Gerardo González-García

Hexacoordinated oligosilanes from a hexacoordinated silicon(IV) complex containing an O,N,N,O salen-type and thiocyanato-N ligands.

Two new neutral hexacoordinated silicon complexes with SiN(4)O(2) (6) and SiN(3)O(2)C (7) coordinating frameworks were synthesized by reaction of the O,N,N,O-donor salen-type ligand 1,2-bis[[(2-hydroxy-4-methoxyphenyl)(phenyl)methylene]amino]ethane (H(2)salen*) with Si(NCS)(4) and HMeSi(NCS)(2), respectively. The complexes 6 [Si(salen*)(NCS)(2)] and 7 [Si(salen*)Me(NCS)] were studied in the solid-state by (29)Si and (15)N CP/MAS NMR and in solution by (1)H, (13)C, and (29)Si insensitive nuclei enhanced by polarization transfer (INEPT) NMR, UV/vis and FT-IR spectroscopy. Elemental analysis and single-crystal X-ray diffraction analysis were used to confirm the composition and structure for compounds 6 and 7. Both complexes contain the dianionic salen-type ligand coordinated in an equatorial fashion to the silicon center, while the axial positions are occupied by two thiocyanato-N ligands for 6 and one thiocyanato-N and one methyl ligand for 7. Complex 6, which contains two Si-NCS functional groups, was used as monomer to produce a mixture of linear oligosilanes with a hexacoordinated silicon backbone (formulated SCN-[Si(salen*)](n)-NCS, n = 2-8) 8, via a Wurtz-type coupling reaction. Oligomers 8 were identified by solid-state (29)Si cross polarization-magic angle spinning NMR and solution (1)H and (29)Si NMR spectroscopy, matrix assisted laser desorption ionization-time of flight (MALDI-TOF), gel-permeation chromatography (GPC), FT-IR, UV/vis spectroscopy and thermogravimetric analysis (TGA). Conclusive evidence of the oligomeric nature of 8 was provided by MALDI-TOF spectrometry and was supported by quantitative solution (29)Si NMR and GPC studies.

Comparison between alumina supported catalytic precursors and their application in thiophene hydrodesulfurization: (NH4)4[NiMo6O24H6]·5H2O/γ-Al2O3 and NiMoOx/γ-Al2O3 conventional systems

The effect of the phase composition of alumina supported NiMo catalytic precursors on thiophene hydrodesulfurization (HDS) was investigated. The catalytic precursors were prepared by impregnation of the commercial γ-Al2O3 with solutions of Anderson-type ammonium salts or co-precipitation of ammonium heptamolybdate and nickel nitrate. The precursors were characterized by XRD, BET specific surface area, pore volume and pore size, XPS, elemental analysis, TGA and 27Al MAS NMR. The chemical analyses by ICP showed for the NiMo-AP compounds a clear agreement between experimental and theoretical values according to stoichiometric values (Mo/Ni = 6), while for NiMo-COP deviations were observed (Mo/Ni ∼ 7). The specific surface area and pore volume of NiMo-AP/γ-Al2O3 precursors were greater than those of the NiMo-COP/γ-Al2O3 precursors, 387/325 m2 g−1 vs. 283/265 m2 g−1, and 0.34/0.27 cm3 g−1 vs. 0.21/0.15 cm3 g−1, respectively; whereas the average pore radius for all systems was 12 A. XRD and XPS analysis confirmed the presence of (NH4)4[NiMo6O24H6]·5H2O and Mo5+/Mo6+ for solids obtained by Anderson-type precursors, whereas NiMo-COP/γ-Al2O3 precursors exhibited Mo6+ from NiMoO4 and MoO3. The NiMo precursor obtained from conventional methods showed a higher amount of sulfur than those synthesized from the Anderson-type phase (6.9 to 4.9 wt%), although this does not mean a highly active sample or optimum sulfided active phase. 27Al solid-state MAS NMR showed higher tetrahedrally coordinated aluminium for the NiMo-COP/γ-Al2O3 catalytic precursors. The catalytic activity was strongly influenced by the type of catalytic precursor and metallic wt%. The activity of the catalysts obtained by the sulfided Anderson-type ammonium salts was greater than the sulfided solids obtained by the conventional method, suggesting that these precursors result in a better active phase with a molar ratio (Ni + Mo)/S = 1.01 (likely “Ni–Mo–S” species), due to lower loss of the Ni promoter into the alumina support (27Al NMR) and the lowest metal–support interaction (TGA). The catalysts obtained the HDS products, butane and cis-butene independent of the precursor type. Furthermore, the catalysts with 15 wt% Mo were more efficient than those obtained with 8 wt% Mo.

Improved properties of composite collagen hydrogels: protected oligourethanes and silica particles as modulators

This paper reports the structure-property relationship of novel biomedical hydrogels derived from collagen, water-soluble oligourethanes, and silica. The molecular weight (MW) of oligourethanes, synthesized from polyoxyethylene diol and hexamethylene, l-lysine, isophorone or trimethylhexamethylene diisocyanates (P(HDI), P(LDI), P(IPDI) and P(TMDI), respectively), is determined by the chemical structure of the starting aliphatic diisocyanate. Thus, the collagen polymerization process and both the characteristics and mechanics of the formed three-dimensional (3D) network had a direct relation with the oligourethane MW. The crosslinking of collagen with oligourethanes was compatible with orthosilicate polycondensation to deposit silica particles on the fibrillar 3D network. A higher crosslinking index was found in hydrogels formulated with P(HDI) and P(LDI) in comparison with P(TMDI) and P(IPDI). In spite of similar crosslinking extensions, P(LDI) induced an enhanced water uptake and enhanced susceptibility to degradation, contrary to the impact of P(HDI). Fibroblasts and macrophages cultured for 3 days on hydrogels formulated with P(LDI) showed a metabolic activity similar to collagen only hydrogels. However, we observed the highest cell metabolic activity on hydrogels formulated with P(LDI) after 7 day culture. After this time lapse, an enhanced secretion of chemoattractant cytokines transforming growth factor-beta1 (TGF-β1) and monocyte chemoattractant protein-1 (MCP-1 or CCL-2) was noted in macrophages cultured on hydrogels crosslinked with P(LDI). These tunable composite collagen hydrogels might be excellent candidates for holding and releasing bioactive molecules and nanomaterials intended to regulate cell behavior via their constituents and properties.

