Understanding the adsorption of salmon calcitonin, antimicrobial peptide AP114 and polymyxin B onto lipid nanocapsules

The adsorption of therapeutic molecules, e.g., peptides, onto nanocarriers is influenced by the properties of the carrier, adsorbed molecule and continuous phase. Hence, through changes in the composition of the nanocarrier and the medium, it should be possible to tune the system to make it capable of efficiently adsorbing peptides. The adsorption of calcitonin, antimicrobial peptide AP114 and polymyxin B onto lipid nanocapsules was investigated. The adsorption data were fitted to a Langmuir isotherm. Dynamic light scattering and laser Doppler velocimetry were used to investigate the changes in the hydrodynamic diameter and zeta potential, respectively, of the nanocarrier. The peptide adsorption was primarily governed by electrostatic forces; however, even without the presence of an ionisable surfactant, a significant amount of each tested molecule was adsorbed due to the enormous surface area of the nanocarriers and to peptide-nanocarrier interactions. The addition of an ionisable lipophilic surfactant, lecithin, improved the adsorption yield, which reached values of up to 100%. The adsorption yield and the properties of the nanocarrier, particularly the zeta potential, depended on the carrier and peptide concentrations and their mixing ratio. The adsorption of all tested molecules obeyed the Langmuir model over a limited concentration range

Vers un environnement pour le déploiement logiciel autonomique

Le déploiement de logiciels répartis dans des environnements à grande échelle et ouverts (tels les systèmes ubiquitaires, les systèmes mobiles et les systèmes P2P) est une problématique actuelle ouverte. Ces environnements sont distribués, hétérogènes et peuvent être de nature instable (dotés d une topologie dynamique du réseau). Le déploiement dans ces environnements met en jeu un très grand nombre de machines, de liens réseau ainsi qu un ensemble de contraintes de déploiement. Quelques solutions de déploiement existent aujourd hui, mais ne sont exploitables que dans le cadre d architectures figées et fiables. Dans la plupart des solutions, une personne en charge du déploiement doit décrire plus ou moins manuellement la topologie. En outre, la majorité de ces outils ne prennent pas en compte les problèmes dûs à la variabilité de la qualité de service du réseau, aux pannes des hôtes, aux défaillances des liens du réseau ou encore aux changements dynamiques de topologie, qui caractérisent les environnements ouverts. Dans ce mémoire, nous présentons les motivations de la réalisation d'une infrastructure de déploiement logiciel autonomique et les exigences sous-jacentes d'une telle plate-forme. Nous présentons un état de l art du déploiement logiciel que nous analysons au regard du contexte visé. Ensuite, nous présentons notre contribution pour le déploiement autonomique. Notre proposition s'appuie sur une combinaison de technologies (composants logiciels, agents mobiles adaptables, intergiciel, langage dédié). Nous proposons j-ASD, un intergiciel qui exploite la complémentarité de ces technologies pour réaliser un déploiement logiciel autonomique. Le processus de déploiement contient trois étapes : description des contraintes de déploiement, résolution, et déploiement autonomique. Pour la première étape, nous avons défini un langage dédié (DSL) comme langage de haut niveau pour exprimer des contraintes de déploiement. Pour la deuxième, nous avons conçu une infrastructure répartie pour collecter les propriétés des sites cibles, ce qui permet de résoudre les contraintes de déploiement. Pour la troisième étape, nous proposons un intergiciel à base d agents mobiles pour la réalisation et la supervision du déploiement autonomique. Enfin, nous donnons les éléments de conception du prototype que nous avons implémenté, ainsi que les résultats de certaines expérimentations pour montrer la validité de notre approcheSoftware deployment in large-scale and open distributed systems (such as ubiquitous systems, mobile systems and P2P systems) is still an open issue. These environments are distributed, heterogeneous and can be naturally unstable (fitted with a dynamic network topology). Deployment in such environments require the management of a large number of hosts, network links and deployment constraints. Existing distributed deployment solutions are usable only within static and reliable topologies of hosts, where a man in charge of the deployment has to describe more or less manually the topology. Moreover, majority of these tools do not take into account network and computer QoS variabilities, hosts crashes, network link failures and network topology changes, which characterize open and mobile environments. In this thesis, we discuss the motivations for an autonomic software deployment and the requirements underlying for such a platform. We carefully study and compare the existing work about software deployment. Then, we propose a middleware framework, designed to reduce the human cost for setting up software deployment and to deal with failure-prone and change-prone environments. We also propose an autonomic deployment process in three steps : deployment constraints description step, constraints resolution step and the autonomic deployment step. For the first step, we defined a high-level constraint-based dedicated language (DSL) as support for expressing deployment constraints. In the second step, we have designed a distributed infrastructure to collect target hosts properties used to solve deployment constraints. For the third step, we propose an agent-based system for establishing and maintaining software deployment. At last, we give an overview of our working prototype with some details on some experimental resultsEVRY-INT (912282302) / SudocSudocFranceF

