Search results for "poros"
showing 10 items of 1076 documents
Enzyme-Controlled Nanodevice for Acetylcholine-Triggered Cargo Delivery Based on Janus Au–Mesoporous Silica Nanoparticles
2017
[EN] This work reports a new gated nanodevice for acetylcholine-triggered cargo delivery. We prepared and characterized Janus Au-mesoporous silica nanoparticles functionalized with acetylcholinesterase on the Au face and with supramolecular b-cyclodextrin: benzimidazole inclusion complexes as caps on the mesoporous silica face. The nanodevice is able to selectively deliver the cargo in the presence of acetylcholine via enzyme-mediated acetylcholine hydrolysis, locally lowering the pH and opening the supramolecular gate. Given the key role played by ACh and its relation with Parkinson's disease and other nervous system diseases, we believe that these findings could help design new therapeuti…
Bio-inorganic Nanomaterials for Biomedical Applications (Bio-silica and Polyphosphate)
2014
Bio-silica represents the main mineral component of the sponge skeletal elements (siliceous spicules), while bio-polyphosphate (polyP), a multifunctional polymer existing in microorganisms and animals, acts, among others, as reinforcement for pores in cell membranes. These natural inorganic bio-polymers, which can be readily prepared, either by recombinant enzymes (bio-silica and polyP) or chemically (polyP), are promising materials/substances for the amelioration and/or treatment of human bone diseases and dysfunctions. Bone defects in human, caused by fractures/nonunions or trauma, have an increasing impact and have become a medical challenge in the present-day aging population. Frequentl…
Growth of human cells on polyethersulfone (PES) hollow fiber membranes.
2004
A novel material of porous hollow fibers made of polyethersulfone (PES) was examined for its ability to support the growth of human cells. This material was made in the absence of solvents and had pore diameters smaller than 100 microm. Human cell lines of different tissue and cell types (endothelial, epithelial, fibroblast, glial, keratinocyte, osteoblast) were investigated for adherence, growth, spread and survival on PES by confocal laser microscopy after staining of the cells with Calcein-AM. Endothelial cell attachment and growth required pre-coating PES with either fibronectin or gelatin. The other cell types exhibited little difference in growth, spread or survival on coated or uncoa…
Design of enzyme-mediated controlled release systems based on silica mesoporous supports capped with ester-glycol groups
2012
[EN] An ethylene glycol-capped hybrid material for the controlled release of molecules in the presence of esterase enzyme has been prepared. The final organic-inorganic hybrid solid S1 was synthesized by a two-step procedure. In the first step, the pores of an inorganic MCM-41 support (in the form of nanoparticles) were loaded with [Ru(bipy) 3]Cl 2 complex, and then, in the second step, the pore outlets were functionalized with ester glycol moieties that acted as molecular caps. In the absence of an enzyme, release of the complex from aqueous suspensions of S1 at pH 8.0 is inhibited due to the steric hindrance imposed by the bulky ester glycol moieties. Upon addition of esterase enzyme, del…
Investigation of characterizing methods for the microstructure of cement
2002
Volumetric, gravimetric, calorimetric, flow methods, mercury porosimetry and laser granulometry were used to investigate the surface structure and the sorption behavior of industrial cements and hydrated cement paste. The suitability of the measuring methods is assessed.
Preparation of synthetic sandstones with variable cementation for studying the physical properties of granular rocks
1997
In this article, we report a new set of procedures to fabricate synthetic analogues of granular rocks. These procedures permit accurate control of the most important structural parameters (i.e., grain size, porosity, cement content). We were thus able to prepare two varieties of synthetic sandstones in which only the cement content significantly varied. Our procedures were also particularly successful in producing materials that were very similar to natural rocks. To demonstrate this similarity, we compared the microstructure, the mechanical properties (i.e., strength, elastic moduli) and the mechanical behaviour (i.e., brittle or ductile) of the synthetic materials to those of various natu…
Porous structure and mechanical strength of cement-lime pastes during setting
2015
Abstract The acceleration of a cement paste setting as a result of lime addition may be shown from isothermal calorimetry measurements. We investigated the underlying mechanisms through two techniques that provide information on porous structure (using Nuclear Magnetic Resonance) and mechanical properties (elastic modulus measured by rheometry). The correlation of the two sets of results on a cement paste clearly reveals the successive steps of setting, and particularly highlights the so-called induction period. We show that this induction period disappears in the presence of lime, leading to an acceleration of the setting. We also show that beyond some critical concentration of added lime …
On the physico-chemical evolution of low-pH and CEM I cement pastes interacting with Callovo-Oxfordian pore water under its in situ CO2 partial press…
2014
International audience; Abstract Within the framework of geological repositories for radioactive waste, structural concretes must be adapted to the underground chemical conditions. CEM I cement-based materials are characterised by high pH that may produce an alkaline plume in the near-field of the repository. In order to avoid this problem, low-pH cements have been designed. This study compares the physico-chemical behaviour of a low-pH material with a CEM I cement paste, both being subjected to leaching by an aqueous solution. An original experimental setup was designed to reproduce the underground conditions using a specific CO2 regulation device. Under these conditions, the low-pH materi…
Mesoporous Silica Nanoparticles in Chemical Detection: From Small Species to Large Bio-Molecules
2021
A recompilation of applications of mesoporous silica nanoparticles in sensing from the last five years is presented. Its high potential, especially as hybrid materials combined with organic or bio-molecules, is shown. Adding to the multiplying effect of loading high amounts of the transducer into the pores, the selectivity attained by the interaction of the analyte with the layer decorating the material is described. Examples of the different methodologies are presented.
Convective mass transfer to partially recessed and porous electrodes
2003
Abstract The diffusional problem of a rotating porous electrode has been analysed based on the mass transfer equations for a partially blocked electrode. It is shown that the porous geometry leads to a dependence of the current on rotation rate identical to that corresponding to a coupled diffusion-activated electron transfer mechanism. The apparent rate constant, however, is related only to the geometry of the porous surface. It is shown that the characteristic diffusional length corresponds to the pore dimension modified by a term including the transition from linear to spherical diffusional geometry at the pore entrance. The theory is compared with experimental results for the reduction …