HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Rheo-SAXS study of a shear-thinning hydrogel containing clay nanoplatelets
No full textInternational audienceShear-induced orientation of clay nanoplatelets within a physically cross-linked hydrogel based on ionenes, positively charged polyelectrolytes, is studied here. Small angle X-ray scattering measurements (SAXS) are performed under shear within a Couette cell cylinder (rheo-SAXS). As the SAXS signal is dominated by that of the clay component, we follow the evolution of the orientational distribution of the clay nanoplatelets within the hydrogel as a function of shear. We investigate the effect of the clay volume fraction, polyelectrolyte concentration, clay charge location and clay charge density by screening three different types of clay: Wyoming and Arizona montmorillonites and Idaho beidellite. The orientational field of clay nanoplatelets in the gel is shown to strongly depend on the clay charge location and shear rate, whereas it is independent of the clay volume fraction. Approaching the critical gelation concentration of the polyelectrolyte system, these features change drastically
Single-emitter super-resolved imaging of radiative decay rate enhancement in dielectric gap nanoantennas
No full textInternational audienceHigh refractive index dielectric nanoantennas strongly modify the decay rate via the Purcell effect through the design of radiative channels. Due to their dielectric nature, the field is mainly confined inside the nanostructure and in the gap, which is hard to probe with scanning probe techniques. Here we use single-molecule fluorescence lifetime imaging microscopy (smFLIM) to map the decay rate enhancement in dielectric GaP nanoantenna dimers with a median localization precision of 14 nm. We measure, in the gap of the nanoantenna, decay rates that are almost 30 times larger than on a glass substrate. By comparing experimental results with numerical simulations we show that this large enhancement is essentially radiative, contrary to the case of plasmonic nanoantennas, and therefore has great potential for applications such as quantum optics and biosensing
Effect of maximum packing fraction of powders on the rheology of metakaolin-based geopolymer pastes
No full textInternational audienceIn this work, we study the effect of maximum packing fraction of powders on the rheology of geopolymer pastes. A large range of metakaolin powders is generated either by blending or grinding powders. Blends of metakaolin with quartz and limestone are also studied. We show that the compressive packing model is able to predict correctly over a wide range of values the maximum packing fraction of these powders. We show that an increase of the maximum packing of powders leads to a decrease of the viscosity of geopolymer suspension at a constant solid volume fraction. We finally show that the viscosity of studied geopolymer suspensions can be well predicted by the Krieger Dougherty relation. We suggest that the highest potential degree of freedom allowing for the control of the viscosity of geopolymer pastes without modifying the composition of the suspension lies in the maximum packing fraction of the solid powders
Complete depolymerization of poly(ester-alt-thioether)s under mild conditions into AB functional monomers
No full textInternational audienceThe chemical recyclability of poly(ester-alt-thioether) structures is investigated. Different polymers were synthesized by alternating anionic ring-opening copolymerization of thiolactone and epoxide monomers using benzyl alcohol -BEMP phosphazene base as initiating system. Controlled structures with number-average molar masses between 2000 and 5000 g.mol -1 were obtained. In a second time, degradation studies were carried out by methanolysis in acidic and basic conditions. The influences of the base/acid concentration and of the epoxide unit lateral substituent on the degradation rate were also investigated. The structure of degradation product has been confirmed by 1 H, 13 C NMR, SEC and ESI mass spectrometry, and corresponds to α-hydroxy-ω-methyl ester repeating unit molecules. These molecules were subsequently used as A-B monomers in step-growth polymerization syntheses using either p-toluene sulfonic acid (PTSA) or titaniumbutoxide (Ti(OBu)4) as catalyst. The resulting condensation polymers were analyzed by NMR, SEC, MALDI ToF, TGA and DSC. Identical structures, comparable molar masses and slightly higher glass transition temperatures have been obtained compared to the ones of the native polymers synthesized by AROP.</div
A closed circulation Langendorff heart perfusion method for cardiac drug screening
No full textInternational audienceCardiovascular diseases represent an economic burden for health systems accounting for substantial morbidity and mortality worldwide. Despite timely and costly efforts in drug development, the cardiovascular safety and efficacy of the drugs are not always fully achieved.These lead to the drugs' withdrawal with adverse cardiac effects from the market or in the late stages of drug development. There is a growing need for a cost-effective drug screening assay to rapidly detect potential acute drug cardiotoxicity. The Langendorff isolated heart perfusion technique, which provides cardiac hemodynamic parameters (e.g., contractile function and heart rate), has become a powerful approach in the early drug discovery phase to overcome drawbacks in the drug candidate's identification. However, traditional ex vivo retrograde heart perfusion methods consume a large volume of perfusate, which increases the cost and limits compound screening. An elegant and cost-effective alternative mode for ex vivo retrograde heart perfusion is the constant-flow with a recirculating circuit (CFCC), which allows assessment of cardiac function using a reduced perfusion volume while limiting adverse effects on the heart. Here, we provide evidence for cardiac parameters stability over time in this mode. Next, we demonstrate that our recycled ex vivo perfusion system and the traditional open one yield similar outputs on cardiac function under basal conditions and upon β-adrenergic stimulation with isoproterenol. Subsequently, we validate the proof of concept of therapeutic agent screening using this efficient method. β-blocker (i.e., propranolol) infusion in closed circulation countered the positive effects induced by isoproterenol stimulation on cardiac function
Overlay databank unlocks data-driven analyses of biomolecules for all
No full textInternational audienceTools based on artificial intelligence (AI) are currently revolutionising many fields, yet their applications are often limited by the lack of suitable training data in programmatically accessible format. Here we propose an effective solution to make data scattered in various locations and formats accessible for data-driven and machine learning applications using the overlay databank format. To demonstrate the practical relevance of such approach, we present the NMRlipids Databank-a community-driven, open-for-all database featuring programmatic access to quality-evaluated atom-resolution molecular dynamics simulations of cellular membranes. Cellular membrane lipid composition is implicated in diseases and controls major biological functions, but membranes are difficult to study experimentally due to their intrinsic disorder and complex phase behaviour. While MD simulations have been useful in understanding membrane systems, they require significant computational resources and often suffer from inaccuracies in model parameters. Here, we demonstrate how programmable interface for flexible implementation of data-driven and machine learning applications, and rapid access to simulation data through a graphical user interface, unlock possibilities beyond current MD simulation and experimental studies to understand cellular membranes. The proposed overlay databank concept can be further applied to other biomolecules, as well as in other fields where similar barriers hinder the AI revolution. © 2024. The Author(s)
Design of Biocompatible and Biodegradable Composite Shape-morphing Hydrogels
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Molecular Weight Determination of Kuhn Monomers from a Dynamic Property of Polymers
No full textInternational audienceDynamic rheological responses of polymer solutions exhibit a range of dynamic modes reflecting the hierarchical structures with different characteristic lengths such as the Kuhn length and mesh size. The polymer contribution to the viscoelastic modulus at each dynamic mode is proportional to the number density of unit segments at the corresponding hierarchical level, allowing for the determination of their molecular weight. This paper evaluates the molecular weight of a Kuhn monomer from the boundary between the Zimm and bending modes, using a worm-like micellar solution of cetylpyridinium chloride/sodium salicylate as a model system. Employing high-frequency diffusing-wave spectroscopy microrheology, we determined the molecular weight, which agrees well with that measured by static light scattering. We showed that the radius of the Kuhn monomer was also accurately estimated from the characteristic volume related with the molecular weight. The proposed method holds potential for application across various dynamic modes and polymer solutions
From gem ‐Dichlorocyclobutenones to Cyclobutenols: Unveiling a Ruthenium‐Catalyzed Allylic Reduction‐Asymmetric Transfer Hydrogenation Cascade
No full textInternational audienceCyclobutenones constitute an appealing class of substrates in catalytic asymmetric transformations leading to diversely substituted enantioenriched four‐membered carbocycles, which are eliciting a growing interest in medicinal chemistry. Whilst several synthetically useful enantioselective conjugate addition reactions have been reported, the catalytic enantioselective reduction of the carbonyl group of simple cyclobutenones remains an elusive transformation. Herein, we disclose the discovery of a novel allylic reduction‐asymmetric transfer hydrogenation cascade, catalyzed by a Noyori‐Ikariya ruthenium complex, from readily available gem ‐dichlorocyclobutenones, leading to 2‐chlorocyclobutenols with high optical purities, which can be engaged in postfunctionalization reactions enabling access to substituted four‐membered rings
