pH-sensitive double-hydrophilic block copolymer micelles for biological applications.

International audienceIn the recent years, double-hydrophilic block copolymer (DHBC) micelles have appeared as potential vectors for pharmaceutical applications due to their simple preparation method in aqueous solvent. The present study aims at underscoring the strategy for the choice of the partners in the formulation of DHBC micelles presenting a good stability in physiological conditions (pH 7.4, 0.15mol/L NaCl) and a pH-sensitivity allowing their disassembly at pH 5. Using light scattering and laser-doppler electrophoresis, micelles of polymethacrylic acid-b-polyethylene oxide complexing either poly-L-lysine (PLL) or an oligochitosan were characterised. Whatever the polyamine counter-polyion considered, the micelles were perfectly formed for an amine/methacrylic acid molar charge ratio of one. They were characterised by a hydrodynamic diameter of 28nm for PLL and 60nm for oligochitosan and by a neutral zeta potential. The stability study as a function of the pH and of the ionic strength revealed different behaviours. Oligochitosan micelles were stable until pH 7 and unstable at 0.15mol/L NaCl. On the contrary, PLL micelles were stable in physiological conditions and disassembled at pH 5. As a conclusion, the choice of the partners to formulate double-hydrophilic block copolymer based-micelles is strategic in order to obtain well-adapted vectors applied to the pharmaceutical field

Porosity of micro-mesoporous zeolites prepared via pseudomorphic transformation of zeolite Y crystals : a combined isothermal sorption and thermodesorption investigation

International audienceThe porosity of micro-mesoporous zeolite crystals was studied by sorption measurements with different probe molecules. Recrystallization of a commercial zeolite Y with addition of a cationic surfactant as the mesostructure directing agent was used as a 'constructive' synthesis route to generate mesoporosity inside the zeolite crystals. The obtained material was characterized by X-ray powder diffraction, scanning and transmission electron microscopy and thermogravimetric analysis. The adsorption-desorption isotherms of N2 and Ar at 77 K and quasi-equilibrated temperature programmed desorption and adsorption (QE-TPDA) of n-hexane and n-nonane were performed in order to characterize the hierarchical porous network. The QE-TPDA of n-hexane on the recrystallized zeolite confirmed the faujasite type structure and showed some distortion of the micropores. The pore size distributions calculated from the QE-TPD of n-nonane are more precise than those determined from nitrogen desorption isotherms, since determined from numerous experimental data points recorded in one desorption cycle

Polymeric micelles based on poly(methacrylic acid) block-containing copolymers with different membrane destabilizing properties for cellular drug delivery

International audiencePoly(methacrylic acid)-b-poly(ethylene oxide) are double hydrophilic block copolymers, which are able to form micelles by complexation with a counter-polycation, such as poly-l-lysine. A study was carried out on the ability of the copolymers to interact with model membranes as a function of their molecular weights and as a function of pH. Different behaviors were observed: high molecular weight copolymers respect the membrane integrity, whereas low molecular weight copolymers with a well-chosen asymmetry degree can induce a membrane alteration. Hence by choosing the appropriate molecular weight, micelles with distinct membrane interaction behaviors can be obtained leading to different intracellular traffics with or without endosomal escape, making them interesting tools for cell engineering. Especially micelles constituted of low molecular weight copolymers could exhibit the endosomal escape property, which opens vast therapeutic applications. Moreover micelles possess a homogeneous nanometric size and show variable properties of disassembly at acidic pH, of stability in physiological conditions, and finally of cyto-tolerance

pH-mediated control over the mesostructure of ordered mesoporous materials templated by polyion complex micelles

Ordered mesoporous silica materials were prepared under different pH conditions by using a silicon alkoxide as a silica source and polyion complex (PIC) micelles as the structure-directing agents. PIC micelles were formed by complexation between a weak polyacid-containing double-hydrophilic block copolymer, poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA), and a weak polybase, oligochitosan-type polyamine. As both the micellization process and the rate of silica condensation are highly dependent on pH, the properties of silica mesostructures can be modulated by changing the pH of the reaction medium. Varying the materials synthesis pH from 4.5 to 7.9 led to 2D-hexagonal, wormlike or lamellar mesostructures, with a varying degree of order. The chemical composition of the as-synthesized hybrid organic/inorganic materials was also found to vary with pH. The structure variations were discussed based on the extent of electrostatic complexing bonds between acrylate and amino functions and on the silica condensation rate as a function of pH

Integrated Process for Structuring and Functionalizing Ordered Mesoporous Silica to Achieve Superprotonic Conductivity

International audiencePolyacid-functionalized inorganic mesoporous materials have attracted considerable interest as catalysts, permselective molecular sieves or drug carriers. Despite their great interest, their synthesis into ordered mesostructures incorporating polyacids densely and homogeneously distributed in the mesopores, is a challenge. Moreover, their properties as conductors for energy applications remain completely unexplored. Here we report an efficient, one-shot environmentally friendly synthesis route to prepare ordered mesoporous silica functionalized with strong polyacids, which exhibits excellent proton conductivity. We used polyion electrostatic complex micelles as structure-directing, functionalizing and pore-generating agents to obtain a material of remarkable textural and functional quality. It presents large and ordered mesopores hosting monodisperse polyacid chains corresponding to a dense and homogeneous functionalization of 1.2 mmolSO 3 H.gSiO 2-1 and a function density of 1 SO3H per nm 3 of mesopore volume. Overcoming the performance-limiting inhomogeneities, we designed a superprotonic conductor, while the high value of the conductivity, 0.024 S cm-1 at 363 K/95% relative humidity, was maintained at least 7 days