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Both cyclodextrin (CD) and porous silica possess interesting properties of adsorption and release. A silica–CD hybrid, therefore, could synergically merge the properties of the two components, giving rise to a material with appealing properties for both environmental and pharmaceutical applications. With this aim, in the present study, a first hybrid is obtained through one-pot sol–gel synthesis starting from CD and tetramethyl orthosilicate (TMOS) as a silica precursor. In particular, methyl-β-cyclodextrin (bMCD) is selected for this purpose. The obtained bMCD–silica hybrid is a dense material containing a considerable amount of bMCD (45 wt.%) in amorphous form and therefore represents a promising support. However, since a high specific surface area is desirable to increase the release/adsorption properties, an attempt is made to produce the hybrid material in the form of an aerogel. Both the synthesis of the gel and its drying in supercritical CO2 are optimized in order to reach this goal. All the obtained samples are characterized in terms of their physico-chemical properties (infra-red spectroscopy, thermogravimetry) and structure (X-ray diffraction, electron microscopy) in order to investigate their composition and the interaction between the organic component (bMCD) and the inorganic one (silica). [ABSTRACT FROM AUTHOR]

Although amorphous silica is used in food products, cosmetics and paints and as vector for drug delivery, data on its potential health hazard are limited. The aim of this study was to investigate the cytotoxic and genotoxic potential of silica particles of different sizes (250 and 500nm) and structures (dense and mesoporous). Dense silica (DS) spheres were prepared by sol–gel synthesis, mesoporous silica particles (MCM-41) were prepared using hexadecyltrimethyl ammonium bromide as a structure-directing agent and tetraethylorthosilicate as silica source. Particles were accurately characterised by dynamic light scattering, nitrogen adsorption, X-ray diffraction and field emission scanning electron microscopy. Murine macrophages (RAW264.7) and human epithelial lung (A549) cell lines were selected for investigation. Genotoxicity was evaluated by Comet assay and micronucleus test. Cytotoxicity was tested by the trypan blue method. Cells were treated with 0, 5, 10, 20, 40 and 80 µg/cm2 of different silica powders for 4 and 24 h. The intracellular localisation of silica was investigated by transmission electron microscopy. Amorphous particles penetrated into the cells, being compartmentalised within endocytic vacuoles. DS and MCM-41 particles induced cytotoxic and genotoxic effects in A549 and RAW264.7 although to different extent in the two cell lines. A549 were resistant in terms of cell viability, but showed a generalised induction of DNA strand breaks. RAW264.7 were susceptible to amorphous silica exposure, exhibiting both cytotoxic and genotoxic responses as DNA strand breaks and chromosomal alterations. The cytotoxic response of RAW264.7 was particularly relevant after MCM-41 exposure. The genotoxicity of amorphous silica highlights the need for a proper assessment of its potential hazard for human health. [ABSTRACT FROM AUTHOR]

Glass–ceramic macroporous scaffolds were prepared using glass powders and polyethylene (PE) particles of two different sizes. The starting glass, named as Fa-GC, belongs to the system SiO2–P2O5–CaO–MgO–Na2O–K2O–CaF2 and was synthesized by a traditional melting-quenching route. The glass was ground and sieved to obtain powders of specific size which were mixed with PE particles and then uniaxially pressed in order to obtain crack-free green samples. The compact of powders underwent a thermal treatment to remove the organic phase and to sinter the Fa-GC powders. Fa-GC scaffolds were characterized by means of X-Ray Diffraction, morphological observations, density measurements, image analysis, mechanical tests and in vitro tests. Composite systems were then prepared combining the drug uptake-delivery properties of MCM-41 silica micro/nanospheres with the Fa-GC scaffold. The system was prepared by soaking the scaffold into the MCM-41 synthesis batch. The composite scaffolds were characterized by means of X-Ray Diffraction, morphological observations, mechanical tests and in vitro tests. Ibuprofen was used as model drug for the uptake and delivery analysis of the composite system. In comparison with the MCM-41-free scaffold, both the adsorption capacity and the drug delivery behaviour were deeply affected by the presence of MCM-41 spheres inside the scaffold. [ABSTRACT FROM AUTHOR]

