Bioencapsulation in Sol-Gel Glasses

1998 ◽  
Vol 519 ◽  
Author(s):  
L. Bergogne ◽  
S. Fennouh ◽  
J. Livage ◽  
C. Roux
Keyword(s):  
Sol Gel ◽  
Porous Silica ◽  
Silica Matrix ◽  
Whole Cells ◽  
The Past ◽  
Wide Range ◽  
Activity Of Enzymes ◽  
Gel Glasses ◽  
Micro Organisms

AbstractBioencapsulation in sol-gel materials has been widely studied during the past decade. Trapped species appear to retain their bioactivity in the porous silica matrix. Small analytes can diffuse through the pores allowing bioreactions to be performed in-situ, inside the sol-gel glass. A wide range of biomolecules and micro-organisms have been encapsulated. The catalytic activity of enzymes is used for the realization of biosensors or bioreactors. Antibody-antigen recognition has been shown to be feasible within sol-gel matrices. Trapped antibodies bind specifically the corresponding haptens and can be used for the detection of traces of chemicals. Even whole cells are now encapsulated without any alteration of their cellular organization. They can be used for the production of chemicals or as antigens for immunoassays.

In Situ Studies of the Processing of Sol-Gel Produced Amorphous Materials Using Xanes, Saxs and Curved Image Plate XRD

1999 ◽  
Vol 590 ◽  
Author(s):  
DM Pickup ◽  
G Mountjoy ◽  
RJ Newport ◽  
ME Smith ◽  
GW Wallidge ◽  
...  
Keyword(s):  
Amorphous Materials ◽  
Sol Gel ◽  
Heat Treatments ◽  
Silica Gels ◽  
Ex Situ ◽  
High Count ◽  
X Ray ◽  
Image Plate ◽  
Wide Range

ABSTRACTSol-gel produced mixed oxide materials have been extensively studied using conventional, ex situ structural techniques. Because the structure of these materials is complex and dependent on preparation conditions, there is much to be gained from in situ techniques: the high brightness of synchrotron x-ray sources makes it possible to probe atomic structure on a short timescale, and hence in situ. Here we report recent results for mixed titania- (and some zirconia-) silica gels and xerogels. Titania contents were in the range 8–18 mol%, and heat treatments up to 500°C were applied. The results have been obtained from intrinsically rapid synchrotron x-ray experiments: i) time-resolved small angle scattering, using a quadrant detector, to follow the initial stages of aggregation between the sol and the gel; ii) the use of a curved image plate detector in diffraction, which allowed the simultaneous collection of data across a wide range of scattering at high count rate, to study heat treatments; and iii) x-ray absorption spectroscopy to explore the effects of ambient moisture on transition metal sites.

Sol-Gel Elaboration and Optical Features of Eu3+-Doped CdS Nanocrystals in SiO2

2007 ◽  
Vol 555 ◽  
pp. 389-393 ◽  
Author(s):  
B. Julián ◽  
J. Planelles ◽  
E. Cordoncillo ◽  
P. Escribano ◽  
C. Sanchez ◽  
...  
Keyword(s):  
Sol Gel ◽  
Silica Matrix ◽  
Cds Nanoparticles ◽  
Rare Earth Ion ◽  
Sio2 Matrix ◽  
Chemical Homogeneity ◽  
Synthesis Conditions ◽  
Cds Nanocrystals ◽  
Back Transfer

In this work, Eu3+-doped CdS nanocrystals embedded in a SiO2 matrix were synthesised by a sol-gel method since this method confers a great chemical homogeneity, and allows in-situ generation and controlled growth of CdS nanocrystals within the silica glass. The influence of the sol-gel conditions on the Eu3+ optical response has been investigated. The synthesis conditions can be varied to modify the structure of the material, and the dispersion of the rare earth ion, within the silica matrix. From the optical analysis an energy transfer appears from CdS nanoparticles to Eu3+ ions but also a back transfer Eu3+ to CdS nanoparticles is evidenced.

Matrix-Assisted Formation of Metal Nanoparticles in Organosilica Sol-Gels

2002 ◽  
Vol 726 ◽  
Author(s):  
Sandie H. Cheung ◽  
Bakul C. Dave
Keyword(s):  
Metal Nanoparticles ◽  
Chemical Reduction ◽  
Sol Gel ◽  
Synthesis Method ◽  
Porous Silica ◽  
Ambient Conditions ◽  
Transmission Electron ◽  
Organically Modified ◽  
Structural Template

AbstractThe use of organosilica sol-gels for controlled in-situ formation of metal nanoparticles is investigated. The use of an organically-modified alkoxysilane precursor provides chemically interacting nanopores for the sequestration and binding of metal ions followed by chemical reduction to form metal nanoparticles. The sol-gel matrix acts as a structural template to enable growth of the metal nanoparticles within its porous silica framework, and prevents clustering to form precipitate. Furthermore, simple redox chemistry is used to convert pre-formed copper nanoparticles in the sol-gel matrix into silver and gold nanoparticles. A particularly important aspect of this synthesis method is that all the reaction chemistry is performed under ambient conditions. The particles are characterized by high resolution transmission electron microscopy for their sizes and size distribution. The elemental composition of the particles is determined by energy dispersive X-ray analysis.