Incorporation of silica particles into decellularized tissue biomaterial and its effect on macrophage activation

This paper describes an optimized procedure to incorporate silica particles by hydrolysis/polycondensation of sodium silicate into pericardial (ECM) matrix scaffolds and elucidates the effect of the biocomposites on the in vitro response of macrophages by assessment of the secretion of signaling molecules. Variables (concentration, pH, time) of the sol–gel process allow a gradual incorporation of silica into the ECM scaffolds as confirmed by gravimetry, FT-IR, SEM and EDX microanalysis. The SiO2 incorporation increases the resistance to in vitro degradation but does not alter either the denaturation temperature or content of free amines of non-crosslinked ECM fibrous scaffolds, however, the properties of oligourethane-crosslinked scaffolds are not modified after silica incorporation. Despite the fact that cell viability is gradually decreased for the ECM materials crosslinked with oligourethane and functionalized with silica, murine RAW264.7 macrophages are able to secrete b-FGF, TGF-β1 and VEGF. Secretion of growth factors by RAW264.7 macrophages after 6 h of culture on scaffolds containing silica was lower but it was sustained for 24 h as compared to cells cultured on silica-free materials. Human peripheral blood macrophages cultured with materials containing silica show a higher production of IL-6, IL-10 or TNF-α than with the silica-free counterparts but in a time-dependent manner from one to four days of culture. Results suggest that stimulation of macrophages is induced by silica particles deposited onto the ECM fibrous network, which represents an opportunity to control the cell response to decellularized tissue-derived biomaterials through strategies intended to stimulate cells via signaling molecules secreted by macrophages.

Design of Silica‐Oligourethane‐Collagen Membranes for Inflammatory Response Modulation: Characterization and Polarization of a Macrophage Cell Line

The polarization of macrophages M0 to M1 or M2 using molecules embedded in matrices and hydrogels is an active field of study. The design of biomaterials capable of promoting polarization has become a paramount need nowadays, since in the healing process macrophages M1 and M2 modulate the inflammatory response. In this work, several immunocytochemistry and ELISA tests strongly suggest the achievement of polarization using collagen-based membranes crosslinked with tri-functionalized oligourethanes and coated with silica. Measuring the amount of TGF-β1 secreted to culture media by macrophages growth on these materials, and quantifying the macrophage morphology, it is proved that it is possible to stimulate the anti-inflammatory pathway toward M2, having measurements with p ≤ 0.05 of statistical significance between the control and the collagen-based membranes. Furthermore, some physicochemical characteristics of the hybrid materials are tested envisaging future applications: collagenase degradation resistance, water uptake, collagen fiber diameter, and deformation resistance are increased for all the crosslinked biomaterials. It is considered that the biological and physicochemical properties make the material suitable for the modulation of the inflammatory response in the chronic wounds and promising for in vivo studies.

Mucilage from cladodes of Opuntia spinulifera Salm-Dyck: chemical, morphological, structural and thermal characterization

ABSTRACT The mucilage obtained from cladodes of Opuntia spinulifera has been used in industries and traditional applications. In the present work, the chemical, morphological, thermal and structural features of cladode mucilage from Opuntia spinulifera Salm-Dyck were studied. The 2D 1H-1H COSY NMR confirmed ten different residues within the repeating saccharide unit, six with α and four with β configurations. The FTIR showed the presence of galactose and pectins. The XRD detected minerals as calcium salts. The SEM exhibited aggregations and irregular morphology of the particles. The TGA registered the highest mass loss between 246–378°C and the DSC showed the transition state at 55.7°C and at 113.2°C was observed the typical endothermic peak, where it corresponds to the organic compound materials.

In vitro evaluation of apoptotic effect of bis(acetylacetonato-k2 O,O′)(1,10-phenanthroline-k2 N,N′)Zn(II) complex

Phenanthroline derivatives have been reported as potential bioactive compounds because of their ability to interact with DNA. To evaluate the antiproliferative effect of bis(acetylacetonate‐k2 O,O)(1,10‐phenanthroline‐k2 N,N)Zn(II) or Zn(acac)2(phen) complex, the compound was obtained in a simple manner and further characterized to determine crystal structure, thermal behavior, morphology, and spectroscopic properties. The structure of the complex was confirmed by X‐ray single structure as well as by 1H and 13C nuclear magnetic resonance (NMR) in dmso‐d6 (dimethyl sulfoxide) solution and in the solid state by 13C CP/MAS. Although preparation of this compound has been described previously, there are no reports on its biological activity; here, we assessed its antiproliferative effect on fibroblasts, A253, FaDu, Cal‐27, RH‐30, RD, U‐373, C6, A‐549, MDA‐MB‐231, and MCF‐7 cancer cell lines at different doses (50–100 and 150 μg/ml). The cell viability was determined by MTT assay and high activity was observed for the most of the cell lines, and TUNEL results showed the induction of apoptosis.