Abstract: Through a one-step procedure, covalent bonding of Disperse-Red-1 (DR1) dye to the internal surface of HMS silica has been achieved, leading to anchored molecules freely accessible to gases. Template removal by different solvents yields surface with different polarities, which affect the optical properties of DR1. This effect is dramatic when extraction is carried out in refluxing ethanol, because ethoxylation of the silica surface occurs. To cite this article: B. Onida et al., C. R. Chimie 8 (2005). [Copyright &y& Elsevier]

Carboxylic groups have been incorporated in ethane-bridged PMO by one-pot synthesis using a triblock copolymer as template; their pKa measured by titration is higher than that of same groups incorporated in SBA-15. [ABSTRACT FROM AUTHOR]

Carboxylic groups have been incorporated in ethane-bridged PMO by one-pot synthesis using a triblock copolymer as template; their pKameasured by titration is higher than that of same groups incorporated in SBA-15. [ABSTRACT FROM AUTHOR]

Abstract: Three ordered mesoporous silica systems (OMS) were synthesized within the channels (120–200nm in diameter, 60μm long) of anodic alumina membranes (AAMs), i.e., systems (i) and (ii) with pore diameters of about 4 and 6nm having a columnar alignment of mesopores and system (iii) featuring 6nm pores arranged in a circular structure. These model systems allow one to eliminate the effect of particle size and particle morphology of the OMS, by using systems without significant external surface. Ibuprofen, an anti-inflammatory drug, was incorporated into these OMS–AAM systems by diffusion from solution. Uptake results showed that the included OMS increases the drug adsorption capacity with respect to the AAM as such. The highest uptake values were reached in the columnar OMS–AAM system with the larger pore diameter. The circular system, having similar structural parameters as the columnar one, i.e. pore size, pore volume and nitrogen surface area, showed the lowest adsorption capacity toward ibuprofen. The low accessibility of circular mesopores through defects creates a significant diffusion resistance for the ibuprofen molecules, thus showing that pore morphology strongly influences molecular diffusion. Drug release in a time window ranging from minutes to weeks was studied in a simulated body fluid (SBF). Concerning the columnar samples, the drug release rate decreased upon reducing the pore diameter. From the circular sample the ibuprofen was released with fast kinetics; it is proposed that the drug did not deeply diffuse into the structure. Nearly 30% of the total amount adsorbed was retained in the circular sample. Furthermore, after about a day the precipitation of hydroxyapatite precursors was detected on the surface of the mesoporous host, showing that the OMS–AAM system exhibits a “bioactive” behavior. This implies that after prolonged release times the diffusion of the drug out of the system can be slowed down through partial pore blocking. [Copyright &y& Elsevier]

A catalytic system where gold nanoparticles are dispersed on the surface of a conventional mesoporous silica was investigated. The sample (2.25 wt% Au) was prepared by functionalizing the silica surface with 3-mercaptopropyltrimethoxysilane, anchoring gold from an HAuCl 4 solution and then reducing it with sodium citrate. Prior to the catalytic runs, the Au/SiO 2 –SH system was submitted to different thermal treatments. The catalyst, either as-made or after each thermal treatment, was characterized by N 2 adsorption–desorption at −196 °C, CHS elemental analysis, solid state 29 Si CPMAS NMR spectroscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy of CO at −196 °C. The bare and functionalized supports were also characterized. Large Au nanoparticles ( ca. 30 nm) form readily by adding the HAuCl 4 solution to the functionalized support and, besides such particles, a second family of small ones originates upon thermal treatment (2–5 nm, depending on the temperature and the atmosphere), leading to a bimodal gold particle size distribution. Remarkable CO conversion is obtained when the catalyst is calcined in air at 560 °C and subsequently treated in H 2 /He at 600 °C or directly treated in H 2 /He at 600 °C. Based on the treatment-induced modifications in the physico-chemical properties of both the carrier and the supported phase, a reaction mechanism is outlined. [ABSTRACT FROM AUTHOR]