Lipid-based nanoformulations for peptide delivery

Nanoformulations have attracted a lot of attention because of their size-dependent properties. Among the array of nanoformulations, lipid nanoformulations (LNFs) have evoked increasing interest because of the advantages of their high degree of biocompatibility and versatility. The performance of lipid nanoformulations is greatly influenced by their composition and structure. Therapeutic peptides represent a growing share of the pharmaceutical market. However, the main challenge for their development into commercial products is their inherent physicochemical and biological instability. Important peptides such as insulin, calcitonin and cyclosporin A have been incorporated into LNFs. The association or encapsulation of peptides within lipid-based carriers has shown to protect the labile molecules against enzymatic degradation. This review describes strategies used for the formulation of peptides and some methods used for the assessment of association efficiency. The advantages and drawbacks of such carriers are also described

Reverse micelle-lipid nanocapsules: a novel strategy for drug delivery of the plectasin derivate AP138 antimicrobial peptide

Introduction: Resistance to traditional antibiotics is an increasingly serious problem. Antimicrobial peptides (AMPs) have emerged as a new therapeutic class with great potential against infectious diseases, as they are less prone to induce resistance. Nanotechnology-based delivery strategies can improve the efficiency and stability of AMPs, particularly against proteolytic degradation. Lipid nanocapsules (LNCs) are a new generation of biomimetic nanocarriers and were used in this study to deliver peptides. Methods: AMP-loaded reverse micelles (RM) were developed and incorpo rated into LNCs by the phase inversion process and the antimicrobial activity of the AMPs-loaded LNC was evaluated by the minimum inhibitory concentration method. We studied the activity of AMP solutions and AMP-loaded LNCs against Gram-positive and Gram-negative bacterial strains and then evaluated the encapsulation of a new cationic AMP called AP138. Finally, we analyzed the effect of enzymatic attack on AP138 and AP138-RM-LNCs after incubation with trypsin. Results: AP138 was efficiently encapsulated in the LNCs (encapsulation efficiency = 97.8% at a drug loading of 0.151%), resulting in protection against degradation by proteases and the preservation of antimicrobial activity against , including . Conclusion: This study shows that RM-LNCs are an excellent candidate system to deliver AMPs

