Polymer vesicles (from virus to cell biomimicry)

Les polymersomes, obtenus par auto-assemblage en solution aqueuse de copolymères à blocs amphiphiles en structure vésiculaire, sont présentés comme d excellent mimes synthétiques des virus, dont les propriétés membranaires principalement élasticité, perméabilité, fonctionnalité- peuvent être très proches. Il y a ainsi un fort engouement quant à leur utilisation en biotechnologie et surtout en vectorisation d actifs pharmaceutiques ou cosmétiques. Afin d aller encore plus loin dans le biomimétisme ou la bio-inspiration, une étape devait être franchie : encapsuler ces polymersomes les uns dans les autres. Ce cloisonnement ou multi-compartimentalisation permet de mimer cette fois la structure d une cellule dite eukaryote, elle-même constituée de compartiments internes (organelles) et d un cytoplasme (lui conférant entre autres une certaine stabilité mécanique) contenues dans le compartiment externe représenté par la membrane cellulaire. Toutefois, l obtention d un simple mime structural d une structure si complexe représente déjà un challenge en soi, nécessitant maîtrise de la physico-chimie des systèmes, de la stabilisation des interfaces et des outils de formulation. Une méthode d émulsion-centrifugation a été développée et a permis d obtenir de telles structures compartimentalisées (mimes d organelles) à cavité gélifiée (mime de cytoplasme). Finalement, différentes voies d exploitation de ces systèmes sont présentées, allant de l encapsulation multiple, la libération contrôlée jusqu au développement de réactions enzymatiques en cascade confinées, mimant ainsi le métabolisme cellulaire.Amphiphilic block copolymers self-assemble in water into vesicles, coined polymersomes ; these vesicles are described as excellent synthetic mimics of viral capsids due to the resemblance of their respective membrane properties (in terms of elasticity, permeability, and functionality). As a result, they were massively investigated over the last years regarding applications in biotechnology and more particularly for the targeted delivery of pharmaceutical or cosmetic actives.In order to go further towards bio-inspiration and cell biomimicry, the next step required the encapsulation of polymersomes in other polymersomes. This multicompartmentalization indeed enables to mimic the structure of an eukaryotic cell; an outer cellular membrane compartment encloses internal compartments (organelles) and a cytoplasm responsible amongst others for a certain mechanic stability. However, alone the controlled formation of a system mimicking such a complex structure represents a technological challenge in terms of control over the physical chemistry of these systems, the stabilization of their interfaces and their formulation. A formation method based upon an emulsion-centrifugation has been developed and enabled the formation of such multicompartmentalized structures (organelle mimics) with a gelified lumen (cytoplasm mimic). Finally, various potential applications of these systems are presented: from multiple encapsulation, controlled drug release, to the development of enzymatic and confined cascade reactions that mimick the cellular metabolism.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Assemblages de copolymères à blocs pour la vectorisation de siRNA

Les siRNA sont des molécules double brin d acide ribonucléique capables d inhiber l expression d un gène spécifique, présentant ainsi un fort potentiel thérapeutique pour les maladies génétiques, les cancers et les infections virales. Cependant, son utilisation in vivo est restreinte par sa sensibilité à la dégradation enzymatique. Le projet de thèse consiste à créer un système de vectorisation des siRNA pour des applications in vivo. Nous avons synthétisé des copolymères à blocs amphiphiles biocompatibles et biodégradables capable de s auto-assembler en diverses structures et d encapsuler les siRNA. Les propriétés physico-chimiques des assemblages formées et l évaluation cellulaire préliminaire est réaliséeAmphiphilic block copolymers are molecules composed of hydrophilic and hydrophobic segments having the capacity to spontaneously self-assemble into a variety of supramolecular structures like micelles and vesicles. Here, we propose an original way to self-assemble amphiphilic block copolymers into a supported bilayer membrane for defined coating of nanoparticles. The heart of the method rests on a change of the amphiphilicity of the copolymer that can be turned off and on by varying the polarity of the solvent. In this condition, the assembly process can take advantage of specific molecular interactions in both organic solvent and water. The higher gene silencing activity of the copolymer-modified complexes over the complexes alone shows the potential of this new type of nanoconstructs for biological applications, especially for the delivery of therapeutic biomolecules.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Organogels from trehalose difatty esters amphiphiles

