Meriem Er-Rafik - Academia.edu (original) (raw)

Papers by Meriem Er-Rafik

MSystems, Oct 26, 2021

The Bacillus cereus group (Bacillus cereus sensu lato) has a diverse ecology, including various s... more The Bacillus cereus group (Bacillus cereus sensu lato) has a diverse ecology, including various species that are vertebrate or invertebrate pathogens. Few isolates from the B. cereus group have however been demonstrated to benefit plant growth. Therefore, it is crucial to explore how bacterial development and pathogenesis evolve during plant colonization. Herein, we investigated Bacillus thuringiensis (Cry 2) adaptation to the colonization of Arabidopsis thaliana roots and monitored changes in cellular differentiation in experimentally evolved isolates. Isolates from two populations displayed improved iterative ecesis on roots and increased virulence against insect larvae. Molecular dissection and recreation of a causative mutation revealed the importance of a nonsense mutation in the rho transcription terminator gene. Transcriptome analysis revealed how Rho impacts various B. thuringiensis genes involved in carbohydrate metabolism and virulence. Our work suggests that evolved multicellular aggregates have a fitness advantage over single cells when colonizing plants, creating a trade-off between swimming and multicellularity in evolved lineages, in addition to unrelated alterations in pathogenicity. IMPORTANCE Biologicals-based plant protection relies on the use of safe microbial strains. During application of biologicals to the rhizosphere, microbes adapt to the niche, including genetic mutations shaping the physiology of the cells. Here, the experimental evolution of Bacillus thuringiensis lacking the insecticide crystal toxins was examined on the plant root to reveal how adaptation shapes the differentiation of this bacterium. Interestingly, evolution of certain lineages led to increased hemolysis and insect larva pathogenesis in B. thuringiensis driven by transcriptional rewiring. Further, our detailed study reveals how inactivation of the transcription termination protein Rho promotes aggregation on the plant root in addition to altered differentiation and pathogenesis in B. thuringiensis.

Polymer Degradation and Stability, Feb 1, 2013

The study of the effect of pH on the behaviour of proteins is still a topic of interest. We here ... more The study of the effect of pH on the behaviour of proteins is still a topic of interest. We here report an unexpected increase of thermal stability of hard alpha-keratins under the influence of pH that is observed when investigating their thermal behaviour by differential scanning calorimetry (DSC). The results, particularly for oxidatively damaged keratin fibres treated with low pH solution, show a significant increase of enthalpy and a shift of the peak temperature towards higher temperature for the endothermic process assigned to the thermal denaturation. We propose a three-phase model for describing the behaviour of fibrous hard alpha-keratins, in which the interface, made of non-helical tail domains of keratin, scaffolds the intermediate filaments and plays an important role. It is strengthen by the action of strong acids and controls the thermal properties of the alpha-helix. The approach is supported by amino-acid analysis, X-ray diffraction, Raman spectroscopy and tensile strength observations.

Soft Matter, 2022

Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

Frontiers in Microbiology, Mar 8, 2021

Phage-based approaches have gained increasing interest as sustainable alternative strategies to a... more Phage-based approaches have gained increasing interest as sustainable alternative strategies to antibiotic treatment or as prophylactic measures against disease outbreaks in aquaculture. The potential of three methods (oral, bath, and injection) for delivering a two-component phage mixture to rainbow trout fry for controlling Flavobacterium psychrophilum infections and reduce fish mortality was investigated using bacteriophages FpV4 and FPSV-D22. For the oral administration experiment, bacteriophages were applied on feed pellets by spraying (1.6 × 10 8 PFU g −1) or by irreversible immobilization (8.3 × 10 7 PFU g −1), using the corona discharge technology (Fixed Phage Ltd.). The fish showed normal growth for every group and no mortality was observed prior to infection as well as in control groups during the infection. Constant detection of phages in the intestine (∼10 3 PFU mg −1) and more sporadic occurrence in kidney, spleen, and brain was observed. When fish were exposed to F. psychrophilum, no significant effect on fish survival, nor a direct impact on the number of phages in the sampled organs, were detected. Similarly, no significant increase in fish survival was detected when phages were delivered by bath (1 st and 2 nd bath: ∼10 6 PFU ml −1 ; 3 rd bath: ∼10 5 PFU ml −1). However, when phages FpV4 and FPSV-D22 (1.7 × 10 8 PFU fish −1) were administered by intraperitoneal injection 3 days after the bacterial challenge, the final percent survival observed in the group injected with bacteriophages FpV4 and FPSV-D22 (80.0%) was significantly higher than in the control group (56.7%). The work demonstrates the delivery of phages to fish organs by oral administration, but also suggests that higher phage dosages than the tested ones may be needed on feed pellets to offer fish an adequate protection against F. psychrophilum infections.

