Redouane Borsali

Elaboration of chitosan-coated nanoparticles loaded with curcumin for mucoadhesive applications.

Polycaprolactone (PCL) nanoparticles decorated with a mucoadhesive polysaccharide chitosan (CS) containing curcumin were developed aiming the buccal delivery of this drug. These nanoparticles were prepared by the nanoprecipitation method using different molar masses and concentrations of chitosan and concentrations of triblock surfactant poloxamer (PEO-PPO-PEO), in order to optimize the preparation conditions. Chitosan-coated nanoparticles showed positive surface charge and a mean particle radius ranging between 114 and 125 nm, confirming the decoration of the nanoparticles with the mucoadhesive polymer, through hydrogen bonds between ether and amino groups from PEO and CS, respectively. Dynamic Light Scattering (DLS) studies at different scattering angles and concentrations have shown that the nanoparticles are monodisperse (polydispersity indices were lower than 0.3). The nanoparticle systems were also examined with Nanoparticle Tracking Analysis (NTA), and the results were in good agreement with those obtained by DLS. Colloidal systems showed mean drug content about 460 μg/mL and encapsulation efficiency higher than 99%. Finally, when coated with chitosan, these nanoparticles show a great ability to interact with mucin indicating also their suitability for mucoadhesive applications.

Ultrastructural aspects of phytoglycogen from cryo-transmission electron microscopy and quasi-elastic light scattering data

Phytoglycogen particles extracted from the sugary maize mutant su 1 and dispersed in water were studied using transmission electron microscopy (TEM) and light scattering. Dried specimens were either negatively stained with uranyl acetate or shadowed with W/Ta. Frozen-hydrated unstained particles embedded in a thin film of vitreous ice were also observed using cryo-TEM. The particles exhibited a spheroidal shape, with a diameter ranging from 30 to 100 nm. Some of them presented a multilobular morphology and appeared to be formed by smaller subunits, 20-30 nm in diameter, resembling the described beta-particles for animal glycogen. The diameter of stained and ice-embedded particles was measured from electron micrographs. The corresponding size distribution histograms showed that the average weight diameter of ice-embedded particles was higher than that of stained ones. In the latter case, a shrinkage of the particle was believed to occur during the drying process. Light scattering experiments confirmed the diameter of ice-embedded particles and indicated that they could be considered as uniformly dense spheroidal objects.

Control of 10 nm scale cylinder orientation in self-organized sugar-based block copolymer thin films

The present paper describes the orientational control of 10 nm scale cylinders in sugar-based block copolymer thin films by simply varying the composition of the annealing co-solvent. The affinity of the block copolymer to the solvent vapor could be systematically adjusted in this way.

Enhancement of Plant and Bacterial Lectin Binding Affinities by Three-Dimensional Organized Cluster Glycosides Constructed on Helical Poly(phenylacetylene) Backbones

A series of poly(phenylacetylene)s bearing diverse saccharide pendants—N‐acetyl‐D‐glucosamine, D‐lactose, and N‐acetyl‐D‐neuraminic acid—were synthesized by rhodium‐mediated polymerizations of the corresponding acetyl‐protected glycosylated phenylacetylenes followed by deprotection. The circular dichroism spectra of these glycosylated poly(phenylacetylene)s each displayed split‐type Cotton effects in the long absorption region of the conjugated polymer backbone (260–500 nm), thus indicating predominantly one‐handed helical conformations in their backbones. The binding affinities of these glycosylated poly(phenylacetylene)s, and those of previously reported phenylacetylenes bearing D‐galactose, towards plant and bacterial lectins were investigated by hemagglutination inhibition assay and isothermal titration calorimetry (ITC). The stoichiometries of binding vary strongly, depending on the lectin binding sites and the accessibilities of the carbohydrate residues in the helices. The measured affinities also vary, with the maximum value observed for the interaction between poly‐PA‐α‐Gal and lectin I from Pseudomonas aeruginosa, with a Kd value of 4 μM per monosaccharide representing a 200‐fold increase relative to the corresponding monomer.

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.

Self-assembled carbohydrate-based micelles for lectin targeting

Biocompatible low-polydispersity micelles designed for lectin targeting have been prepared by spontaneous self-assembly in water of macromolecular glycosylated amphiphiles. Propargyl-β-lactoside and N-acetyl-β-D-glucosaminide were conjugated by copper-catalyzed Huisgen cycloaddition to azide-terminated PEG 900 stearate. Upon dissolution in water, the resulting amphiphiles immediately self-assemble into highly regular micelles having a mean diameter of 10 nm. Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) and Small-Angle X-ray Scattering (SAXS) were used to investigate the structure of the self-assembled saccharidic amphiphiles micelles. The presence of the carbohydrate epitopes on the surface of the micelles and their bioavailability for lectin targeting were also demonstrated by light scattering measurements. Specific interaction of the GlcNac and Lac residues with Wheat Germ Agglutinin (WGA) and Peanut Agglutinin (PNA) respectively, unveils potential applications of such carbohydrate-derived surfactants as simple and site-specific vectorization systems for drug delivery.