Non-invasive diagnostic tests for Helicobacter pylori infection

BACKGROUND: Helicobacter pylori (H pylori) infection has been implicated in a number of malignancies and non-malignant conditions including peptic ulcers, non-ulcer dyspepsia, recurrent peptic ulcer bleeding, unexplained iron deficiency anaemia, idiopathic thrombocytopaenia purpura, and colorectal adenomas. The confirmatory diagnosis of H pylori is by endoscopic biopsy, followed by histopathological examination using haemotoxylin and eosin (H & E) stain or special stains such as Giemsa stain and Warthin-Starry stain. Special stains are more accurate than H & E stain. There is significant uncertainty about the diagnostic accuracy of non-invasive tests for diagnosis of H pylori. OBJECTIVES: To compare the diagnostic accuracy of urea breath test, serology, and stool antigen test, used alone or in combination, for diagnosis of H pylori infection in symptomatic and asymptomatic people, so that eradication therapy for H pylori can be started. SEARCH METHODS: We searched MEDLINE, Embase, the Science Citation Index and the National Institute for Health Research Health Technology Assessment Database on 4 March 2016. We screened references in the included studies to identify additional studies. We also conducted citation searches of relevant studies, most recently on 4 December 2016. We did not restrict studies by language or publication status, or whether data were collected prospectively or retrospectively. SELECTION CRITERIA: We included diagnostic accuracy studies that evaluated at least one of the index tests (urea breath test using isotopes such as13C or14C, serology and stool antigen test) against the reference standard (histopathological examination using H & E stain, special stains or immunohistochemical stain) in people suspected of having H pylori infection. DATA COLLECTION AND ANALYSIS: Two review authors independently screened the references to identify relevant studies and independently extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We performed meta-analysis by using the hierarchical summary receiver operating characteristic (HSROC) model to estimate and compare SROC curves. Where appropriate, we used bivariate or univariate logistic regression models to estimate summary sensitivities and specificities. MAIN RESULTS: We included 101 studies involving 11,003 participants, of which 5839 participants (53.1%) had H pylori infection. The prevalence of H pylori infection in the studies ranged from 15.2% to 94.7%, with a median prevalence of 53.7% (interquartile range 42.0% to 66.5%). Most of the studies (57%) included participants with dyspepsia and 53 studies excluded participants who recently had proton pump inhibitors or antibiotics.There was at least an unclear risk of bias or unclear applicability concern for each study.Of the 101 studies, 15 compared the accuracy of two index tests and two studies compared the accuracy of three index tests. Thirty-four studies (4242 participants) evaluated serology; 29 studies (2988 participants) evaluated stool antigen test; 34 studies (3139 participants) evaluated urea breath test-13C; 21 studies (1810 participants) evaluated urea breath test-14C; and two studies (127 participants) evaluated urea breath test but did not report the isotope used. The thresholds used to define test positivity and the staining techniques used for histopathological examination (reference standard) varied between studies. Due to sparse data for each threshold reported, it was not possible to identify the best threshold for each test.Using data from 99 studies in an indirect test comparison, there was statistical evidence of a difference in diagnostic accuracy between urea breath test-13C, urea breath test-14C, serology and stool antigen test (P = 0.024). The diagnostic odds ratios for urea breath test-13C, urea breath test-14C, serology, and stool antigen test were 153 (95% confidence interval (CI) 73.7 to 316), 105 (95% CI 74.0 to 150), 47.4 (95% CI 25.5 to 88.1) and 45.1 (95% CI 24.2 to 84.1). The sensitivity (95% CI) estimated at a fixed specificity of 0.90 (median from studies across the four tests), was 0.94 (95% CI 0.89 to 0.97) for urea breath test-13C, 0.92 (95% CI 0.89 to 0.94) for urea breath test-14C, 0.84 (95% CI 0.74 to 0.91) for serology, and 0.83 (95% CI 0.73 to 0.90) for stool antigen test. This implies that on average, given a specificity of 0.90 and prevalence of 53.7% (median specificity and prevalence in the studies), out of 1000 people tested for H pylori infection, there will be 46 false positives (people without H pylori infection who will be diagnosed as having H pylori infection). In this hypothetical cohort, urea breath test-13C, urea breath test-14C, serology, and stool antigen test will give 30 (95% CI 15 to 58), 42 (95% CI 30 to 58), 86 (95% CI 50 to 140), and 89 (95% CI 52 to 146) false negatives respectively (people with H pylori infection for whom the diagnosis of H pylori will be missed).Direct comparisons were based on few head-to-head studies. The ratios of diagnostic odds ratios (DORs) were 0.68 (95% CI 0.12 to 3.70; P = 0.56) for urea breath test-13C versus serology (seven studies), and 0.88 (95% CI 0.14 to 5.56; P = 0.84) for urea breath test-13C versus stool antigen test (seven studies). The 95% CIs of these estimates overlap with those of the ratios of DORs from the indirect comparison. Data were limited or unavailable for meta-analysis of other direct comparisons. AUTHORS' CONCLUSIONS: In people without a history of gastrectomy and those who have not recently had antibiotics or proton ,pump inhibitors, urea breath tests had high diagnostic accuracy while serology and stool antigen tests were less accurate for diagnosis of Helicobacter pylori infection.This is based on an indirect test comparison (with potential for bias due to confounding), as evidence from direct comparisons was limited or unavailable. The thresholds used for these tests were highly variable and we were unable to identify specific thresholds that might be useful in clinical practice.We need further comparative studies of high methodological quality to obtain more reliable evidence of relative accuracy between the tests. Such studies should be conducted prospectively in a representative spectrum of participants and clearly reported to ensure low risk of bias. Most importantly, studies should prespecify and clearly report thresholds used, and should avoid inappropriate exclusions

