Search

The present invention concerns amphiphilic copolymers that may be photo- or redox-cleavable and that may assemble into polymersomes. It also concerns their process of preparation and their use as drug carriers.; La présente invention concerne des copolymères amphiphiles qui peuvent être photo-clivables ou clivables par oxydoréduction et qui peuvent s'assembler en polymersomes. L'invention concerne également leur procédé de préparation et leur utilisation en tant que supports de médicament.

Micelles composed of block copolymers of poly(ethylene glycol)-b-poly(N-2-benzoyloxypropyl methacrylamide) (mPEG-b-p(HPMA-Bz)) have shown great promise as drug-delivery carriers due to their excellent stability and high loading capacity. In the present study, parameters influencing micelle size were investigated to tailor sizes in the range of 25-100 nm. Micelles were prepared by a nanoprecipitation method, and their size was modulated by the block copolymer properties such as molecular weight, their hydrophilic-to-hydrophobic ratio, homopolymer content, as well as formulation and processing parameters. It was shown that the micelles have a core-shell structure using a combination of dynamic light scattering and transmission electron microscopy analysis. By varying the degree of polymerization of the hydrophobic block (NB) between 68 and 10, at a fixed hydrophilic block mPEG5k (NA = 114), it was shown that the hydrophobic core of the micelle was collapsed following the power law of (NB × Nagg)1/3. Further, the calculated brush height was similar for all the micelles examined (10 nm), indicating that crew-cut micelles were made. Both addition of homopolymer and preparation of micelles at lower concentrations or lower rates of addition of the organic solvent to the aqueous phase increased the size of micelles due to partitioning of the hydrophobic homopolymer chains to the core of the micelles and lower nucleation rates, respectively. Furthermore, it was shown that by using different solvents, the size of the micelles substantially changed. The use of acetone, acetonitrile, ethanol, tetrahydrofuran, and dioxane resulted in micelles in the size range of 45-60 nm after removal of the organic solvents. The use of dimethylformamide and dimethylsulfoxide led to markedly larger sizes of 75 and 180 nm, respectively. In conclusion, the results show that by modulating polymer properties and processing conditions, micelles with tailorable sizes can be obtained.

Red luminescent and superparamagnetic &beta, NaY0.8Eu0.2F4@&gamma, Fe2O3 nanoparticles, made of a 70 nm-sized &beta, NaY0.8Eu0.2F4 single crystal core decorated by a 10 nm-thick polycrystalline and discontinuous &gamma, Fe2O3 shell, have been synthesized by the polyol process. Functionalized with citrate ligands they show a good colloidal stability in water making them valuable for dual magnetic resonance and optical imaging or image-guided therapy. They exhibit a relatively high transverse relaxivity r2 = 42.3 mM&minus, 1&middot, s&minus, 1 in water at 37 &deg, C, for an applied static magnetic field of 1.41 T, close to the field of 1.5 T applied in clinics, as they exhibit a red emission by two-photon excited fluorescence microscopy. Finally, when brought into contact with healthy human foreskin fibroblast cells (BJH), for doses as high as 50 &micro, g&middot, mL&minus, 1 and incubation time as long as 72 h, they do not show evidence of any accurate cytotoxicity, highlighting their biomedical applicative potential.

The careful design of nanoparticles, in terms of size and morphology, is of great importance to developing effective drug delivery systems. The ability to precisely tailor nanoparticles in size and morphology during polymer self-assembly was therefore investigated. Four poly(ethylene glycol)-b-poly(N-2-benzoyloxypropyl methacrylamide) mPEG-b-p(HPMA-Bz) block copolymers with a fixed hydrophilic block of mPEG 5 kDa and a varying molecular weight of the hydrophobic p(HPMA-Bz) block (A: 17.1, B: 10.0, C: 5.2 and D: 2.7 kDa) were self-assembled into nanoparticles by nanoprecipitation under well-defined flow conditions, using microfluidics, at different concentrations. The nanoparticles from polymer A, increased in size from 55 to 90 nm using lower polymer concentrations and slower flow rates and even polymer vesicles were formed along with micelles. Similarly, nanoparticles from polymer D increased in size from 35 to 70 nm at slower flow rates and also formed vesicles along with micelles, regardless of the used concentration. Differently, polymers B and C mainly self-assembled into micelles at the different applied flow rates with negligible size difference. In conclusion, this study demonstrates that the self-assembly of mPEG-b-p(HPMA-Bz) block copolymers can be easily tailored in size and morphology using microfluidics and is therefore an attractive option for further scaled-up production activities.Keywords: block copolymers; nanoparticles; micelles; polymersomes; HPMA; size control; nanoprecipitation; microfluidics; micromixer

International audience; In medicine, medical imaging has a leading place in the diagnosis setting. This is why some researches are continually carried out to improve the available techniques. One of the most used techniques to obtain anatomical information is magnetic resonance imaging (MRI). The commercially available contrast agents are based on gadolinium complexes. Recently, it has been shown that gadolinium can lead, mainly for patients with renal disfunctions, to a pathology named NSF (nephrogenic systemic fibrosis). It is thus interesting to develop efficient contrast agents based on another paramagnetic ion such as manganese. The macrocycle used in this work is a pyclen derivative which is functionalized to respect protection anddeprotection steps. Their efficacy as contrast agents for MRI was evaluated by relaxometry and 17O NMR and even if the results are encouraging, the manganese ion is, as expected, less effective than the gadolinium ion. So, it could be interesting to encapsulate the Mn-complexes in nanostructure like polymersomes which allow a fast exchange of the water molecules through the pores. The complexes could thus be encapsulated inside the polymersomes or in the membrane in order to improve the relaxivity through an increase of the rotational correlation time.

International audience; Intimate mixing of phospholipids and amphiphilic copolymers within same membrane of a giant vesicle requires particulate attention on both the molecular design and on the self-assembly process for synergetic benefits from both components.

International audience; The structural, microstructural, and magnetic properties of ~5‐nm‐sized Co0.6Zn0.4Fe2−xGdxO4 nanoparticles were investigated in order to evaluate their capability to enhance the magnetic resonance imaging contrast as high magnetization agents. A focus was made on the solubility of Gd3+ cations within the spinel lattice. By coupling X‐ray diffraction to X‐ray fluorescence spectroscopy, we demonstrated that only a limited fraction of Gd3+ can substitute Fe3+ ions into the whole crystal structure and does not exceed 6 at.‐%. At this concentration, the room temperature (27°C) saturation magnetizations of the prepared superparamagnetic nanocrystals were found to be close to 80 emu g−1. Coating these nanoparticles with hydrophilic dopamine ligands leads to the formation of ~50‐nm‐sized clusters in water. As a consequence, relatively high r2/r1 ratios of transverse to longitudinal proton relaxivities and high r2 values were measured in the resulting colloids at physiological temperature (37°C) for an applied magnetic field of 1.41 T: 33 and 188 mM−1 sec−1, respectively, for the richest system in gadolinium. Moreover, after incubation with healthy human model cells (fibroblasts) at doses as high as 10 μg mL−1, they induce neither cellular death nor acute cellular damage making the engineered probes particularly valuable for negative magnetic resonance imaging contrasting.