Amphiphilic copolymers based on polyoxazoline and grape seed vegetable oil derivatives: self-assemblies and dynamic light scattering

The self-assembly in solution of original structures of amphiphilic partially natural copolymers based on polyoxazoline [more precisely poly(2-methyl-2-oxazoline) (POx)] and grape seed vegetable oil derivatives (linear, T-, and trident-structure) is investigated. The results show that such systems are found, using dynamic light scattering (DLS), to spontaneously self-organize into monomodal, narrow-size, and stable nanoparticles in aqueous medium. The obtained hydrodynamic diameters (Dh) range from 8.6 to 32.5xa0nm. Specifically, such size increases strongly with increasing natural block (i.e., lipophilic species) length due to higher hydrophobic interactions (from 10.1xa0nm for C19 to 19.2xa0nm for C57). Furthermore, increasing the polyoxazoline (i.e., hydrophilic block) length leads to a moderate linear increase of the Dh-values. Therefore, the first-order size effect comes from the natural lipophilic block, whereas the characteristic size can be tuned more finely (i.e., in a second-order) by choosing appropriately the polyoxazoline length. The DLS results in terms of characteristic size are corroborated using nanoparticle tracking analysis (NTA), and also by atomic force microscopy (AFM) and transmission electron microscopy (TEM) imaging where well-defined spherical and individual nanoparticles exhibit a very good mechanical resistance upon drying. Moreover, changing the lipophilic block architecture from linear to T-shape, while keeping the same molar mass, generates a branching and thus a shrinking by a factor of 2 of the nanoparticle volume, as observed by DLS. In this paper, it is clearly shown that the self-assemblies of amphiphilic block copolymer obtained from grape seed vegetable oil derivatives (sustainable renewable resources) as well as their tunability are of great interest for biomass valorization at the nanoscale level [continuation of the article by Stemmelen et al. (Polym Chem 4:1445–1458, 2013)].Graphical AbstractAmphiphilic copolymers based on polyoxazoline and grape seed vegetable oil derivatives: Self-assemblies and dynamic light scattering Christophe Travelet, Mylène Stemmelen, Vincent Lapinte, Frédéric Dubreuil, Jean-Jacques Robin, Redouane Borsali

Preparation and enzymatic hydrolysis of nanoparticles made from single xyloglucan polysaccharide chain

In this work, polysaccharide nanoparticles based on tamarind seeds xyloglucan are prepared, analyzed in term of characteristic sizes and morphology, and degraded by the action of a glycoside-hydrolase. Obtained in an aqueous NaNO2 solution (0.1M), these unaggregated nanoparticles have a characteristic diameter of ca. 60 nm (DLS, AFM and TEM measures). They are not compact, but highly swollen and look like hyperbranched and dendrimer-like (soft sphere model) structures. This observation is coherent with the native structure of the xyloglucan macromolecules which are themselves branched. The enzymatic hydrolysis by cellulase of Trichoderma reesei of the xyloglucan nanoparticles is investigated. In particular, the apparent mass molecular weight drastically decreases meaning that the xyloglucan nanoparticles are effectively fully hydrolyzed by the endo-β-(1,4)-glucanase. Furthermore, we observe that the enzyme has to uncoil the nanoparticles before cutting the β-(1→4) bonds and digesting the xyloglucan.

Dynamic Light Scattering Evidence for a Ligand-Induced Motion between the Two Domains of Glucoamylase G1 ofAspergillus niger with Heterobivalent Substrate Analogues

Heterobifunctional ligands that bind at the same time to the catalytic domain and to the starch-binding domain of glucoamylase induce a conformational change of the protein, as shown by dynamic light scattering. The ligands consist of acarbose and β-cyclodextrin linked together by oligoethylene glycols of variable length (see the schematic diagram).

Micellar transformations of poly(styrene-b-isoprene) block copolymers in selective solvents

The morphology of micelles formed from linear and cyclic poly(styrene-b-isoprene) copolymers (PS166-b-PI278) has been studied in solvents with different selectivity for the two block components: heptane and decane, good solvents for the PI block, and DMF, a good solvent for the PS block. Using small and ultra small angle X-ray scattering experiments, SAXS and USAXS, respectively, morphological changes were monitored as a function of the temperature. While micelles formed in DMF were stable and no morphological changes occurred as a function of the temperature, transformations from cylinder-like micelles to vesicles-like objects were observed in both decane and heptane above 60 °C for the linear PS-b-PI copolymer. The transition occurred through intermediate steps, where the coexistence between different micellar morphologies was observed. On the contrary, the morphology of the block copolymers with the cyclic architecture was found to be independent of temperature and concentration. For linear blocks, a demicellization was detected at higher temperatures (above 80 °C) and the process was fully reversible when the solution was cooled down to ambient temperature. These results are consistent with complementary dynamic light scattering (DLS) observations.