Emulsions stabilised by whey protein microgel particles: Towards food-grade Pickering emulsions

We have investigated a new class of food-grade particles, whey protein microgels, as stabilisers of triglyceride-water emulsions. The sub-micron particles stabilized oil-in-water emulsions at all pH with and without salt. All emulsions creamed but exhibited exceptional resistance to coalescence. Clear correlations exist between the properties of the microgels in aqueous dispersion and the resulting emulsion characteristics. For conditions in which the particles were uncharged, fluid emulsions with relatively large drops were stabilised, whereas emulsions stabilized by charged particles contained smaller flocculated drops. A combination of optical microscopy of the drops and spectrophotometry of the resolved aqueous phase allowed us to estimate the interfacial adsorption densities of the particles using the phenomenon of limited coalescence. We deduce two classes of particle arrangement. Complete adsorption of the particles was obtained when they were neutral or when their charges were screened by salt resulting in at least one particle monolayer at the interface. By contrast, only around 50% of the particles adsorbed when they were charged with emulsion drops being covered by less than half a monolayer. These findings were supported by direct visualization of drop interfaces using cryo-scanning electron microscopy. Uncharged particles were highly aggregated and formed a continuous 2-D network at the interface. Otherwise particles organized as individual aggregates separated by particle-free regions. In this case, we suggest that some particles spread at the interface leading to the formation of a continuous protein membrane. Charged particles displayed the ability to bridge opposing interfaces of neighbouring drops to form dense particle disks protecting drops against coalescence; this is the main reason for the flocculation and stability of emulsions containing sparsely covered drops. © 2014 the Partner Organisations

Comment évaluer les effets du Plan Marshall2.Vert ?

Evaluer une politique, c’est la questionner d’une manière particulière, en vue de porter un jugement et d’éclairer les décideurs. Lorsque la politique à évaluer est le Plan Marshall2.Vert, qui couvre la plupart des compétences du Gouvernement wallon, l’évaluation est d’une grande complexité. L’objet de cet article est de décrire la démarche adoptée par l’IWEPS pour préparer l’évaluation du Plan Marshall2.Vert : analyse de la logique d’intervention, construction d’un référentiel d’évaluation, traduction des objectifs en indicateurs de résultat, constitution d’un programme d’évaluations partielles sont les principales étapes de cette démarche.

La maladie à virus Ebola : pathosystèmes forestiers et risques zoonotiques

La récente (2014-2016) épidémie de maladie à virus Ebola en Afrique de l'Ouest conduit la communauté scientifique à accentuer ses recherches sur les origines et les probabilités de transmission entre animaux et populations humaines. De nombreuses inconnues subsistent quant aux modes et voies de circulation selvatique et zoonotique du virus Ebola. Le rôle des chauves-souris et d'autres espèces de mammifères sauvages et domestiques doit être analysé plus précisément dans les divers écosystèmes forestiers africains. Des systèmes de surveillance adaptés au suivi de la faune sauvage sont nécessaires. Enfin, la répartition géographique des différents virus Ebola, les risques de diffusion au niveau régional et international et les modalités de transmission à l'Homme sont à étudier

Thiol groups controls on arsenite binding by organic matter: New experimental and modeling evidence

