28 research outputs found
SynthÚse et caractérisation de dérivés amphiphiles du xanthane : application à la stabilisation d'émulsions
Amphiphilic polysaccharides are composed of a hydrophilic backbone grafted with hydrophobic moieties. They show specific rheological properties due to their capacity to self-associate in solution, but also interfacial properties due to their ability to adsorb at the water/oil interface. However, only few studies describe the chemical modification of complex heteropolysaccharides regarding their structure or their conformation, such as xanthan. Indeed, this polysaccharide can adopt in solution two distinct conformations depending on experimental conditions: an ordered rigid helix or a disordered flexible coil.The objective of this work is to determine the impact of the chain stiffness of hydrophobically modified xanthan on associative properties in solution, but also on stabilizing properties in emulsion.The conformation adopted by the polymer during the grafting procedure has a major impact on the rheological properties: xanthan modified under disordered conformation is an associative polysaccharide, contrary to xanthan modified under its ordered conformation.In addition, hydrophobically modified xanthan is able, under certain conditions, to form and stabilize O/W emulsion, without further addition of molecular surfactant, by partitioning between stabilization of the water/oil interface and viscosifying the continuous aqueous phase.Les polysaccharides amphiphiles sont constituĂ©s dâun squelette hydrophile sur lequel sont greffĂ©s des groupements hydrophobes. Ils possĂšdent des propriĂ©tĂ©s rhĂ©ologiques accrues dues Ă leur capacitĂ© dâauto-organisation en solution aqueuse mais Ă©galement interfaciales dues Ă leurs propriĂ©tĂ©s dâadsorption aux interfaces eau/huile. NĂ©anmoins, peu dâĂ©tudes sâintĂ©ressent Ă confĂ©rer ce type de propriĂ©tĂ©s Ă des polysaccharides complexes en termes de structure ou de conformation, comme le xanthane. En effet, ce polymĂšre adopte en solution deux conformations distinctes selon les conditions expĂ©rimentales : une forme ordonnĂ©e hĂ©licoĂŻdale rigide et une forme dĂ©sordonnĂ©e de type pelote flexible.Partant de ce constat, lâobjectif de ce travail de thĂšse est de dĂ©terminer lâimpact de la rigiditĂ© du squelette du xanthane modifiĂ© hydrophobiquement sur les propriĂ©tĂ©s amphiphiles en solution mais Ă©galement sur les propriĂ©tĂ©s stabilisantes en Ă©mulsion.Il sâavĂšre que la conformation adoptĂ©e par le polymĂšre pendant le processus de greffage a un impact majeur sur ses propriĂ©tĂ©s rhĂ©ologiques : le xanthane modifiĂ© sous forme dĂ©sordonnĂ©e possĂšde un caractĂšre associatif, contrairement au xanthane modifiĂ© sous forme ordonnĂ©e.De plus, le xanthane modifiĂ© hydrophobiquement est capable, sous certaines conditions, de former et de stabiliser des Ă©mulsions H/E, sans ajout de tensioactif molĂ©culaire, en se partitionnant entre stabilisation de lâinterface eau/huile et maintien de la viscositĂ© de la phase aqueuse continue
Cellular sources and impact of interleukin 22 binding protein (IL-22BP) on the molecular response induced by interleukins 22 and 17 during Crohn's disease
Les interleukines IL-22 (IL-22) et IL- 17 (IL-17) exercent des actions bĂ©nĂ©fiques sur les cellules Ă©pithĂ©liales intestinales (CEI) en renforçant les propriĂ©tĂ©s de barriĂšre de la muqueuse intestinale via lâinduction de peptides antimicrobiens ou encore lâinduction de processus de rĂ©paration. Dans un objectif de dĂ©velopper de nouvelles stratĂ©gies thĂ©rapeutiques dans la prise en charge des maladies inflammatoires chroniques de lâintestin (MICI), nous avons voulu Ă©valuer au cours de ce projet, lâintĂ©rĂȘt dâun renforcement de leurs actions. Pour cela, nous nous sommes intĂ©ressĂ©s Ă lâinhibiteur soluble et spĂ©cifique de lâIL-22 : lâinterleukine-22 binding protein (IL-22BP). De nombreux travaux ont clairement admis sa capacitĂ© Ă bloquer les actions de lâIL-22 in vivo et in vitro, tandis que dâautres ont identifiĂ© les cellules dendritiques et les Ă©osinophiles comme ces principales sources de production dans lâintestin. Au niveau des muqueuses inflammatoires de patients MICI, lâIL-22BP est augmentĂ©, suggĂ©rant quâil pourrait inhiber les actions induites par lâIL-22. Ce travail prĂ©sente donc pour objectifs principaux dâĂ©valuer au cours de la maladie de Crohn (MC) lâimpact de lâIL-22BP sur la rĂ©ponse molĂ©culaire induite par lâIL-22 et IL-17, prĂ©alablement caractĂ©risĂ©e Ă partir de donnĂ©es de transcriptomique issues de la stimulation ex-vivo de biopsies intestinales saines. Dans un objectif secondaire, et au vue des rĂ©centes donnĂ©es de la littĂ©rature, nous avons caractĂ©risĂ© les sources cellulaires dâIL- 22BP au cours de la MC. Ainsi une meilleure comprĂ©hension de lâIL-22BP permettra de mieux apprĂ©hender lâintĂ©rĂȘt dâune modulation de lâinteraction IL-22/IL-22BP au cours de la MC.The interleukins IL-22 (IL-22) and IL- 17 (IL-17) exert beneficial and synergistic actions