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Wet Gels (wet + gel)
Selected AbstractsModifications in the correlation function in poly(vinyl alcohol)/silica hybrid wet gelsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2009Dimas R. Vollet Small-angle X-ray scattering was used to study structural modifications in tetraethoxysilane-derived poly(vinyl alcohol) (PVA)/silica hybrids. The basic structure of the wet gels can be described as a mass-fractal structure with fractal dimension D equal to 2 and characteristic length ,, which increases with addition of PVA. Wet gels with high PVA content exhibit a positive deviation from the mass-fractal power-law scattering at low q; this deviation is associated with additional scattering due to a second large correlation distance ,, reinforced by the addition of PVA. The fraction of both contributions to the total correlation function was estimated; this is the first time that such a study has been carried out for mass-fractal structures. [source] Covalent immobilization of ,-galactosidase on carrageenan coated with chitosanJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Magdy M.M. Elnashar Abstract ,-Galactosidase was covalently immobilized to carrageenan coated with chitosan for the hydrolysis of lactose. The chitosan-carrageenan polyelectrolyte interaction was found to be dependent on the chitosan pH. At pH 4, the chitosan reached its maximum binding of 28.5% (w/w) where the chitosan surface density was 4.8 mg chitosan/cm2 g of carrageenan gel disks, using Muzzarelli method. Glutaraldehyde was used as a mediator to incorporate new functionality, aldehydic carbonyl group, to the bio-polymers for covalent attachment of ,-galactosidase. The enzyme was covalently immobilized to the biopolymer at a concentration of 2.73 mg protein per g of wet gel. FTIR proved the incorporation of the aldehydic carbonyl group to the carrageenan coated with chitosan at 1720 cm,1. The optimum time for enzyme immobilization was found to be 16 h, after which a plateau was reached. The enzyme loading increased from 2.65 U/g (control gel) to 10.92 U/g gel using the covalent technique. The gel's modification has shown to improve the carrageenan gel thermal stability as well as the immobilized enzyme. For example, the carrageenan gel treated with chitosan showed an outstanding thermal stability at 95°C compared with 35°C for the untreated carrageenan gel. Similarly, the immobilization process shifted the enzyme's optimum temperature from 50°C for the free enzyme towards a wider temperature range 45,55 °C indicating that the enzyme structure is strengthened by immobilization. In brief, the newly developed immobilization method is simple; the carrier is cheap, yet effective and can be used for the immobilization of other enzymes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Modifications in the correlation function in poly(vinyl alcohol)/silica hybrid wet gelsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2009Dimas R. Vollet Small-angle X-ray scattering was used to study structural modifications in tetraethoxysilane-derived poly(vinyl alcohol) (PVA)/silica hybrids. The basic structure of the wet gels can be described as a mass-fractal structure with fractal dimension D equal to 2 and characteristic length ,, which increases with addition of PVA. Wet gels with high PVA content exhibit a positive deviation from the mass-fractal power-law scattering at low q; this deviation is associated with additional scattering due to a second large correlation distance ,, reinforced by the addition of PVA. The fraction of both contributions to the total correlation function was estimated; this is the first time that such a study has been carried out for mass-fractal structures. [source] Ketoprofen nanoparticle gels formed by evaporative precipitation into aqueous solutionAICHE JOURNAL, Issue 7 2006Xiaoxia Chen Abstract Aqueous nanoparticle gels of a poorly-water soluble drug, ketoprofen, were produced by evaporative precipitation into aqueous solution (EPAS). Liquid droplets of surfactant stabilized ketoprofen containing residual solvent were dispersed in water from 60 to 90°C below the melting point of pure ketoprofen. The carboxylic acid group in ketoprofen dissociates in pure water, providing electrostatic stabilization of the droplets to complement steric stabilization. Stable amorphous ketoprofen particles with a mean size of 135 nm, measured by dynamic light scattering, were formed with only 0.1% w/v poloxamer 407, resulting in an exceptionally high drug-to-surfactant ratio of 10:1. For 5% w/v poloxamer 407, interactions with ketoprofen produced a bluish, transparent gel composed of ,50 nm particles. In 2 min, 98% of the ketoprofen in the gel nanoparticles dissolved. The favorable interactions between the ketoprofen and poloxamer 407, along with the electrostatic and steric stabilization, lead to gelation, which further stabilizes the unusually small particles. The rapidly dissolving wet gels with extremely small particle sizes, one month stability, and relatively low viscosities, are of interest in transdermal and parenteral delivery; furthermore, the gels may be dried for oral delivery. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] | ||||||||||