Microparticulated systems based on chitosan and poly(vinyl alcohol) with potential ophthalmic applications.

Spherical microparticles for encapsulation of drugs for the treatment of diseases, with a diameter ranging between 2 and 4 µm, were obtained by double crosslinking (ionic and covalent) of chitosan and poly(vinyl alcohol) blend in a water-in-oil emulsion. Microparticles characterisation was carried out in terms of structural, morphological and swelling properties in aqueous media. The presence of chitosan in particles composition confers them a pH-sensitive character. Toxicity and hemocompatibility tests prove the biocompatible character of microparticles. The pilocarpine loading capacity is high as well as the release efficiency which increases up to 72 and 82% after 6 h. The obtained results recommend the microparticles as sustained release drug carriers for the treatment of eye diseases.

Sub-micronic capsules based on gelatin and poly(maleic anhydride-alt-vinyl acetate) obtained by interfacial condensation with potential biomedical applications.

New sub-micronic capsules based on a copolymer of maleic anhydride-alt-vinyl acetate and a natural polymer (gelatin) using an interfacial condensation method were obtained. Sub-micronic capsules were characterized by Fourier Transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) method, zeta-potential, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties were investigated by thermogravimetric analysis (TGA). According to some parameters of the synthesis reaction (polymer weight ratio, acetone/water ratio, surfactant concentration), the mean diameter of the sub-micronic capsules can be tuned from 200 to 760 nm. The sub-micronic capsules show a higher agglomeration tendency as the amount of gelatin in their composition increases. The swelling capacity in aqueous solutions is dependent on the composition and size of the sub-micronic capsules, decreasing with their diameter and gelatin composition. The drug loading and release capacity was studied using Penicillin G (sodium salt) (PG), and it has been proved that it is influenced by the sub-micronic capsules morphology induced by preparation parameters. Encapsulation and controlled release of small molecule were successfully carried out, demonstrating the potential biomedical applications of these new easily obtained sub-micronic capsules.

How to improve Nafion with tailor made annealing.

A tailor-made annealing procedure was developed for Nafion in order to avoid a critical degradation of the mechanical properties associated with a decrease of the ionic conductivity. The formation of layered morphologies, prevalently oriented in the direction parallel to the membrane surface, is responsible of the decay in fuel cell operation conditions. Nafion membranes are annealed at 140 °C over 7 days in the presence of dimethylsulfoxide (DMSO) as a proton-acceptor solvent. The important increase of mechanical stability is related to the formation of a crystalline phase, which acts as a physical cross-linker. The procedure is followed by hydrothermal annealing in liquid water in order to obtain an optimal water uptake at equilibrium (tailor made). To better understand the behavior of these polymers, we use the INCA method (Ionomer n c Analysis) and compare with dynamic mechanical analysis (DMA). The stabilized materials are proposed for use in intermediate temperature fuel cells, where the mechanical stabilization by the annealing procedure plays a fundamental role.

Low-Permeability Poly(ether Ether Ketone)-Based Ampholytic Membranes.

Ion-exchange membranes based on sulfonated and sulfaminated poly(ether ether ketone) were prepared by a modified sulfamination route. In a first step, poly(ether ether ketone) was sulfonated. The sulfonic acid groups were then transformed into chlorosulfonic moieties by reaction with thionyl chloride. A proportion of the chlorosulfonic functionalities reacted with dimethylamine to give basic sulfonamide groups, whereas those remaining were hydrolyzed back to sulfonate moieties obtaining, after immersion in acidic solution, an ampholytic polymer. The thermal, mechanical, electrical, and permeability properties of these amphoteric membranes were characterized. These membranes exhibit good thermal and mechanical stability and ultra-low vanadium ion permeability. The type and value of ion conductivity can be adjusted by the choice of acidic or basic medium. The tunable ion conductivity and the low ion permeability are suitable characteristics for the development of high-performance separator membranes.

Morphology and thermal properties of PLA-cellulose nanofibers composites.

Biodegradable nanocomposites were obtained from polylactic acid (PLA) and cellulose nanofibers with diameters ranging from 11 nm to 44 nm. The influence of treated (with 3-aminopropyltriethoxysilane) and untreated nanofibers on the thermal properties of PLA was investigated in detail using multiple session Differential Scanning Calorimetry (DSC) analysis. The nucleating effect of the cellulose nanofibers was confirmed by all the DSC runs (two melting and two crystallization steps). The morphology of both neat PLA and nanocomposites was explored for the first time using a new powerful AFM technique, Peak Force QNM (Quantitative Mechanical Property Mapping at the Nanoscale), which emphasized the nanolevel characteristics by elastic modulus mapping. QNM analyses showed a better dispersion of the silane treated nanofibers in the matrix as compared to the untreated ones. Moreover, a higher degree of crystallinity was detected in the PLA composites containing untreated nanofibers compared to the composites with treated ones.