Investigating the Interaction of Water Vapour with Aminopropyl Groups on the Surface of Mesoporous Silica Nanoparticles.

The interaction of water molecules with the surface of hybrid silica-based mesoporous materials is studied by 29 Si, 1 H and 13 C solid-state NMR and IR spectroscopy, with the support of ab initio calculations. The surface of aminopropyl-grafted mesoporous silica nanoparticles is studied in the dehydrated state and upon interaction with controlled doses of water vapour. Former investigations described the interactions between aminopropyl and residual SiOH groups; the present study shows the presence of hydrogen-bonded species (SiOH to NH2 ) and weakly interacting "free" aminopropyl chains with restricted mobility, together with a small amount of protonated NH3+ groups. The concentration of the last-named species increased upon interaction with water, and this indicates reversible and fast proton exchange from water molecules to a fraction of the amino groups. Herein, this is discussed and explained for the first time, by a combination of experimental and theoretical approaches.

Delivery of Gemcitabine Prodrugs Employing Mesoporous Silica Nanoparticles.

In this paper, mesoporous silica nanoparticles (MSNs) were studied as vehicles for the delivery of the antitumoral drug gemcitabine (GEM) and of its 4-(N)-acyl derivatives, (4-(N)-valeroyl-(C5GEM), 4-(N)-lauroyl-(C12GEM) and 4-(N)-stearoyl-gemcitabine (C18GEM)). The loading of the GEM lipophilic prodrugs on MSNs was explored with the aim to obtain both a physical and a chemical protection of GEM from rapid plasmatic metabolization. For this purpose, MSNs as such or with grafted aminopropyl and carboxyethyl groups were prepared and characterized. Then, their different drug loading capacity in relation to the nature of the functional group was evaluated. In our experimental conditions, GEM was not loaded in any MSNs, while C12GEM was the most efficiently encapsulated and employed for further evaluation. The results showed that loading capacity increased with the presence of functional groups on the nanoparticles; similarly, the presence of functional groups on MSNs' surface influenced the drug release profile. Finally, the cytotoxicity of the different preparations was evaluated and data showed that C12GEM loaded MSNs are less cytotoxic than the free drug with an activity that increased with the incubating time, indicating that all these systems are able to release the drug in a controlled manner. Altogether, the results demonstrate that these MSNs could be an interesting system for the delivery of anticancer drugs.

NIR persistent luminescence of lanthanide ion-doped rare-earth oxycarbonates: the effect of dopants.

A series of luminescent rare-earth ion-doped hexagonal II-type Gd oxycarbonate phosphors Gd2-xRExO2CO3 (RE = Eu(3+), Yb(3+), Dy(3+)) have been successfully synthesized by thermal decomposition of the corresponding mixed oxalates. The Yb(3+) doped Gd-oxycarbonate has evidenced a high persistent luminescence in the NIR region, that is independent from the temperature and makes this materials particular attractive as optical probes for bioimaging.

MCM-41 as a useful vector for rutin topical formulations: synthesis, characterization and testing.

Rutin, the glycoside of quercetin, could be used in topical preparations because of its antioxidant and radical scavenging properties, but its employ in cosmetic and pharmaceutical products is limited by poor physico-chemical stability. These issues were addressed by preparing, characterizing and testing rutin inclusion complexes with MCM-41 mesoporous silica. The effect of surface functionalization with aminopropyl groups (NH2-MCM-41) on the molecules properties was studied. The organic/inorganic interaction was confirmed by many techniques. In particular, the high inclusion of rutin in the pores of NH2-MCM-41 was assessed by XRD, TGA, gas-volumetric analysis (BET), while FTIR spectroscopy allowed to analyse with great detail the molecular interaction with the inorganic surface. Rutin was stabilized against UV degradation, mostly by its inclusion in NH2-MCM-41. Ex vivo studies showed a greater accumulation in porcine skin in the case of rutin complexed with NH2-MCM-41. Not only antioxidant properties of rutin were maintained after immobilization but, with aminopropyl silica, the metal-chelating activity increased noticeably. The immobilization of rutin in aminopropyl silica resulted in better performance in terms of activity and photostability, suggesting the importance of functionalization in stabilizing organic molecules within silica pores.

Bright photoluminescent hybrid mesostructured silica nanoparticles.

Bright photoluminescent mesostructured silica nanoparticles were synthesized by the incorporation of fluorescent cyanine dyes into the channels of MCM-41 mesoporous silica. Cyanine molecules were introduced into MCM-41 nanoparticles by physical adsorption and covalent grafting. Several photoluminescent nanoparticles with different organic loadings have been synthesized and characterized by X-ray powder diffraction, high resolution transmission electron microscopy and nitrogen physisorption porosimetry. A detailed photoluminescence study with the analysis of fluorescence lifetimes was carried out to elucidate the cyanine molecules distribution within the pores of MCM-41 nanoparticles and the influence of the encapsulation on the photoemission properties of the guests. The results show that highly stable photoluminescent hybrid materials with interesting potential applications as photoluminescent probes for diagnostics and imaging can be prepared by both methods.

Photoactive Ru complex embedded in mesostructured MCM-41 nanoparticles.

The synthesis and characterization of photoactive hybrid materials based on [Ru(bpy)(3)](2+) physically adsorbed within the channels of mesoporous MCM-41 silica nanoparticles is presented. A set of photoactive mesostructured hybrids with different guest loading has been prepared and characterized by X-ray diffraction, High Resolution Transmission Electron Microscopy, volumetric analyses, Diffuse Reflectance UV-Vis and Photoluminescence spectroscopies and lifetime measurements. The hybrids synthesis and the washing procedures, performed to investigate the host-guest interaction and the stability of the complex within the mesopores, didn't affect the integrity of the structure and morphology of MCM-41 nanoparticles. The dispersion of [Ru(bpy)(3)](2+) within the channels varied depending on the loading value and this is reflected in the different and peculiar photoluminescence features of the resulting hybrid materials. Photoluminescence spectroscopy evidenced that the use of MCM-41 nanoparticles ensures a better dispersion of the complex within the mesopores, if compared with traditional MCM-41. Further studies are in progress to investigate the interesting and promising features exhibited by such photoactive systems for advanced applications of electrochemiluminescence in optoelectronics and diagnostics.

The role of isolated active centres in high-performance bioinspired selective oxidation catalysts.

Transition-metal complexes containing amino acids encapsulated within solid supports generate isolated active centres that function as effective selective oxidation catalysts using benign oxidants such as air and display high turnovers and selectivity in industrially significant oxidation reactions.