Search results for "microsphere"
showing 10 items of 108 documents
Characterization of materials toward toluene traces detection for air quality monitoring and lung cancer diagnosis
2017
International audience; The aim of this work was to identify a nanoporous material able to trap toluene traces in order to develop a gas detection device for indoor air quality monitoring or biomedical diagnosis. A set of various adsorbents such as zeolites and activated carbon microspheres was studied here. First a detailed characterization of their porous properties was performed by nitrogen adsorption. Then adsorption of toluene and other interfering compounds which can selectively adsorbed with it, such as water and carbon dioxide, was studied in order to select the most suitable material. Results revealed that the activatedcarbon microspheres W5 and the zeolite NaY, which exhibit high …
Adhesion and Friction Forces between Spherical Micrometer-Sized Particles
1999
An experimental setup, based on the principles of atomic force microscopy (AFM), was used to measure directly the adhesion and rolling-friction forces between individual silica microspheres of radii between 0.5 and 2.5 \ensuremath{\mu}m. It showed that the linear dependence of the pull-off force on the particle radius is still valid for micron-sized particles. Rolling-friction forces between silica microspheres were measured for the first time by combining AFM methods and optical microscopy: They are $\ensuremath{\sim}100$ times lower than the corresponding adhesion forces.
Fibrin-chitosan composite substrate for in vitro culture of chondrocytes
2013
The aim of this study was to develop a biocompatible monolayer substrate based on fibrin and chitosan for in vitro culture of chondrocytes. Fibrin-chitosan composite substrates combined the proved cell adhesion properties of fibrin with the hydrophilicity and poor adhesion capacity of chitosan. Chitosan microspheres were produced by coacervation method, agglomerated within a fibrin network and subsequently crosslinked with genipin. The composite substrate was stable for 28 days of culture due to the high crosslinking density. Human chondrocytes cultured on the composite substrate were viable during the culture period. At the end of culture time (28 days) the composite substrate showed low c…
Drug release from alpha,beta-poly(N-2-hydroxyethyl)-DL-aspartamide-based microparticles.
2004
Abstract Spherical pH-sensitive microparticles have been prepared by reverse phase suspension polymerization technique. Starting polymer has been α , β -poly( N -2-hydroxyethyl)- dl -aspartamide (PHEA) partially derivatized with glycidylmethacrylate (GMA). PHEA-GMA copolymer (PHG) has been crosslinked in the presence of acrylic acid (AA) or methacrylic acid (MA) at various concentration. The obtained microparticles have been characterized by FT-IR spectrophotometry, particle size distribution analysis and scanning electron microscopy. In order to have information about water affinity of the prepared samples, swelling measurements have been carried out in aqueous media which simulate some bi…
Bioinspired Fabrication of Bio-Silica-Based Bone-Substitution Materials
2010
The gold standard for bone reconstruction is the use of autogeneic grafts from various donor regions, since they possess osteoinductive as well as osteoconductive potential. Only a few synthetic materials possess/display properties that allow optimal bone reconstitution. Previously, we showed that the natural product, bio-silica, comprises osteoinductive, and probably also osteoconductive activity. Bio-silica is formed enzymatically via silicatein; this enzyme has been isolated from siliceous sponges and has also been cloned and prepared recombinantly. In the present study, silicatein was encapsulated together with its substrate, sodium metasilicate, in poly(D,L-lactide)/poly(vinyl pyrrolid…
Response charactterization of ammonium tartrate solid state pellets for ESR dosimetry with radiotherapeutic photon and electron beams.
2001
Solid state pellets (1 mm thick) for electron spin resonance (ESR) dosimetry were made using ammonium tartrate as the radiation-sensitive substance. Their behaviour was experimentally investigated as a function of dose with 60Co gamma rays. The calibration function obtained permits measurements of absorbed dose in the 2-50 Gy range, with a combined uncertainty of +/-4%. The lowest detectable dose was about 0.5 Gy. These properties are comparable with or even better than those of ESR dosimeters made from other materials. The time stability of the ESR signal of ammonium tartrate dosimeters at different storage conditions after irradiation was studied. A rather complex behaviour was observed, …
Germanium microparticles as optically induced oscillators in optical tweezers
2019
Oscillatory dynamics is a key tool in optical tweezers applications. It is usually implemented by mechanical interventions that cannot be optically controlled. In this work we show that Germanium semiconductor beads behave as optically induced oscillators when subjected to a highly focused laser beam. Such unusual motion is due to the competition between the usual optical forces [1-3] and the radiometric force related to thermal effects, which pushes the beads from the focal region [4]. We characterize the behavior of the Germanium beads in detail and propose a model accounting for the related forces, in good agreement with the experimental data. The well defined direction of oscillations c…
Immobilization and controlled release of prostaglandin E2 from poly-L-lactide-co-glycolide microspheres.
2009
Prostaglandin E(2) (PGE(2)) is an arachidonic acid metabolite involved in physiological homeostasis and numerous pathophysiological conditions. Furthermore, it has been demonstrated that prostaglandins have a stimulating effect not only on angiogenesis in situ and in vitro but also on chondrocyte proliferation in vitro. Thus, PGE(2) represents an interesting signaling molecule for various tissue engineering strategies. However, under physiological conditions, PGE(2) has a half-life time of only 10 min, which limits its use in biomedical applications. In the present study, we investigated if the incorporation of PGE(2) into biodegradable poly-L-lactide-co-glycolide microspheres results in a …
Amoxicillin-loaded polyethylcyanoacrylate nanoparticles: influence of PEG coating on the particle size, drug release rate and phagocytic uptake.
2001
Polyethyleneglycol (PEG)-coated polyethylcyanoacrylate (PECA) nanoparticles loaded with amoxicillin were prepared and the influence of the PEG coating on the particle size, zeta potential, drug release rate and phagocytic uptake by murine macrophages was studied. Experimental results show that this colloidal drug delivery system could be useful for intravenous or oral administration. The profile of amoxicillin release from PECA nanoparticles system was studied under various conditions similar to those of some corporeal fluids. In all these experiments, amoxicillin release in the free form was studied by HPLC analysis. Experimental results showed that at pH 7.4 drug release rises when molecu…
Quantum Dots Luminescence Collection Enhancement and Nanoscopy by Dielectric Microspheres
2019
In recent years, dielectric microspheres have been used in conjunction with optical microscopes to beat the diffraction limit and to obtain superresolution imaging. The use of microspheres on quantum dots (QDs) is investigated, for the first time, to enhance the light coupling efficiency. The enhancement of the QD luminescence collection in terms of extraction and directionality is demonstrated, as well as the enhancement of spatial resolution. In particular, it is found that a dielectric microsphere, placed on top of an epitaxial QD, increases the collected radiant energy by about a factor of 42, when a low numerical aperture objective is used. Moreover, if two or more QDs are present belo…