Search results for "silicon dioxide"
showing 10 items of 278 documents
Multifunctional two-photon active silica-coated Au@MnO Janus particles for selective dual functionalization and imaging.
2014
Monodisperse multifunctional and nontoxic Au@MnO Janus particles with different sizes and morphologies were prepared by a seed-mediated nucleation and growth technique with precise control over domain sizes, surface functionalization, and dye labeling. The metal oxide domain could be coated selectively with a thin silica layer, leaving the metal domain untouched. In particular, size and morphology of the individual (metal and metal oxide) domains could be controlled by adjustment of the synthetic parameters. The SiO2 coating of the oxide domain allows biomolecule conjugation (e.g., antibodies, proteins) in a single step for converting the photoluminescent and superparamagnetic Janus nanopar…
Biofabrication of biosilica-glass by living organisms
2008
Biosilicification is an evolutionarily old and widespread type of biomineralization both in unicellular and multicellular organisms, including sponges, diatoms, radiolarians, choanoflagellates, and higher plants. In the last few years combined efforts in molecular biology, cell biology, and inorganic and analytical chemistry have allowed the first insight into the molecular mechanisms by which these organisms form an astonishing variety of siliceous structures that cannot be achieved by chemical methods. Here we report about the present stage of knowledge on structure, biochemical composition, and mechanisms of biosilica formation, focusing our attention particularly on sponges because of t…
Evaluation of 2,3-epoxypropyl groups and functionalization yield in glycidyl methacrylate monoliths using gas chromatography
2014
Abstract Poly(glycidyl methacrylate- co -ethylene dimethacrylate) (poly(GMA- co -EDMA)) is most frequently used as parent monolith to obtain stationary phases with a variety of surface chemistries for liquid chromatography and capillary electrochromatography. Functionalization is performed by opening the accessible 2,3-epoxypropyl groups of the monolith with a suitable reagent. The number of 2,3-epoxypropyl groups which are accessible before and after the functionalization reaction, and the grafting yield, are important parameters, required both to optimize functionalization and to interpret the chromatographic performance of functionalized monoliths. In this work, a method capable of provi…
Synthesis and Spectroscopic Properties of Silica−Dye−Semiconductor Nanocrystal Hybrid Particles
2010
We prepared silica-dye-nanocrystal hybrid particles and studied the energy transfer from semiconductor nanocrystals (= donor) to organic dye molecules (= acceptor). Multishell CdSe/CdS/ZnS semiconductor nanocrystals were adsorbed onto monodisperse Stöber silica particles with an outer silica shell of thickness 2-23 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the energy transfer efficiency, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of nanocrystals with increasing dye amount. Our conclusions were underlined by…
Mesoporous inorganic nanoscale particles for drug adsorption and controlled release.
2018
The review provides an overview of the mesoporous inorganic particles employed as drug delivery systems for controlled and sustained release of drugs. We have classified promising nanomaterials for drug delivery on the basis of their natural or synthetic origin. Nanoclays are available in different morphologies (nanotubes, nanoplates and nanofibers) and they are typically available at low cost from natural resources. The surface chemistry of nanoclays is versatile for targeted modifications to control loading and release properties. Synthetic nanomaterials (imogolite, laponite and mesoporous silica) present the advantages of well-established purity and availability with size features that …
Efficacy of budesonide-loaded mesoporous silica microparticles capped with a bulky azo derivative in rats with TNBS-induced colitis.
2019
Abstract A colon targeted drug delivery system for inflammatory bowel diseases (IBD), consisting in budesonide loaded mesoporous silica microparticles functionalized with a selective azo-molecular gate (M-Bud), has been evaluated for in vivo efficacy. Experimental colitis in male Wistar rats was induced by rectal instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS). M-Bud was orally administered to the rats as a suspension in water. Colon/body weight ratio, clinical activity score, and histological evaluation were used as inflammatory indices to measure the performance of the microparticles. The formulation was compared with a suspension prepared from the commercial drug Entocord®. Sta…
Inkjet printing methodologies for drug screening
2010
We show for the first time a contactless, low-cost, and rapid drug screening methodology by employing inkjet printing for molecular dispensing in a microarray format. Picoliter drops containing a model substrate (D-glucose)/ inhibitor (D-glucal) couple were accurately dispensed on a single layer consisting of the enzymatic target (glucose oxidase) covalently linked to a functionalized silicon oxide support. A simple colorimetric detection method allowed one to prove the screening capability of the microarray with the possibility to assay with high reproducibility at the single spot level. Measurements of the optical signal as a function of concentration and of time verified the occurrence a…
Luminescence of gamma-radiation-induced defects in alpha-quartz
2004
Optical transitions associated with gamma-radiation-induced defects in crystalline a-quartz were investigated by photoluminescence excited by both pulsed synchrotron radiation and steady-state light. After a 10 MGy gamma-dose we observed two emissions at 4.9 eV (ultraviolet band) and 2.7 eV (blue band) excitable in the range of the induced absorption band at 7.6 eV. These two luminescence bands show a different temperature dependence: the ultraviolet band becomes bright below 80 K; the blue band increases below 180 K, but drops down below 80 K. Both emissions decay in a timescale of a few ns under pulsed excitation, however the blue band could also be observed in slow recombination processe…
Siliceous spicules in marine demosponges (example Suberites domuncula)
2005
All metazoan animals comprise a body plan of different complexity. Since-especially based on molecular and cell biological data-it is well established that all metazoan phyla, including the Porifera (sponges), evolved from a common ancestor the search for common, basic principles of pattern formation (body plan) in all phyla began. Common to all metazoan body plans is the formation of at least one axis that runs from the apical to the basal region; examples for this type of organization are the Porifera and the Cnidaria (diploblastic animals). It seems conceivable that the basis for the formation of the Bauplan in sponges is the construction of their skeleton by spicules. In Demospongiae (w…
Combined Effects of 50 Hz Electromagnetic Field and SiO2 Nanoparticles on Oxidative Stress in Plant’s Gametic Cells / Zemfrekvences (50 Hz) Elekromag…
2015
Abstract The paper presents the results of combined effects of an extremely low frequency electromagnetic field (50 Hz) (ELF EMF) and SiO2 nanoparticles on fluorescence of plant gametic cells (immature microspores). The data were recorded by a BD FACSJazz® cell sorter after cell irradiation by blue laser (488 nm). A significant difference of fluorescence was observed between gametic cells after 1 hour incubation in suspension of SiO2 nanoparticles and the control gametic cells. It was observed that fluorescence intensity of gametic cell was higher with ELF EMF treatment in comparison to control cells, but it was statistically significant only for cells treated with electromagnetic radiation…