Carbohydrate Polymers, Nov 1, 2019

J o u r n a l P r e-p r o o f Highlights Bullet points:  Multi-reactive Dextran-based transurfs ... more J o u r n a l P r e-p r o o f Highlights Bullet points:  Multi-reactive Dextran-based transurfs (RAFT agent and surfactant) are designed  Dithiobenzoate groups of transurf confine RAFT polymerization at o/w interface  RAFT miniemulsion polymerization of MMA from transurf is controlled  Dextran-covered nanocapsules with PMMA shell and oily core are produced  Nanocapsules seem to be cytocompatible with vascular smooth muscle cells ABSTRACT A multi-reactive polysaccharide-based transurf (acting both as macro-Chain Transfer Agent and stabilizer) was used to confine RAFT polymerization of methyl methacrylate (MMA) at the oil/water (o/w) miniemulsion interface. Dithiobenzoate groups and hydrophobic aliphatic side chains were introduced onto dextran, conferring it both transfer agent properties and ability to stabilize direct miniemulsion of MMA in the presence of a biocompatible oil, used as costabilizer. Because of their amphiphilic character, transurfs were initially adsorbed at the (o/w) interface and their reactive sites mediated RAFT polymerization via the R-group approach. PMMA-grafted dextran glycopolymers were consequently produced at the o/w interface, thus leading to dextran coverage/PMMA shell/oily core nanocapsules (NCs) as evidenced by Cryo-J o u r n a l P r e-p r o o f 3 TEM analyses. The influence of dextran-based transurf chemistry and oil amount on MMA RAFT polymerization control was investigated. Positive preliminary results on NCs cytotoxicity suggest the potential of these objects for biomedical applications.

Soft Matter

Tear, a direct physical damage of lipid bilayers, can be inflicted by small enough nanoparticles.

Environmental Science: Nano, 2021

nHAP (mainly composed of Ca and P, but also spiked with Sr, V and Ce tracers) initially adheres t... more nHAP (mainly composed of Ca and P, but also spiked with Sr, V and Ce tracers) initially adheres to the surface of roots, before penetrating and dissolving in the plant.

Die vorliegende Erfindung betrifft bestimmte funktionalisierte Polysiloxane oder Silane zur Behan... more Die vorliegende Erfindung betrifft bestimmte funktionalisierte Polysiloxane oder Silane zur Behandlung von kristallinen cellulosehaltigen Substraten.

Vaccines, 2021

Viral Nervous Necrosis (VNN) causes high mortality and reduced growth in farmed European sea bass... more Viral Nervous Necrosis (VNN) causes high mortality and reduced growth in farmed European sea bass (Dicentrarchus labrax) in the Mediterranean. In the current studies, we tested a novel Pichia-produced virus-like particle (VLP) vaccine against VNN in European sea bass, caused by the betanodavirus “Red-Spotted Grouper Nervous Necrosis Virus” (RGNNV). European sea bass were immunized with a VLP-based vaccine formulated with different concentrations of antigen and with or without adjuvant. Antibody response was evaluated by ELISA and serum neutralization. The efficacy of these VLP-vaccine formulations was evaluated by an intramuscular challenge with RGNNV at different time points (1, 2 and 10 months post-vaccination) and both dead and surviving fish were sampled to evaluate the level of viable virus in the brain. The VLP-based vaccines induced an effective protective immunity against experimental infection at 2 months post-vaccination, and even to some degree at 10 months post-vaccinati...

Bacillus cereus group (Bacillus cereus sensu lato) has a diverse ecology, including various speci... more Bacillus cereus group (Bacillus cereus sensu lato) has a diverse ecology, including various species that are vertebrate or invertebrate pathogens. Few isolates from the B. cereus group have however been demonstrated to benefit plant growth. Therefore, it is crucial to explore how bacterial development and toxicity evolves during plant colonization. Herein, we investigated Bacillus thuringiensis (Cry-) adaptation to the colonization of Arabidopsis thaliana roots, and monitored changes in cellular differentiation in experimentally evolved isolates. Isolates from two populations displayed improved iterative ecesis on roots and increased toxicity against insect larvae. Molecular dissection and recreation of a causative mutation revealed the importance of a non-sense mutation in the rho transcription terminator gene. Transcriptome analysis revealed how Rho impacts various B. thuringiensis genes involved in carbohydrate metabolism and virulence. Our work suggests that evolved multicellula...

