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Monodispersed Mesoporous Silica Nanoparticles with Very Large Pores for Enhanced Adsorption and Release of DNA

Silica nanoparticles with controlled diameter (approximately 70-300 nm) and with uniform pores of 20 nm are prepared by a low temperature (10 degrees C) synthetic method in the presence of a dual surfactant system. While a triblock copolymer (Pluronic F127) acts as supramolecular template and coassembles with hydrolyzed silica species to develop a partially ordered mesophase with face-centered cubic symmetry, a fluorocarbon surfactant with high surface activity (FC-4) surrounds the silica particles through S+X-I+ interactions, thereby limiting their growth. The final textural properties of this material are achieved by means of a subsequent hydrothermal treatment to yield high pore volume mesoporous silica nanoparticles with the largest pore entrance size (17 nm) and cavity diameter (20 nm) reported up to now. After surface modification with aminopropyl groups, the nanoparticles are able to encapsulate inside the pores molecules of the firefly luciferase plasmid DNA (pGL3-Control, 5256 pb), leading to stable conjugates with up to 0.07 microg DNA m(-2), which is the highest content achieved with silica-based materials. Furthermore, plasmid DNA becomes protected from enzymatic degradation when conjugated with the mesostructured nanoparticles.

Selective Oxidation of Propane to Acrylic Acid on MoVNbTe Mixed Oxides Catalysts Prepared by Hydrothermal Synthesis

MoVNbTe mixed oxides have been prepared by both hydrothermal synthesis and slurry methods and have been tested in the selective oxidation of propane to acrylic acid. For comparative purpose, ternary metal oxides have also been prepared and tested. Characterisation results (X-ray diffraction and EPR) show important differences between the catalysts prepared hydrothermally and one prepared by a slurry method. The catalysts prepared hydrothermally show a higher activity and selectivity to acrylic acid than those prepared by slurry method. A reaction network for the partial oxidation reaction is tentatively proposed from the catalytic results obtained during the oxidation of propane and propylene on these catalysts.

The selective oxidative dehydrogenation of ethane over hydrothermally synthesised MoVTeNb catalysts

Mo-V-Te-Nb metal oxide catalysts prepared by hydrothermal synthesis and heat-treated in N2 at high temperatures (600-700 degrees C) show high activity and selectivity for the oxidative dehydrogenation of ethane to ethene. Yields of ethene of 75% have been obtained at 400 degrees C on the best catalysts.

Preparation, characterisation and catalytic behaviour of a new TeVMoO crystalline phase

TeMxMo1.7O mixed oxides (M = V and/or Nb; x = 0-1.7) have been prepared by calcination of the corresponding salts at 600 °C in an atmosphere of N2. A new crystalline phase, with a Te/V/Mo atomic ratio of 1/0.2-1.5/1.7, has been isolated and characterised by XRD and IR spectroscopy. This phase is observed in the TeVMo or TeVNbMo mixed oxide but not in the TeNbMo mixed oxide. The new crystalline phase shows an XRD pattern similar to Sb4Mo10O31 and probably corresponds to the M1 phase recently proposed by Aouine et al. (Chem. Commun. 1180, 2001) to be present in the active and selective MoVTeNbO catalysts. Although these catalysts present a very low activity in the propane oxidation, they are active and selective in the oxidation of propene to acrolein and/or acrylic acid. However, the product distribution depends on the catalyst composition. Acrolein or acrylic acid can be selectively obtained from propene on Nb-free or Nb-containing TeVMo catalysts, respectively. The presence of both V and Nb, in addition to Mo and Te, appears to be important in the formation of acrylic acid from propene.

Surface-modified silica nanoparticles for tumor-targeted delivery of camptothecin and its biological evaluation

Here we report the design, synthesis and biological evaluation of surface-modified silica nanoparticles (SNP) for the delivery of camptothecin (CPT). Drug has been covalently linked to the nanoparticle through an ester bond with the 20-hydroxy moiety, in order to stabilize its lactone ring and to avoid unspecific release of the drug. The obtained material is highly stable in plasma, with low release of the cargo at physiological pH. Cell internalization and in vitro efficacy assays demonstrated that nanoparticles carrying CPT (SNP-CPT) entered cells via endocytosis and the intracellular release of the cargo induced cell death with half maximal inhibitory concentration (IC₅₀) values and cell cycle distribution profiles similar to those observed for the naked drug. Further, in vivo biodistribution, therapeutic efficacy and biocompatibility of the SNP-CPT were evaluated in human colorectal cancer xenografts using in vivo fluorescence or bioluminescence optical imaging. In vivo tumor-accumulation and whole-body tissue distribution were carried out based on the acquisition of fluorescence emission of a fluorophore (Cy5.5) conjugated to the SNP-CPT, as well as by HPLC quantification of tissue CPT levels. The results showed that, although SNP-CPT tended to accumulate in organs of the reticulo-endothelial system, nanoparticles boost CPT concentration in tumor vs administration of the free drug. Accordingly, SNP-CPT treatment delayed the growth of subcutaneous tumors while significantly reducing the systemic toxicity associated with CPT administration. These results indicate that the SNP-CPT could be used as a robust drug delivery system for antitumoral treatments based on CPT.