With the current increase of asymmetric conflicts, a bioterrorist attack against the French armed forces or on the national territory is unfortunately no longer excluded. FASTGENE technology enables the sensitive, specific and inexpensive detection of the presence of pathogens in a sample in less than 8 minutes. This dual technology can be applied to many other applications outside the field of defense and security, Avec l'accroissement actuel des conflits asymétriques, une attaque bioterroriste à l'encontre des forces armées françaises ou sur le territoire national n'est malheureusement plus à exclure. Avec le soutien de la DGA, nous avons développé la technologie FASTGENE qui permet la détection sensible, spécifique et peu coûteuse, de la présence d'agents pathogènes dans un échantillon en moins de 8 minutes. Cette technologie duale peut s'appliquer de nombreuses autres applications en dehors du domaine de la défense et de la sécurité. Détecter et identifier rapidement les microorganismes: un besoin essentiel pour contrer les bioterroristes Le risque bioterroriste est particulièrement préoccupant puisqu'il se différencie des autres risques terroristes par des effets initialement masqués, puis amplifiés exponentiellement par le caractère contagieux d'un nombre croissant d'infections. La capacité de défense vis-à-vis de ce risque repose sur plusieurs piliers parmi lesquels la surveillance de l'environnement et la reconnaissance d'une agression jouent un rôle central. Une surveillance permanente et une reconnaissance rapide permettent en principe de limiter au maximum les conséquences d'une attaque. A la suite de l'attaque par lettres contenant des bacilles du charbon en 2001, les autorités des États-Unis ont décidé de déployer au niveau fédéral un système de surveillance de la qualité biologique de l'air, appelé Biowatch (1). Ce système est composé d'un grand nombre de capteurs d'aérosols déployés dans les 30 plus grandes agglomérations. Les aérosols ainsi collectés sont analysés périodiquement par un réseau de laboratoires. Bien que ce système unique n'ait heureusement jamais été confronté à une attaque bioterroriste, son exploitation permet de tirer plusieurs enseignements capitaux sur les caractéristiques que doivent réunir un tel système

Magnetic nanoparticles present some attractive applications in biomedicine. First, they can be prepared from a size ranging from a few nanometers up to hundreds of nanometers, which places the particles at dimensions that are smaller than or comparable to those of cells (10–100 μm), virus (20–450 nm), proteins (5–50 nm) and genes (2 nm wide and 10–100 nm long). As a consequence they can “get close” to these biological entities. Furthermore, when coated with appropriate molecules magnetic nanoparticles can interact or bind to biological entities, which provides a mean of actuating on these entities by noncontact magnetic forces. This ‘action at a distance’, combined with the intrinsic penetrability of magnetic fields into biological tissues, possibilities a number of biomedical applications of magnetic nanoparticles.In this seminar, a revision of the state of the art in the fields of synthesis, properties and biomedical applications of magnetic nanoparticles is presented. This seminar is organized as it follows:1. Chemistry of iron oxides and oxo-hydroxides: Diversity of methods to prepare colloidal nanoparticles, either in non aqueous solvents: hydrothermal synthesis, polyol synthesis, thermal decomposition… or in water: co-precipitation of iron salts2. Magnetic behavior: ferro- /ferri- /antiferro- /superpara– magnetism, magnetophoresis (magnetic guiding)3. Optical properties: UV-vis absorption, circular dichroism (Faraday rotation), magnetic birefringence4. Relaxivity properties (T1/T2 of H spins): Contrast agents in MRI5. Magnetic relaxations in radiofrequency (kHz-MHz) fields: Magnetic hyperthermia and RF-induced drug release

International audience; Reflets de la physique constitue avec le site web l outil de communication privilégié de la SFP auprès de ses membres

International audience; Phase separation in hybrid polymer/lipid giant unillamelar vesicles (GHUVs) has been described over the last few years. However there is still a lack of understanding in physical and molecular factors governing the phase separation in such systems. Among these parameters it has been suggested that in analogy to multicomponent lipid vesicles that hydrophobic mismatchs as well as lipid fludity play a role.In this work, we aim to map a global picture of phase separation and domain formation in membrane of GHUVs by using various copolymers based on poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) (PEO) with different architectures (grafted, triblock) and molar masses, combined with lipid at fluid (POPC) or gel state (DPPC) at room temperature. From confocal imaging and fluorescence lifetime imaging microscopy technique (FLIM), the phase separation into either micro- or nano- domains within GHVs were studied. In particular, our systematic studies demonstrate that in addition to lipid/polymer fraction or lipid physical state, important factors such as line tension at lipid polymer/lipid boundaries can be finely modulated by the molar mass and architecture of the copolymer and lead to the formation of stable lipid domains with different sizes and morphologies in such GHUVs.

Phase separation in hybrid polymer/lipid giant unillamelar vesicles (GHUVs) has been described over the last few years. However there is still a lack of understanding in physical and molecular factors governing the phase separation in such systems. Among these parameters it has been suggested that in analogy to multicomponent lipid vesicles that hydrophobic mismatchs as well as lipid fludity play a role.In this work, we aim to map a global picture of phase separation and domain formation in membrane of GHUVs by using various copolymers based on poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) (PEO) with different architectures (grafted, triblock) and molar masses, combined with lipid at fluid (POPC) or gel state (DPPC) at room temperature. From confocal imaging and fluorescence lifetime imaging microscopy technique (FLIM), the phase separation into either micro- or nano- domains within GHVs were studied. In particular, our systematic studies demonstrate that in addition to lipid/polymer fraction or lipid physical state, important factors such as line tension at lipid polymer/lipid boundaries can be finely modulated by the molar mass and architecture of the copolymer and lead to the formation of stable lipid domains with different sizes and morphologies in such GHUVs.

The polyol route is a versatile and up-scalable method to produce large batches of iron oxide nanoparticles with well-defined structure and magnetic properties. Controlling parameters such as temperature and duration of reaction, heating profile, nature of polyol solvent or of organometallic precursors were reported in previous studies of literature, but none of them described yet the crucial role of water in the forced hydrolysis pathway, whose presence is mandatory for nanoparticle production. This communication investigates the influence of the water amount and temperature at which it is injected in the reflux system for either pure polyol or mixture with a poly(hydroxy) amine. Distinct morphologies of nanoparticles were thereby obtained, from ultra-ultra-small smooth spheres down to 4 nm in diameter to large ones up to 37 nm in diameter. Nanoflowers were also synthesized, which are well-defined multi-core assemblies with narrow grain size dispersity. A diverse and large library of samples was obtained by playing on the nature of solvents and amount of water traces while keeping all the other parameters fixed. The varied morphologies lead to magnetic nanoparticles well-fitting to required applications among magnetic hyperthermia and MRI contrast agent, or both., Comment: Main text: 36 pages, 8 figures; Supporting information: 10 pages, 15 figures (including graphical abstract)

International audience; Hybrid vesicles resulting from the combined self-assembly of both amphiphilic copolymers and lipids have attracted particular interest from chemists and (bio)physicists over the last five years. Such assemblies may be viewed as an advanced vesicular structure compared to their liposome and polymersome forerunners as the best characteristics from the two different systems can be integrated in a new, single vesicle. To afford such a design, the different parameters controlling both self-assembly and membrane structure must be tuned. This highlight aims to present a comprehensive overview of the fundamental aspects related to these structures, and discuss emerging developments and future applications in this field of research.

