Caracterización estructural de vidrios del sistema SiO2- B2O3-Na2O mediante espectroscopías IR y Raman

Infrared and Raman spectroscopies have been used to analyze two series of sodium silicoborate glasses with 10 % and 20 % of Na2O. The obtained results are in accordance with those found in literature when using Raman and Infrared spectroscopies, however here it has been analyze in more detail the Polimerization Index (IP) of both systems. It has been observed that IP decreases with B concentration except for low B content glasses. This result has been assigned to an incomplete melting of such glasses due to the high temperatures needed to obtain well-melting glasses. Finally, it has been analyzed the BO4/BO3 ratio as a function of the Na2O concentration, showing that as it would be expected the high BO4 concentration appears when the Na2O concentration is between 0.3 – 0.4 in moles.Peer reviewe

Chitosan and Kappa-Carrageenan Vaginal Acyclovir Formulations for Prevention of Genital Herpes. In Vitro and Ex Vivo Evaluation

Vaginal formulations for the prevention of sexually transmitted infections are currently gaining importance in drug development. Polysaccharides, such as chitosan and carrageenan, which have good binding capacity with mucosal tissues, are now included in vaginal delivery systems. Marine polymer-based vaginal mucoadhesive solid formulations have been developed for the controlled release of acyclovir, which may prevent the sexual transmission of the herpes simplex virus. Drug release studies were carried out in two media: simulated vaginal fluid and simulated vaginal fluid/simulated seminal fluid mixture. The bioadhesive capacity and permanence time of the bioadhesion, the prepared compacts, and compacted granules were determined ex vivo using bovine vaginal mucosa as substrate. Swelling processes were quantified to confirm the release data. Biocompatibility was evaluated through in vitro cellular toxicity assays, and the results showed that acyclovir and the rest of the materials had no cytotoxicity at the maximum concentration tested. The mixture of hydroxyl-propyl-methyl-cellulose with chitosan- or kappa-carrageenan-originated mucoadhesive systems that presented a complete and sustained release of acyclovir for a period of 8-9 days in both media. Swelling data revealed the formation of optimal mixed chitosan/hydroxyl-propyl-methyl-cellulose gels which could be appropriated for the prevention of sexual transmission of HSV. © 2015 by the authors; licensee MDPI, Basel, Switzerland.This work was supported by the Spanish Ministry of Economy and Competitiveness (MAT2012-34552). We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).Peer Reviewe

Eudragit® L100/chitosan composite thin bilayer films for intravaginal pH-responsive release of Tenofovir

[EN] The high rate of HIV new infections and AIDS-related deaths each year make prevention tools still necessary today. Different dosage forms – including films – for vaginal administration of antiretroviral drugs have been developed for this purpose. Six batches of Tenofovir-loaded films were formulated based on Eudragit® L100 (EL100) and chitosan, containing triethyl citrate and glycerol. In all the cases films structured in two layers – the upper layer mainly attributed to EL100 and the lower layer to chitosan – were revealed by SEM. A higher content in EL100 and plasticizers improves the mechanical properties and control over drug release in the vaginal medium without affecting mucoadhesion. The EL100-based layer acts as a structuring agent that controls Tenofovir release for days in the vaginal medium while it occurs in a few hours in the presence of seminal fluid. Bilayer films with the highest tested content of EL100 and plasticizers would be the most suitable as vaginal microbicides as they are easier to administer due to their excellent mechanical properties and they offer more comfortable posology and enhanced protection against HIV during intercourse due to their pH-responsive release of Tenofovir.This work was supported by the Spanish Research Agency and the European Regional Development Fund (AEI/FEDER, UE) [MAT2016-76416-R]

Amino Functionalized Micro-Mesoporous Hybrid Particles for the Sustained Release of the Antiretroviral Drug Tenofovir

© 2020 by the authors.The sustained release of an antiretroviral agent to women mucosa has been proved as an excellent strategy to reduce the sexual transmission of HIV. Hybrid micro-mesoporous particles have been synthesized and functionalized with a silane coupling agent followed by loading the antiretroviral tenofovir. It has been observed that the disposition of the silane molecule on the surface of the particles determines the interaction mechanism with the antiretroviral molecule loaded independently on the surface area of the particles. In this sense, available and free amino groups are required to achieve a smart pH-responsive material, a condition that is only achieved in those materials containing a silane chemisorbed monolayer. Moreover, the modulation of the release kinetics attributed to the presence of the silane monolayer covering the mesopores has been confirmed by fitting the releasing curves to the first order and Weibull models. The developed micro-mesoporous particles have been demonstrated to be excellent smart-release vehicles for antiviral agents and can be safely used in polymer mucoadhesive vaginal gels.This work was supported by the Spanish Research Agency and the European Regional Development Fund (AEI/FEDER, UE), grant number MAT2016-76416-R.Peer reviewe

Estudio cinético sobre el efecto de agregar P2O5 a la vitrocerámica LMAS

[EN] Glasses in the LMAS (Li2O, MgO, Al2O3, SiO2) system containing F, CaO, ZrO2, and TiO2weresubjected to crystallization by incorporating P2O5. The glass stability, glass forming ability,and crystallization kinetics have been determined. Crystals of Lithium Aluminum Silicate(LixAlxSi1−xO2), Enstatite (MgSi2O6) and -spodumene (LiAlSi2O6) were detected in the sam-ples containing F, but -spodumene was not observed in the glass-ceramic in its absence.Glasses containing F show a dependence of the activation with the addition of P2O5withenergy values ranging from 426 kJ mol−1to 483 kJ mol−1, being this maximum found for P2O5amounts up to 3 mol%. High concentrations of P2O5and Al2O3improve the glass stability andincrease the crystallization temperature. The most common crystallization mechanism is ofbulk type with a constant number of nuclei. Tw o - and three-dimensional growth of crystalswas observed in glasses containing F but in its absence and at high Al2O3concentration bulkcrystallization with two- and one-dimensional growth is observed.[ES] Vidrios del sistema LMAS (Li2O, MgO, Al2O3, SiO2) y que contienen además F, Ca, ZrO2y TiO2han sido llevados a cristalización mediante la adición de P2O5. La estabilidad vítrea, capaci-dad formadora de vidrio y cinética de cristalización han sido estudiadas. Se ha determinadola presencia de cristales de aluminosilicato de litio (LixAlxSi1−xO2), enstatita (MgSi2O6) y -espodumena (LiAlSi2O6) en los vidrios que contenían F; sin embargo, sin la presenciade este, no se ha podido detectar -espodumena. Los vidrios que contenían F muestranuna dependencia en la energía de activación con el contenido en P2O5, encontrándose val-ores que oscilaban entre 426 kJ/mol y 483 kJ/mol, este último, el máximo encontrado paracontenidos en P2O5de hasta un 3%. A altas concentraciones de P2O5y Al2O3se observó un aumento de la estabilidad vítrea y de la temperatura de cristalización. Durante la cristal-ización, el mecanismo más común observado es una cristalización masiva con un númeroconstante de núcleos. Se observó un crecimiento en dos y tres dimensiones en los cristalesque contenían F, pero en aquellos preparados sin F y a altas concentraciones de Al2O3, lacristalización masiva con crecimiento uni- y bidimensional se apreció preferentemente.The present work was supported by the Algerian Ministry of Higher Education and Scientific Research (Algerian programP. N . E 2016–2017 scholarship fund) and with the collabora-tion of the Institute of Ceramic and Glass ICV-CSIC, Madrid,Spain. This work was developed under the frame of the project MAT2016-78700-RPeer reviewe

Highly micro- and mesoporous oxycarbide derived materials from HF etching of silicon oxycarbide materials