The selective oxidation of propane on Mo-V-Te-Nb-O catalysts: The influence of Te-precursor

Abstract Mo-V-Te-Nb-O catalysts have been prepared by hydrothermal synthesis and have been tested in the selective oxidation of propane to acrylic acid. The catalysts have been prepared by using different Te- and Mo-starting compounds. Both the catalyst characterization results (XRD, SEM–EDX, FTIR and XPS) and the catalytic tests show important differences depending on the Te- and Mo-starting compounds used in the hydrothermal synthesis. The most active and selective catalysts for the oxidation of propane to acrylic acid were those prepared from Te(VI)-compounds, i.e. telluric acid or an Anderson-type telluromolybdate. However, catalysts prepared from Te(IV)-compounds, i.e. TeO 2 or (NH 4 ) 4 TeMo 6 O 22 ·2H 2 O, presented both low activity and low selectivity to acrylic acid. In the best catalysts, several crystalline phases were observed: Mo 5 TeO 16 , (Mo 0.93 V 0.07 ) 5 O 14 , and/or Nb 0.09 Mo 0.91 O 2.80 and new Te-V-Nb-Mo-oxide crystalline phases. The presence of small crystals of MoO 3 in active and selective catalysts can also be proposed. The different catalytic performance of these catalysts could be related to the different incorporation of Te, V and Nb ions, which depends strongly on the Te-compound introduced in the synthesis gel.

Degradation of Methylene Blue Using Porous WO3, SiO2–WO3, and Their Au-Loaded Analogs: Adsorption and Photocatalytic Studies

A facile sonochemical approach was used to deposit 3-5 nm monodisperse gold nanoparticles on porous SiO2-WO3 composite spheres, as confirmed by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). High-resolution TEM (HR-TEM) and energy dispersive X-ray spectroscopy (EDS) further characterized the supported Au nanoparticles within the Au-SiO2-WO3 composite. These analyses showed isolated Au nanoparticles within both SiO2- and WO3-containing regions. Selective etching of the SiO2 matrix from Au-SiO2-WO3 yielded a pure Au-WO3 material with well-dispersed 10 nm Au nanoparticles and moderate porosity. This combined sonochemical-nanocasting technique has not been previously used to synthesize Au-WO3 photocatalysts. Methylene blue (MB) served as a probe for the adsorption capacity and visible light photocatalytic activity of these WO3-containing catalysts. Extensive MB demethylation (azures A, B, C, and thionine) and polymerization of these products occurred over WO3 under dark conditions, as confirmed by electrospray ionization mass spectrometry (ESI-MS). Photoirradiation of these suspensions led to further degradation primarily through demethylation and polymerization pathways, regardless of the presence of Au nanoparticles. Ring-opening sulfur oxidation to the sulfone was a secondary photocatalytic pathway. According to UV-vis spectroscopy, pure WO3 materials showed superior MB adsorption compared to SiO2-WO3 composites. Compared to their respective nonloaded catalysts, Au-SiO2-WO3 and Au-WO3 catalysts exhibited enhanced visible light photocatalytic activity toward the degradation of MB. Specifically, the rates of MB degradation over Au-WO3 and Au-SiO2-WO3 during 300 min of irradiation were faster than those over their nonloaded counterparts (WO3 and SiO2-WO3). These studies highlight the ability of Au-WO3 to serve as an excellent adsorbant and photodegradation catalyst toward MB.

On the shape selective acylation of 2-methoxynaphthalene over polymorph C of Beta (ITQ-17)

Abstract 2-Methoxynaphthalene (2-MN) has been acylated with acetic anhydride on polymorph C of Beta (ITQ-17), and 2-acetylmethoxynaphthalene (2-AMN) and 1-acetylmethoxynaphthalene (1-AMN) have been obtained. The diffusivity of the two isomer products, as determined by molecular dynamics, shows that the ratio of the diffusion coefficients for 2-AMN/1-AMN is one order of magnitude larger for polymorph C than for polymorphs A and B (Beta zeolite). This corresponds very well with experimental acylation results that show a higher selectivity for 2-AMN on polymorph C when reaction is carried out in batch as well as in a fixed-bed continuous reactor.

Synthesis of ordered mesoporous silica templated with biocompatible surfactants and applications in controlled release of drugs

A novel series of mesoporous silica materials has been developed by using non-ionic, biocompatible alkyl maltoside surfactants as organic structure directing agents and working under biomimetic conditions (e.g., room temperature and almost neutral pH) to avoid modifications of potential drugs occluded within. The obtained mesophases were tuned by changing the template and its concentration. These sugar surfactant–silica platforms were used as drug delivery carriers for ibuprofen, by encapsulating drug molecules within the hydrophobic core of the template micelles. The obtained surfactant-assisted delivery systems constitute a new approach towards controlled release of small therapeutic molecules.

Selective oxidation of propene to acrolein on Mo-Te mixed oxides catalysts prepared from ammonium telluromolybdates

(NH4)6TeMo6O24·nH2O and (NH4)4TeMo6O22·2H2O telluromolybdates have been prepared by using a solution reaction and a hydrothermal synthesis, respectively. They have been decomposed in the presence of air or N2 in order to achieve mixed metal oxides to be used as catalysts in the selective oxidation of propene. Both the characterisation and the catalytic results suggest important differences in the catalysts depending on the starting material and the calcination conditions. In this way, active and selective catalysts for the oxidation of propene to acrolein have been obtained by using (NH 4)4TeMo6O22·2H2O (prepared by hydrothermal synthesis) as starting material.