Drug Release from Microspheres and Nanospheres of Poly(lactide-co-glycolide) without Sphere Separation from the Release Medium

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A new technique using diffuse reflectance spectroscopy was developed that enables the monitoring of encapsulated drug release without particle separation from the assayed medium. Studies of chloro(5,10,15,20-tetraphenylporphyrinato)indium(III) (InTPP) release from microspheres and nanospheres of poly(lactide-co-glycolide) (PLGA) were performed using this new technique. The release of InTPP was biphasic, with an initial fast release followed by a second slower release. Mathematical models applied to the release profiles showed that the release of InTPP from the nanospheres was controlled by diffusion, which is to be expected for a substance homogeneously dispersed within the spheres. However, due to the large size distribution of the microspheres loaded with InTPP, the release profiles were irregular, hampering an adequate fit to mathematical models. Confocal analysis of microparticles showed that the InTPP appeared to be homogenously distributed within the microspheres and no preferential distribution of InTPP towards the interior or towards the surface of the spheres was observed.212214225Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Estadual de CampinasFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

MODIFICATION OF FOAM DRAINAGE BY ELECTROOSMOTIC EFFECT

1664765

PARALLEL ELECTRIC-FIELD IN FLUX RESTORATION DURING ULTRAFILTRATION

Ultrafiltration membrane permeability may be restored by applying an electric field parallel to the plane of the membrane in the feed compartment of ultrafiltration cells. Two different electrode arrangements are described. Under some conditions, flux restoration is complete. An electric field parallel to the membrane can thus be used to eliminate membrane polarization and fouling.26683184

Light-scattering investigation on microemulsion formation in mixtures of diesel oil (or hydrocarbons) plus ethanol plus additives

Ethanol and diesel oil mixtures are potential candidates as fuels which display advantages such as a reduced emission of particulates and the use of a renewable fuel (ethanol). However, their use is hampered because of limited miscibility, especially at lower temperatures. This problem can be overcome with the use of certain additives, which produce increased miscibility. This work investigates the role of these additives in this mixing process, with particular emphasis on assessing earlier propositions that microemulsions are formed in such mixtures. Results obtained from light-scattering measurements provide the first direct evidence for microemulsion formation both in diesel oil and ethanol and in synthetic diesel (a mixture of hydrocarbons that mimic diesel oil properties) and ethanol and additives. The effects of the additive type and concentration, temperature, and volume fraction of the ethanol on these microemulsion droplets' radii are presented, and their trends were found to follow those established for water-in-oil microemulsion systems.21122222

Easy polymer latex self-assembly and colloidal crystal formation: the case of poly[styrene-co-(2-hydroxyethyl methacrylate)]

Poly[styrene-co-(2-hydroxyethyl methacrylate)] core and shell latex particles easily undergo self-ordering, as evidenced by the iridescence of dispersions and dry solids. Microscopic (scanning electron microscopy) observation of the dry latex and fracture surfaces reveals the coexistence of different crystallographic arrangements. Many domains are observed, in which particle positions are correlated for tens of crystallographic planes. Isotherms of latex monolayers were also obtained, showing a strong interparticle repulsion. The ease of particle self-assembly in this latex is assigned to two factors: (i) the existence of strong repulsive interparticle interactions? which allows particle ordering at long distances, while particle diffusion throughout the dispersion is still possible: (ii) the hydrophilic surface layer, which allows for strong capillary adhesion during the whole drying process, according to Nagayama's model (Nature. 361 (1993) 26). (C) 1998 Elsevier Science B.V. All rights reserved.1444169920721

Flexibility of the triblock copolymers modulating their penetration and expulsion mechanism in Langmuir monolayers of dihexadecyl phosphoric acid

The surface activity of the poly-[block (ethylene oxide)]-poly [block (propylene oxide)]-poly [block (ethylene oxide)] copolymers (EO)(x)-(PO)(x)-(EO)(x) adsorbed together with dihexadecyl phosphoric acid (DHP), a synthetic phospholipid. is analyzed from their surface pressure and surface potential isotherms. The block copolymers of (EO)(x)-(PO)(y)-(EO)(x) with variable molecular weight (1100-14000) were dissolved in the subphase for DHP monolayers. The concentration of the copolymers within the aqueous subphase were selected to render an initial surface tension of 60 mN/m. The simultaneous adsorption of the copolymer and DHP is attested by the observation of a liquid expanded state at large areas, absent for pure DHP monolayers, Above some critical surface pressure all copolymers cited above are expelled from the interface. The surface potential isotherms., which give information on the component of the molecular dipole moment normal to the plane of the monolayer, are interpreted in terms of changes in the copolymer conformation as well as in terms of the copolymer desorption from the air-liquid interface. For an equal hydrophobic/hydrophilic ratio. the size of the chains or molecular weight is decisive in the mechanism of the copolymer expulsion from the air-liquid interface. (C) 2001 Elsevier Science B.V. All rights reserved.22430932

ISOTOPIC-SEPARATION OF DEUTERIUM AND PRODUCTION OF HEAVY-WATER

55433935