Dynamic light scattering and viscosimetry of aqueous solutions of pectin, sodium alginate and their mixtures: effects of added salt, concentration, counterions, temperature and chelating agent

The effects of added salt, concentration, counterions, temperature and chelating agent on aqueous solutions of pectin, sodium alginate and their mixtures were analyzed by viscosimetry and dynamic light scattering (DLS) techniques. The intrinsic viscosity of the binary systems decreased with the addition of salt and with temperature, while it was found to be insensitive to the addition of NaEDTA. As expected the intrinsic viscosity of the ternary alginate/pectin/water system was equal to the average of the intrinsic viscosity for the binary systems. The DLS studies indicated a bimodal distribution (fast and slow relaxation modes) for both binary and ternary systems at 25 °C, reflecting aggregation. A significant increase in the hydrodynamic radius, in the case of the slow mode, was observed for the binary and ternary systems in the presence of NaCl and KCl at 25 °C. However, at 80 °C the hydrodynamic radius for the slow mode in KCl solutions was practically constant for all the studied systems, except for the alginate binary solutions in which were not observed

Photodimerization as an alternative to photocrosslinking of nanoparticles: proof of concept with amphiphilic linear polyoxazoline bearing coumarin unit

International audiencePhotosensitive amphiphilic linear polyoxazolines (CoumC 11-POx n) bearing alkyl chain decorated by a UV-active coumarin end group have been synthesized by cationic ring-opening polymerization (CROP). Using DLS and DOSY NMR experiments, their self-assemblies in water were compared with those of homologous photo-unreactiveamphiphilic polyoxazolines (C m-POx n). In both cases, spherical nanoparticles with D H-values around 10 nm were observed. The CoumC 11-POx n nanoparticles were illuminated upon 300 nm inducing the photo-dimerization of the coumarin units located in theinnercompartment of the nanoparticles. Finally, the pros and the cons of the photo-dimerization of linear copolymersrelated to the photo-crosslinking of graft copolymerswere discussed

Design and Characterization of Maltoheptaose-b-Polystyrene Nanoparticles, as a Potential New Nanocarrier for Oral Delivery of Tamoxifen

Tamoxifen citrate (TMC), a non-steroidal antiestrogen drug used for the treatment of breast cancer, was loaded in a block copolymer of maltoheptaose-b-polystyrene (MH-b-PS) nanoparticles, a potential drug delivery system to optimize oral chemotherapy. The nanoparticles were obtained from self-assembly of MH-b-PS using the standard and reverse nanoprecipitation methods. The MH-b-PS@TMC nanoparticles were characterized by their physicochemical properties, morphology, drug loading and encapsulation efficiency, and release kinetic profile in simulated intestinal fluid (pH 7.4). Finally, their cytotoxicity towards the human breast carcinoma MCF-7 cell line was assessed. The standard nanoprecipitation method proved to be more efficient than reverse nanoprecipitation to produce nanoparticles with small size and narrow particle size distribution. Moreover, tamoxifen-loaded nanoparticles displayed spherical morphology, a positive zeta potential and high drug content (238.6 ± 6.8 µg mL−1) and encapsulation efficiency (80.9 ± 0.4 %). In vitro drug release kinetics showed a burst release at early time points, followed by a sustained release profile controlled by diffusion. MH-b-PS@TMC nanoparticles showed higher cytotoxicity towards MCF-7 cells than free tamoxifen citrate, confirming their effectiveness as a delivery system for administration of lipophilic anticancer drug

Les polyélectrolytes en étoile (synthèse et étude par diffusion de rayonnement et rhéologie)

Les polyélectrolytes sont des polymères chargés qui présentent, du fait des charges qu'ils contiennent le long de leur chaîne, des interactions électrostatiques. Ces dernières confèrent au matériau des propriétés différentes vis à vis de celles des polymères neutres qui ont souvent été décrites comme anormales, particulières ou extraordinaires. Même si les recherches sur les polyélectrolytes linéaires sont nombreuses, les études concernant des systèmes avec une architecture contrôlée plus complexe, comme les étoiles, demeurent rares d'un point de vue expérimental. L'idée maîtresse de notre étude consiste à combiner deux facteurs fondamentaux, du point de vue des propriétés qui en découlent : l'aspect polyélectrolyte et l'aspect architectural. Dans un premier temps, la synthèse d'étoiles polyélectrolytes de type polyacrylate avec différents contre-ions (sodium, césium et rubidium) et avec deux fonctionnalités (quatre et six branches) a été réalisée. Ensuite, cette étude, l'une des premières sur des systèmes polyélectrolytes en étoile d'un point de vue expérimental, a pu mettre en évidence la structure et la dynamique de ces systèmes par diffusion de rayonnement (lumière, neutrons, RX) et rhéologie.Polyelectrolytes which are charged polymers present electrostatic interactions due to the charges along the polymer chains. These interactions lead to different properties as compared with neutral polymers. These properties were often described as anomalous, particular or extraordinary. Even if linear polyelectrolyte studies are numerous, there are only few experimental research works regarding systems with more complex architecture like stars. The aim of this work is to associate two fundamental aspects : architectural and polyelectrolyte aspects. First, we performed the synthesis of polyacrylate polyelectrolyte stars with different counterions (sodium, cesium and rubidium) and with two functionalities (4-arm and 6-arm stars). Then, we showed clearly the system structure and dynamic using scattering techniques (light, neutrons or X-ray) and viscosimetric results. To our knowledge, this work is one of the first experimental study regarding polyelectrolyte stars.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Advances in the encapsulation of hydrophobic molecules via self-assembly of amphiphilic block copolymers