Langmuir, 2017

Hybrid, i.e. intimately mixed polymer/phospholipid vesicles can potentially marry in a single mem... more Hybrid, i.e. intimately mixed polymer/phospholipid vesicles can potentially marry in a single membrane the best characteristics of the two separate components. The ability of amphiphilic copolymers and phospholipids to selfassemble into hybrid membranes has been studied until now at the sub-micron scale using optical microscopy on Giant Hybrid Unilamellar Vesicles (GHUVs), but limited information is available on Large Hybrid Unilamellar Vesicles (LHUVs). In this work, copolymers based on poly(dimethyl siloxane) and poly(ethylene oxide) with different molar masses and architectures (graft, triblock) were associated with 1,2-di-palmitoyl-sn-glycero-3-phosphocholine (DPPC). Classical protocols of LUV formation were used to obtain nano-sized self-assembled structures. Using Small Angle Neutron Scattering (SANS), Time Resolved Förster Resonance Energy Transfer (TR-FRET) and Cryo-Transmission Electron Microscopy (Cryo-TEM), we show that copolymer architecture and molar mass have a direct consequence on the formation of hybrid nanostructures that can range from worm-like hybrid micelles to hybrid vesicles presenting small lipid nanodomains. Hybrid polymer/phospholipid vesicles are emerging structures that combine the biocompatibility and biofunctionality of liposomes, with the robustness, low permeability, and functional variability conferred by copolymer chains. This should become of great interest in pharmaceutical applications for which a few formulations based on liposomes are commercially available despite decades of research, viz. DaunoXome ® , Doxil ® /Caelyx ® , Thermodox ® , Visudyne ® .

Polymer Degradation and Stability, 2013

The study of the effect of pH on the behaviour of proteins is still a topic of interest. We here ... more The study of the effect of pH on the behaviour of proteins is still a topic of interest. We here report an unexpected increase of thermal stability of hard alpha-keratins under the influence of pH that is observed when investigating their thermal behaviour by differential scanning calorimetry (DSC). The results, particularly for oxidatively damaged keratin fibres treated with low pH solution, show a significant increase of enthalpy and a shift of the peak temperature towards higher temperature for the endothermic process assigned to the thermal denaturation. We propose a three-phase model for describing the behaviour of fibrous hard alpha-keratins, in which the interface, made of non-helical tail domains of keratin, scaffolds the intermediate filaments and plays an important role. It is strengthen by the action of strong acids and controls the thermal properties of the alpha-helix. The approach is supported by amino-acid analysis, X-ray diffraction, Raman spectroscopy and tensile strength observations.

Biophysical Journal, 2004

Despite investigation since the 1950s, the molecular architecture of intermediate filaments has n... more Despite investigation since the 1950s, the molecular architecture of intermediate filaments has not yet been fully elucidated. Reliable information about the longitudinal organization of the molecules within the filaments and about the lateral interfilament packing is now available, which is not the case for the transverse architecture. Interesting results were recently obtained from in vitro microscopy observations and cross-linking of keratin, desmin, and vimentin analyses. The structural features that emerge from these analyses could not be fully representative of the in vivo architecture because intermediate filaments are subject to polymorphism. To bring new light to the transverse intermediate filament architecture, we have analyzed the x-ray scattering equatorial profile of human hair. Its comparison with simulated profiles from atomic models of a real sequence has allowed results to be obtained that are representative of hard a-keratin intermediate filaments under in vivo conditions. In short, the a-helical coiled coils, which are characteristic of the central rod of intermediate filament dimers, are straight and not supercoiled into oligomers; the radial density across the intermediate filament section is fairly uniform; the coiled coils are probably assembled into tetrameric oligomers, and finally the oligomer positions and orientations are not regularly ordered. These features are discussed in terms of filament self-assembling and structural variability.

Carbohydrate Polymers, 2019

J o u r n a l P r e-p r o o f Highlights Bullet points:  Multi-reactive Dextran-based transurfs ... more J o u r n a l P r e-p r o o f Highlights Bullet points:  Multi-reactive Dextran-based transurfs (RAFT agent and surfactant) are designed  Dithiobenzoate groups of transurf confine RAFT polymerization at o/w interface  RAFT miniemulsion polymerization of MMA from transurf is controlled  Dextran-covered nanocapsules with PMMA shell and oily core are produced  Nanocapsules seem to be cytocompatible with vascular smooth muscle cells ABSTRACT A multi-reactive polysaccharide-based transurf (acting both as macro-Chain Transfer Agent and stabilizer) was used to confine RAFT polymerization of methyl methacrylate (MMA) at the oil/water (o/w) miniemulsion interface. Dithiobenzoate groups and hydrophobic aliphatic side chains were introduced onto dextran, conferring it both transfer agent properties and ability to stabilize direct miniemulsion of MMA in the presence of a biocompatible oil, used as costabilizer. Because of their amphiphilic character, transurfs were initially adsorbed at the (o/w) interface and their reactive sites mediated RAFT polymerization via the R-group approach. PMMA-grafted dextran glycopolymers were consequently produced at the o/w interface, thus leading to dextran coverage/PMMA shell/oily core nanocapsules (NCs) as evidenced by Cryo-J o u r n a l P r e-p r o o f 3 TEM analyses. The influence of dextran-based transurf chemistry and oil amount on MMA RAFT polymerization control was investigated. Positive preliminary results on NCs cytotoxicity suggest the potential of these objects for biomedical applications.

