take advantage of this in the classroom by not promoting activities that enrich their students’ cultural and linguistic culture. In this context, the possibilities for an education in/with HL, as a pedagogical and didactic project, are not yet present in the school curriculum and habitus, on the one hand, because there are no educational language policies that incorporate it, and on the other hand, because both school and teachers do not seem to value the role and usefulness of HL in the promotion of an intercultural and multilingual education

A plasmonically enhanced route to faster and more energy-efficient phase-change integrated photonic memory and computing devices

This is the author accepted manuscript. The final version is available from AIP Publishing via the DOI in this recordData availability: The data that support the findings of this study are available from the corresponding author upon reasonable request.Over the past 30 years or more, chalcogenide phase-change materials and devices have generated much scientific and industrial interest, particularly as a platform for non-volatile optical and electronic storage devices. More recently, the combination of chalcogenide phase-change materials with photonic integrated circuits has begun to be enthusiastically explored, and among many proposals, the all-photonic phase-change memory brings the memristor-type device concept to the integrated photonic platform, opening up the route to new forms of unconventional (e.g., in-memory and neuromorphic) yet practicable optical computing. For any memory or computing device, fast switching speed and low switching energy are most attractive attributes, and approaches by which speed and energy efficiency can be improved are always desirable. For phase-change material-based devices, speed and energy consumption are both enhanced the smaller the volume of phase-change material that is required to be switched between its amorphous and crystalline phases. However, in conventional integrated photonic systems, the optical readout of nanometric-sized volumes of phase-change material is problematic. Plasmonics offers a way to bypass such limitations: plasmonic resonant structures are inherently capable of harnessing and focussing optical energy on sub-wavelength scales, far beyond the capabilities of conventional optical and photonic elements. In this work, we explore various approaches to combine the three building blocks of Si-photonics, resonant plasmonic structures, and phase-change materials to deliver plasmonically enhanced integrated phase-change photonic memory and computing devices and systems, underlining the inherent technical and theoretical challenges therein.European Union Horizon 2020Engineering and Physical Sciences Research Council (EPSRC

Sub-wavelength plasmonic-enhanced phase-change memory

This is the author accepted manuscript. The final version is available from the Society of Photo-optical Instrumentation Engineers via the DOI in this record The Ge2Sb2Te5 phase-change alloy (GST) is known for its dramatic complex refractive index (and electrical) contrast between its amorphous and crystalline phases. Switching between such phases is also non-volatile and can be achieved on the nanosecond timescale. The combination of GST with the widespread SiN integrated optical waveguide platform led to the proposal of the all-optical integrated phase-change memory, which exploits the interaction of the guided mode evanescent field with a thin layer of GST on the waveguide top surface. The relative simplicity of the architecture allows for its flexible application for data storage, logic gating, arithmetic and neuromorphic computing. Read operation relies on the transmitted signal optical attenuation, due to the GST extinction coefficient. Write/erase operations are performed via the same optical path, with a higher power ad-hoc pulsing scheme, which locally increases the temperature and triggers either the melt-quench process (write) or recrystallization (erase), encoding the information into the GST crystal fraction. Here we investigate the physical mechanisms involved in the write/erase and read processes via computational methods, with the view to explore novel architecture concepts that improve memory speed, energy efficiency and density. We show the achievements of the development of a 3D simulation framework, performing self-consistent calculations for wavepropagation, heat diffusion and phase-transition processes. We illustrate a viable memory optimization route, which adopts sub-wavelength plasmonic dimer nanoantenna structures to harvest the optical energy and maximize light-matter interaction. We calculate both a speed and energy efficiency improvement of around one order of magnitude, with respect to the conventional (non-plasmonic) device architecture.European CommissionEngineering and Physical Sciences Research Council (EPSRC)Deutsche Forschungsgemeinschaf

Performance characteristics of phase-change integrated silicon nitride photonic devices in the O and C telecommunications bands

