Search results for "Particle size"

Conditioning following powder micronization: influence on particle growth of salbutamol sulfate.

2003

Micronization is a high-energy process that induces changes in the crystallinity of materials. As a result, the crystalline structures on the particles' surface are being destroyed and amorphous areas are formed. After micronization of salbutamol sulfate to be used in dry powder inhalers, only small amounts of amorphous material are produced. Nevertheless, even these small amounts can have important effects on the physical stability of the powder. The amorphous state is thermodynamically unstable and tends to convert to the stable, crystalline state. The recrystallization process of disordered regions on the particles' surface leads to particle growth of milled particles. In this case, brid…

Entrapment of Phenytoin into Microspheres of Oleaginous Materials: Process Development and in Vitro Evaluation of Drug Release

1997

AbstractA novel multiparticulate preparation of the antiepileptic agent phenytoin (1) was developed and evaluated in vitro. The preparation consists of gastroresistant microparticulate drug delivery system formulated with oleaginous material (lipospheres) to minimize unwanted effects of l on gastric apparatus. The drug was dispersed in a spherical micromatrix consisting of a mixture of stearyl alcohol and glycerol esters of various fatty acids. The best mixture to obtain discrete, reproducible, free-flowing lipospheres consisted of glyceryl monostearate dilaurate and stearyl alcohol (ratio 3: 17). The lipospheres were obtained by a technique involving melting and dispersion of drug-containi…

Preparation of white beeswax microspheres loaded with valproic acid and kinetic study of drug release

1995

AbstractThe well known antiepileptic valproic acid (1) due to the long treatment of epilepsy may induce many adverse side effects on various systems. To minimize unwanted toxic effects by kinetic control of drug release, 1 was physically entrapped into white beeswax microspheres using the meltable dispersion process utilizing wetting agents. Solid, discrete, reproducible free flowing microspheres were obtained converting the liquid drug droplets into solid material. The average drug content was 17% w/w. More than 95% of the isolated microspheres were of particle size range 200-425 µm. The microspheres were analyzed to quantify the amount of incorporated drug and to characterize the in vitro…

Carnauba wax microspheres loaded with valproic acid: Preparation and evaluation of drug release

1995

AbstractTo minimize unwanted toxic effects of valproic acid (1) by the kinetic control of drug release, gastroresistant carnauba wax microspheres loaded with the antiepileptic agent were prepared. The preparation was based on a technique involving melting and dispersion of drug-containing wax in an aqueous medium. The resulting emulsion after cooling under rapid stirring produced solid, discrete, reproducible free flowing microspheres which converted the liquid drug droplets into solid material. About 94% of the isolated microspheres were of particle size range 200-425 μm. The microspheres were analyzed to determine the drug content in various particle size range and to characterize the in …

Hydrolytic action of phospholipase A2 in monolayers in the phase transition region: direct observation of enzyme domain formation using fluorescence …

1990

Phospholipase A2, a ubiquitous lipolytic enzyme highly active in the hydrolysis of organized phospholipid substrates, has been characterized optically in its action against a variety of phospholipid monolayers using fluorescence microscopy. By labeling the enzyme with a fluorescent marker and introducing it into the subphase of a Langmuir film balance, the hydrolysis of lipid monolayers in their liquid-solid phase transition region could be directly observed with the assistance of an epifluorescence microscope. Visual observation of hydrolysis of different phospholipid monolayers in the phase transition region in real-time could differentiate various mechanisms of hydrolytic action against …

Thermodynamic considerations of the grain size dependency of material properties

1994

Phase transitions which depend on grain size induce very interesting properties in materials such as zirconia or barium titanate. A new and rigorous thermodynamic treatment of this type of phase transition is proposed with consideration of the surface phenomena. An interpretation is given of the observed differences when the material—particularly BaTiO3—under consideration is a fine grain powder or is a fine grain ceramic.

Nanosized shape-changing colloids from liquid crystalline elastomers.

2010

A method to prepare shape-changing nanospheres from liquid crystalline elastomers is reported. The nanosized colloids are prepared by a miniemulsion process. During this process, colloids are prepared from a liquid crystalline (LC) main-chain polyester and subsequently crosslinked into a nanometer-sized LC elastomer. The ability of these LC elastomers to change their shape at the phase transition temperature from the smectic A to the isotropic phase was detected by temperature-dependent transmission electron microscopy. The phase transition-induced shape change leads to strongly shape anisotropic nanosized elastomer particles.

Photosensitised Seeding of Thiolate-Stabilised Gold Nanoparticles

2010

Growth of tin oxide thin films composed of nanoparticles on hydrophilic and hydrophobic glass substrates by spray pyrolysis technique

2015

Abstract In this paper, we have demonstrated the growth of tin oxide (SnO 2 ) thin films composed of nanoparticles on hydrophobic (siliconized) and hydrophilic (non-siliconized) glass substrates by using the spray pyrolysis technique. X-ray diffraction (XRD) analysis confirmed the formation of SnO 2 thin films with tetragonal rutile-phase structure. Average particle size of nanoparticles was determined to be in the range of 3–4 nm measured from the front view images obtained by a field emission gun scanning electron microscope (FESEM), while the size of nanoparticle clusters, when present, were in the range of 11–20 nm. Surface morphology of SnO 2 films grown over hydrophobic substrates rev…

Modification of Structural and Luminescence Properties of Graphene Quantum Dots by Gamma Irradiation and Their Application in a Photodynamic Therapy

2015

Herein, the ability of gamma irradiation to enhance the photoluminescence properties of graphene quantum dots (GQDs) was investigated. Different doses of gamma-irradiation were used on GQDs to examine the way in which their structure and optical properties can be affected. The photoluminescence quantum yield was increased six times for the GQDs irradiated with high doses compared to the nonirradiated material. Both photoluminescence lifetime and values of optical band gap were increased with the dose of applied gamma irradiation. In addition, the exploitation of the gamma-irradiated GQDs as photosensitizers was examined by monitoring the production of singlet oxygen under UV illumination. T…