International audienceSaccharide diesters have been recently shown to be excellent gelators of vegetable oils. In this paper, different fatty acid trehalose diesters were synthesized by a selective enzymatic transesterification performed only on the primary hydroxyl group of the trehalose. The resulting trehalose diesters demonstrated their ability to self-assemble in a large variety of edible vegetable oils with a minimum gelation concentration of 0.25 wt%/v. Microscopic analysis and X-ray scattering studies indicate that the gels are obtained by the self-assembly of trehalose diesters in crystalline fibers constituting the tridimensional network. The rheological study revealed that the properties of the gels depend on the kind of fatty acid grafted on the trehalose but are also influenced by the vegetable oil composition

Thermosensitive polymer-grafted iron oxide nanoparticles studied by in situ dynamic light backscattering under magnetic hyperthermia

© 2015 IOP Publishing Ltd. Thermometry at the nanoscale is an emerging area fostered by intensive research on nanoparticles (NPs) that are capable of converting electromagnetic waves into heat. Recent results suggest that stationary gradients can be maintained between the surface of NPs and the bulk solvent, a phenomenon sometimes referred to as \u27cold hyperthermia\u27. However, the measurement of such highly localized temperatures is particularly challenging. We describe here a new approach to probing the temperature at the surface of iron oxide NPs and enhancing the understanding of this phenomenon. This approach involves the grafting of thermosensitive polymer chains to the NP surface followed by the measurement of macroscopic properties of the resulting NP suspension and comparison to a calibration curve built up by macroscopic heating. Superparamagnetic iron oxide NPs were prepared by the coprecipitation of ferrous and ferric salts and functionalized with amines, then azides using a sol-gel route followed by a dehydrative coupling reaction. Thermosensitive poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) with an alkyne end-group was synthesized by controlled radical polymerization and was grafted using a copper assisted azide-alkyne cycloaddition reaction. Measurement of the colloidal properties by dynamic light scattering (DLS) indicated that the thermosensitive NPs exhibited changes in their Zeta potential and hydrodynamic diameter as a function of pH and temperature due to the grafted PDMAEMA chains. These changes were accompanied by changes in the relaxivities of the NPs, suggesting application as thermosensitive contrast agents for magnetic resonance imaging (MRI). In addition, a new fibre-based backscattering setup enabled positioning of the DLS remote-head as close as possible to the coil of a magnetic heating inductor to afford in situ probing of the backscattered light intensity, hydrodynamic diameter, and temperature. This approach provides a promising platform for estimating the response of magnetic NPs to application of a radiofrequency magnetic field or for understanding the behaviour of other thermogenic NPs

Auto-assemblages biofonctionnels à base de conjugués polymère-b-peptide

La thèse présentée décrit la préparation et l étude d auto-assemblages élaborés à partir de conjugués amphiphiles Tat-b-poly(triméthylène carbonate) (Tat-b-PTMC) doués de propriétés d internalisation cellulaire conférées par le segment peptidique Tat. L objectif principal de ces travaux était d établir et de comprendre les liens entre la structure macromoléculaire, les caractéristiques colloïdales et l activité biologique de ces systèmes. Les efforts de précision moléculaire et de caractérisation fournispour la synthèse des chimères Tat-b-PTMC a permis de corréler finement leurs structures chimiquesaux paramètres physico-chimiques des nanoparticules obtenues. Grâce à une approche expérimentale transverse combinant des études de biologie cellulaire et de biophysique, le mécanisme d interaction in vitro de ces nanoparticules avec les cellules HeLa a pu être en partie élucidé. Enfin, un camouflage électrostatique pH-sensible a été mis au point pour tenter de moduler leur activité et d augmenter leur sélectivité vis-à-vis de l environnement tumoral.This thesis work deals with preparation and study of cell-penetrating self-assemblies from amphiphilicpolymer-b-peptide Tat-b-poly(trimethylene carbonate) conjugates. Tat-b-PTMC chimeras withtunable hydrophilic fractions were synthesized, thoroughly characterized and self-assembled inaqueous buffer into size-tunable, highly monodisperse core-shell nanoparticles, presenting a full Tatcorona. Their physico-chemical profiles were assessed by complementary imaging (AFM, TEM) andscattering techniques (multiangle DLS, SANS) and correlated with their molecular architectures.Their transduction ability in vitro on HeLa cells and interaction mode with phospholipid membraneswere studied with a view to correlate their physico-chemical profiles with their biological properties.This interdisciplinary approach partially shed light on the interactions at play in the cellular uptakeprocess. With the ultimate goal of improving pharmacological characteristics, we finally endeavoredto develop an ON/OFF PEGylation strategy to harness the cell penetrating power of thosebiomacromolecular self-assembled systems.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Adv Drug Deliv Rev