The ability of certain lipids to self-assemble in water as bilayers is crucial for the properties of the outer membrane of biological cells and many of their internal structures as well (Golgi apparatus, endosomes, lysosomes, ...). Usually we call a vesicle such a bilayer membrane forming a closed shape with both an inner and an outer aqueous compartments separated by a hydrophobic barrier with a nearly zero permeability to hydrophilic solutes. This vesicular morphology well-known for liposomes prepared from either natural or artificial lipids was also obtained recently for polymersomes, which membrane is made of block copolymers[1]. It is worth noticing that unlike other manmade capsules or natural shells, the membrane of liposomes and polymerosomes is a 2-dimensional fluid. The result is a large flexibility of the shape and a mobility of the molecules within the membrane. The encapsulation of the magnetic nanoparticles of ferrofluids into vesicles was motivated by the idea of controlling their shape by an external magnetic field. Giant magneto-liposomes were first obtained by pre-hydrating a synthetic phospholipid (DOPC) with an aqueous “citrated” ferrofluid at pH7 and subsequent swelling of the bilayers by water[2]. Their diameters ranging from 5 to 20 um, it was possible to use optical microscopy to study their elongation in a homogeneous magnetic field and deduce the bending modulus of the DOPC bilayers Kb=20kBT from those measurements. In following experimental[3] and theoretical[4] works, it was shown that a magnetic field could produce either a prolate or an oblate ellipsoidal deformation of the magnetic liposomes depending on another control parameter important for ionic ferrofluids: the citrate salt concentration. When the concentration of those small ions is small indeed, the spontaneous curvature due to the difference between the Debye lengths on each side of the bilayer becomes sensitive to the presence of the nanoparticles inside and their absence outside. It was shown that the bending energy dominates over the magnetic energy in that case, and thus that an oblate flattening of the vesicle near the magnetic poles is preferred to the prolate elongation observed at high salinity. The citrate salt concentration in the outer medium of the giant magneto-liposomes was also used as an osmotic agent to measure the permeability of water through DOPC bilayers[5]. In other experiments, tubular giant magneto-liposomes were favoured by shearing the bilayers during their swelling by water[6]. The true morphology was rather like dumbbells because the cylindrical portions of membranes were connecting two quasi-spherical vesicles with a high concentration of ferrofluid inside. The deformation of such connected vesicles by an applied magnetic field is much larger than for isolated vesicles because the connected tubules act as reservoirs of lipids adding to the surface area of the spherical parts. Above a threshold field intensity, a pearling instability of the tubules is induced by the increase of the surface tension. Current researches on giant magneto-liposomes deal with their use as directly observable objects (under an optical microscope) to visualize the intermediate steps during the solubilization of lipid bilayers by n-octylglucoside (OG), a non ionic surfactant commonly used in pharmacology. By using the deformation experiment with a magnetic field to probe the membrane elasticity, it was shown that at bulk concentrations below the CMC, the penetration of surfactants in the bilayers causes a 10% relative increase of their surface area and a lowering of Kb down to 5 kBT. [7] At a lower (sub-micronic) scale, large unilamellar vesicles (LUV) were successfully prepared with a high encapsulation yield of magnetic nanoparticles[8] (Fig. 1), which could be used as new magnetic vectors In spite of the lack of experimental example, the deformation by a field of a vesicle with a fluid and magnetic membrane was addressed theoretically[9]. Having managed to confine magnetic nanoparticles in the membrane of polymersomes (Fig. 2) much thicker than lipid bilayers[10], we are now studying their response to a field.for drug targeting or contrast agents in MRI.