This is the final version. Available on open access from the Optical Society via the DOI in this recordData Availability: Data relating to this manuscript can be obtained from the authors.The evaluation and comparison of the optical properties in the O and C bands of silicon nitride rib waveguides with integrated Ge2Sb2Te5 phase-change cells is reported. In straight rib waveguides, a high transmission contrast is observed in both bands when the Ge2Sb2Te5 cell is switched between states, being up to 2.5 dB/μm in the C-band and 6.4 dB/μm in the O-band. In the case of silicon nitride ring resonator waveguides, high quality factor resonances (Q ∼ 105) are found in both bands, leading to the provision of an ON-OFF switch characterized by an extinction ratio of 12 and 18 dB in O and C bands respectively. Finally, with the view to provide a comparison of the wavelength-dependent optical switching of the phase-change cell, a 3-dimensional finite-element method simulation is performed and a comparison of the optical-to-thermal energy conversion in both bands given.European Union Horizon 2020Engineering and Physical Sciences Research Council (EPSRC

Kamishibai plurilingue: da criação à execução: guia de acompanhamento

Sem resumo disponível.publishe

Dicationic Alkylammonium Bromide Gemini Surfactants. Membrane Perturbation and Skin Irritation

Dicationic alkylammonium bromide gemini surfactants represent a class of amphiphiles potentially effective as skin permeation enhancers. However, only a limited number of studies has been dedicated to the evaluation of the respective cytotoxicity, and none directed to skin irritation endpoints. Supported on a cell viability study, the cytotoxicity of gemini surfactants of variable tail and spacer length was assessed. For this purpose, keratinocyte cells from human skin (NCTC 2544 cell line), frequently used as a model for skin irritation, were employed. The impact of the different gemini surfactants on the permeability and morphology of model vesicles was additionally investigated by measuring the leakage of calcein fluorescent dye and analyzing the NMR spectra of 31P, respectively. Detail on the interaction of gemini molecules with model membranes was also provided by a systematic differential scanning calorimetry (DSC) and molecular dynamics (MD) simulation. An irreversible impact on the viability of the NCTC 2544 cell line was observed for gemini concentrations higher than 25 mM, while no cytotoxicity was found for any of the surfactants in a concentration range up to 10 mM. A higher cytotoxicity was also found for gemini surfactants presenting longer spacer and shorter tails. The same trend was obtained in the calorimetric and permeability studies, with the gemini of longest spacer promoting the highest degree of membrane destabilization. Additional structural and dynamical characterization of the various systems, obtained by 31P NMR and MD, provide some insight on the relationship between the architecture of gemini surfactants and the respective perturbation mechanism

Evaluation of lipid-based reagents to mediate intracellular gene delivery

We characterized different cationic lipid-based gene delivery systems consisting of both liposomes and nonliposomal structures, in terms of their in vitro transfection activity, resistance to the presence of serum, protective effect against nuclease degradation and stability under different storage conditions. The effect of lipid/DNA charge ratio of the resulting complexes on these properties was also evaluated. Our results indicate that the highest levels of transfection activity were observed for complexes prepared from nonliposomal structures composed of FuGENE 6. However, their DNA protective effect was shown to be lower than that observed for cationic liposome formulations when prepared at the optimal (+/-) charge ratio. Our results suggest that lipoplexes are resistant to serum up to 30% when prepared at a 2:1 lipid/DNA charge ratio. However, when they were prepared at higher (+/-) charge ratios, they become sensitive to serum for even lower concentrations (10%). Replacement of dioleoyl-phosphatidylethanolamine (DOPE) by cholesterol enhanced the resistance of the complexes to the inhibitory effect of serum. This different biological activity in the presence of serum was attributed to different extents of binding of serum proteins to the complexes, as evaluated by the immunoblotting assay. Studies on the stability under storage show that lipoplexes maintain most of their biological activity when stored at -80 °C, following their fast freezing in liquid nitrogen.http://www.sciencedirect.com/science/article/B6T1T-46NX62B-1/1/a1db498d437540e814e17abb9395e51