Solubility enhancement of ibuprofen using tri-ureasil-PPO hybrid: structural,cytotoxic, and drug release investigation

Herein, we used tri-ureasil organic–inorganic hybrid material (tU5000) in order to enhance the solubility of nonsteroidal anti-inflammatory drugs and fine tuning the drug delivery profile. For the first time, we used tU5000 as a film-forming agent in order to provide an alternative vehicle for transdermal drug delivery systems which the cell viability of practically 100 % for the highest and the lowest tested concentrations of pure tU5000 indicated that the material was not cytotoxic. The physicochemical properties of the tU5000 drug carrier and drug-loaded hybrids were systematically studied using powder X-ray diffraction, differential scanning calorimetry, small-angle X-ray scattering, and Fourier-transform infrared spectroscopy. The structural changes of tU5000 as well as the relationships between the drug content and in vitro drug release behaviors were investigated. The results showed that the ibu molecules were homogeneously distributed in the tU5000 xerogels contributing to fine-tuning the drug delivery profile. Considering the ability to incorporated high drug content, simple and mild preparation procedure by one-pot sol–gel route, high stability of the materials, sustained-release property, this class of hybrid based on polymers and inorganic compounds may have potential applications in the design of pharmaceutical formulation as ophthalmic (contact lenses), transdermal (patches) and implantable (soft tissue) drug delivery systems.     

Homogeneous and heterogeneous olefin epoxidation catalyzed by a binuclear Mn(II)Mn(III) complex

The synthesis and characterization of a binuclear carboxylated bridged manganese complex containing the heptadentate ligand N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-methylpyridyl)-2-ol-1,3-propanediamine (H₃bbppnol) is reported. This complex was characterized by elemental analysis; infrared, electronic (UV–vis) and EPR spectroscopy; and conductivity measurements. The complex was immobilized on silica by either adsorption or entrapment via a sol–gel route. The obtained solids were characterized by thermogravimetric analyses (TG and DSC), UV–vis and infrared spectroscopy, and X-ray diffraction. The catalytic performance of the binuclear manganese complex in epoxidation reactions was evaluated for both homogeneous and heterogeneous systems. The catalytic investigation revealed that the complex performs well as an epoxidation catalyst for the substrates cyclohexene (26–39%) and cyclooctene (29–74%). The solids containing the immobilized complex can be recovered from the reaction medium and reused, maintaining good catalytic activity.     

Influence of Catalyses on the Preparation of YVO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> Phosphors by the Sol–gel Methodology

YVO(4):Eu(3+) phosphors have been prepared by the hydrolytic sol-gel methodology, with and without alkaline catalyst. The solid powder was obtained by reaction between yttrium III chloride and vanadium alkoxides; the europium III chloride was used as structural probe. The powder was treated at 100, 400, 600, or 800 °C for 4 h. The samples were characterized by X-ray diffraction, thermal analysis, and photoluminescence. The XRD patterns revealed YVO(4) crystalline phase formation for the sample prepared without the catalyst and heat-treated at 600 °C and for the sample prepared in the presence of ammonium as catalyst and heat-treated at 100 °C. The average nanosized crystallites were estimated by the Scherrer equation. The sample which was produced via alkaline catalysis underwent weight loss in two stages, at 100 and 400 °C, whereas the sample obtained without catalyst presented four stages of weight loss, at 150, 250, 400, and 650 °C. The excitation spectra of the samples treated at different temperatures displayed the charge transfer band (CTB) at 320 nm. PL data of all the samples revealed the characteristic transition bands arising from the (5)D(0) → (5)F(J) (J = 0, 1, 2, 3, and 4) manifolds under maximum excitation at 320, 394, and 466 nm in all cases. The (5)D(0) → (7)F(2) transition often dominates the emission spectra, indicating that the Eu(3+) ion occupies a site without inversion center. The long lifetime suggests that the matrix can be applied as phosphors. In conclusion, the sol-gel methodology is a very efficient approach for the production of phosphors at low temperature.     

Encapsulation of Tetraazaannulenato Compounds in Matrix by Sol-Gel Process

The hybrid organic-inorganic catalyst constituted by {5,7,12,14-tetramethyldibenzo[b,i]-1,4,8,11-tetraaza[14]annulenato} nickel (II), NiTMTAA, encapsulated in an alumina matrix has been prepared. NiTMTAA was synthesized by the reaction of nickel acetate with o-phenylenediamine in the presence of 2,4-pentanedione under argon atmosphere. The alumina hybrid material was obtained by a non hydrolytic sol-gel route, through the condensation of aluminum chloride with diisopropylether in the presence of NiTMTAA. The material has been prepared through precipitation from a gel. Characterization of the alumina hybrid material has been performed by ultra violet-visible spectroscopy, electron spectroscopic imaging, surface area, atomic absorption, infrared spectroscopy, and thermogravimetric analysis. The ultra violet-visible absorption spectrum of the hybrid material has bands characteristic of the NiTMTAA compound showing that the structure of NiTMTAA has been preserved in the hybrid material. The new material has a surface area of 300 m²/g. The electron image was that of a non-crystalline microstructure. Comparison between the leaching of NiTMTAA from NiTMTAA adsorbed on commercial neutral alumina confirm that in the non-hydrolytic materials the NiTMTAA is entrapped and not only adsorbed on the alumina surface. The use of conventional hydrolytic sol-gel process leads to the complete leaching of NiTMTAA from matrix, underlining the importance of the non-hydrolytic alumina gel process in the matrix preparation. The new catalysts prepared were tested for their ability to catalyze the epoxidation of (Z)-cyclooctene using iodosylbenzene as oxygen donor, giving moderate yields in the epoxidation (40%), while the homogeneous NiTMTAA is inactive due to NiTMTAA bleaching. These results emphasize the effect of the non-hydrolytic alumina matrix to prevent chemical degradation of NiTMTAA.     