Magnetic beads are very useful for purification steps in biotechnology as well as for certain micro-manipulation experiments in biophysics. The “superparamagnetic beads” commercially available are suitable for most of these applications due to their high magnetic load (typically 50 weight %), their good monodispersity in sizes (from 200 nm to a few µm) and the control of their surface coating (typically amino or carboxy moities, but also antibodies for the grafting of biomolecules). However in the field of drug-delivery, there is a strong demand of magnetic multi-responsive objects, i.e. carriers of drugs that would respond to at least two different stimuli: temperature, pH, solute concentration, ..., combined to the long distance action of a magnetic field. Contrary to the well documented studies on magnetic beads made of surfactant coated magnetic nanoparticles embedded in polymer shells, we chose to explore the route of hydrogel microparticles combined with ionic ferrofluids. Being highly swollen by water, these magnetic microgels exhibit a softness that leads to their fast response to the solvent quality and to certain shape instabilities. Preparation We have published recently the preparation of magnetic microgels and minigels from the polymerization of the neutral hydrophilic monomer acrylamide (AM) cross-linked by N,N'-methylene-bisacrylamide (BAM) in an inverse (W/O) emulsion . After dispersing in oil an aqueous ferrofluid and a polymerization mixture localized together in water droplets, we achieve free radical polymerization, followed by rinsing steps. We obtain spherical particles made of a hydrophilic polymer matrix entrapping magnetic nanoparticles with a high encapsulation yield and a homogeneous dispersion state. By preparing either a conventional emulsion or a mini-emulsion, we reach two ranges of sizes: either microgels of 2 – 20 µm diameters visible by optical microscopy or sub-micron minigels, which in addition present a good colloidal stability. Due to their magnetic load, microgels and minigels both react to a field by chaining and to a field gradient by migration (magnetophoresis). Preparation We have published recently the preparation of magnetic microgels and minigels from the polymerization of the neutral hydrophilic monomer acrylamide (AM) cross-linked by N,N'-methylene-bisacrylamide (BAM) in an inverse (W/O) emulsion . After dispersing in oil an aqueous ferrofluid and a polymerization mixture localized together in water droplets, we achieve free radical polymerization, followed by rinsing steps. We obtain spherical particles made of a hydrophilic polymer matrix entrapping magnetic nanoparticles with a high encapsulation yield and a homogeneous dispersion state. By preparing either a conventional emulsion or a mini-emulsion, we reach two ranges of sizes: either microgels of 2 – 20 µm diameters visible by optical microscopy or sub-micron minigels, which in addition present a good colloidal stability. Due to their magnetic load, microgels and minigels both react to a field by chaining and to a field gradient by migration (magnetophoresis). Swelling degree and dynamics The initially liquid droplets are efficiently converted to gel beads. The most direct evidence is to show their ability to absorb a good solvent (water), by following their volume increase compared to a bad solvent (ethanol) or to the dry state. The amount of water at the swelling equilibrium results from a balance between the free energy of mixing (of polymer and water) and the elastic constraints on the network. The degree of swelling is thus expected to be reduced by increasing the cross-linking density, as we check by looking at microgels containing either 2.5 or 5 weight % of BA compared to AM. The observation of magnetic microgels during swelling under the optical microscope shows: the penetration of the water front towards the dry core; the overall increase of the outer diameter; the spreading onto the glass slide (i. e. the decrease of the contact angle); and sometimes also a transient rippling instability of the free surface, that T. Tanaka has shown a long time ago with macroscopic hydrogels . The quantitative analysis of the volume increase of a given bead from optical observations is difficult due to those phenomena at the gel/glass and gel/solution interfaces. On the contrary, minigels are properly dispersed in the medium and their average diameter is in the right range to be measured by multi-angle dynamic light scattering. The hydrodynamic diameter varies indeed from 158 nm in ethanol to 195 nm in water, which corresponds to almost a two fold increase of volume (on average) when the beads are transferred from a bad to a good solvent. Concerning now dynamics, we know that swelling is a diffusive process, and thus its characteristic time scale varies like the inverse of the bead diameter . Therefore it take only a few seconds for microgels around 10µm in size to change their size, while it takes hours for beads in the mm range (or even days for cm large gels). Sub-micron minigels change their volume in even shorter times, which makes them quite interesting for multi-responsive biomedical carriers. Shape instabilities Even if there is an analogy between a microgel wetting a flat surface or squeezed between two plates and a pure viscous liquid droplet in the same situations, there are also noticeable differences due to the elastic nature of the gel. It has been predicted theoretically that the shape of a soft elastic bead on an adhesive substrate is not a perfect spherical cap as a liquid droplet . More precisely, the wedge makes an extension, which typical size L is the ratio of the spreading parameter (S≡10-2 J/m) by the shear modulus of the network (G≡104 Pa for soft elastomers). Using several microscopies (SEM, TEM, AFM, optical microscopy) and either hydrophilic or hydrophobic substrates, we show that such “feet” exist around the magnetic microgels, and that their length is about 1 µm and becomes longer when the gel is softer (at lower BA/AM ratio). When we look at a microgel drying slowly in a thin cell made of two glass slides, we observe the well known Saffman-Taylor instability due to penetration of air and retraction of fluid. However, the dried microgel exhibits a more branched structure of the gel “fingers” compared to pure viscous fingering, as was previously observed for a visco-elastic gel . Conclusion and perspectives We prepare magnetic gels in two ranges of sizes. Being colored by the iron oxide, the larger microgels can be easily handled under an optical microscope equipped with magnets. They can serve as model systems for shape instabilities of soft elastic objects during swelling, wetting or drying. The sub-micron microgels are intended for biotechnological applications. We plan to improve them by incorporating a polymer like poly(NIPAM), with a volume transition as a function of temperature. T. Tanaka T, S.-T. Sun, Y. Hirokawa, S. Katayama, J. Kucera Y. Hirose, T. Amiya, Nature (1987) 325, 796 T. Tanaka, D. J. Fillmore, J. Chem. Phys. (1979) 70, 1214 J.-F. Joanny, Johner, Vilgis, Eur. Phys. J. E (2001) 6, 201 A. Lindner, P. Coussot, D. Bonn, Phys. Rev. Lett. 85 (2000), 314-317

Giant vesicles are artificial objects used to mimic the lipid envelope of biological cells, or plasma membrane, delimiting the cell interior from the outer medium. Among all the systems modeling biological membranes (monomolecular layers at the air/water interface, bilayers supported on a solid substrate, black lipid membranes, etc.…), giant vesicles are the softest and the easiest to change their shapes. Their membrane is a thin fluid sheet with indeed almost no surface tension. Nevertheless, it can be stretched by an external action. The value of the so created mechanical tension lies far below the usual interfacial tensions of liquids. However, with giant vesicles, the necessity to relax this low tension is a sufficient factor to cause major reorganizations of lipids. This work highlights two types of transformation: i) transient rupture of the membrane, and the leakage of the inner fluid through a giant macroscopic pore; ii) fusion of neighboring membranes, via the steps of hemifusion and then of a fusion pore. Experimental observations have been obtained mainly by fluorescence microscopy. A simple hydrodynamic theory describes the viscous dissipation inside the membrane and in the surrounding solvent. Besides, a novel imaging technique developed recently, namely the second harmonic generation (SHG) microscopy provides complementary information about the distance profile of adhering membranes. Finally, giant vesicles decorated with proteins enable to get a little closer to the reality of cell adhesion.Chapter I presents the general characteristics of vesicles, and the manipulations enabling to put them under tension. The experimental protocols are described in chapter II, to prepare on the one hand suspensions of giant vesicles in various mediums, on the other hand adhesive coatings on glass. Chapter III details the methods of optical microscopy, in order to observe the lipid membranes with the best contrast. After a brief state of the art about the break-down of lipid bilayers, chapter IV describes the complete dynamics of transient pores, both theoretically and experimentally. In particular, we shall see how the increased viscosity of the medium leads to longer lifetimes together with larger sizes. Chapter V just reveals descriptively the foams of giant vesicles. Depending on the type of interaction, vesicles either remain tense as soap bubbles, or they relax their tension by mixing part of their membranes., Les vésicules géantes sont des objets artificiels utilisés pour mimer l’enveloppe lipidique des cellules biologiques, la membrane plasmique, qui sépare l’intérieur de la cellule de son milieu extérieur. Parmi tous les systèmes censés modéliser les membranes biologiques (couches monomoléculaires à l’interface eau/air, bicouches supportées sur un substrat solide, films noirs lipidiques, etc...) les vésicules géantes sont les plus molles et les plus déformables. En effet, leur membrane est une mince couche fluide dont la tension de surface est pratiquement nulle. Néanmoins, elle peut être tendue progressivement par une action extérieure. La tension mécanique qui apparaît alors reste très en deçà des tensions interfaciales usuelles des liquides. Mais, sur des vésicules géantes, la relaxation de cette tension suffit pour provoquer des réorganisations importantes des lipides. Ce travail met en lumière deux types de transformation : i) la rupture transitoire de la membrane, et la fuite du liquide interne à travers un pore macroscopique géant ; ii) la fusion de deux membranes adjacentes, qui passe par les étapes intermédiaires d’hémifusion puis d’un pore de fusion. Les observations expérimentales ont été réalisées principalement en microscopie de fluorescence. Un modèle hydrodynamique simple étudie la dissipation visqueuse à l’intérieur de la membrane et dans le solvant alentour. En parallèle, une nouvelle imagerie mise au point récemment, la microscopie par génération de second harmonique (SHG), apporte des informations complémentaires sur le profil de distance des membranes adhérentes. Enfin, des vésicules géantes décorées par des protéines permettent de s’approcher un peu plus de la réalité de l’adhésion cellulaire.Le chapitre I présente les caractéristiques générales des vésicules, ainsi que les manipulations permettant de les mettre sous tension. Les protocoles expérimentaux sont décrits au chapitre II, pour préparer d’une part des suspensions de vésicules géantes dans différents milieux, d’autre part des traitements de surfaces adhésifs sur le verre. Les méthodes de microscopie optique, nécessaires pour observer les membranes lipidiques avec un contraste optimal, sont détaillées au chapitre III. La suite aborde les deux voies adoptées par les vésicules géantes pour relaxer une tension de surface. Après un bref état de l’art sur les ruptures de bicouches lipidiques, le chapitre IV décrit, sur le plan théorique puis expérimental, la dynamique complète des pores transitoires. Nous verrons en particulier comment la viscosité accrue du milieu augmente à la fois leur durée de vie et leur taille. Le chapitre V ne fait qu’aborder, d’une manière surtout descriptive, les mousses de vésicules géantes. Suivant leur type d’interaction, soit les vésicules restent tendues comme des bulles de savon, soit elles relaxent leur tension, en mélangeant partiellement leurs membranes.