Nature is an everlasting source of inspiration for chemical and polymer scientists seeking to develop ever more innovative materials with greater performances. Natural structural proteins are particularly scrutinized to design biomimetic materials. Often characterized by repeat peptide sequences, that together interact by inter- and intramolecular interactions and form a 3D skeleton, they contribute to the mechanical properties of individual cells, tissues, organs, and whole organisms. (Numata, K. Polymer Journal 2020, 52, 1043-1056) Among them elastin, and its main repeat sequences, have been a source of intense studies for more than 50 years resulting in the specific research field dedicated to elastin-like polypeptides (ELPs). These are currently widely investigated in different applications, namely protein purification, tissue engineering, and drug delivery, and some technologies based on ELPs are currently explored by several start-up companies. In the present review, we have summarized pioneering contributions on ELPs, progress made in their genetic engineering, and understanding of their thermal behavior and self-assembly properties. Considered as intrinsically disordered protein polymers, we have finally focused on the works where ELPs have been conjugated to other synthetic macromolecules as covalent hybrid, statistical, graft, or block copolymers, highlighting the huge opportunities that have still not been explored so far.Développement de squelettes polypeptidiques recombinants pour la synthèse de glycoconjugués multivalents parfaitement défini

Nanoparticules hybrides thermosensibles pour la théranostique

Cette étude concerne le développement de nanoparticules hybrides offrant de nouvelles stratégies pour la thérapie et le diagnostic médical. Elles sont constituées d un cœur magnétique jouant le rôle d agent de contraste pour l IRM et d inducteur de chaleur par hyperthermie, d une couronne de polymère thermosensible permettant d encapsuler des principes actifs et de peptides de reconnaissance biologique. Une grande partie de l étude a consisté à étudier les processus d'adsorption de copolymères poly(éther)-b-poly(L-lysine) de composition variable sur les particules magnétiques et à comprendre le rôle de la conformation des chaînes polymère à la surface des particules sur la stabilité des colloïdes en milieu physiologique. Un agent antitumoral a été encapsulé puis libéré de façon contrôlée sous l effet d un champ magnétique alternatif en exploitant le caractère thermosensible des blocs polyéthers. Des séquences peptidiques ciblant les zones d inflammation de la barrière hémato-encéphalique ont été greffées sur les copolymères. L efficacité du ciblage a été validée par IRM et fluorescence sur un modèle animal démontrant ainsi la multifonctionnalité des nanoparticules.This work deals with the development of hybrid nanoparticles that could offer new strategies for therapy and diagnostic. These are based on a magnetic core which can play the role of contrast agent for MRI as well as heat inductor in AC magnetic field. This inorganic core is surrounded by a thermo-responsive polymeric brush that controls the loading and the release of drugs, and can be functionalized by specific ligands ensuring the targeting specificity. A large part of this work consists in studying the adsorption mechanism of poly(ether)-b-poly(L-lysine) based block copolymers onto magnetic particle and to better understand the influence of the polymer chain conformation at particles surface on the colloidal stability under physiological conditions. An anticancer drug has been loaded and released in a controlled manner under alternative magnetic field by taking advantage from the thermosensitivity of the polyether block. Targeting peptides specific of inflammation sites at the blood brain barrier have been grafted onto copolymers. The targeting specificity has been demonstrated by MRI and fluorescence imaging in rats attesting the multifunctionality of such nanoparticles.PARIS-BIUP (751062107) / SudocSudocFranceF

Synthèse et auto-assemblage de copolymères amphiphiles en étoile de type "miktoarm"

L'objectif de ce travail est l'étude de l'influence de l'architecture des copolymères à blocs sur les propriétés d'auto-assemblage en solution et en masse. Dans un premier temps, de nouvelles étoiles miktoarm amphiphiles AB2 à base d'un bloc A hydrophobe de polystyrène et de différents blocs B hydrophiles de poly(acide acrylique), de poly(acide glutamique) et de poly(oxyde d'éthylène)- ont été élaborées en utilisant une stratégie de synthèse originale, fondée sur la combinaison de méthodes de polymérisation "vivante/contrôlée" et de réactions de modification chimique des bouts de chaîne. Ensuite, nous avons comparé les comportements auto-associatifs en solution diluée des étoiles miktoarm amphiphiles PS-b-(PAA)2 et PS-b-(PGA)2 avec ceux des copolymères à blocs linéaires de même composition. Nous avons également étudié l'effet de deux stimuli externes sur le comportement des objets auto-assemblés: la force ionique de trois familles de copolymères à blocs: un système "flexible-flexible" PS-b-(PAA)n=1;2 et deux systèmes "rigide-flexible" PS-b-(PGA)n=1;2 et PS-b-(PBLG)n=1;2.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF