Antibacterial Polysiloxane Polymers and Coatings for Cochlear Implants

Within this study, new materials were synthesized and characterized based on polysiloxane modified with different ratios of N-acetyl-l-cysteine (NAC) and crosslinked via UV-assisted thiol-ene addition, in order to obtain efficient membranes able to resist bacterial adherence and biofilm formation. These membranes were subjected to in vitro testing for microbial adherence against S. pneumoniae using standardized tests. WISTAR rats were implanted for 4 weeks with crosslinked siloxane samples without and with NAC. A set of physical characterization methods was employed to assess the chemical structure and morphological aspects of the new synthetized materials before and after contact with the microbiological medium

On the feasibility of chemical reactions in the presence of siloxane-based surfactants

International audienceSiloxane-containing surfactants have been tested as stabilizers for the preparation of polymer nanoparticles by three types of chemical reactions. Two crosslinking reactions were used to obtain silicone elastomers particles: one involved HO-terminated polydimethylsiloxane and tetraethoxysilane, while the other one was a crosslinking via polyhydrosilylation. The third reaction was a linear polycondensation between a diamine and a siloxane dialdehyde. The monitoring of the reactions has been made by infrared spectroscopy and the resulting particles have been analyzed in dispersion by light scattering and in dry state by electron microscopy and atomic force microscopy. The particles size was of hundreds of nanometers and their spherical shape was generally maintained after drying. The spectral and microscopy data proved efficient stabilization, which allowed the reactions to evolve after the formation of the particle

Functionalized Mesoporous Silica as Doxorubicin Carriers and Cytotoxicity Boosters

Mesoporous silica nanoparticles (MSNs) bearing methyl, thiol or glucose groups were synthesized, and their encapsulation and release behaviors for the anticancer drug Doxorubicin (Dox) were investigated in comparison with nonporous homologous materials. The chemical modification of thiol-functional silica with a double bond glucoside was completed for the first time, by green thiol-ene photoaddition. The MSNs were characterized in terms of structure (FT-IR, Raman), morphology (TEM), porosity (nitrogen sorption–desorption) and Zeta potential measurements. The physical interactions responsible for the Dox encapsulation were investigated by analytic methods and MD simulations, and were correlated with the high loading efficiency of MSNs with thiol and glucose groups. High release at pH 5 was observed in most cases, with thiol-MSN exhibiting 98.25% cumulative release in sustained profile. At pH 7.4, the glucose-MSN showed 75.4% cumulative release, while the methyl-MSN exhibited a sustained release trend. The in vitro cytotoxicity was evaluated on NDHF, MeWo and HeLa cell lines by CellTiter-Glo assay, revealing strong cytotoxic effects in all of the loaded silica at low equivalent Dox concentration and selectivity for cancer cells. Atypical applications of each MSN as intravaginal, topical or oral Dox administration route could be proposed

Polar silicones: structure-dielectric properties relationship

<p>A series of polar silicones was synthesized in order to compare their dielectric properties. Different substituents with high dipole moment (epoxy, pyridyl, aldehyde, cyano-, nitroazobenzene) were attached by hydrosilylation to a poly(dimethyl-methylhydro)siloxane. Thiol-ene addition on a dimethyl-methylvinyl siloxane copolymer with similar composition was also used for chemical modifications with chloro- or carboxy- derivatives. This approach allowed comparison of properties with emphasis on dielectric behavior measured in liquid state, as a preliminary step in design and preparation of materials suitable for dielectric elastomers. Although a relatively low content of polar groups was used (8%), permittivity values of 5.4 and even 7.4 were achieved (at 10 kHz), either due to the large dipole moment or to the presence of important amounts of moisture. The water sorption capacity of the polar silicones was investigated by dynamic vapor sorption, while structural parameters of model molecules were calculated, in order to correlate the dielectric properties with the polarity/hydrophilicity of the substituents to the silicone chain. A combined effect of the calculated dipole moment, molar polarizability, molar volume, and the measured water sorption capacity on dielectric permittivity was observed.</p

Nanomaterials Developed by Processing Iron Coordination Compounds for Biomedical Application

The iron oxides, widespread in nature, are used in numerous applications in practice due to their well-known properties. These properties can be modified by size lowering at nanoscale. Some applications, such as biomedical, require a rigorous selection of nanoparticles by size, shape, and surface functionality. In other applications, such as catalysis or magnetism, the composition (generally mixed oxides) and morphology of the nanoparticles are of high importance. The preparation of iron oxide nanoparticles (IONPs) is a complex process whose control raises a number of issues. The first challenge is finding the optimal experimental conditions, which would lead to the preparation of monodisperse nanoparticles. Another issue is the selection or setting a reproducible and clean manufacturing process without a need of complex purification. Even though at the moment several methods for preparing IONPs are known, there are still concerns in the scientific world to further improve existing methods or create new protocols. Therefore, the establishment of optimal methods for preparing IONPs with predetermined structural, dimensional, and morphological characteristics is an important task of scientists. Most of the methods reported in literature for the preparation of IONPs use proper metal salts as precursors. Recently, the use of the organometallic and coordination compounds of iron as precursors for IONPs has emerged as an alternative for a better control of these. Here, achievements reported in the literature in this direction are reviewed and critically analysed in relation to the conventional method based on iron salts