Julián Jiménez Reinosa

Ordered arrays of polymeric nanopores by using inverse nanostructured PTFE surfaces

We present a simple, efficient, and high-throughput methodology for the fabrication of ordered nanoporous polymeric surfaces with areas in the range of cm(2). The procedure is based on a two-stage replication of a master nanostructured pattern. The process starts with the preparation of an ordered array of poly(tetrafluoroethylene) (PTFE) free-standing nanopillars by wetting self-ordered porous anodic aluminum oxide templates with molten PTFE. The nanopillars are 120 nm in diameter and approximately 350 nm long, while the array extends over cm(2). The PTFE nanostructuring process induces surface hydrocarbonation of the nanopillars, as revealed by confocal Raman microscopy/spectroscopy, which enhances the wettability of the originally hydrophobic material and facilitates its subsequent use as an inverse pattern. Thus, the PTFE nanostructure is then used as a negative master for the fabrication of macroscopic hexagonal arrays of nanopores composed of biocompatible poly(vinylalcohol). In this particular case, the nanopores are 130-140 nm in diameter and the interpore distance is around 430 nm. Features of such characteristic dimensions are known to be easily recognized by living cells. Moreover, the inverse mold is not destroyed in the pore array demolding process and can be reused for further pore array fabrication. Therefore, the developed method allows the high-throughput production of cm(2)-scale biocompatible nanoporous surfaces that could be interesting as two-dimensional scaffolds for tissue repair or wound healing. Moreover, our approach can be extrapolated to the fabrication of almost any polymer and biopolymer ordered pore array.

Moving into advanced nanomaterials. Toxicity of rutile TiO2 nanoparticles immobilized in nanokaolin nanocomposites on HepG2 cell line

Abstract Immobilization of nanoparticles on inorganic supports has been recently developed, resulting in the creation of nanocomposites. Concerning titanium dioxide nanoparticles (TiO2 NPs1), these have already been developed in conjugation with clays, but so far there are no available toxicological studies on these nanocomposites. The present work intended to evaluate the hepatic toxicity of nanocomposites (C‐TiO22), constituted by rutile TiO2 NPs immobilized in nanokaolin (NK3) clay, and its individual components. These nanomaterials were analysed by means of FE‐SEM4 and DLS5 analysis for physicochemical characterization. HepG2 cells were exposed to rutile TiO2 NPs, NK clay and C‐TiO2 nanocomposite, in the presence and absence of serum for different exposure periods. Possible interferences with the methodological procedures were determined for MTT,6 neutral red uptake, alamar blue (AB), LDH,7 and comet assays, for all studied nanomaterials. Results showed that MTT, AB and alkaline comet assay were suitable for toxicity analysis of the present materials after slight modifications to the protocol. Significant decreases in cell viability were observed after exposure to all studied nanomaterials. Furthermore, an increase in HepG2 DNA damage was observed after shorter periods of exposure in the absence of serum proteins and longer periods of exposure in their presence. Although the immobilization of nanoparticles in micron‐sized supports could, in theory, decrease the toxicity of single nanoparticles, the selection of a suitable support is essential. The present results suggest that NK clay is not the appropriate substrate to decrease TiO2 NPs toxicity. Therefore, for future studies, it is critical to select a more appropriate substrate for the immobilization of TiO2 NPs. HighlightsOnly the MTT and AB assays were found to be suitable for cytotoxicity assessment.Alkaline comet assay was also appropriate for genotoxicity evaluation.All nanomaterials decreased the HepG2 cell viability and caused DNA damage.Nanokaolin is not a suitable clay substrate for the immobilization of TiO2 NPs.Further toxicity studies must be performed in other clays to support nanoparticles.

Effect of fugitive phase addition on porosity evolution and properties of stoneware tiles

Abstract Abstract Different percentages of fugitive phase with three different average particles were added to the green porcelain compositions. The fugitive phase was burnt out during the sintering, and the shrinkage of the samples was proportional to the added volume. The lower the particle size of the fugitive phase was, the higher the shrinkage became. The properties of stoneware tiles as apparent density, linear shrinkage, modulus of rupture, porosity, roughness and water absorption were studied as function of the added fugitive phase. A reduction of the porosity was obtained when the added fugitive phase was <5 vol.-%. The modulus of rupture improvement was found in samples with higher density. The surface roughness increased by both the volume and the particle size of fugitive phase. Large added porosity volume was effectively eliminated, and the porosity was equilibrated to a fixed value related to the initial particle size of the fugitive phase. The main mechanism that contributed to the elimination of porosity during liquid assisted sintering was the gas diffusion. Large pores were hindered by the crystalline phases, and thus pore, coalescence was avoided in the porcelain stoneware.