[EN] Highly micro-mesoporous silicon oxycarbide-derived carbon materials (SiOC-DC) with elevated specific surface area up to 895 mg and high pore volumes of mesopores (0.3 cmg) and micropores (0.2 cmg) have been obtained by direct etching of SiOC with HF. Initial organic-inorganic hybrids were synthesized by the sol-gel method employing triethoxysilane and polydimethylsiloxane (PDMS) of different molecular weights (550, 1750 and 4200 gmol). These hybrids were pyrolyzed from 1100 to 1400 °C. Short PDMS chains (550 gmol) within the hybrid structure rendered dense SiOC materials after pyrolysis, however long PDMS chains (1750 and 4200 gmol) produced highly micro-mesoporous SiOC materials up to 1300 °C. The etching of SiOC employing HF produced the selective removing of silica nano-domains and as a result highly micro-mesoporous SiOC-DC materials were created. In dense SiOC the HF attack is favoured at the highest temperatures (1400 °C) when the SiOC is more phase separated. On the other hand, in porous SiOC there is an agreement between the pyrolysis temperature and the porosity and, therefore the SiOC materials are etched easier at 1200 °C. SiOC-DC materials are composed by a porous glassy network enriched with carbon (graphene-like carbon and turbostratic carbon) and SiC which present an incipient crystallization.This work was supported by project MAT2016-78700-R financed bySp anish Research Agency and European Regional Development Fund (AEI/FEDER, UE). The authors are also grateful to C. Díaz Dorado forher help with FE-SEM and HR-TEM images

Cobalt-catalyzed tunable carbon microstructures fromhalogenated SiC preceramic precursors

[EN] Carbide-derived carbons (CDCs) with highly graphitized domains, linear, oval-shaped, and barrel-like structures have been prepared from a silicon carbide preceramic precursor containing catalytic amounts of cobalt. The chlorination temperature as well as the amount of catalysts will determine the specific surface area, pore size, and morphology of the obtained carbons. At low chlorination temperature, an amorphous network with significant amount of double or single oxygenated bonds was obtained. At 700 and 800°C both linear graphitic domains and barrel-like carbon dominate the microstructure with an increased presence of microporosity. There barrel-like structures provided increased specific capacitance, although the high anisotropy of the structure compromises the energy density of the device. At 900°C, despite the disappearance of this cropped surface, the hierarchical pore distribution and low O content also induce an increase of the specific capacitance of the CDC samples regardless of their high percentage of micropores.This research has been developed under the frame of the project MAT2016-78700-R supported by Spanish Research Agency and European Regional Development Fund (AEI/FEDER, UE).Peer reviewe

Defective structure of doped carbons obtained frompreceramic polymers through Cl2-andNH3-assisted thermolysis

[EN] The processing parameters such as the heat treatment temperature, type of preceramic precursor, and post-synthesis treatments are key factors for the development the different microstructures in polymer-derived ceramics. Moreover, doping with different heteroatoms has increased the ability of the polymer-derived ceramics to produce tunable nanostructures with a controlled pore size and distributions. A preceramic precursor containing P has been prepared from a commercial polysiloxane polymer and a phosphate alkoxide. It has been subjected to thermal treatments in N2, NH3, and Cl2 atmospheres in different order sequences to create differentiated microstructures either in the ceramic matrix and the carbon phase. The structural, textural, and spectroscopic characterization revealed that the P atoms play a key role in the evolution of the microstructure during the thermal treatments. If the chlorination is carried out before the treatment in NH3, a silicophosphate matrix is formed and prevents from nitrogen incorporation into the free carbon phase. On contrary, if the NH3 treatment is carried out before the chlorination, the carbon phase is predominantly modified by the incorporation of P atoms within the free carbon network.Perez acknowledges Comunidad de Madrid for the grant IND2020/IND-17375 pertaining to the program “Doctora-dos Industriales.”Peer reviewe

Combined pyrolysis-ammonolysis treatment to retain C during nitridation of SiBOCN ceramics

Two sets of solgel derived glass materials have been prepared and subjected to different thermal treatments. Pyrolysis in inert atmosphere lead to the formation of amorphous Si(B)CO ceramics whereas if the inert atmosphere is changed to NH once the carbon substituents of the preceramic hybrid material transform to a glassy network, the nitrogen is incorporated efficiently while the carbon is retained into the structure, as revealed by Si NMR analysis. Raman spectra show a less graphitized structure in the case of B-rich materials because of the reduced mobility of the C atoms due to the formation of mixed (B)CN bonds