Polymer architecture dictates thermoreversible gelation in engineered emulsions stabilised with branched copolymer surfactants

© The Royal Society of Chemistry 2022. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.The generation of materials that switch from a liquid to gel state upon warming can enable new healthcare technologies with improved functionality, such as in situ gel-forming materials for drug delivery to topical or parenteral sites. The majority of these materials are aqueous polymer solutions, which then suffer from an inability to solubilise hydrophobic drugs. This study investigates the generation of thermoresponsive “engineered emulsions” which are low-viscosity emulsions at low temperature and switch to a gel state upon warming. This is achieved by the synthesis of novel branched copolymer surfactants (BCS) containing di(ethylene glycol) methyl ether methacrylate (DEGMA) as a thermoresponsive component giving a lower critical solution temperature (LCST). The copolymers were employed as emulsifiers to prepare 1 : 1 dodecane:water emulsion systems. The effect of polymer architecture is shown to be intimately linked to the rheology of these systems, where branching, elevation of molecular weight, and the presence of hydrophobic end groups is demonstrated to be commensurate with gel formation upon heating. Mechanisms of gel formation were probed by small-angle neutron scattering, which demonstrated that the branched copolymer surfactants formed oblate ellipsoids in solution that grew anisotropically with temperature, forming larger disk-like nanoparticles. The formation of these elongated particles leads to thickening of the emulsions, whilst connectivity of the aggregates and BCS at the oil–water interface is required for gel formation to occur. Overall, the study provides design principles for this novel class of thermoresponsive material with great potential in healthcare, cosmetic, and energy applications.Peer reviewe

Thermoresponsive Triblock‐Copolymers of Polyethylene Oxide and Polymethacrylates: Linking Chemistry, Nanoscale Morphology, and Rheological Properties

© 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, https://creativecommons.org/licenses/by/4.0/Abstract: Thermoreversible gels switch from a free‐flowing liquid state to an elastic gel mesophase upon warming, displaying the reverse transition upon cooling. While this phenomenon makes these advanced materials highly attractive in numerous fields, the generation of optimal materials of tailored rheology and transition temperatures is stifled by the lack of design principles. To address this need, a library of ABA copolymers has been prepared with “A” blocks exhibiting thermoresponsive behavior and “B” blocks of poly(ethylene glycol). This library evaluates the effect of “A” chemistry, probing three polymer classes, and A/B block molecular weight on thermally‐induced phase changes in solutions of the polymers. An exploration by rheometry coupled to Small‐Angle Neutron Scattering (SANS) elucidates temperature‐dependent hierarchical self‐assembly processes occurring on the nanoscale as well as bulk rheology. This process deciphered links between rheology and supracolloidal assemblies (sphere, ellipses, and cylinders) within the gel state with interactions probed further via structure factors. Several design principles are identified to inform the genesis of next‐generation thermoreversible gels, alongside novel materials exhibited thermoresponsive behavior in the solution state for use in applied healthcare technologies.Peer reviewedFinal Published versio

Engineering thermoresponsive emulsions with branched copolymer surfactants

© 2022 The Authors. Macromolecular Materials and Engineering published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, https://creativecommons.org/licenses/by/4.0/This study describes thermo‐rheological properties of branched copolymer surfactants (BCSs) stabilizing oil‐in‐water emulsions to generate materials exhibiting temperature‐dependent gelation with the ability to solubilize a broad range of molecules. Four poly(N‐isopropylacrylamide‐ran‐poly(ethylene glycol) methacrylate) (poly(NIPAM‐ran‐PEGMA)) BCSs with varying molecular weight (Mn), 4.7; 7.0; 7.8 and 9.0 kg mol−1, are investigated via oscillatory shear rheology, small angle neutron scattering (SANS), and neutron reflectivity (NR). Rheological thermoscans show that emulsions stabilized by the BCS with the lowest Mn (4.7 kg mol−1) are thermo‐thinning, while with the other BCSs the emulsions display a thermo‐thickening behavior. Emulsions stabilized with the BCS with Mn = 7.8 kg mol−1 form gels within a precise temperature window depending on BCS concentration. Small angle neutron scattering data analysis suggests that the BCS is present in two forms in equilibrium, small aggregates dispersed in the bulk water and an adsorbed polymeric layer at the oil/water interface. Changes in dimensions of these structures with temperature correlate with the macroscopic thermo‐thinning/thermo‐thickening behavior observed. Neutron reflectivity is conducted at the oil/water interface to allow further elucidation of BCS behavior in these systems.Peer reviewe