International audienceAlthough it has been suggested that several mechanisms can describe the direct binding ofAs(III) to organic matter (OM), more recently, the thiol functional group of humic acid (HA)was shown to be an important potential binding site for As(III). Isotherm experiments onAs(III) sorption to HAs, that have either been grafted with thiol or not, were thus conducted toinvestigate the preferential As(III) binding sites. There was a low level of binding of As(III) toHA, which was strongly dependent on the abundance of the thiols. Experimental datasetswere used to develop a new model (the modified PHREEQC-Model VI), which defines HA asa group of discrete carboxylic, phenolic and thiol sites. Protonation/deprotonation constantswere determined for each group of sites (pKA = 4.28 ± 0.03; ΔpKA = 2.13 ± 0.10; pKB = 7.11 ±0.26; ΔpKB = 3.52 ± 0.49; pKS = 5.82 ± 0.052; ΔpKS = 6.12 ± 0.12 for the carboxylic, phenolicand thiols sites, respectively) from HAs that were either grafted with thiol or not. The pKSvalue corresponds to that of single thiol-containing organic ligands. Two binding models weretested: the Mono model, which considered that As(III) is bound to the HA thiol site asmonodentate complexes, and the Tri model, which considered that As(III) is bound astridentate complexes. A simulation of the available literature datasets was used to validate2the Mono model, with log KMS = 2.91 ± 0.04, i.e. the monodentate hypothesis. This studyhighlighted the importance of thiol groups in OM reactivity and, notably, determined theAs(III) concentration bound to OM (considering that Fe is lacking or at least negligible) andwas used to develop a model that is able to determine the As(III) concentrations bound toOM

Effects of Fe competition on REE binding to humic acid: Origin of REE pattern variability in organic waters

International audienceCompetitivemechanisms between rare earth elements (REE) and iron (Fe) for humic acid (HA) bindingwere investigated by coupling laboratory experiments and modeling calculations using PHREEQC/Model VI. This study aims, firstly, at determining the effect of Fe on REE-HA binding, in order to explain the REE pattern variability observed in natural organic-rich waters. Secondly, it has previously been shown that light and heavy REE (Land HREE) speciation with HA molecules differ with pH. Therefore, REE-HA complexation patterns have been used as a probe of Fe-HA binding mechanisms. At pH 3, i.e. pH conditions at which Fe3+ binds to HA, Fe is shown to be a strong competitor for heavy REE (HREE), suggesting that Fe3+ has a marked affinity for the few strong HA multidentate sites. At pH 6, i.e. under pH conditions atwhich hydrolyzed Fe species bind to HA, Fe appears to compete equally for every REE, thereby indicating that Fe has the samerelative affinity for carboxylic and phenolic HA sites as LREE and HREE, respectively. Fractionation of REE in organic-rich natural waters depends mainly on the coupling of two factors: (i) the total dissolved metal concentration (i.e. the HA metal loading) and (ii) the competition between REE and major cations (i.e. Fe and Al). The pH, which regulates the speciation of these competitive metals, is, therefore, indirectly the main controlling factor of REE fractionation in organic-rich waters

Brief report: Beyond clinical experience: Features of data collection and interpretation that contribute to diagnostic accuracy

BACKGROUND: Clinical experience, features of data collection process, or both, affect diagnostic accuracy, but their respective role is unclear. OBJECTIVE, DESIGN: Prospective, observational study, to determine the respective contribution of clinical experience and data collection features to diagnostic accuracy. METHODS: Six Internists, 6 second year internal medicine residents, and 6 senior medical students worked up the same 7 cases with a standardized patient. Each encounter was audiotaped and immediately assessed by the subjects who indicated the reasons underlying their data collection. We analyzed the encounters according to diagnostic accuracy, information collected, organ systems explored, diagnoses evaluated, and final decisions made, and we determined predictors of diagnostic accuracy by logistic regression models. RESULTS: Several features significantly predicted diagnostic accuracy after correction for clinical experience: early exploration of correct diagnosis (odds ratio [OR] 24.35) or of relevant diagnostic hypotheses (OR 2.22) to frame clinical data collection, larger number of diagnostic hypotheses evaluated (OR 1.08), and collection of relevant clinical data (OR 1.19). CONCLUSION: Some features of data collection and interpretation are related to diagnostic accuracy beyond clinical experience and should be explicitly included in clinical training and modeled by clinical teachers. Thoroughness in data collection should not be considered a privileged way to diagnostic succes

Critical role of surface chemical modifications induced by length shortening on multi-walled carbon nanotubes-induced toxicity.

