Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Elaboration et caractérisation d'hygrogels à base de polysaccharides (pullulane) (application à la séquestration et à la libération contrôlée de molécules et de macromolécules)

L'objectif de cette étude est de proposer un hydrogel adaptatif en fonction d'un principe actif (PA) à encapsuler et des conditions de libération. La matrice de base est constituée de pullulane, un polysaccharide hydrosoluble, flexible qui sera utilisé sous sa forme initiale neutre, sous une forme anionique après carboxyméthylation ou amphiphile après greffage de chaînons octyle. Pour l'agent réticulant nous avons choisi le sodium triméthaphosphate (STMP) qui est couramment utilisé en agroalimentaire en raison de sa non toxicité. Il apporte des charges négatives sur la matrice ainsi qu'un élément spécifique, le phosphore, qui permet un dosage de celui-ci. Afin d'appréhender a mieux ce système, le mécanisme de réticulation a été déterminé par RMN du phosphore. Cette étude a montré la forte complexité de la réaction ainsi que la coexistence de lien monophosphate et pyrophosphate intermoléculaire et intramoléculaire, et la présence de monophosphate, pyrophosphate et polyphosphate sous forme greffé. La connaissance du maillage du réseau est primordiale au vue de l'application visée. Ce maillage est fortement dépendant des paramètres de synthèse (concentration des réactifs) dû d'une part aux fortes concentrations en pullulane nécessaires pour obtenir un hydrogel et d'autre part à la réactivité spécifique du STMP. L'influence des ces paramètres se répercute également sur la taille des microgels élaborés (hydrogel sous forme particulaire). Enfin, il est possible d'encapsuler et de libérer des PA moléculaires ou macromoléculaires. De plus, selon le type de matrice choisi la libération de PA macromoléculaire (comme le PEI ou le lysozyme) est possible ou impossible en milieu salin, en fonction de la taille du PA et du gonflement de l'hydrogel. Pour les microgels amphiphiles la libération de lysozyme ne peut être réalisée en milieu salin qu'après rupture des chaînons hydrocarbonés.The aim of this study is to propose an adaptive hydrogel according to an active substance (AS) to encapsulate and conditions of the release. The basic matrix consists of pullulane, a water-soluble polysaccharide, flexible which will be used in its initial neutral form, in a form anion after carboxymethylation or amphiphilic after grafting of octyl links. For the reticulation agent we've chosen the sodium triméthaphosphate (STMP) which is usually used into agroalimentary because of its non toxicity. Moreover it brings negative charges on the matrix, as well as a specific element, the phosphorus, which allows a proportioning of this one. In order to apprehend at best this system, the mechanism of reticulation was determined by phosphorus NMR. This study showed the strong complexity of the reaction as well as the coexistence of monophosphate and pyrophosphate bonds (intermolecular and intramolecular), and the presence of grafted monophosphate, pyrophosphate and polyphosphate. The knowledge of the network mesh is of primary importance with the sight of the concerned application. This grid is strongly depending on the synthesis parameters (concentration of the reagents...) due on the one hand to the strong concentrations in pullulane necessary to obtain a hydrogel and on the other hand with the specific reactivity of the STMP. The influence of these parameters is also reflected on the size of the elaborate microgels (hydrogel in particulate form). Lastly, it is possible to encapsulate and release an molecular AS or macromolecular AS. Moreover, according to the selected type of matrix the release of macromolecular AS (like PEI or lysozyme) is possible or impossible in saline medium, according to the size of the AS and the hydrogel swelling. For the amphiphilic microgels the release of lysozyme can be carried out in saline medium only after rupture of the hydrocarbon links.ROUEN-BU Sciences (764512102) / SudocSudocFranceF

Characterization of insoluble calcium alginates by solid-state NMR

International audienceThree series of 9 insoluble calcium alginate powders with different average calcium contents (1.5, 3.5 and 8%, w/w) are investigated by means of C-13 solid-state NMR spectroscopy. The effect of the increased calcium content on the determination of the mannuronate (M) to guluronate (G) ratio from spectral deconvolution of the C-13 CP/MAS spectra is discussed, and the variations observed are commented in function of possible structural modifications related to the interaction with the divalent cations. The possibility fusing solid-state NMR spectroscopy for the quantification of the calcium content in unknown alginate samples is explored performing principal component analysis (PCA) of the spectra. The results obtained show that: a clear separation of alginates with slightly different calcium content is possible. The proposed method relies on the sole use of the chemical shifts of the signals corresponding to pyranose carbons, suggesting that PCA of solid-state NMR data holds promises as a rapid and undestructive method for screening the calcium content of alginate-based materials with biomedical uses. (C) 2011 Elsevier Ltd. All rights reserved

High-resolution nuclear magnetic resonance spectroscopy studies of polysaccharides crosslinked by sodium trimetaphosphate: a proposal for the reaction mechanism

International audienceAn NMR spectroscopy study (31P, 1H, 13C) of the postulated crosslinking mechanism of sodium trimetaphosphate (STMP) on polysaccharides is reported using methyl α-d-glucopyranoside as a model. In a first step, reaction of STMP with Glc-OMe gives grafted sodium tripolyphosphate (STPPg). On the one hand, STTPg can react with a second alcohol functionality to give a crosslinked monophosphate. On the other hand, a monophosphate (grafted phosphate) could be obtained by alkaline degradation of STPPg. NMR spectroscopy allows to detect the various species formed and to obtain the crosslinking density of STMP–polysaccharides hydrogels

