Probing the Structure of Liquids with 129Xe NMR Spectroscopy: n-Alkanes, Cycloalkanes, and Branched Alkanes

The liquid organization of linear, branched, and cyclic alkanes was studied using atomic 129Xe as a NMR probe. 129Xe chemical shifts have been experimentally determined for xenon dissolved in a total of 21 alkanes. In order to allow the comparison of the different solvents at similar thermodynamic conditions, the measurements were performed over a wide range of temperatures, from the melting point of the solvent up to 350 K. The results were rationalized in terms of the density, nature, and organization of the chemical groups within xenon’s coordination sphere. Additionally, molecular dynamics simulations were performed using established atomistic force fields to interpret and clarify the conclusions suggested by the experimental results. The analysis is able to interpret previous results in the literature for ethane and propane at very different experimental conditions

On the Behavior of Solutions of Xenon in Liquid n-Alkanes: Solubility of Xenon in n-Pentane and n-Hexane

The solubility of xenon in liquid n-pentane and n-hexane has been studied experimentally, theoretically, and by computer simulation. Measurements of the solubility are reported for xenon + n-pentane as a function of temperature from 254 to 305 K. The uncertainty in the experimental data is less than 0.15%. The thermodynamic functions of solvation such as the standard Gibbs energy, enthalpy, and entropy of solvation have been calculated from Henry’s law coefficients for xenon + n-pentane solutions and also for xenon + n-hexane, which were reported in previous work. The results provide a further example of the similarity between the xenon + n-alkane interaction and the n-alkane + n-alkane interactions. Using the SAFT-VR approach we were able to quantitatively predict the experimental solubility for xenon in n-pentane and semiquantitatively that of xenon in n-hexane using simple Lorentz−Berthelot combining rules to describe the unlikely interaction. Henry’s constants at infinite dilution for xenon + n-pentane and xenon + n-hexane were also calculated by Monte Carlo simulation using a united atom force field to describe the n-alkane and the Widom test particle insertion method

On the Behaviour of Solutions of Xenon in Liquid Cycloalkanes: Solubility of Xenon in Cyclopentane

The solubility of xenon in liquid cyclopentane has been studied experimentally and theoretically. Measurements of the solubility of xenon in liquid cyclopentane are reported as a function of temperature from 254.60Kto 313.66 K. The imprecision of the experimental data is less than 0.3%. The thermodynamic functions of solvation of xenon in cyclopentane, such as the standard Gibbs energy, enthalpy, entropy and heat capacity of solvation, have been calculated from the temperature dependence of Henry’s law coefficients. The results provide further information about the differences between the xenon + cycloalkanes and the xenon + n-alkane interactions. In particular, interaction enthalpies between xenon and CH2 groups in nalkanes and cycloalkanes have been estimated and compared. Using a version of the soft-SAFT approach developed to model cyclic molecules, we were able to reproduce the experimental solubility for xenon in cyclopentane using simple Lorentz-Berthelot rules to describe the unlike interaction

Polyurea dendrimer for efficient cytosolic siRNA delivery

PEst-OE/SAU/UI0009/2013 SFRH/BD/62957/2009The design of small interfering RNA (siRNA) delivery materials showing efficacy in vivo is at the forefront of nanotherapeutics research. Polyurea (PURE-type) dendrimers are 'smart' biocompatible 3D polymers that unveil a dynamic and elegant back-folding mechanism involving hydrogen bonding between primary amines at the surface and tertiary amines and ureas at the core. Similarly, to a biological proton pump, they are able to automatically and reversibly transform their conformation in response to pH stimulus. Here, we show that PURE-G4 is a useful gene silencing platform showing no cellular toxicity. As a proof of concept we investigated the PURE-G4-siRNA dendriplex, which was shown to be an attractive platform with high transfection efficacy. The simplicity associated with the complexation of siRNA with polyurea dendrimers makes them a powerful tool for efficient cytosolic siRNA delivery.authorsversionpublishe

Evaluation of novel 3D architectures based on knitting technologies for engineering biological tissues

Textile-based technologies are considered as potential routes for the production of 3D porous architectures for tissue engineering applications. We describe the use of two polymers, namely polybutylene succinate (PBS) and silk fibroin (SF) to produce fiber-based finely tuned porous architectures by weft and warp knitting. The obtained knitted constructs are described in terms of their morphology, mechanical properties, swelling ability, degradation behaviour and cytotoxicity. Each type of polymer fibers allow for the processing of a very reproducible intra-architectural scaffold geometry, with distinct characteristics in terms of the surface physicochemistry, mechanical performance and degradation capability, which has an impact on the resulting cell behaviour at the surface of the respective biotextiles. Preliminary cytotoxicity screening shows that both materials can support cell adhesion and proliferation. Furthermore, different surface modifications were performed (acid/alkaline treatment, UV radiation and plasma) for modulating cell behavior. An increase of cell-material interactions were observed, indicating the important role of materials surface in the first hours of culturing. Human Adipose-derived Stem Cells (hASCs) became an emerging possibility for regenerative medicine and tissue replacement therapies. The potential of the recently developed silk-based biotextile structures to promote hASCs adhesion, proliferation and differentiation is also evaluated. The obtained results validate the developed constructs as viable matrices for TE applications. Given the processing efficacy and versatility of the knitting technology, and the interesting structural and surface properties of the proposed polymer fibers, it is foreseen that our developed systems can be attractive for the functional engineering of tissues such as bone, skin, ligaments or cartilage and also for develop more complex systems for further industrialization of TE products.(undefined