Développement et caractérisation de nanoparticules chargées en peptides antimicrobiens pour le traitement d’infections bactériennes

La multiplication des résistances aux antibiotiques constitue une grave menace qui nécessite de nouvelles stratégies antimicrobiennes. Le but de ce travail est d'étudier le potentiel des nanocapsules lipidiques (NCLs) pour l'administration de peptides antimicrobiens (PAMs). Les premiers travaux ont porté sur le développement et l'optimisation de NCLs chargées en PAMs. Différentes stratégies d’association ont été testé (adsorption à la surface ou encapsulation dans le coeur de NCLs). Les résultats ont démontré une efficacité d'association comprise entre 20 et 40%, lorsque les peptides sont adsorbés à la surface et plus de 80%,lorsqu’ils sont encapsulés. La deuxième partie s’est concentrée sur l'évaluation de l’activité des complexes PAMs et NCLs ainsi que leur stabilité vis-à-vis des protéases. Les résultats ont montré que l'adsorption entraîne une potentialisation de l'activité antimicrobienne des PAMs, associée à une protection partielle contre la dégradation enzymatique. Inversement, l’encapsulation des PAMs montre une meilleure stabilité aux enzymes, corrélée à une efficacité d'encapsulation supérieure sans amélioration de l'activité antimicrobienne in vitro. Dans une troisième partie, les mécanismes impliqués dans les interactions LNC/PAM ainsi que l'interaction du complexe avec un modèle de membrane bactérienne ont été étudiés. Il a été montré que la structure et la flexibilité des PAMs aux interfaces solide-liquide gouverneraient l'adsorption des peptides à la surface des NCLs, entrainant un changement de leur comportement avec les membranes bactériennes. L’ensemble de ces résultats démontre le potentiel prometteur des NCLs en tant que vecteur de PAMs.The rapid increase in drug-resistant infections presents an acute problem in the healthcare sector, generating interest in novel antimicrobial strategies. The aim of this work is to explore the potential of lipid nanocapsules (LNCs) for Antimicrobial peptides (AMPs) delivery. Firstly, the experiments were focused on the development and optimization of AMP-loaded LNCs. Different strategies were investigated to deliver AA230,LL37 and DPK060 using LNCs (peptides adsorption atthe surface or encapsulated in the core of modified LNCs). The results demonstrated an association efficiency of 20 to 40%, when peptide is adsorbed, and over 80% encapsulation efficiency, when peptides are encapsulated. The second part concerned the study ofthe influence of peptides loading on their activity and stability against proteases. The results showed that peptides adsorption induced a potentiation of the antimicrobial activity of the native peptides, with a partial protection against proteolytic degradation. Conversely, peptides encapsulation allowed better peptide stability, correlated with higher encapsulation efficiencies and a preservation of the in vitro antimicrobial activity. In a third part, the mechanisms involved in LNC/AMP interactions and the complex interaction with model bacterial membrane have been evaluated. It has shown that structure and flexibility at solid-liquid interfaces govern peptide adsorption on the surface of the LNCs, which in turn is expected to change LNCs properties and interaction with bacterial membranes. Taken together, these results demonstrate the potential of LNCto deliver AMPs as an alternative anti-infective therapy