Carbohydrate Polymers, 2013

Usage of supercritical carbon dioxide as a medium for finishing cotton fabrics with modified dime... more Usage of supercritical carbon dioxide as a medium for finishing cotton fabrics with modified dimethylsiloxane polymers terminated with silanol groups was investigated, different cross-linkers namely 3-isocyanatepropyltriethoxysilane (IPES) and tetraethylorthosilicate (TEOS) were used for covalently bonding between silicon and cellulose. The presence and the amount of PDMS compounds on the treated fabrics were characterized by FT-IR. Qualitative and quantitative information on the distribution of the silicon molecules across the fibre cross section was provided by SEM/EDX analysis and Confocal Raman microscopy (CRM) respectively. The results confirm that all fibres treated with PDMS and IPES have larger silicon amounts than those treated with TEOS. SC-CO 2 medium provides good coating of cotton surface with a 3D network of DMS compound and cross linker, and leads to forming highest DMS concentration in a layer between 1 and 2 under the surface of cotton fabrics.

Carbohydrate Polymers, 2013

PDMS compound was chosen as a molecule-model for investigating the diffusion of silicon products ... more PDMS compound was chosen as a molecule-model for investigating the diffusion of silicon products into cotton bulk. The study demonstrates the suitability of Confocal Raman microscopy (CRM) to monitor the distribution of poly(dimethylsiloxane) (PDMS) molecules into cotton fibres. Different molecular weights of PDMS compounds were used in two different solvents (water and hexane) at various temperatures (25, 50 and 60 • C). The surfaces of the fibres were studied with scanning electron microscopy and Confocal Raman microscopy was run to detect the PDMS on the surface and in the bulk of treated fabrics. We concluded that all PDMS compounds, irrespectively their molecular weights and the silicon oil infiltrate into cotton fibre. The penetration is strongly dependent on the solvent used. Water proved suitable for assisting the infiltration of low and medium molecular weight PDMS, at elevated temperatures. High molecular weight PDMS infiltrates better from hexane and at room temperature than from water.

Journal of Structural Biology, 2006

Several aspects of the intermediate filaments' molecular architecture remain mysterious despite d... more Several aspects of the intermediate filaments' molecular architecture remain mysterious despite decades of study. The growth process and the final architecture may depend on the physical, chemical, and biochemical environment. Aiming at clarifying this issue, we have revisited the structure of the human hair follicle by means of X-ray microdiffraction. We conclude that the histology-based growth zones along the follicle are correlated to the fine architecture of the filaments deduced from X-ray microdiffraction. Our analysis reveals the existence of two major polymorph intermediate filament architectures. Just above the bulb, the filaments are characterized by a diameter of 100 Å and a low-density core. The following zone upwards is characterized by the lateral aggregation of the filaments into a compact network of filaments, by a contraction of their diameter (to 75 Å) and by the setting up of a long-range longitudinal ordering. In the upper zone, the small structural change associated with the tissue hardening likely concerns the terminal domains. The architecture of the intermediate filament in the upper zones could be specific to hard a-keratin whilst the other architecture found in the lower zone could be representative for intermediate filaments in a different environment.

Langmuir : the ACS journal of surfaces and colloids, Feb 6, 2018

In this paper, superparamagnetic iron oxide nanoparticles (SPIONs, around 6 nm) encapsulated in p... more In this paper, superparamagnetic iron oxide nanoparticles (SPIONs, around 6 nm) encapsulated in poly(methyl methacrylate) nanoparticles (PMMA NPs) with controlled sizes ranging from 100 to 200 nm have been successfully produced. The hybrid polymeric NPs were prepared following two different methods: (1) nanoprecipitation and (2) nanoemulsification-evaporation. These two methods were implemented in two different microprocesses based on the use of an impact jet micromixer and an elongational-flow microemulsifier. SPIONs-loaded PMMA NPs synthesized by the two methods presented completely different physicochemical properties. The polymeric NPs prepared with the micromixer-assisted nanoprecipitation method showed a heterogeneous dispersion of SPIONs inside the polymer matrix, an encapsulation efficiency close to 100 wt %, and an irregular shape. In contrast, the polymeric NPs prepared with the microfluidic-assisted nanoemulsification-evaporation method showed a homogeneous dispersion, an...