Complex 3D architectures using a textile technology for bone tissue engineering applications

Textile-based technologies are particularly interesting in tissue engineering since they allow producing finely tuned fibre-based porous structures, offering superior control over the material design (size, porosity, fibre alignment) and manufacturing. Scaffolds with very reproducible and interconnected intra-architectural geometry can be processed increasing the surface area for cell attachment and tissue ingrowth. This work aims to evaluate the potential of recently developed 3D textile structures based on silk fibroin (SF) to support human Adipose-derived Stem Cells (hASCs) adhesion, proliferation and osteogenic differentiation. These cells constitute an emerging possibility for regenerative medicine, including for bone tissue regeneration. A comparative analysis was performed with a more stable polymeric system, polyethylene terephthalate (PET). SF and PET yarns were processed into 3D spacer structures using warp-knitting technology. The obtained complex 3D architectures are composed of two knitted layers assembled/spaced by a PET monofilament to increase the tri-dimensionality of the scaffold. Cells were able to attach to the fibres, proliferate and differentiate into the osteogenic lineage. hASCs were able to deeply penetrate into the scaffold and colonize its interior with great evidences of extracellular matrix mineralization (Fig.1). The efficiency and high level of control of the warpknitting technology together with the interesting structural properties of the resulting constructs makes this a very versatile and adaptable system to the specific bone tissue anatomy and function.info:eu-repo/semantics/publishedVersio

Influence of different surface modification treatments on silk biotextiles for tissue engineering applications

Biotextile structures from silk fibroin have demonstrated to be particularly interesting for tissue engineering (TE) applications due to their high mechanical strength, interconnectivity, porosity, and ability to degrade under physiological conditions. In this work, we described several surface treatments of knitted silk fibroin (SF) scaffolds, namely sodium hydroxide (NaOH) solution, ultraviolet radiation exposure in an ozone atmosphere (UV/O3) and oxygen (O2) plasma treatment followed by acrylic acid (AAc), vinyl phosphonic acid (VPA), and vinyl sulfonic acid (VSA) immersion. The effect of these treatments on the mechanical properties of the textile constructs was evaluated by tensile tests in dry and hydrated states. Surface properties such as morphology, topography, wettability and elemental composition were also affected by the applied treatments. The in vitro biological behavior of L929 fibroblasts revealed that cells were able to adhere and spread both on the untreated and surface-modified textile constructs. The applied treatments had different effects on the scaffoldsâ surface properties, confirming that these modifications can be considered as useful techniques to modulate the surface of biomaterials according to the targeted application.Contract grant sponsor: Portuguese Foundation for Science and Technology under POCTI and/or FEDER programs under the scope of the project TISSUE2TISSUE; contract grant number: PTDC/CTM/105703/2008Contract grant sponsor: Investigator FCT program (to A.N.L.); contract grant number: IF/00411/201

Anesthesiology Consensus in the Management of the Airway

Os consensos na gestão clínica da via aérea em anestesiologia pretendem disponibilizar informação, baseada na evidência atual ou, na falta desta, na opinião de peritos, no que respeita à abordagem da via aérea difícil previsível ou não previsível. Reforçamos a importância da avaliação da via aérea e da identificação de potenciais problemas que possam condicionar dificuldade na sua abordagem e a adoção de uma estratégia segura que permita identificar e responder em crescendo de intervenção às dificuldades encontradas. Na impossibilidade de intubação traqueal (não intubo) otimizada e limitada a 4 tentativas, da impossibilidade de ventilar e oxigenar (não oxigeno) após 2 tentativas de usar um dispositivo supraglótico ou de uso de máscara facial inicialmente adequada é importante realizar, em tempo útil, uma cricotirotomia para assegurar oxigenação. As situações clínicas de exceção só com planos simples, conhecidos por todos e regularmente treinados e adaptados à nossa atividade clinica podem assegurar melhores “outcomes”. O registo destes eventos e a informação ao nosso doente da dificuldade encontrada e modo como foi resolvido o problema é essencial e constitui ainda um desafio a alargar a uma base nacional.info:eu-repo/semantics/publishedVersio

Atraumatic restorative treatment-sealed versus nonsealed first permanent molars: a 3-year split-mouth clinical trial

To investigate the efficacy of atraumatic restorative treatment (ART) sealants vs. no sealant in preventing the development of dentine caries lesions in first permanent molars over a period of 3 years. A total of 187 schoolchildren (aged 6–8 years) from a low-income population presenting the 4 first permanent molars without clinically detectable dentine caries lesions were selected to be part of a split-mouth clinical trial. All 4 first permanent molars were investigated in this trial and the children’s mouth was split vertically into left and right sides; therefore, 2 molars were randomly allocated to receive ART sealants, while the other 2 molars remained nonsealed. All children received toothbrushing instructions and dietary advice every 6 months for a period of 3 years. Clinical evaluations were performed after 3, 6, 12, 18, 24, and 36 months and both sealant retention and dental caries were scored. Kaplan-Meier survival analysis, log-rank test, and Cox regression with shared frailty analysis were performed. A cavitated dentine caries lesion was considered a failure. The cumulative survival rates of dentine cavity-free first permanent molars were 90% for ART-sealed molars and 90.8% for nonsealed molars, with no statistically significantly difference between sealed and nonsealed molars (p = 0.70). The retention of sealants was not associated with the development of cavitated dentine caries and children presenting a higher baseline caries experience had greater chances of developing dentine lesions. In conclusion, the application of ART sealants was not more efficacious than nonsealing in reducing the development of dentine cavitated lesions in first permanent molars