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Nature provides a wide range of entities and/or systems with different functions that may serve as a source of bioinspiration for material chemists. Actually, materials exhibiting a 3D porous texture (combining pores at different scales, from macro-to meso-up to micropores) mimic the hierarchical structure of different systems found in living organisms (e.g., the blood circulation or the respiratory system in mammalians). Structural organization at different scales is ultimately responsible for the outstanding properties offered by hierarchical materials (not only as stationary phases in separation and catalytic processes, [1] but also as electrodes in fuel cells and capacitors)[2] because they offer not only large surface areas, but also accessibility to such a surface.A number of synthetic routes have been explored by using different carbonaceous precursors [3] and either exo or endo templates to modulate the porous texture of the resulting carbon structures.[4] Recent efforts have also been focused on the preparation of porous carbon composites containing graphitic carbon entities (e.g., carbon nanotubes [5] and nanohorns, [6] or even graphene oxide [7] ) the challenge of which is double and resides in 1) the achievement of a homogenous dispersion of these entities throughout the monolith structure and 2) the preservation of high surface areas. Baumann and co-workers have recently performed a quite extensive and stimulating work on single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) synthesized by resorcinol-formaldehyde polycondensation.[5] Particularly interesting in terms of conductivity and surface area were those composites based on DWCNTs, although the authors expressed the convenience of substituting the surfactants used for carbon-nanotube (CNT) dispersion.[5d]Ionic liquids (ILs) [8] and deep eutectic solvents (DESs, a new class of ILs obtained by complexion of quaternary ammonium salts with hydrogen-bond donors, such as acids, amines, and alcohols) [9] have lately been the solvent of choice in a number of chemical processes because of special features: for example, they are nonreactive with water, nonvolatile, and biodegradable as well as excellent solvents for a wide variety of solutes, such as different substrates, enzymes, and even microorganisms of catalytic and biocatalytic interest.[10] Of particular interest for the purpose of this work are those processes for which the capability both as solvents for CNT dispersion [11] and structure-directing agents in the synthesis of different materials [12] was demonstrated. Actually, ILs and DESs have been used as solvents for preparation of CNT-based carbon composites [13] and even as carbonaceous precursors of both nontextured and textured carbons. [14] In particular, we have recently described the preparation of DESs based on mixtures of resorcinol and choline chloride, the rupture of which (via resorcinol polycondensation and subsequent segregation of choline chloride) resulted in the formation of bimodal porous ca...

Vaginal microbicides have the potential to give women at high risk of contracting HIV the option of self-protection by preventing the sexual transmission of the virus. In this paper, mucoadhesive vaginal tablets based on chitosan, alone and in combination with pectin and locust bean gum, were developed for the sustained release of tenofovir (an antiretroviral drug). The formulations were placed in simulant vaginal fluid (SVF) to swell, and Hg porosity and SEM microscopy were used for the microstructural characterization of the swelling witnesses. The results show that the association of pectin and chitosan generated polyelectrolyte complexes and produced a robust system able to maintain its structure during the swelling process, when small pores are formed. Drug release and bovine vaginal mucoadhesion studies were performed in SVF showing that tenofovir-controlled dissolution profiles and adhesion to the mucosa were conditioned by the swelling processes of the polymer/s in each formulation. Tablets based on chitosan/pectin have the most homogeneous tenofovir dissolution profiles and last up to 96 h, remaining attached to the vaginal mucosa for the same period. These formulations can therefore be considered a good option for the self-protection of women from the sexual transmission of HIV.

The presence of nanodomains in polymer‐derived ceramics constitutes one of the most intriguing features of this class of materials. In the present work, the nanostructure of novel carbon‐rich silicon carbonitride (SiCN) ceramics synthesized via thermolysis of poly(methylphenylsilylcarbodiimide), –[Ph(CH3) Si‐NCN]n–, at 1300°, 1500°, 1700°, and 2000°C is investigated by micro‐Raman spectroscopy, X‐ray powder diffractometry, and small‐angle X‐ray scattering (SAXS). The structural information obtained from these experimental methods is combined together with theoretical modeling of the SAXS data to obtain a detailed model of the temperature‐dependent evolution of nanodomains comprised of free carbon, SiC, and Si3N4 in SiCN‐based ceramics.

The main challenges facing efforts to prevent the transmission of human immunodeficiency virus (HIV) are the lack of access to sexual education services and sexual violence against young women and girls. Vaginal formulations for the prevention of sexually transmitted infections are currently gaining importance in drug development. Vaginal mucoadhesive tablets can be developed by including natural polymers that have good binding capacity with mucosal tissues, such as chitosan or guar gum, semisynthetic polymers such as hydroxypropylmethyl cellulose, or synthetic polymers such as Eudragit® RS. This paper assesses the potential of chitosan for the development of sustained-release vaginal tablets of Tenofovir and compares it with different polymers. The parameters assessed were the permanence time of the bioadhesion—determined ex vivo using bovine vaginal mucosa as substrate—the drug release profiles from the formulation to the medium (simulated vaginal fluid), and swelling profiles in the same medium. Chitosan can be said to allow the manufacture of tablets that remain adhered to the vaginal mucosa and release the drug in a sustained way, with low toxicity and moderate swelling that ensures the comfort of the patient and may be useful for the prevention of sexual transmission of HIV.

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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.

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