MSystems, Oct 26, 2021

The Bacillus cereus group (Bacillus cereus sensu lato) has a diverse ecology, including various s... more The Bacillus cereus group (Bacillus cereus sensu lato) has a diverse ecology, including various species that are vertebrate or invertebrate pathogens. Few isolates from the B. cereus group have however been demonstrated to benefit plant growth. Therefore, it is crucial to explore how bacterial development and pathogenesis evolve during plant colonization. Herein, we investigated Bacillus thuringiensis (Cry 2) adaptation to the colonization of Arabidopsis thaliana roots and monitored changes in cellular differentiation in experimentally evolved isolates. Isolates from two populations displayed improved iterative ecesis on roots and increased virulence against insect larvae. Molecular dissection and recreation of a causative mutation revealed the importance of a nonsense mutation in the rho transcription terminator gene. Transcriptome analysis revealed how Rho impacts various B. thuringiensis genes involved in carbohydrate metabolism and virulence. Our work suggests that evolved multicellular aggregates have a fitness advantage over single cells when colonizing plants, creating a trade-off between swimming and multicellularity in evolved lineages, in addition to unrelated alterations in pathogenicity. IMPORTANCE Biologicals-based plant protection relies on the use of safe microbial strains. During application of biologicals to the rhizosphere, microbes adapt to the niche, including genetic mutations shaping the physiology of the cells. Here, the experimental evolution of Bacillus thuringiensis lacking the insecticide crystal toxins was examined on the plant root to reveal how adaptation shapes the differentiation of this bacterium. Interestingly, evolution of certain lineages led to increased hemolysis and insect larva pathogenesis in B. thuringiensis driven by transcriptional rewiring. Further, our detailed study reveals how inactivation of the transcription termination protein Rho promotes aggregation on the plant root in addition to altered differentiation and pathogenesis in B. thuringiensis.

Polymer Degradation and Stability, Feb 1, 2013

The study of the effect of pH on the behaviour of proteins is still a topic of interest. We here ... more The study of the effect of pH on the behaviour of proteins is still a topic of interest. We here report an unexpected increase of thermal stability of hard alpha-keratins under the influence of pH that is observed when investigating their thermal behaviour by differential scanning calorimetry (DSC). The results, particularly for oxidatively damaged keratin fibres treated with low pH solution, show a significant increase of enthalpy and a shift of the peak temperature towards higher temperature for the endothermic process assigned to the thermal denaturation. We propose a three-phase model for describing the behaviour of fibrous hard alpha-keratins, in which the interface, made of non-helical tail domains of keratin, scaffolds the intermediate filaments and plays an important role. It is strengthen by the action of strong acids and controls the thermal properties of the alpha-helix. The approach is supported by amino-acid analysis, X-ray diffraction, Raman spectroscopy and tensile strength observations.

Soft Matter, 2022

Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

Frontiers in Microbiology, Mar 8, 2021

Phage-based approaches have gained increasing interest as sustainable alternative strategies to a... more Phage-based approaches have gained increasing interest as sustainable alternative strategies to antibiotic treatment or as prophylactic measures against disease outbreaks in aquaculture. The potential of three methods (oral, bath, and injection) for delivering a two-component phage mixture to rainbow trout fry for controlling Flavobacterium psychrophilum infections and reduce fish mortality was investigated using bacteriophages FpV4 and FPSV-D22. For the oral administration experiment, bacteriophages were applied on feed pellets by spraying (1.6 × 10 8 PFU g −1) or by irreversible immobilization (8.3 × 10 7 PFU g −1), using the corona discharge technology (Fixed Phage Ltd.). The fish showed normal growth for every group and no mortality was observed prior to infection as well as in control groups during the infection. Constant detection of phages in the intestine (∼10 3 PFU mg −1) and more sporadic occurrence in kidney, spleen, and brain was observed. When fish were exposed to F. psychrophilum, no significant effect on fish survival, nor a direct impact on the number of phages in the sampled organs, were detected. Similarly, no significant increase in fish survival was detected when phages were delivered by bath (1 st and 2 nd bath: ∼10 6 PFU ml −1 ; 3 rd bath: ∼10 5 PFU ml −1). However, when phages FpV4 and FPSV-D22 (1.7 × 10 8 PFU fish −1) were administered by intraperitoneal injection 3 days after the bacterial challenge, the final percent survival observed in the group injected with bacteriophages FpV4 and FPSV-D22 (80.0%) was significantly higher than in the control group (56.7%). The work demonstrates the delivery of phages to fish organs by oral administration, but also suggests that higher phage dosages than the tested ones may be needed on feed pellets to offer fish an adequate protection against F. psychrophilum infections.