International audience

Fluorescent organic nanoparticles (FON) made of small molecules recently arouse considerable interest in biomedical imaging and opto-electronics as potential microlasers or emitting displays.2 Their collective emission largely enhanced with respect to dilute media and their reduced sensitivity to external bleaching and quenching effects make them very attractive when powerful excitation is required as in multiphoton fluorescence spectroscopy. Fluorescence in the solid state is however facing two deleterious effects: competitive non-radiative quenching processes caused by strong intermolecular aggregation, and emission reabsorption owing to the inherent high chromophore density. The main strategies consist in introducing bulky substituents to prevent the formation of non-emissive π−π stacked assemblies as well as elaborating materials with a large optical Stokes shift. Hydrophobic materials are often obtained and considered of little use in bioimaging. We want to report herein the synthesis and the properties of a new family of push-pull amorphous compounds which form strong one-and two-photon emitting nanoparticles that can efficiently be utilized to image lipophilic cell membranes despite their water insolubility. The present series of fluorescent compounds consists in polar triphenylamino derivatives substituted by bulky tert-butylphenyl groups following a Suzuki aromatic cross coupling reaction as a final step. Both the twisted star-shaped triphenylamino-core and peripheral hindered substituents prevent deleterious π−π stacking and ensure high solubility in polar and apolar organic solvents.

In this poster we show two types of nanocomposite materials consisting of nanoparticles embedded in polymer matrices. On the one hand, a matrix with a high degree of organization is investigated for visible light optics and hyper-frequencies applications (reflectors, guides, antennae). On the other hand, a gel matrix with an isotropic loading of nanoparticles can exhibit a swelling transition triggered by an external field (electric or magnetic) or by temperature. The first system combines the self-assembly of a symmetrical diblock copolymer matrix poly(n-butylmethacrylate)-b–poly(styrene) (PBMA-b-PS) and the orientation properties under magnetic field of Γ-Fe2O3 nanoparticles. To confine the nanoparticles within the layers of PBMA-b-PS (Fig.1a), those were coated by a polymeric shell grown by surface initiation polymerization of PS ("grafting from"). Thin films obtained by spin-coating and annealing above the glass temperature Tg were doped with nanoparticles. The lamellar order was investigated by neutron reflectivity experiments (Fig.1b) which enable to fit the density profile of the films and to localize precisely the nanoparticles within the first PS blocs. The second system consists of the same iron oxide nanoparticles, which are confined this time within spherical clusters of PTEA-PAM (Fig.2a., cf. Pr. Perzynski), dispersed into a thermosensitive hydrogel of poly(N-isopropylacrylamide) PNIPAM. The deswelling of the matrix above the transition temperature causes the decrease of the average distance between those clusters, as shown by small angle neutron scattering experiment (Fig.2b).

Conférence orale présentée par Bruno Frka-Petesic; International audience; Mixing in aqueous solutions polyelectrolyte-neutral block copolymers with oppositely charged species, spontaneously forms stable core-shell complexes, which are electrostatically driven. We report here on the structural and orientational properties of such mixed magnetic nanoclusters made of magnetic iron oxide nanoparticles (MNP) and polyelectrolyte-neutral block copolymers. Small Angle Neutron Scattering and Transmission Electron Microscopy experiments allows to probe the innercore nanoparticle organization, leading to an average inter-particle distance and confirming the hierarchical internal structure of the clusters. Thanks to the MNP optical anisotropy, we also probe the under-magnetic field orientational properties of the core-shell clusters and their dynamical rotational relaxation.

Nanocomposite materials which associate inorganic nanoparticles and polymers with a high degree of organization are highly interesting for their applications in visible light optics (reflectors and guides) and hyper-frequencies (antennae and switches). We focus our study on a complex system combining the self-organization of a symmetrical poly(n-butylmethacrylate)-b– poly(styrene) diblock copolymer (PBMAb- PS) and the orientation properties under magnetic field of inorganic magnetic nanoparticles made of gamma-Fe2O3 iron oxide. To confine those magnetic nanoparticles within the layers of diblock copolymer and thus obtain a lamellar order, it is necessary to coat these nanoparticles with a polymer of the same nature than one bloc of the copolymer. Such a polymeric shell can be grown by initiating polymerization of PS chains at the surface of the nanoparticles ("grafting from") or by adsorbing endfunctionnalized PS chains ("grafting on"). By spin-coating a solution of PBMA-b-PS with or without PS coated nanoparticles in a volatile solvent on a flat silicon wafer and annealing above the glass temperature, we obtain the ordering of the thin film into layers of PBMA alternating with layers of PS doped with nanoparticles. This lamellar order is detected by AFM observation showing characteristic defects such as "islands" and "holes" and by measurements of the lamellar period by Neutron Reflectivity experiments.

Poster présenté par Vincent Dupuis

Nanocomposite materials which associate inorganic nanoparticles and polymers with a high degree of organization are highly interesting for their applications in visible light optics (reflectors and guides) and hyper-frequencies (antennae and switches). We focus our study on a complex system combining self-organization of a diblock copolymer A-B and orientation properties under magnetic field of inorganic magnetic nanoparticles. We present here an experimental protocol for the synthesis by Atom Transfer Radical Polymerization (ATRP) of the symmetrical poly(n-butylmethacrylate)-b–poly(styrene) diblock copolymer (PBMA-b-PS) with high molar masses (about 100 000 g/mol). After spin-coating on a flat substrate (float glass, silicone or alumina) from a solution in a volatile solvent and annealing above the glass temperature, a thin film of such well-defined symmetrical diblocks are expected to self-organize into a lamellar (smectic type) order. The second component of the system consists in nanoparticles made of either superparamagnetic maghemite oxide Γ-Fe2O3 (soft magnets) or ferrimagnetic cobalt ferrite CoO.Fe2O3 (strong magnets). We are working on the proper dispersion of these nanoparticles within the PS blocks in order to obtain “sandwiches” made of magnetic thin layers alternating with the lamellae of the copolymer matrix. Optical Reflection Interference Contrast Microscopy (RICM) is convenient and fast to measure the thickness of the films (from a number of fringes) directly on their substrate and to detect characteristic defects of the long-range organization of the films (like holes). High resolution microscopies such as AFM and TEM will enable to measure the lamellar period but require to prepare thin films cross-sections.