Differential sensitivity of 16S rRNA targeted oligonucleotide probes used for fluorescence in situ hybridization is a result of ribosomal higher order structure

1996 ◽  
Vol 42 (10) ◽  
pp. 1061-1071 ◽  
Author(s):  
Marc E. Frischer ◽  
Peter J. Floriani ◽  
Sandra A. Nierzwicki-Bauer
Keyword(s):  
In Situ Hybridization ◽  
16S Rrna ◽  
Fluorescence In Situ Hybridization ◽  
Differential Sensitivity ◽  
Probe Design ◽  
Oligonucleotide Probes ◽  
Whole Cells ◽  
Gene Probes ◽  
Wide Range

The use of 16S rRNA targeted gene probes for the direct analysis of microbial communities has revolutionized the field of microbial ecology, yet a comprehensive approach for the design of such probes does not exist. The development of 16S rRNA targeted oligonucleotide probes for use with fluorescence in situ hybridization (FISH) procedures has been especially difficult as a result of the complex nature of the rRNA target molecule. In this study a systematic comparison of 16S rRNA targeted oligonucleotide gene probes was conducted to determine if target location influences the hybridization efficiency of oligonucleotide probes when used with in situ hybridization protocols for the detection of whole microbial cells. Five unique universal 12-mer oligonucleotide sequences, located at different regions of the 16S rRNA molecule, were identified by a computer-aided sequence analysis of over 1000 partial and complete 16S rRNA sequences. The complements of these oligomeric sequences were chemically synthesized for use as probes and end labeled with either [γ-32P] ATP or the fluorescent molecule tetramethylrhodamine-5/-6. Hybridization sensitivity for each of the probes was determined by hybridization to heat-denatured RNA immobilized on blots or to formaldehyde fixed whole cells. All of the probes hybridized with equal efficiency to denatured RNA. However, the probes exhibited a wide range of sensitivity (from none to very strong) when hybridized with whole cells using a previously developed FISH procedure. Differential hybridization efficiencies against whole cells could not be attributed to cell wall type, since the relative probe efficiency was preserved when either Gram-negative or -positive cells were used. These studies represent one of the first attempts to systematically define criteria for 16S rRNA targeted probe design for use against whole cells and establish target site location as a critical parameter in probe design.Key words: 16S rRNA, oligonucleotide probes, in situ hybridization.

VOC decomposition over a wide range of temperatures using thermally stable Cr6+ sites in a porous silica matrix

2015 ◽  
Vol 72 ◽  
pp. 161-164 ◽  
Author(s):  
Shoichi Somekawa ◽  
Hiroto Watanabe ◽  
Yuya Oaki ◽  
Hiroaki Imai
Keyword(s):  
Porous Silica ◽  
Silica Matrix ◽  
Thermally Stable ◽  
Wide Range

scholarly journals Magnetic Study of CuFe2O4-SiO2 Aerogel and Xerogel Nanocomposites

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2680
Author(s):  
Alizé V. Gaumet ◽  
Francesco Caddeo ◽  
Danilo Loche ◽  
Anna Corrias ◽  
Maria F. Casula ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Sol Gel ◽  
Porous Silica ◽  
Chemical Properties ◽  
Silica Matrix ◽  
Superparamagnetic Nanoparticles ◽  
Blocking Temperature ◽  
Copper Ferrite ◽  
Transmission Electron ◽  
Magnetic Features

CuFe2O4 is an example of ferrites whose physico-chemical properties can vary greatly at the nanoscale. Here, sol-gel techniques are used to produce CuFe2O4-SiO2 nanocomposites where copper ferrite nanocrystals are grown within a porous dielectric silica matrix. Nanocomposites in the form of both xerogels and aerogels with variable loadings of copper ferrite (5 wt%, 10 wt% and 15 wt%) were synthesized. Transmission electron microscopy and X-ray diffraction investigations showed the occurrence of CuFe2O4 nanoparticles with average crystal size ranging from a few nanometers up to around 9 nm, homogeneously distributed within the porous silica matrix, after thermal treatment of the samples at 900 °C. Evidence of some impurities of CuO and -Fe2O3 was found in the aerogel samples with 10 wt% and 15 wt% loading. DC magnetometry was used to investigate the magnetic properties of these nanocomposites, as a function of the loading of copper ferrite and of the porosity characteristics. All the nanocomposites show a blocking temperature lower than RT and soft magnetic features at low temperature. The observed magnetic parameters are interpreted taking into account the occurrence of size and interaction effects in an ensemble of superparamagnetic nanoparticles distributed in a matrix. These results highlight how aerogel and xerogel matrices give rise to nanocomposites with different magnetic features and how the spatial distribution of the nanophase in the matrices modifies the final magnetic properties with respect to the case of conventional unsupported nanoparticles.

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