Microfluidics-assisted generation of stimuli-responsive hydrogels based on alginates incorporated with thermo-responsive and amphiphilic polymers as novel biomaterials

International audienceWe used a droplet-based microfluidics technique to produce monodisperse responsive alginate-block-polyetheramine copolymer microgels. The polyetheramine group (PEA), corresponding to a propylene oxide /ethylene oxide ratio (PO/EO) of 29/6 (Jeffamine (R) M2005), was condensed, via the amine link, to alginates with various mannuronic/guluronic acids ratios and using two alginate:jeffamine mass ratios. The size of the grafted-alginate microgels varied from 60 to 80 mu m depending on the type of alginate used and the degree of substitution. The droplet-based microfluidics technique offered exquisite control of both the dimension and physical chemical properties of the grafted-alginate microgels. These microgels were therefore comparable to isolated grafted-alginate chains in retaining both their amphiphilic and thermo-sensitive properties. Amphiphilicity was demonstrated at the oil-water interface where grafted-alginate microgels were found to decrease interfacial tension by similar to 50%. The thermo-sensitivity of microgels was clearly demonstrated and a 10 to 20% reduction in size between was evidenced on increasing the temperature above the lower critical solution temperature (T-LCST) of Jeffamine. In addition, the reversibility of thermo-sensitivity was demonstrated by studying the oil-water affinity of microgels with temperature after Congo red labeling. Finally, droplet-based microfluidics was found to be a good and promising tool for generating responsive biobased hydrogels for drug delivery applications and potential new colloidal stabilizers for dispersed systems such as Pickering emulsions. (C) 2015 Elsevier B.V. All rights reserved

DEVELOPMENT OF ANTIBIOFILM DRESSINGS WITH NATURAL ACTIVE INGREDIENTS FOR THE TREATMENT OF INFECTED WOUNDS

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Hydrogels Based on Pullulan Crosslinked with sodium trimetaphosphate (STMP): Rheological study

International audienceHydrogels from pullulan crosslinked with sodium trimetaphosphate (STMP) under alkaline condition have been investigated by rheological measurements. The influence of reagents concentration (pullulan, STMP, NaOH) on kinetics of reaction and rheological properties is reported. Increasing concentrations of any reagents lead to an increase of the crosslinking kinetics. Increasing the polymer concentration leads to a “stronger” gel whereas an increase of crosslinking reagent (STMP) evidences a critical concentration above which the rheological properties of the gel do not change anymore. This may be explained by the specificity of the system for which the polymer concentration is high and negative charges appear

A Combination of the Natural Molecules Gallic Acid and Carvacrol Eradicates <i>P. aeruginosa</i> and <i>S. aureus</i> Mature Biofilms

Wound infection, especially the development of bacterial biofilms, delays wound healing and is a major public health concern. Bacteria in biofilms are more tolerant to antimicrobial agents, and new treatments to eradicate mature biofilms are needed. Combining antimicrobial molecules with different mechanisms of action is an attractive strategy to tackle the heterogeneous nature of microbial communities in biofilms. This study focused on three molecules of natural origin: gallic acid (G), carvacrol (K) and curcumin (Q). Their abilities, individually or in combination, to eradicate biofilms were quantified on mono- and dual-species mature biofilms of Pseudomonas aeruginosa and Staphylococcus aureus, the strains most commonly found in infected wounds. G presented biofilm eradicating activity on P. aeruginosa, whereas K had biofilm eradicating activity on S. aureus and P. aeruginosa. Q had no potent biofilm eradicating activity. The combination of G and K increased the effects previously observed on P. aeruginosa biofilm and led to complete eradication of S. aureus biofilm. This combination was also efficient in eradicating a dual-species biofilm of S. aureus and P. aeruginosa. This work demonstrates that K and G used in combination have a strong and synergistic eradicating activity on both mono- and dual-species mature biofilms of S. aureus and P. aeruginosa and may therefore represent an efficient alternative for the treatment of biofilms in wounds

Processing and antibacterial properties of chitosan-coated alginate fibers

International audienceThe preparation of chitosan-coated alginate fibers by a wet spin process is presented and the characterization of the antibacterial activities of these fibers is discussed. Preformed calcium alginate fibers were passed in chitosan acetate solutions. The coagulation method of the coating consisted in the immersion of fibers in a bath of calcium dihydroxide solution (0.1 M). The antibacterial evaluation was achieved by a CFU (Colony-Forming Units) counting method after 6 h of incubation at 37 °C. The incorporation of chitosan on calcium alginate fibers brings antibacterial activities against Staphylococcus epidermidis, Escherichia coli and various Staphylococcus aureus strains namely MSSA (Methicillin Sensitive Staphylococcus aureus), CA-MRSA (Community Associated Methicillin Resistant Staphylococcus aureus) and HA-MRSA (Healthcare Associated Methicillin Resistant Staphylococcus aureus) which make these chitosan-coated fibers potential candidates for wound dressing materials. Developing a wound dressing with the haemostatic and healing properties of alginate combined with antibacterial properties of chitosan is envisioned for fighting against the infections and more particularly nosocomial diseases