Le concept de limite de fonction. Une analyse des schèmes d’étudiants à la transition secondaire-supérieur en France et au Brésil

The levels of education and the ways to teach the limits of function are different in France and in Brazil. However, we make the hypothesis that the schemes developed by students regarding the concept of limit can be compared. In this article, we develop a methodology to analyze the students' schemes involving the concept of limit of function with two aims: to finely analyze the processes of today's students (in France and in Brazil) at the beginning of the learning of this concept and to highlight the evolution of their schemes, taking into account that these two countries are different in terms of the teaching of this concept.Les niveaux de scolarité et les modes d’enseignement des limites de fonction sont différents en France et au Brésil. Nous faisons l’hypothèse que les schèmes développés par les étudiants sur ce concept peuvent cependant être comparés. Nous développons dans cet article une méthodologie pour analyser les schèmes des étudiants sur le concept de limite de fonction avec un double objectif : analyser finement les processus d’étudiants d’aujourd’hui (en France et au Brésil) en début d’apprentissage du concept de limite de fonction et mettre en évidence l’évolution des schèmes dans ces deux pays, différents quant à l’enseignement de ce concept

Characterization of Group B Streptococcus strains isolated from neonatal invasive diseases in Belgium, 2018.

peer reviewedIntroduction Despite advances in preventive strategies, Group B Streptococcal(GBS) disease is still a leading cause of severe neonatal infections. The Belgian National Reference Centre (NRC) routinely performs surveillances of GBS invasive strains isolated in Belgium. Methods All GBS strains isolated from neonatal invasive diseases sent on a voluntary-base to the NRC during the year 2018 were characterized: capsular polysaccharide (CPS)-typing by agglutination and/or PCR, pili-typing with PCR, antimicrobial susceptibility testing, and detection of resistance genes with PCR. Results A total of 58 GBS strains isolated from neonatal invasive diseases were available: 33 and 27 from Early-Onset (EOD) and Late-Onset Diseases (LOD). The ratio EOD/LOD is of 1.22. Overall, CPS-type III was predominant (46.9% in EOD and 91.3% in LOD cases) followed by Ia, V, Ib, IV, IX and II in EOD (21.9%, 9.4%, 6.2%, 3.1%, 3.1%, 0.1%). All strains were susceptible to penicillin. Rate of resistance to macrolides and lincosamides was 28%. The main resistant gene detected among these resistant isolates was the ErmB gene (81,3%). About pili-typing, all strains harboured one of the PI-2 variants alone or in combination: the predominant type was PI1, PI2a (39.2%) followed by PI1, PI2b (29.4%), PI2a (21.6%) and PI2b (9.8%). Bacteriemia was the predominant manifestation with meningitis in 12% of EOD and 40% of LOD cases. Conclusion The burden of neonatal GBS diseases remains important and prevention strategies need to be improved. CPS-type and pili-type distributions, and resistance rate to macrolides/lincosamides are quite similar to European/North American observations done during the last decade

Adhesive Hydrogels for Maxillofacial Tissue Regeneration Using Minimally Invasive Procedures

Minimally invasive surgical procedures aiming to repair damaged maxillofacial tissues are hampered by its small, complex structures and difficult surgical access. Indeed, while arthroscopic procedures that deliver regenerative materials and/or cells are common in articulating joints such as the knee, there are currently no treatments that surgically place cells, regenerative factors or materials into maxillofacial tissues to foster bone, cartilage or muscle repair. Here, hyaluronic acid (HA)-based hydrogels are developed, which are suitable for use in minimally invasive procedures, that can adhere to the surrounding tissue, and deliver cells and potentially drugs. By modifying HA with both methacrylate (MA) and 3,4-dihydroxyphenylalanine (Dopa) groups using a completely aqueous synthesis route, it is shown that MA-HA-Dopa hydrogels can be applied under aqueous conditions, gel quickly using a standard surgical light, and adhere to tissue. Moreover, upon oxidation of the Dopa, human marrow stromal cells attach to hydrogels and survive when encapsulated within them. These observations show that when incorporated into HA-based hydrogels, Dopa moieties can foster cell and tissue interactions, ensuring surgical placement and potentially enabling delivery/recruitment of regenerative cells. The findings suggest that MA-HA-Dopa hydrogels may find use in minimally invasive procedures to foster maxillofacial tissue repair.</p