Maîtrise et optimisation des microstructures des superalliages à base de nickel

This work was undertaken to enhance the current knowledge about the hot deformation of nickel-based superalloys. The main objective was to establish the influence of niobium in solid solution on the behavior of hot working of binary alloys of high purity nickel. For this purpose, different model materials (i.e. Ni-0, 01, 0.1, 1, 2, 5 and 10% Nb + pure Ni) were prepared and hot deformed by torsion test at different temperatures (800, 900 and 1000°C) and strain rates (0,03, 0,1 and 0,3 s-1). This wide range of experimental conditions were found able to determine, in a first step, the basic rheological characteristics and the influence of niobium addition in high purity nickel on the behavior of dynamic recrystallization during hot deformation. The parameters relating to the strain rate sensitivity (m) and the apparent activation energy (Q) were derived from the stress-strain curves. Moreover, the parameters h and r, which describe the hardening and dynamic recovery, were also deduced either directly from the experimental curves using an analytical adjustment method that integrates two types of the classical laws (Law Yoshi-Lasraoui and Jonas [YLJ ] and power law [PW]), or from a procedure based on a direct passage without thereby using this adjustment. The relevance of this procedure lies in its contribution in modeling discontinuous dynamic recrystallization and determining the mobility of grain boundaries. A second step of the experimental program, equally important, relates to the micro-structural/textural characterization through conventional techniques (metallography (OM) and backscattered electron (SEM-EBSD)). Based on the obtained results (microstructures and EBSD cartographies), there were a procession of three different mechanisms operating during the DRX: Continuous-Discontinuous-Geometric (DDRX-CDRX-GDRX). In a third and final step, a formulation for the passage between the two abovementioned laws, was introduced and the concept of the size quantification of the microstructural components (i.e. grains and sub-grains) was also introduced in the DDRX model by comparing the two classical methods of measurement that are the Intercept and the Equivalent Diameter.Ce travail de thèse a été entrepris dans le but d’améliorer les connaissances actuelles sur la déformation à chaud des superalliages à base de nickel. L'objectif principal est d'établir l'influence de la teneur en niobium en solution solide sur le comportement de déformation à chaud d’alliages binaires de haute pureté à base de nickel. Pour ce faire, différents matériaux modèles Ni-Nb (Ni-0,01, 0,1, 1, 2, 5 et 10%Nb, + Ni pur), ont été élaborés et déformés en torsion à chaud à différentes températures (800, 900 et 1000°C) et vitesses de déformation (0.03, 0.1 et 0.3 s-1). Cette large gamme de conditions expérimentales est en mesure de déterminer, dans une première étape, les caractéristiques rhéologiques essentielles et l’influence de l’addition de niobium sur le comportement de la recristallisation dynamique. Les paramètres relatifs à la sensibilité à la vitesse de déformation (m) et à l'énergie d'activation apparente (Q) ont été dérivés à partir des courbes contrainte-déformation. En outre, les paramètres h et r, quantifiant l'écrouissage et la restauration dynamique, ont pu être également déduits soit directement à partir des courbes expérimentales en utilisant une méthode analytique d'ajustement qui intègre deux types de lois classiques (loi Yoshi-Lasraoui et Jonas [YLJ], et loi puissance [PW]), soit à partir d'une procédure de passage direct sans pour autant passer par cet ajustement. La pertinence de cette procédure réside dans sa contribution à modéliser la recristallisation dynamique discontinue et à déterminer la mobilité des joints de grains. Une deuxième étape du programme expérimental, non moins importante, se rapporte à la caractérisation microstructurale/texturale des ces matériaux moyennant les techniques classiques de la métallographie (MO) et celles des électrons rétrodiffusés (MEB-EBSD). Sur la base des résultats obtenus (microstructures et cartographies EBSD), une procession de trois différents mécanismes opérant au cours de la DRX a été observée : Continue-Discontinue-Géométrique (DDRX-CDRX-GDRX). Dans une troisième et finale étape, une formulation permettant le passage entre les deux lois citées précédemment a été introduite et le concept de la quantification de la taille des composantes microstructurales (grains, sous-joints) a été également initié dans le modèle DDRX par la comparaison de deux méthodes classiques de mesure qui sont l’Intercept moyen et le diamètre équivalen