on intestinal epithelial cells (IECs) by reinforcing the barrier properties of the intestinal mucosa through the induction of antimicrobial peptides or the induction of repair processes. With the objective of developing new therapeutic strategies in the management of chronic inflammatory bowel diseases (IBD), we wanted to evaluate during this project, the interest of strengthening their actions. We focused on the soluble and specific inhibitor of IL-22: the interleukin 22 binding protein (IL- 22BP). Numerous studies have clearly recognized its ability to block the actions of IL- 22 in vivo and in vitro, while others have identified dendritic cells and eosinophils as the main sources of production in the gut. In the inflammatory mucosa of IBD patients, IL-22BP is increased, suggesting that it may inhibit IL- 22-induced actions. The main objectives of this work are therefore to evaluate the impact of IL-22BP on the molecular response induced by IL-22 and IL-17 during Crohn's disease (CD), previously characterised using transcriptomic data from ex-vivo stimulation of healthy intestinal biopsies. As a secondary objective, and in view of recent data in the literature, we have characterised the cellular sources of IL-22BP during CD. Thus, a better understanding of IL- 22BP will allow to better apprehend the interest of a modulation of the IL-22/IL-22BP interaction during CD
Synthesis and characterization of amphiphilic xanthan derivatives : application as emulsions stabilizers
Les polysaccharides amphiphiles sont constituĂ©s dâun squelette hydrophile sur lequel sont greffĂ©s des groupements hydrophobes. Ils possĂšdent des propriĂ©tĂ©s rhĂ©ologiques accrues dues Ă leur capacitĂ© dâauto-organisation en solution aqueuse mais Ă©galement interfaciales dues Ă leurs propriĂ©tĂ©s dâadsorption aux interfaces eau/huile. NĂ©anmoins, peu dâĂ©tudes sâintĂ©ressent Ă confĂ©rer ce type de propriĂ©tĂ©s Ă des polysaccharides complexes en termes de structure ou de conformation, comme le xanthane. En effet, ce polymĂšre adopte en solution deux conformations distinctes selon les conditions expĂ©rimentales : une forme ordonnĂ©e hĂ©licoĂŻdale rigide et une forme dĂ©sordonnĂ©e de type pelote flexible.Partant de ce constat, lâobjectif de ce travail de thĂšse est de dĂ©terminer lâimpact de la rigiditĂ© du squelette du xanthane modifiĂ© hydrophobiquement sur les propriĂ©tĂ©s amphiphiles en solution mais Ă©galement sur les propriĂ©tĂ©s stabilisantes en Ă©mulsion.Il sâavĂšre que la conformation adoptĂ©e par le polymĂšre pendant le processus de greffage a un impact majeur sur ses propriĂ©tĂ©s rhĂ©ologiques : le xanthane modifiĂ© sous forme dĂ©sordonnĂ©e possĂšde un caractĂšre associatif, contrairement au xanthane modifiĂ© sous forme ordonnĂ©e.De plus, le xanthane modifiĂ© hydrophobiquement est capable, sous certaines conditions, de former et de stabiliser des Ă©mulsions H/E, sans ajout de tensioactif molĂ©culaire, en se partitionnant entre stabilisation de lâinterface eau/huile et maintien de la viscositĂ© de la phase aqueuse continue.Amphiphilic polysaccharides are composed of a hydrophilic backbone grafted with hydrophobic moieties. They show specific rheological properties due to their capacity to self-associate in solution, but also interfacial properties due to their ability to adsorb at the water/oil interface. However, only few studies describe the chemical modification of complex heteropolysaccharides regarding their structure or their conformation, such as xanthan. Indeed, this polysaccharide can adopt in solution two distinct conformations depending on experimental conditions: an ordered rigid helix or a disordered flexible coil.The objective of this work is to determine the impact of the chain stiffness of hydrophobically modified xanthan on associative properties in solution, but also on stabilizing properties in emulsion.The conformation adopted by the polymer during the grafting procedure has a major impact on the rheological properties: xanthan modified under disordered conformation is an associative polysaccharide, contrary to xanthan modified under its ordered conformation.In addition, hydrophobically modified xanthan is able, under certain conditions, to form and stabilize O/W emulsion, without further addition of molecular surfactant, by partitioning between stabilization of the water/oil interface and viscosifying the continuous aqueous phase
Stable emulsifier-free oil-in-water emulsions using an original hydrophobically modified xanthan
International audienc
Hydrophobically modified xanthan as an efficient stabilizer for Oil-in-water emulsions
International audienc
Impact of backbone stiffness and hydrophobic chain length of modified xanthan on oil in water emulsion stabilization
International audienc
Original xanthan amphiphilic derivatives for stabilizing surfactant-free O/W emulsions
International audienc
Hydrophobically modified xanthan: Thickening and surface active agent for highly stable oil in water emulsions
International audienc