Acute diarrhea in adults consulting a general practitioner in France during winter: incidence, clinical characteristics, management and risk factors

International audienceBackgroundData describing the epidemiology and management of viral acute diarrhea (AD) in adults are scant. The objective of this study was to identify the incidence, clinical characteristics, management and risk factors of winter viral AD in adults.MethodsThe incidence of AD in adults during two consecutive winters (from December 2010 to April 2011 and from December 2011 to April 2012) was estimated from the French Sentinelles network. During these two winters, a subset of Sentinelles general practitioners (GPs) identified and included adult patients who presented with AD and who filled out a questionnaire and returned a stool specimen for virological examination. All stool specimens were tested for astrovirus, group A rotavirus, human enteric adenovirus, and norovirus of genogroup I and genogroup II. Age- and sex-matched controls were included to permit a case¿control analysis with the aim of identifying risk factors for viral AD.ResultsDuring the studied winters, the average incidence of AD in adults was estimated to be 3,158 per 100,000 French adults (95% CI [2,321 ¿ 3,997]). The most reported clinical signs were abdominal pain (91.1%), watery diarrhea (88.5%), and nausea (83.3%). GPs prescribed a treatment in 95% of the patients with AD, and 80% of the working patients with AD could not go to work. Stool examinations were positive for at least one enteric virus in 65% (95% CI [57 ¿ 73]) of patients with AD with a predominance of noroviruses (49%). Having been in contact with a person who has suffered from AD in the last 7 days, whether within or outside the household, and having a job (or being a student) were risk factors significantly associated with acquiring viral AD.ConclusionsDuring the winter, AD of viral origin is a frequent disease in adults, and noroviruses are most often the cause. No preventable risk factor was identified other than contact with a person with AD. Thus, at the present time, reinforcement of education related to hand hygiene remains the only way to reduce the burden of disease

Evaluation of Whole-Genome Sequencing combined with a bioinformatics tool for the complete characterization of Streptococcus agalactiae infection

peer reviewedBackground: Our aim was to evaluate the Whole-Genome Sequencing (WGS), as a new tool, in order to implement the method within the activities of the Belgian National Reference Centre Streptococcus agalactiae (NRC). The analysis of the bacterial genome by WGS could replace some current standard methods used at the NRC, unifying laboratory workflow, diminishing workload, enhancing molecular surveillance. Methods: To determine the reliability of the WGS, the results were compared with those obtained by the standard methods used by the NRC (multiplex PCRs and MLST). The raw sequence data from WGS were analyzed with the bioinformatics tool "WGS-typer" (Hedera22, Liège, Belgium), specially designed for the NRC needs. 37 strains isolated from vaginal colonization, or invasive infections in adults and infants were selected for their varied characteristics from the NRC collection. Capsular serotype, pili proteins genes, macrolides/lincosamides/streptogramins (MLS) resistance genes and sequence types were determined by both approaches. Results: Regarding capsular serotype and pili protein genes, the results reported by conventional PCR methods were perfectly confirmed by the WGS (100% concordance). However, for MLS resistance genes and sequence types, the comparison highlights one and three discrepancies respectively. A new sequence type 1655 was listed in the PUBMLST database thanks to this research. Conclusion: WGS is a promising approach that can compete with the conventional methods currently used in laboratories. Indeed, this technology allows, at lower costs and workload, a complete characterization of the GBS and a huge concordance between WGS and conventional methods has been observed

Genome analysis of the necrotrophic fungal pathogens Sclerotinia sclerotiorum and Botrytis cinerea

Sclerotinia sclerotiorum and Botrytis cinerea are closely related necrotrophic plant pathogenic fungi notable for their wide host ranges and environmental persistence. These attributes have made these species models for understanding the complexity of necrotrophic, broad host-range pathogenicity. Despite their similarities, the two species differ in mating behaviour and the ability to produce asexual spores. We have sequenced the genomes of one strain of S. sclerotiorum and two strains of B. cinerea. The comparative analysis of these genomes relative to one another and to other sequenced fungal genomes is provided here. Their 38–39 Mb genomes include 11,860–14,270 predicted genes, which share 83% amino acid identity on average between the two species. We have mapped the S. sclerotiorum assembly to 16 chromosomes and found large-scale co-linearity with the B. cinerea genomes. Seven percent of the S. sclerotiorum genome comprises transposable elements compared t