Photopatternable di-ureasil-zirconium oxocluster organic-inorganic hybrids as cost effective integrated optical substrates

Organic-inorganic hybrids containing methacrylic acid (McOH, CH(2)= C(CH(3))COOH)) modified zirconium tetrapropoxide, Zr(OPr(n))(4), classed as di-ureasil-zirconium oxo-cluster hybrids, have been prepared and structurally characterized by X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), Fourier transform infrared (FT-IR) and Raman (FT-Raman) spectroscopies, Si and C nuclear magnetic resonance (NMR), and atomic force microscopy (AFM). XRD and SAXS results have pointed out the presence of Si- and Zr-based nanobuilding blocks (NBBs) dispersed into the organic phase. Inter-NBBs correlation distances have been estimated for the pure di-ureasil and a model compound obtained. by hydrolysis/condensation of Zr(OPr(n))(4):McOH (molar ratio 1: 1): d(Si) approximate to 26 +/- 1 angstrom and d(Zr) approximate to 16 +/- 1 angstrom, respectively. In the case of the di-ureasil-zirconium oxo-cluster hybrids, these distances depend on the Zr relative molar percentage (rel. mol. Zr %) (d(Si) ranges from 18 to 25 angstrom and d(Zr) from 14 to 23 angstrom, as the rel. mol. Zr % increases from 5 to 75), suggesting that the Si- and Zr-based clusters are interconstrained. Complementary data from FT-IR, FT-Raman, (29)Si and (13)C NMR, and AFM support to a structural model where McOH-modified Zr-based NBBs (Zr-OMc) are present over the whole range of composition. At low Zr-OMc contents (rel. mol. Zr % <30) the clusters are well-dispersed within the di-ureasil host, whereas segregation occurs at the 0.1 mu m scale at high Zr-OMc concentration (rel. mol. Zr % = 50). No Zr-O-Si heterocondensation has been discerned. Monomode waveguides, diffractions gratings, and Fabry-Perot cavities have been written through the exposure of the hybrid monoliths to UV light. FT-Raman has shown that the chemical process that takes place under illumination is the polymerization of the methacrylate groups of the Zr-OMc NBBs. The guidance region in patterned channels is a Gaussian section located below the exposed surface with typical dimensions of 320 mu m wide and 88 mu m deep. The effective refractive index is 1.5162 (maximum index contrast on the order of 1 x 10(-4)) and the reflection coeficient of the Fabry-Perot cavity (formed by a grating patterned into a 0.278 cm channel) is 0.042 with a free spectral range value of 35.6 GHz.

A systematic study of transfection efficiency and cytotoxicity in HeLa cells using iron oxide nanoparticles prepared with organic and inorganic bases

Magnetic iron oxide nanoparticles (magnetite) (MNPs) were prepared using different organic and inorganic bases. Strong inorganic base (KOH) and organic bases (NH4OH and 1,4-diazabicyclo[2.2.2]octane (DABCO)) were used in the syntheses of the MNPs. The MNPs were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FT-IR) and magnetization measurements. MNPs prepared with strong inorganic base yielded an average size of 100 nm, whereas the average size of the MNPs prepared with the organic bases was 150 nm. The main competitive phase for MNPs prepared with the strong inorganic and organic bases was maghemite; however, syntheses with KOH yielded a pure magnetite phase. The transfection study performed with the MNPs revealed that the highest transfection rate was obtained with the MNPs prepared with KOH (74%). The correlation between the magnetic parameters and the transfection ratio without transfection agents indicated that MNPs prepared with KOH were a better vector for possible applications of these MNPs in biomedicine. HeLa cells incubated with MNP-KOH at 10 mu g/mL for 24 and 48 h exhibited a decrease in population in comparison with the control cells and it was presumably related to the toxicity of the MNPs. However, the cells incubated with MNP-KOH at 50 and 100 mu g/mL presented a very small difference in the viability between the cell populations studied at 24 and 48 h. These data illustrate the viability of HeLa cells treated with MNP-KOH and suggest the potential use of these MNPs in biomedical applications. (C) 2012 Elsevier B.V. All rights reserved.