Présentation orale, présentée par E. Dubois

Poster

Meyer, oral

International audience; In Ref. 1, Eq. (2) should read as, (2)Eq. (3) should read as, (3)and the right-hand side of Eq. (4) should bemultiplied by 2*2^0.5.Finally, our discussion on the N.A. dependenceof PSHG is somewhat erroneous. In fact, PSHG isroughly independent of N.A. for low N.A.’s.

International audience; This chapter contains sections titled:IntroductionLiposome PreparationObservationsAnalysis of Deformations Under a Magnetic FieldInterpretation

Langmuir : the ACS journal of surfaces and colloids 34(50), 15495-15506 (2018). doi:10.1021/acs.langmuir.8b03576, Published by ACS Publ., Washington, DC

Ein Aspekt dieser Beschreibung bezieht sich auf eine Vorrichtung (100) zur Bestimmung charakteristischer Parameter der Abmessungen von in einer Flüssigkeit suspendierten Nanopartikeln.Die Vorrichtung (100) umfasst eine Lichtemissionseinrichtung (101), die so konfiguriert ist, dass sie einen einfallenden Strahl (Bi) emittiert, der entlang einer Polarisationsachse (P1) linear polarisiert ist; eine Erfassungseinheit (102), die einen Messarm (120) umfasst, der um eine Drehachse (∆) drehbar ist, wobei die Erfassungseinheit einen ersten und einen zweiten Erfassungskanal (151, 161) umfasst, die durch ein Polarisationstrennungselement (125) getrennt sind, das an dem Messarm angeordnet ist; einen festen Probenträger (103), der zur Aufnahme eines zylindersymmetrischen Behälters (10) der Probe konfiguriert ist, wobei eine Symmetrieachse des Behälters mit der Drehachse des Messarms zusammenfällt; eine Steuereinheit (104). Das Polarisationsteilerelement (125) des Messarms ist so konfiguriert, dass es gleichzeitig auf jedem der ersten und zweiten Detektionskanäle jeweils eine erste und eine zweite polarisierte Komponente (BS1, BS2) des von der Probe gestreuten Strahls (BS) sendet, wobei die Polarisationsachsen der ersten und zweiten polarisierten Komponenten senkrecht sind.Die Steuereinheit (104) ist so konfiguriert, dass sie aus den Signalen, die den auf jedem der Detektionskanäle detektierten polarisierten Komponenten entsprechen, als Funktion der Zeit mindestens zwei Parameter bestimmt, die für die Abmessungen der Nanopartikel charakteristisch sind., According to one aspect, the subject of the present description is a device (100) for determining characteristic parameters of the dimensions of nanoparticles in suspension in a liquid. The device (100) comprises light-emitting means (101) configured to emit an incident light beam (Bi) that is linearly polarized along a polarization axis (P1); a detecting unit (102) comprising a measurement arm (120) that is rotatable with respect to an axis of rotation (∆), said detecting unit comprising first and second detection channels (151, 161) that are separated by a polarization-splitting element (125) arranged in said measurement arm; a fixed sample holder (103), configured to receive a container (10) of cylindrical symmetry of said sample, an axis of symmetry of the container being coincident with the axis of rotation of the measurement arm; and a control unit (104). The polarization-splitting element (125) of the measurement arm is configured to simultaneously send, over each of the first and second detection channels, respectively, a first and second polarized component (BS1, BS2) of the beam (BS) scattered by the sample, the polarization axes of the first and second polarized components being perpendicular. The control unit (104) is configured to determine, from signals corresponding to the polarized components detected in each of the detection channels as a function of time, at least two characteristic parameters of the dimensions of the nanoparticles., Selon un aspect, la présente description a pour objet un dispositif (100) de détermination de paramètres caractéristiques des dimensions de nanoparticules en suspension dans un liquide.Le dispositif (100) comprend des moyens d’émission lumineuse (101) configurée pour émettre un faisceau incident (Bi) polarisé linéairement selon un axe de polarisation (P1); une unité de détection (102) comprenant un bras de mesure (120) mobile en rotation autour d’un axe de rotation (∆), ladite unité de détection comprenant une première et une deuxième voies de détection (151, 161) séparées par un élément séparateur de polarisation (125) agencé sur ledit bras de mesure; un support d’échantillon fixe (103), configuré pour recevoir un contenant (10) à symétrie cylindrique dudit échantillon, un axe de symétrie du contenant étant confondu avec l’axe de rotation du bras de mesure; une unité de contrôle (104). L’élément séparateur de polarisation (125) du bras de mesure est configuré pour envoyer simultanément, sur chacune des première et deuxième voies de détection, respectivement une première et une deuxième composantes polarisées (BS1, BS2) du faisceau (BS) diffusé par l’échantillon, les axes de polarisation des première et deuxième composantes polarisées étant perpendiculaires.L’unité de contrôle (104) est configurée pour déterminer, à partir de signaux correspondant aux composantes polarisées détectées sur chacune des voies de détection en fonction du temps, au moins deux paramètres caractéristiques des dimensions des nanoparticules.

International audience; In this study, an original method of macromolecular design was used to develop a hyaluronidase‐1 (HYAL1) inhibitor from its principal substrate, hyaluronic acid (HA). HA‐based nanoparticles (HA‐NP) were obtained by copolymer self‐assembly and their effects on HYAL1 activity were investigated by combining different analytical tools. Compared to HA, HA‐NP exhibited an enhanced stability against HYAL1 degradation while maintaining its interaction with HA receptors CD44 and aggrecan. HA‐NP displayed a strong and selective inhibition of HYAL1 activity and retarded the hydrolysis of higher molar mass HA in solution. A co‐nanoprecipitation process was used to formulate a range of hybrid nanoparticle samples, which demonstrated the specificity and efficiency of HA‐NP in HYAL1 inhibition.

Blending amphiphilic copolymers and lipids constitutes a novel approach to combine the advantages of polymersomes and liposomes into a new single hybrid membrane. Efforts have been made to design stimuli-responsive vesicles, in which the membrane&rsquo, s dynamic is modulated by specific triggers. In this investigation, we proposed the design of pH-responsive hybrid vesicles formulated with poly(dimethylsiloxane)-block-poly(ethylene oxide) backbone (PDMS36-b-PEO23) and cationic switchable lipid (CSL). The latter undergoes a pH-triggered conformational change and induces membrane destabilization. Using confocal imaging and DLS measurements, we interrogated the structural changes in CSL-doped lipid and hybrid polymer/lipid unilamellar vesicles at the micro- and nanometric scale, respectively. Both switchable giant unilamellar lipid vesicles (GUV) and hybrid polymer/lipid unilamellar vesicles (GHUV) presented dynamic morphological changes, including protrusions and fission upon acidification. At the submicron scale, scattered intensity decreased for both switchable large unilamellar vesicles (LUV) and hybrid vesicles (LHUV) under acidic pH. Finally, monitoring the fluorescence leakage of encapsulated calcein, we attested that CSL increased the permeability of GUV and GHUV in a pH-specific fashion. Altogether, these results show that switchable lipids provide a pH-sensitive behavior to hybrid polymer/lipid vesicles that could be exploited for the triggered release of drugs, cell biomimicry studies, or as bioinspired micro/nanoreactors.