Carbohydrate Polymers, Nov 1, 2019

J o u r n a l P r e-p r o o f Highlights Bullet points:  Multi-reactive Dextran-based transurfs ... more J o u r n a l P r e-p r o o f Highlights Bullet points:  Multi-reactive Dextran-based transurfs (RAFT agent and surfactant) are designed  Dithiobenzoate groups of transurf confine RAFT polymerization at o/w interface  RAFT miniemulsion polymerization of MMA from transurf is controlled  Dextran-covered nanocapsules with PMMA shell and oily core are produced  Nanocapsules seem to be cytocompatible with vascular smooth muscle cells ABSTRACT A multi-reactive polysaccharide-based transurf (acting both as macro-Chain Transfer Agent and stabilizer) was used to confine RAFT polymerization of methyl methacrylate (MMA) at the oil/water (o/w) miniemulsion interface. Dithiobenzoate groups and hydrophobic aliphatic side chains were introduced onto dextran, conferring it both transfer agent properties and ability to stabilize direct miniemulsion of MMA in the presence of a biocompatible oil, used as costabilizer. Because of their amphiphilic character, transurfs were initially adsorbed at the (o/w) interface and their reactive sites mediated RAFT polymerization via the R-group approach. PMMA-grafted dextran glycopolymers were consequently produced at the o/w interface, thus leading to dextran coverage/PMMA shell/oily core nanocapsules (NCs) as evidenced by Cryo-J o u r n a l P r e-p r o o f 3 TEM analyses. The influence of dextran-based transurf chemistry and oil amount on MMA RAFT polymerization control was investigated. Positive preliminary results on NCs cytotoxicity suggest the potential of these objects for biomedical applications.

Soft Matter

Tear, a direct physical damage of lipid bilayers, can be inflicted by small enough nanoparticles.

Environmental Science: Nano, 2021

nHAP (mainly composed of Ca and P, but also spiked with Sr, V and Ce tracers) initially adheres t... more nHAP (mainly composed of Ca and P, but also spiked with Sr, V and Ce tracers) initially adheres to the surface of roots, before penetrating and dissolving in the plant.

Die vorliegende Erfindung betrifft bestimmte funktionalisierte Polysiloxane oder Silane zur Behan... more Die vorliegende Erfindung betrifft bestimmte funktionalisierte Polysiloxane oder Silane zur Behandlung von kristallinen cellulosehaltigen Substraten.

Vaccines, 2021

Viral Nervous Necrosis (VNN) causes high mortality and reduced growth in farmed European sea bass... more Viral Nervous Necrosis (VNN) causes high mortality and reduced growth in farmed European sea bass (Dicentrarchus labrax) in the Mediterranean. In the current studies, we tested a novel Pichia-produced virus-like particle (VLP) vaccine against VNN in European sea bass, caused by the betanodavirus “Red-Spotted Grouper Nervous Necrosis Virus” (RGNNV). European sea bass were immunized with a VLP-based vaccine formulated with different concentrations of antigen and with or without adjuvant. Antibody response was evaluated by ELISA and serum neutralization. The efficacy of these VLP-vaccine formulations was evaluated by an intramuscular challenge with RGNNV at different time points (1, 2 and 10 months post-vaccination) and both dead and surviving fish were sampled to evaluate the level of viable virus in the brain. The VLP-based vaccines induced an effective protective immunity against experimental infection at 2 months post-vaccination, and even to some degree at 10 months post-vaccinati...

Bacillus cereus group (Bacillus cereus sensu lato) has a diverse ecology, including various speci... more Bacillus cereus group (Bacillus cereus sensu lato) has a diverse ecology, including various species that are vertebrate or invertebrate pathogens. Few isolates from the B. cereus group have however been demonstrated to benefit plant growth. Therefore, it is crucial to explore how bacterial development and toxicity evolves during plant colonization. Herein, we investigated Bacillus thuringiensis (Cry-) adaptation to the colonization of Arabidopsis thaliana roots, and monitored changes in cellular differentiation in experimentally evolved isolates. Isolates from two populations displayed improved iterative ecesis on roots and increased toxicity against insect larvae. Molecular dissection and recreation of a causative mutation revealed the importance of a non-sense mutation in the rho transcription terminator gene. Transcriptome analysis revealed how Rho impacts various B. thuringiensis genes involved in carbohydrate metabolism and virulence. Our work suggests that evolved multicellula...