Ce manuscrit décrit le développement de nouvelles stratégies pour la préparation des nanoparticules (micelles et vésicules) ayant une excellente capacité d'encapsuler, retenir, transporter et délivrer des molécules hydrophobes (médicaments, fragrances, agents de contraste, etc.). Sept systèmes de copolymères à blocs amphiphiles ont été synthétisés et caractérisés. Leur faculté de s'auto-organiser a été utilisée pour obtenir des nanoparticules, dont les propriétés physico-chimiques ont été étudie es par des techniques de diffusion de lumière et d'imagerie. Dans une seconde étape le processus d'encapsulation de différentes molécules hydrophobes par ces nanoparticules a été mis a profit et exploré en détails. Les résultats suggèrent très clairement que la capacité d'encapsulation des systèmes micellaires stimulables que nous avons développés peut être contrôlée avantageusement via les propriétés structurelles des molécules hydrophobes et des blocs formant le coeur de la nanoparticule.This work contemplated the design of original approaches to prepare stimuli-responsive nanoparticles having excellent ability to encapsulate, retain, transport and deliver hydrophobic guest molecules (probes such as drugs, fragrances, contrast agents, pesticides, etc.). Seven well-defined amphiphilic block copolymer systems were synthesized by (ATRP) and characterized. Subsequently, such macromolecules were used as building-blocks to obtain self-assembled spherical nanoparticles whose physical chemical parameters were investigated in detail by light scattering and imaging techniques. In the last and most important step of this investigation, the loading of hydrophobic probes into the micelles was assessed. The results clearly suggest that the loading capacity of block copolymer micelles can be tailored through the rational design of core-forming blocks and hydrophobic guest molecules.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Soft-Matter Characterization

Progress in basic soft matter research is driven largely by the experimental techniques available. Much of the work is concerned with understanding them at the microscopic level, especially at the nanometer length scales that give soft matter studies a wide overlap with nanotechnology. This 2 volume reference work, split into 4 parts, presents detailed discussions of many of the major techniques commonly used as well as some of those in current development for studying and manipulating soft matter. The articles are intended to be accessible to the interdisciplinary audience (at the graduate student level and above) that is or will be engaged in soft matter studies or those in other disciplines who wish to view some of the research methods in this fascinating field. Part 1 contains articles with a largely (but, in most cases, not exclusively) theoretical content and/or that cover material relevant to more than one of the techniques covered in subsequent volumes. It includes an introductory chapter on some of the time and space-time correlation functions that are extensively employed in other articles in the series, a comprehensive treatment of integrated intensity (static) light scattering from macromolecular solutions, as well as articles on small angle scattering from micelles and scattering from brush copolymers. A chapter on block copolymers reviews the theory (random phase approximation) of these systems, and surveys experiments on them (including static and dynamic light scattering, small-angle x-ray and neutron scattering as well as neutron spin echo (NSE) experiments). This chapter describes block copolymer behavior in the "disordered phase" and also their self-organization. The volume concludes with a review of the theory and computer simulations of polyelectrolyte solutions. Part 2 contains material on dynamic light scattering, light scattering in shear fields and the related techniques of fluorescence recovery after photo bleaching (also called fluorescence photo bleaching recovery to avoid the unappealing acronym of the usual name), fluorescence fluctuation spectroscopy, and forced Rayleigh scattering. Volume 11 concludes with an extensive treatment of light scattering from dispersions of polysaccharides. Part 3 presents articles devoted to the use of x-rays and neutrons to study soft matter systems. It contains survey articles on both neutron and x-ray methods and more detailed articles on the study of specific systems- gels, melts, surfaces, polyelectrolytes, proteins, nucleic acids, block copolymers. It includes an article on the emerging x-ray photon correlation technique, the x-ray analogue to dynamic light scattering (photon correlation spectroscopy). Part 4 describes direct imaging techniques and methods for manipulating soft matter systems. It includes discussions of electron microscopy techniques, atomic force microscopy, single molecule microscopy, optical tweezers (with applications to the study of DNA, myosin motors, etc.), visualizing molecules at interfaces, advances in high contrast optical microscopy (with applications to imaging giant vesicles and motile cells), and methods for synthesizing and atomic force microscopy imaging of novel highly branched polymers.. Soft matter research is, like most modern scientific work, an international endeavor. This is reflected by the contributions to these volumes by leaders in the field from laboratories in nine different counties. An important contribution to the international flavor of the field comes, in particular, from x-ray and neutron experiments that commonly involve the use of a few large facilities that are multinational in their staff and user base

3. Electrospun biomaterials

International audienc