In the emerging field of hybrid polymer/lipid vesicles, relatively few copolymers have been evaluated regarding their ability to form these structures and the resulting membrane properties have been scarcely studied. Here, we present the synthesis and self-assembly in solution of poly(dimethylsiloxane)-block-poly(ethylene oxide) diblock copolymers (PDMS-b-PEO). A library of different PDMS-b-PEO diblock copolymers was synthesized using ring-opening polymerization of hexamethylcyclotrisiloxane (D3) and further coupling with PEO chains via click chemistry. Self-assembly of the copolymers in water was studied using Dynamic Light Scattering (DLS), Static Light Scattering (SLS), Small Angle Neutron Scattering (SANS), and Cryo-Transmission Electron Microscopy (Cryo-TEM). Giant polymersomes obtained by electroformation present high toughness compared to those obtained from triblock copolymer in previous studies, for similar membrane thickness. Interestingly, these copolymers can be associated to phospholipids to form Giant Hybrid Unilamellar Vesicles (GHUV), preliminary investigations of their mechanical properties show that tough hybrid vesicles can be obtained.

In pharmaceutical technology, lipids and polymers are considered pillar excipients for the fabrication of most dosage forms, irrespective of the administration route. They play various roles ranging from support vehicles to release rate modifiers, stabilizers, solubilizers, permeation enhancers and transfection agents. Focusing on selected applications, which were discussed at the Annual Scientific Meeting of the Gattefossé Foundation 2018, this manuscript recapitulates the fundamental roles of these two important classes of excipients, either employed alone or in combination, and provides insight on their functional properties in various types of drug formulations. Emphasis is placed on oral formulations for the administration of active pharmaceutical ingredients with low aqueous solubilities or poor permeation properties. Additionally, this review article covers the use of lipids and polymers in the design of colloidal injectable delivery systems, and as substrates in additive manufacturing technologies for the production of tailor-made dosage forms., International Journal of Pharmaceutics, 558, ISSN:0378-5173, ISSN:1873-3476, ISSN:0378 -5173

International audience; Despite significant progress in the field of biomaterials for bone repair, the lack of attention to the vascular and nervous networks within bone implants could be one of the main reasons for the delayed or impaired recovery of bone defects. The design of innovative biomaterials should improve the host capacity of healing to restore a functional tissue, taking into account that the nerve systems closely interact with blood vessels in the bone tissue. The aim of this work is to develop a cell-free and growth factor-free hydrogel capable to promote angiogenesis and innervation. To this end, we have used elastin-like polypeptides (ELPs), poly(ethylene glycol) (PEG) and increasing concentrations of the adhesion peptide IKVAV (25% (w/w) representing 1.7 mM and 50% (w/w) representing 4.1 mM) to formulate and produce hydrogels. When characterized in vitro, hydrogels have fine-tunable rheological properties, microporous structure and are biocompatible. At the biological level, 50% IKVAV composition up-regulated Runx2, Osx, Spp1, Vegfa and Bmp2 in mesenchymal stromal cells and Tek in endothelial cells, and sustained the formation of long neurites in sensory neurons. When implanted subcutaneously in mice, hydrogels induced no signals of major inflammation and the 50% IKVAV composition induced higher vessel density and formation of nervous terminations in the peripheral tissue. This novel composite has important features for tissue engineering, showing higher osteogenic, angiogenic and innervation potential in vitro, being not inflammatory in vivo, and inducing angiogenesis and innervation subcutaneously. STATEMENT OF SIGNIFICANCE: One of the main limitations in the field of tissue engineering remains the sufficient vascularization and innervation during tissue repair. In this scope, the development of advanced biomaterials that can support these processes is of crucial importance. Here, we formulated different compositions of Elastin-like polypeptide-based hydrogels bearing the IKVAV adhesion sequence. These compositions showed controlled mechanical properties, and were degradable in vitro. Additionally, we could identify in vitro a composition capable to promote neurite formation and to modulate endothelial and mesenchymal stromal cells gene expression, in view of angiogenesis and osteogenesis, respectively. When tested in vivo, it showed no signs of major inflammation and induced the formation of a highly vascularized and innervated neotissue. In this sense, our approach represents a potential advance in the development of new strategies to promote tissue regeneration, taking into account both angiogenesis and innervation.

International audience; Elastin-like polypeptides (ELPs) are biocompatible-engineered polypeptides, with promising interest in tissue engineering due to their intrinsic biological and physical properties, and their ease of production. The IKVAV (Ile-Lys-Val-Ala-Val) laminin-1 sequence has been shown to sustain neuron attachment and growth. In this study, the IKVAV adhesion sequence, or a scrambled VKAIV sequence, were incorporated by genetic engineering in the structure of an ELP, expressed in Escherichia coli and purified. The transition temperatures of the ELP-IKVAV and ELP-VKAIV were determined to be 23 °C. Although the phase transition was fully reversible for ELP-VKAIV, we observed an irreversible aggregation for ELP-IKVAV. The corresponding aggregates shared some characteristics with amyloid-like polypeptides. The two ELPs were then reacted with functionalized polyethylene glycol (PEG) to form hydrogels. These hydrogels were characterized for rheological properties, tested with cultures of rat primary sensory neurons, and implanted subcutaneously in mice for 4 weeks. Sensory neurons cultured on high IKVAV concentration hydrogels (20%) formed longer neurite than those of neurons grown on hydrogels containing the scrambled IKVAV sequence. Finally, in vivo evaluation showed the absence of detectable inflammation. In conclusion, this functionalized ELP-IKVAV biomaterial shows interesting properties for tissue engineering requiring neurotization.

Tissue engineering is a promising alternative to autografts, allografts, or biomaterials to address the treatment of severe and large bone lesions. Classically, tissue engineering products associate a scaffold and cells and are implanted or injected into the lesion. These cells must be embedded in an appropriate biocompatible scaffold, which offers a favourable environment for their survival and differentiation. Here, we designed a composite hydrogel composed of collagen I, an extracellular matrix protein widely used in several therapeutic applications, which we associated with a physical hydrogel generated from a synthetic small amphiphilic molecule. This composite showed improved mechanical and biological characteristics as compared with gels obtained from each separate compound. Incorporation of the physical hydrogel prevented shrinkage of collagen and cell diffusion out of the gel and yielded a gel with a higher elastic modulus than those of gels obtained with each component alone. The composite hydrogel allowed cell adhesion and proliferation in vitro and long-term cell survival in vivo. Moreover, it promoted the differentiation of human adipose-derived stem cells in the absence of any osteogenic factors. In vivo, cells embedded in the composite gel and injected subcutaneously in immunodeficient mice produced lamellar osteoid tissue and differentiated into osteoblasts. This study points this new composite hydrogel as a promising scaffold for bone tissue engineering applications.