Clotrimazole, a poorly water soluble antifungal active principle widely used in dermatology, was incorporated inside Ordered Mesoporous Silica (OMS) of the MSU-H type, using supercritical CO 2 (scCO 2 ) as solvent. The pristine OMS was characterized by a specific surface area of about 600 m 2 /g, a total specific pore volume of 0.900 cm 3 /g and an average pore size of 8.5 nm. The incorporation process was carried out in a high pressure stainless steel vessel at 25.0 MPa and 50.0 MPa, at 373 K. The time of incorporation process was varied from 6 to 18 h. The amount of incorporated clotrimazole was observed to increase with increasing incorporation time up to 12 h. Longer times (18 h) did not affect the incorporated amount. The maximum drug loading was 34% w/w, three times higher than that obtained by adsorption from ethanol solution (9.0% w/w). The clotrimazole-containing OMS was characterized by X-ray diffraction, field emission scanning electron microscopy, thermogravimetry, infrared spectroscopy and nitrogen adsorption. The clotrimazole resulted not crystalline and homogenously distributed inside the mesopores. A model of mesopores occupation by clotrimazole molecules in the form of a molecular layer is proposed. [ABSTRACT FROM AUTHOR]

Abstract: MCM-41 silica particles have been synthesized with size in the low submicron range, loaded with ibuprofen and characterized by means of XRD, N2 adsorption and scanning electron microscopy, coupled with EDS analysis both before and after contact with different volumes of simulated body fluid (SBF) at 37°C up to 10h. The particles do not show any change in morphology, composition and mesostructure as a consequence of soaking. MCM-41 spheres, though, are not inert towards SBF. Two processes take place, showing features independent from the soaking volume: (i) one within 1–2h, bringing about dissolution of silica into the liquid phase up to a concentration of 2.2mM and no change in the mesopore volume; (ii) the second, after an induction period of 1–2h, bringing about a limited increase in the concentration of dissolved silica, but affecting severely the mesoporous volume, which decreases exponentially with time. Delivery curves differ significantly when varying the volume of SBF used. To account for release kinetics under the circumstances observed, a mathematical model is proposed, based on the standard Noyes–Whitney equation, taking into account both the SBF volume used and the mesopores occlusion, this latter through a time-dependent diffusion coefficient. A satisfactory agreement is observed, without the intervention of any adjustable parameter. [Copyright &y& Elsevier]

Abstract: The retention properties of a SBA-15 mesoporous silica functionalized with –(CH2)3COOH groups, synthesized by a co-condensation route, were investigated for the ion chromatography of different cationic species. A systematic study on the effect of different eluent compositions containing non-complexing (methanesulfonic acid) or complexing (oxalic or pyridine-2,6-dicarboxylic acids) eluents, in the presence of organic modifiers (CH3CN, CH3OH, CH3NH2) on the retention of cations (Li+, Na+, K+, Ca2+, Mg2+, Sr2+, Ba2+, NH4 +, Cu2+, Ni2+, Zn2+, Cd2+, Co2+, Pb2+, Fe3+) chosen as model analytes and for their environmental importance, allowed us to elucidate the mechanisms (cation-exchange or complexation) involved in the retention on the SBA-15 phase. For the first time separations of cations on SBA-15 based stationary phases are investigated, providing the basis for further development of mesoporous silica chemistry for in-flow ion-exchange applications. [Copyright &y& Elsevier]

Abstract: The effect of post-synthesis hydrothermal treatments on MCM-48 has been studied by 29Si MAS-NMR and IR spectroscopies, X-ray diffraction, thermal gravimetry, and gas volumetry. Special attention has been given to the characterisation of the precursors before calcination and a method to evaluate the pore opening of MCM-48 from diffraction and volumetric data is given. The hydrothermal treatment does not affect the organisation of the cetyltrimethylammonium mesophase but extracts a fraction of the surfactant and increases the thickness of the silica wall. The lower area of the silica-surfactant interface after hydrothermal treatment brings about an improved stability of MCM-48 during calcination and allows the pore size of the precursor to be preserved in the calcined solid. After calcination, the hydrothermally treated samples are less prone to rehydrate and, as a consequence, their stability upon storage in moist atmosphere is dramatically improved. [Copyright &y& Elsevier]