Search results for "Particle size"
showing 10 items of 631 documents
Partially Reversible Adsorption of Annexin A1 on POPC/POPS Bilayers Investigated by QCM Measurements, SFM, and DMC Simulations
2005
The kinetics of annexin A1 binding to solid-supported lipid bilayers consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS; 4:1) has been investigated as a function of the calcium ion concentration in the bulk phase. Quartz crystal microbalance measurements in conjunction with scanning force microscopy, fluorescence microscopy, and computer simulations indicate that at a given Ca2+ concentration annexin A1 adsorbs irreversibly on membrane domains enriched in POPS. By contrast, annexin A1 adsorbs reversibly on the POPC-enriched phase, which is composed of single POPS molecules embedded within a POPC matrix. The overall are…
Prostaglandin E(2)-loaded microspheres as strategy to inhibit phagocytosis and modulate inflammatory mediators release.
2008
PGE(2), an arachidonic acid metabolite produced by various type of cells regulates a broad range of physiological activities in the endocrine, cardiovascular, gastrointestinal, and immune systems, and is involved in maintaining the local homeostasis. In the immune system, PGE(2) is mainly produced by APCs and it can suppress the Th1-mediated immune responses. The aim of this study was to develop PGE(2)-loaded biodegradable MS that prolong and sustain the in vivo release of this mediator. An o/w emulsion solvent extraction-evaporation method was chosen to prepare the MS. We determined their diameters, evaluated the in vitro release of PGE(2), using enzyme immunoassay and MS uptake by periton…
Nano into Micro Formulations of Tobramycin for the Treatment of Pseudomonas aeruginosa Infections in Cystic Fibrosis.
2017
Here, nano into micro formulations (NiMs) of tobramycin for the treatment of Pseudomonas aeruginosa airway infections in cystic fibrosis (CF) are described. NiMs were produced by spray drying a solution containing polymers or sugars and a nanometric polyanion–tobramcyin complex (PTC), able to achieve a prolonged antibiotic release. NiMs properties were compared to TOBIPodhaler(Novartis), the only one commercially available dry powder inhalatory formulation based on porous microparticles. Produced NiMs showed adequate characteristics for pulmonary administration, as spherical shape, micrometric size, and high cytocompatibility toward human bronchial epithelial cells. Contrarily to TOBIPodhal…
Phosphorus Loss in Overfertilized Soils: The Selective P Partitioning and Redistribution Between Particle Size Separates
2007
Using 12 well-characterised European soils contrasting in their physical and chemical properties, we demonstrate significant differences in the partitioning of phosphorus (P) between various particle size separates. Samples of each soil were subjected to one of three methods of increasingly aggressive dispersion in the order water (WD), mechanical (MD) or chemical (CD). A general, although not exclusive, inverse relationship existed between the concentration of various attributes (these included organic carbon, oxalate and dithionite iron contents, total P, resin and water extractable P) and particle size. The quantity, composition and physico-chemical properties of individual size separate…
Synthesis and Characterization of Monodisperse Manganese Oxide Nanoparticles−Evaluation of the Nucleation and Growth Mechanism
2009
Magnetic nanoparticles of the 3d transition metal oxides have gained enormous interest for applications in various fields such as data storage devices, catalysis, drug-delivery, and biomedical imaging. One major requirement for these applications is a narrow size distribution of the particles. We have studied the nucleation and growth mechanism for the formation of MnO nanoparticles synthesized by decomposition of a manganese oleate complex in high boiling nonpolar solvents using TEM, FT-IR, and AAS analysis. The exceptionally narrow size distribution indicates that nucleation and growth are clearly separated. This leads to a uniform growth with a very narrow size distribution on the existi…
Multilayer capsules: a promising microencapsulation system for transplantation of pancreatic islets
2001
In 1980, Lim and Sun introduced a microcapsule coated with an alginate/polylysine complex for encapsulation of pancreatic islets. Characteristic to this type of capsule is, that it consists of a plain membrane which is formed during a single procedural step. With such a simple process it is difficult to obtain instantly a membrane optimized with respect to all the properties requested for islet transplantation. To overcome these difficulties, it is recommended to build up the membrane in several consecutive steps, each optimized for a certain property. In this study, we have analysed such a multilayer microcapsule for the encapsulation of pancreatic islets. Therefore, empty and islet contai…
Climatology of the average water-soluble volume fraction of atmospheric aerosol
2007
The average water-soluble volume fraction of atmospheric aerosol particles was inferred from measurements at three different locations across Central Europe. Together with a comprehensive literature review these data sets are classified into four aerosol types. The classified data are parameterized as a function of particle size using a logarithmic normal distribution function, which seems most appropriate to represent the hygroscopicity maximum in the accumulation size range. This parameterization can be used as a simplified input parameter for various model calculations. In addition, a summary on water-soluble volume fractions and hygroscopic growth factors is presented along with a short…
Synthesis of spherical porous silicas in the micron and submicron size range: challenges and opportunities for miniaturized high-resolution chromatog…
2000
Classical silica technology has reached its limit with respect to an ultimate minimum particle size of about 2 microm in diameter. Here, a novel process is presented which allows one to synthesize porous silica beads and control their particle diameter in situ, within the range of 0.2-2.0 microm. As a result, no sizing is required and losses of silica are avoided. Furthermore, the process enables one to control in situ the pore structural parameters and the surface chemistry of the silica beads. Even though surface funtionalized silicas made according to this process can principally be applied in fast HPLC the column pressure drop will be high even for short columns. In addition, the column…
The impact of whey protein preheating on the properties of emulsion gel bead
2014
Thermal treatment effect (70 or 80 °C for 5 or 30 min) was evaluated on functional properties of whey protein isolate (WPI) dispersions used for the development of novel vitamin A delivery systems based on emulsion gel beads. This process combines an (O/W) emulsion diluted by a polysaccharide solution and a cold-set gelation induced by salt addition. Pre-heated WPI had a significant impact on the denaturation degree and on the surface hydrophobicity, respectively studied by differential scanning calorimetry and fluorescence. Stronger heating conditions (i.e. duration or temperature) induced complete denaturation, an increase of surface hydrophobicity and of viscosity. Under these conditions…
Applications of mathematical modelling to the simulation of binary perfusion chromatography
1993
Abstract A mathematical model of binary (competitive adsorption involving two components) perfusion chromatography is used to simulate and study the behavior of a binary adsorption system. The dynamic behavior of column systems (frontal analysis) is examined for different particles sizes, column fluid superficial velocities, Vf, and intraparticle fluid velocities, νp. Column systems with perfusive (νp > 0) and purely diffusive (νp = 0) adsorbent particles are studied. The results obtained from the binary system studied in this work suggest that the times at which breakthrough begins for components 1 and 2, and the dynamic (unsteady state) relative separation between components 1 and 2 obtai…