Langmuir, 2017

Hybrid, i.e. intimately mixed polymer/phospholipid vesicles can potentially marry in a single mem... more Hybrid, i.e. intimately mixed polymer/phospholipid vesicles can potentially marry in a single membrane the best characteristics of the two separate components. The ability of amphiphilic copolymers and phospholipids to selfassemble into hybrid membranes has been studied until now at the sub-micron scale using optical microscopy on Giant Hybrid Unilamellar Vesicles (GHUVs), but limited information is available on Large Hybrid Unilamellar Vesicles (LHUVs). In this work, copolymers based on poly(dimethyl siloxane) and poly(ethylene oxide) with different molar masses and architectures (graft, triblock) were associated with 1,2-di-palmitoyl-sn-glycero-3-phosphocholine (DPPC). Classical protocols of LUV formation were used to obtain nano-sized self-assembled structures. Using Small Angle Neutron Scattering (SANS), Time Resolved Förster Resonance Energy Transfer (TR-FRET) and Cryo-Transmission Electron Microscopy (Cryo-TEM), we show that copolymer architecture and molar mass have a direct consequence on the formation of hybrid nanostructures that can range from worm-like hybrid micelles to hybrid vesicles presenting small lipid nanodomains. Hybrid polymer/phospholipid vesicles are emerging structures that combine the biocompatibility and biofunctionality of liposomes, with the robustness, low permeability, and functional variability conferred by copolymer chains. This should become of great interest in pharmaceutical applications for which a few formulations based on liposomes are commercially available despite decades of research, viz. DaunoXome ® , Doxil ® /Caelyx ® , Thermodox ® , Visudyne ® .

Polymer Degradation and Stability, 2013

The study of the effect of pH on the behaviour of proteins is still a topic of interest. We here ... more The study of the effect of pH on the behaviour of proteins is still a topic of interest. We here report an unexpected increase of thermal stability of hard alpha-keratins under the influence of pH that is observed when investigating their thermal behaviour by differential scanning calorimetry (DSC). The results, particularly for oxidatively damaged keratin fibres treated with low pH solution, show a significant increase of enthalpy and a shift of the peak temperature towards higher temperature for the endothermic process assigned to the thermal denaturation. We propose a three-phase model for describing the behaviour of fibrous hard alpha-keratins, in which the interface, made of non-helical tail domains of keratin, scaffolds the intermediate filaments and plays an important role. It is strengthen by the action of strong acids and controls the thermal properties of the alpha-helix. The approach is supported by amino-acid analysis, X-ray diffraction, Raman spectroscopy and tensile strength observations.

Biophysical Journal, 2004

Despite investigation since the 1950s, the molecular architecture of intermediate filaments has n... more Despite investigation since the 1950s, the molecular architecture of intermediate filaments has not yet been fully elucidated. Reliable information about the longitudinal organization of the molecules within the filaments and about the lateral interfilament packing is now available, which is not the case for the transverse architecture. Interesting results were recently obtained from in vitro microscopy observations and cross-linking of keratin, desmin, and vimentin analyses. The structural features that emerge from these analyses could not be fully representative of the in vivo architecture because intermediate filaments are subject to polymorphism. To bring new light to the transverse intermediate filament architecture, we have analyzed the x-ray scattering equatorial profile of human hair. Its comparison with simulated profiles from atomic models of a real sequence has allowed results to be obtained that are representative of hard a-keratin intermediate filaments under in vivo conditions. In short, the a-helical coiled coils, which are characteristic of the central rod of intermediate filament dimers, are straight and not supercoiled into oligomers; the radial density across the intermediate filament section is fairly uniform; the coiled coils are probably assembled into tetrameric oligomers, and finally the oligomer positions and orientations are not regularly ordered. These features are discussed in terms of filament self-assembling and structural variability.

Carbohydrate Polymers, 2019

J o u r n a l P r e-p r o o f Highlights Bullet points:  Multi-reactive Dextran-based transurfs ... more J o u r n a l P r e-p r o o f Highlights Bullet points:  Multi-reactive Dextran-based transurfs (RAFT agent and surfactant) are designed  Dithiobenzoate groups of transurf confine RAFT polymerization at o/w interface  RAFT miniemulsion polymerization of MMA from transurf is controlled  Dextran-covered nanocapsules with PMMA shell and oily core are produced  Nanocapsules seem to be cytocompatible with vascular smooth muscle cells ABSTRACT A multi-reactive polysaccharide-based transurf (acting both as macro-Chain Transfer Agent and stabilizer) was used to confine RAFT polymerization of methyl methacrylate (MMA) at the oil/water (o/w) miniemulsion interface. Dithiobenzoate groups and hydrophobic aliphatic side chains were introduced onto dextran, conferring it both transfer agent properties and ability to stabilize direct miniemulsion of MMA in the presence of a biocompatible oil, used as costabilizer. Because of their amphiphilic character, transurfs were initially adsorbed at the (o/w) interface and their reactive sites mediated RAFT polymerization via the R-group approach. PMMA-grafted dextran glycopolymers were consequently produced at the o/w interface, thus leading to dextran coverage/PMMA shell/oily core nanocapsules (NCs) as evidenced by Cryo-J o u r n a l P r e-p r o o f 3 TEM analyses. The influence of dextran-based transurf chemistry and oil amount on MMA RAFT polymerization control was investigated. Positive preliminary results on NCs cytotoxicity suggest the potential of these objects for biomedical applications.