New synthesis strategies for effective functionalization of kaolinite and saponite with silylating agents

Functionalization of Brazilian São Simão kaolinite and Spanish Yunclillos saponite with the alkoxysilanes 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane is reported. The resulting hybrids were characterized by X-ray diffraction, thermal analysis, infrared absorption spectroscopy, and scanning electron microscopy, which demonstrated the effectiveness of the interlamellar grafting process. The X-ray diffractograms revealed incorporation of the alkoxide molecules into the interlayer space of the clays. The displacement of the stretching bands of interlayer hydroxyls in the infrared spectra of the modified kaolinites and the increased intensity of the Mg–OH vibrations in the spectra of the modified saponites confirmed the functionalization of the clays. The thermal behavior of the organoclays confirmed the stability of the hybrids, which was dependent on the clay used for preparation of the materials.     

Coating of polyamide 12 by sol–gel methodology

The combination of sol–gel methodology with rapid prototyping (RP) produces functionalized 3D structures with potential applications in various fields. However, this combination has been little explored. In this paper, we used the sol–gel method to deposit vanadium isopropoxide onto polyamide (PA12) constructed by RP and pretreated with acetic acid, to obtain a functionalized substrate with new thermal, physical, and chemical properties. Vanadium isopropoxide (one, five, or ten layers) was deposited onto the PA12 piece by dip-coating. We characterized the coated PA12 by thermal analyses, X-ray diffraction, and infrared spectroscopy, which revealed that V=O and Si–O–Si groups exist on the PA12 surface. PA12 coating with vanadium isopropoxide enhanced the decomposition temperature. Differential scanning calorimetry revealed increased fusion and decomposition enthalpy as a function of the PA12 coating. Therefore, deposition of vanadium isopropoxide onto PA12 pretreated with acetic acid improves the thermal stability of PA12 prepared by RP.     

Antioxidant protection in cultured corneal cells and whole corneas submitted to UV-B exposure

Several corneal pathologies are characterized by the presence of reactive oxygen species (ROS); therefore, we evaluated the protection afforded by pirenoxine and melatonin to corneal cell culture and whole rabbit cornea from ultraviolet exposure and other oxidant systems. Rabbit cornea cell (SIRC) plates and whole corneas were exposed to UV-B (80 or 800 mJ/cm2) or incubated with fMLP-stimulated autologous macrophages, in the presence or absence of pirenoxine or melatonin (10(-5) M). The protective activity of compounds was assessed by measuring superoxide anion formation, inhibition of oxidation and mitochondrial viability. Moreover the ex vivo protective effect of pirenoxine and melatonin was verified in the whole cornea submitted to UV-B exposure in vitro. Our experimental data demonstrate that pirenoxine and melatonin were able to inhibit the superoxide formation and oxidative effect in cell culture and whole rabbit corneas submitted to UV-B exposure or to incubation with fMLP-stimulated autologous macrophages. Mitochondrial viability was restored in epithelial cells of rabbit cornea but not in SIRCs. Moreover, both compounds are also able to increase ex vivo epithelial corneal cell defences against the in vitro UV-B induced lipid peroxidation.     

Eu(III) incorporation in sol-gel aluminum-yttrium matrix by non-hydrolytic route

The sol-gel method using metal alkoxide has been investigated to prepare aluminum-yttrium oxide as yttrium-aluminum garnet (YAG) matrix composite fiber. In this paper we investigate the influence of yttrium content and temperature in the synthesis of Eu(III)-doped aluminum-yttrium oxide by non-hydrolytic sol-gel route. The formation process and the local structure of the samples were discussed by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. For temperatures around 800 °C, initial crystallization was observed and the phases Y₄Al₂O₉ (YAM) and Y₃Al₅O₁₂ (YAG) appear. For samples treated at 800 and 1500 °C the emission spectra display preferentially the f-f transitions characteristic of the YAM monoclinic phase, whereas the YAG cubic appears as the favored phase at 1100 °C, in accordance with the Eu(III) centrosymmetrical local site.     

Nitro-Porphyrin Entrapped in a Silica Matrix by Sol-Gel Methodology

This work describes the preparation of the iron (III) porphyrin, FeTDCNO₂, entrapped in a silica matrix in the form of powder (FePD) or thin film using the sol-gel process. The films were obtained from sols using the dip-coating technique. The variables involved in the FePD preparation were analysed by a fractional factorial design with resolution 5, designated by 2 _V ^{5 – 1}. The variables which present a positive effect and maximise the loading of the studied ironporphyrin on the FePD material are solvent, water volume and reaction time. The utilization of pyridine or imidazole as template does not affect the preparation of the FePD material. The UV-visible absorption spectra of all prepared materials present the characteristic Soret band of ironporphyrins at 419–420 nm.The materials were analysed by thermogravimetric analysis, isotherm of nitrogen adsorption, ²⁹Si NMR and scanning electron micrograph. The catalytic performance of FePD-imidazole on the epoxidation of z-cyclooctene with iodosylbenzene is similar to that of FeTDCNO₂ in homogeneous solution (60 and 52%).