International audienceABSTRACT: Given the increasing use of carbon nanotubes (CNT) in composite materials and their possible expansion to new areas such as nanomedicine which will both lead to higher human exposure, a better understanding of their potential to cause adverse effects on human health is needed. Like other nanomaterials, the biological reactivity and toxicity of CNT were shown to depend on various physicochemical characteristics, and length has been suggested to play a critical role.We therefore designed a comprehensive study that aimed at comparing the effects on murine macrophages of two samples of multi-walled CNT (MWCNT) specifically synthesized following a similar production process (aerosol-assisted CVD), and used a soft ultrasonic treatment in water to modify the length of one of them.We showed that modification of the length of MWCNT leads, unavoidably, to accompanying structural (i.e. defects) and chemical (i.e. oxidation) modifications that affect both surface and residual catalyst iron nanoparticle content of CNT. The biological response of murine macrophages to the two different MWCNT samples was evaluated in terms of cell viability, pro-inflammatory cytokines secretion and oxidative stress. We showed that structural defects and oxidation both induced by the length reduction process are at least as responsible as the length reduction itself for the enhanced pro-inflammatory and pro-oxidative response observed with short (oxidized) compared to long (pristine) MWCNT.In conclusion, our results stress that surface properties should be considered, alongside the length, as essential parameters in CNT-induced inflammation, especially when dealing with a safe design of CNT, for application in nanomedicine for example

Structure in Nascent Carbon Nanotubes Revealed by Spatially Resolved Raman Spectroscopy

The understanding of carbon nanotubes (CNT) growth is crucial for the control of their production. In particular, the identification of structural changes of carbon possibly occurring near the catalyst particle in the very early stages of their formation is of high interest. In this study, samples of nascent CNT obtained during nucleation step and samples of vertically aligned CNT obtained during growth step are analysed by combined spatially resolved Raman spectroscopy and X-Ray diffraction measurements. Spatially resolved Raman spectroscopy reveals that iron-based phases and carbon phases are co-localised at the same position, and indicates that sp2 carbon nucleates preferentially on iron-based particles during this nucleation step. Depth scan Raman spectroscopy analysis, performed on nascent CNT, highlights that carbon structural organisation is significantly changing from defective graphene layers surrounding the iron-based particles at their base up to multi-walled nanotube structures in the upper part of iron-based particles

Comparison of two enzymatic immunoassays, high resolution mass spectrometry method and radioimmunoassay for the quantification of human plasma histamine

International audienceHistamine (HA) is one of the main immediate mediators involved in allergic reactions. HA plasma concentration is well correlated with the severity of vascular and respiratory signs of anaphylaxis. Consequently, plasma quantification of HA is useful to comfort the diagnosis of anaphylaxis. Currently, radioimmunoassay (RIA) is the gold standard method to quantify HA due to its high sensitivity, but it is time consuming, implicates specific formations and cautions for technicians, and produces hazardous radioactive wastes. The aim of this study was to compare two enzymatic immunoassays (EIA) and one in-house liquid chromatography high-resolution mass spectrometry method (LC-HRMS) with the gold standard method for HA quantification in plasma samples of patients suspected of anaphylaxis reactions. Ninety-two plasma samples were tested with the 4 methods (RIA, 2 EIA and LC-HRMS) for HA quantification. Fifty-eight samples displayed HA concentrations above the positive cut-off of 10 nM evaluated by RIA, including 18 highly positive samples (>100 nM). Our results showed that Immunotech® EIA and LC-HRMS concentrations were highly correlated with RIA values, in particular for samples with a HA concentration around the positive cut-off. In our hands, plasma concentrations obtained with the Demeditec Diagnostics® EIA correlated less with results obtained by RIA, and an underestimation of plasma HA levels led to a lack of sensitivity. In conclusion, this study demonstrates that Immunotech® EIA and LC-HRMS method could be used instead of RIA to assess plasma HA in human diagnostic use