International audience; Combinations of therapeutic agents could synergistically enhance the response of lung cancer cells. Co-delivery systems capable of transporting chemotherapeutics with different physicochemical properties and with the simultaneous release of drugs remain elusive. Here, we assess the ability of nanoparticles of 30-nm diameter obtained from the self-assembly of hyaluronan-based copolymer targeting CD44 receptors to encapsulate both gefitinib and vorinostat for effective combinational lung cancer treatment. Drug loading was performed by nanoprecipitation. Drug release experiments showed a slow release of both drugs after 5 days. Using two- and three-dimensional lung adenocarcinoma cell cultures, we observed that the nanoparticles were mostly found at the periphery of the CD44-expressing spheroids. These drug-loaded nanoparticles were as cytotoxic as free drugs in the two- and three-dimensional systems and toxicity was due to apoptosis induction. In mouse models, intravenous injection of hyaluronan-based nanoparticles showed a selective delivery to subcutaneous CD44-overexpressing tumors, despite a significant liver capture. In addition, the systemic toxicity of the free drugs was reduced by their co-delivery using the nanoparticles. Finally, intrapulmonary administration of drug-loaded nanoparticles, to avoid a possible hepatic toxicity due to their accumulation in the liver, showed a stronger inhibition of orthotopic lung tumor growth compared to free drugs. In conclusion, hyaluronan-based nanoparticles provide active targeting partially mediated by CD44, less-toxic drug release and improved antitumor efficiency.

International audience; PEGylated magnetic iron oxide nanoparticles (IONPs) were synthesised with the aim to provide proof of concept results of remote cancer cell killing by magnetic fluid hyperthermia. The IONPs were produced by the polyol synthetic route also called “forced hydrolysis pathway” yielding highly superparamagnetic, readily-dispersible, and biocompatible IONPs. As shown previously, adjusting parameters of the reaction led to either monocore or multicore IONPs, with on-demand morphology and magnetic properties. Polyethylene glycol (PEG) was grafted onto the nanoparticles in a single final step, using a phosphonic acid-terminated PEG synthesised separately, a strategy named “convergent”. The magnetic properties of the IONPs were preserved in physiological media thanks to this biocompatible shell. The interaction of the PEGylated IONPs with a glioblastoma cell line was studied, from the stability of IONPs in appropriate cell culture medium to the remotely magnetically triggered cell death. Cellular internalisation of the IONPs was studied, along with their fate after application of an alternating magnetic field (AMF). This investigation highlights the superior efficiency of multicore (nanoflowers) vs monocore (nanospheres) IONPs for magnetic hyperthermia, leading to 80 % cancer cells death in medically translatable conditions.

Interactions of polymers with the biological environments Polymers have gradually entered into the composition of biomaterials or drug formulations with respect to their biocompatible and biodegradable features, but also to their structural versatility. A new era in the biomedical fields has nevertheless begun, where polymers are no longer passive components but actors that interact directly with the biological environments. This article covers the cases of polymers that are intrinsically bioactive, but also those coupled to ligands or biomolecules, or responding to endo-or exogenous stimuli. Then a new approach to the synthesis of polymers with high added value by biotechnology is mentioned., Les polymères sont progressivement entrés dans la composition des biomatériaux ou des formulations médicamenteuses au regard de leurs caractères biocompatibles, biodégradables mais également de leur polyvalence structurelle. Une nouvelle ère dans les domaines biomédicaux est néanmoins largement amorcée, où les polymères ne sont plus des composants passifs, mais de véritables acteurs pour interagir directement avec les interlocuteurs des milieux biologiques. Cet article aborde les cas des polymères intrinsèquement bioactifs, mais aussi des polymères couplés à des ligands ou des biomolécules, ou encore de ceux répondant à des stimuli endo-ou exogènes. Puis une nouvelle approche de synthèse de polymères à haute valeur ajoutée par voie biotechnologique est mentionnée.

Hybrid copolymer/lipid vesicle are recently developed self-assembled structures that could present biocompatibility and biofunctionality of liposomes, as well as robustness, low permeability and functionality variability conferred by the copolymer chains. However, to date, physical and molecular parameters governing copolymer/lipid phase separation in these hybrid membranes are not well understood. In this work, we studied in detail the formation and phase separation in the membranes of both Giant Unilamellar Hybrid Vesicles(GHUVs) and Large Unilamellar Hybrid Vesicles (LHUVs) obtained from the mixture of phospholipids in the fluid (liquid disordered) or gel state (solid ordered) with various copolymers based on poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) (PEO) with different architectures (grafted, triblock) and molar masses. For GHUVs, phase separation at the micron scale and nanoscale was evaluated through confocal microscopy, and Fluorescence lifetime imaging microscopy technique (FLIM) respectively, where as acombination of Small angle neutron scattering (SANS), Cryo-transmission electron microscopy (Cryo-TEM) and Time-resolved Förster resonance energy transfer (TR-FRET) techniques was used for LHUVs. We demonstrate that the lipid/polymer fraction, lipid physical state, and the line tension at lipid polymer/lipid boundaries which can be finely modulated by the molar mass and architecture of the copolymer are important factors that govern the formation and structuration of hybrid vesicles. We also evidence that elasticity ofthe hybrid membrane can be modulated via the lipid polymer composition, through the use of micropipettes techniques., Les vésicules hybrides polymère/lipides sont des structures récemment développées dans la littérature. Idéalement, celles-ci peuvent présenter la biocompatibilité et la biofonctionnalité des liposomes, ainsi que la robustesse, la faible perméabilité et la versatilité de fonctionnalisation chimique conférées par les chaînes de copolymères. Cependant, à ce jour, les facteurs régissant la séparation des phases dans ces membranes hybrides ne sont pas bien compris. Dans ce travail, nous avons étudié en détail la formation et la séparation de phases dans les membranes de vésicules géantes (GHUVs) et de taille nanométriques(100nm) (LHUVs) constituées de phospholipides en phase fluide ou gel et de copolymères à base de poly (diméthylsiloxane) et de poly (éthylène glycol). Différentes architectures(greffée, tribloc) et masses molaires ont été utilisées. La séparation de phase a été étudiée sur les vésicules géantes à l’échelle micrométrique et nanométrique respectivement par microscopie confocale et imagerie de fluorescence résolue en temps (FLIM), tandis que pour les LHUVs, différentes techniques comme la diffusion de neutrons, la Cryo-microscopie et la spectroscopie de fluorescence résolue dans le temps ont été combinées. Nous avons pu montrer que la fraction lipide/polymère, l'état physique du lipide et la tension de la ligne aux interfaces lipide/polymère modulable par la masse molaire et l'architecture du copolymère sont les facteurs importants régissant la formation et la structuration des vésicules hybrides. Enfin, nous avons montré que les propriétés élastiques de la membrane peuvent être modulées via la composition polymère lipide.