Carbohydrate Polymers, 2013

Usage of supercritical carbon dioxide as a medium for finishing cotton fabrics with modified dime... more Usage of supercritical carbon dioxide as a medium for finishing cotton fabrics with modified dimethylsiloxane polymers terminated with silanol groups was investigated, different cross-linkers namely 3-isocyanatepropyltriethoxysilane (IPES) and tetraethylorthosilicate (TEOS) were used for covalently bonding between silicon and cellulose. The presence and the amount of PDMS compounds on the treated fabrics were characterized by FT-IR. Qualitative and quantitative information on the distribution of the silicon molecules across the fibre cross section was provided by SEM/EDX analysis and Confocal Raman microscopy (CRM) respectively. The results confirm that all fibres treated with PDMS and IPES have larger silicon amounts than those treated with TEOS. SC-CO 2 medium provides good coating of cotton surface with a 3D network of DMS compound and cross linker, and leads to forming highest DMS concentration in a layer between 1 and 2 under the surface of cotton fabrics.

Carbohydrate Polymers, 2013

PDMS compound was chosen as a molecule-model for investigating the diffusion of silicon products ... more PDMS compound was chosen as a molecule-model for investigating the diffusion of silicon products into cotton bulk. The study demonstrates the suitability of Confocal Raman microscopy (CRM) to monitor the distribution of poly(dimethylsiloxane) (PDMS) molecules into cotton fibres. Different molecular weights of PDMS compounds were used in two different solvents (water and hexane) at various temperatures (25, 50 and 60 • C). The surfaces of the fibres were studied with scanning electron microscopy and Confocal Raman microscopy was run to detect the PDMS on the surface and in the bulk of treated fabrics. We concluded that all PDMS compounds, irrespectively their molecular weights and the silicon oil infiltrate into cotton fibre. The penetration is strongly dependent on the solvent used. Water proved suitable for assisting the infiltration of low and medium molecular weight PDMS, at elevated temperatures. High molecular weight PDMS infiltrates better from hexane and at room temperature than from water.

Journal of Structural Biology, 2006

Several aspects of the intermediate filaments' molecular architecture remain mysterious despite d... more Several aspects of the intermediate filaments' molecular architecture remain mysterious despite decades of study. The growth process and the final architecture may depend on the physical, chemical, and biochemical environment. Aiming at clarifying this issue, we have revisited the structure of the human hair follicle by means of X-ray microdiffraction. We conclude that the histology-based growth zones along the follicle are correlated to the fine architecture of the filaments deduced from X-ray microdiffraction. Our analysis reveals the existence of two major polymorph intermediate filament architectures. Just above the bulb, the filaments are characterized by a diameter of 100 Å and a low-density core. The following zone upwards is characterized by the lateral aggregation of the filaments into a compact network of filaments, by a contraction of their diameter (to 75 Å) and by the setting up of a long-range longitudinal ordering. In the upper zone, the small structural change associated with the tissue hardening likely concerns the terminal domains. The architecture of the intermediate filament in the upper zones could be specific to hard a-keratin whilst the other architecture found in the lower zone could be representative for intermediate filaments in a different environment.

Langmuir : the ACS journal of surfaces and colloids, Feb 6, 2018

In this paper, superparamagnetic iron oxide nanoparticles (SPIONs, around 6 nm) encapsulated in p... more In this paper, superparamagnetic iron oxide nanoparticles (SPIONs, around 6 nm) encapsulated in poly(methyl methacrylate) nanoparticles (PMMA NPs) with controlled sizes ranging from 100 to 200 nm have been successfully produced. The hybrid polymeric NPs were prepared following two different methods: (1) nanoprecipitation and (2) nanoemulsification-evaporation. These two methods were implemented in two different microprocesses based on the use of an impact jet micromixer and an elongational-flow microemulsifier. SPIONs-loaded PMMA NPs synthesized by the two methods presented completely different physicochemical properties. The polymeric NPs prepared with the micromixer-assisted nanoprecipitation method showed a heterogeneous dispersion of SPIONs inside the polymer matrix, an encapsulation efficiency close to 100 wt %, and an irregular shape. In contrast, the polymeric NPs prepared with the microfluidic-assisted nanoemulsification-evaporation method showed a homogeneous dispersion, an...