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Water-in-oil Microemulsion (water-in-oil + microemulsion)
Selected AbstractsStudy of association thermodynamics between crystal violet and sodium bis(2-ethylhexyl)sulfosuccinate and kinetics of basic fading of crystal violet in microemulsionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2008Zhi Yun Chen The thermodynamics of the association between 4,4,,4,-tris(dimethyl-amino)triphenylmethyl chloride (crystal violet or CV) and sodium bis(2-ethylhexyl)-sulfosuccinate (aerosol OT or AOT) in water/AOT/n -decane microemulsion and the kinetics of the basic hydrolysis of CV in a water-in-oil microemulsion were investigated by UV,vis spectroscopic measurements. An association model of CV and AOT was used to analyze the experimental data to obtain the association constants at various temperatures. By taking the association into account, the "actual" rate constants and the activation energies of the basic hydrolysis of CV in the media of water/AOT/oil were obtained. The difference in thermodynamics and kinetics between the two media of water/AOT/n -decane and water/AOT/isooctane is discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 294,300, 2008 [source] IPM/DOSS/water microemulsions as reactors for silver sulfadiazine nanocrystal synthesisJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2005Jerry Nesamony Abstract The first goal of this work was the preparation of a water-in-oil microemulsion from components generally regarded as safe for use in humans. Stable formulations without need of a co-surfactant were prepared from isopropyl myristate (IPM), dioctyl sodium sulfosuccinate (DOSS), and water. A ternary phase diagram was prepared for the IPM/DOSS/water system. The IPM/DOSS/water microemulsions were characterized by conductivity and dynamic laser light scattering (DLS). The results obtained from conductivity experiments indicate conductivity values of less than 1 ,S/cm and were consistent with the formation of w/o microemulsions. The DLS results showed that the emulsified water droplets had an average diameter range of 9.2 to 19.7 nm, depending on composition. Modulation of the droplet size is possible by varying the water to DOSS molar ratio and DOSS to IPM ratio. The second goal of this work was the preparation of silver sulfadiazine (AgSD) nanoparticles. It was hypothesized that two separate microemulsions containing dispersed aqueous droplets of either sodium sulfadiazine or silver nitrate would react when mixed. The DLS results are consistent with the successful formation of submicron AgSD crystals. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:1310,1320, 2005 [source] Dermal delivery of desmopressin acetate using colloidal carrier systemsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2005Melkamu Getie Recently, the transdermal route has received attention as a promising means to enhance the delivery of drug molecules, particularly peptides, across the skin. In this work, the skin penetration profiles of desmopressin acetate from a colloidal system (water-in-oil microemulsion) and an amphiphilic cream, a standard formulation, were determined using Franz diffusion cells and compared. In the case of the microemulsion, the total percentages of dose obtained from different skin layers (stratum corneum to subcutaneous tissue) were 3.30 ± 0.67, 7.37 ± 2.43 and 15.54 ± 2.72 at 30, 100 and 300 min, respectively. Similarly, 5.19 ± 0.96, 8.04 ± 0.97 and 14.4 ± 5.15% of the dose applied was extracted from the skin treated with the cream. About 6% of the applied dose reached the acceptor compartment from the microemulsion instead of 2% from the cream within 300 min. The concentration of drug that penetrated into the upper layers of the skin was higher from the cream than from the microemulsion at all time intervals. On the other hand, a higher amount of drug was found in the deeper skin layers and in the acceptor compartment from the microemulsion. [source] In-vitro release and oral bioactivity of insulin in diabetic rats using nanocapsules dispersed in biocompatible microemulsionJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2002Suchat Watnasirichaikul This study evaluated the potential of poly(iso -butyl cyanoacrylate) (PBCA) nanocapsules dispersed in a biocompatible microemulsion to facilitate the absorption of insulin following intragastric administration to diabetic rats. Insulin-loaded PBCA nanocapsules were prepared in-situ in a biocompatible water-in-oil microemulsion by interfacial polymerisation. The microemulsion consisted of a mixture of medium-chain mono-, di- and tri-glycerides as the oil component, polysorbate 80 and sorbitan mono-oleate as surfactants and an aqueous solution of insulin. Resulting nanocapsules were approximately 200 nm in diameter and demonstrated a high efficiency of insulin entrapment (> 80%). In-vitro release studies showed that PBCA nanocapsules could suppress insulin release in acidic media and that release at near neutral conditions could be manipulated by varying the amount of monomer used for polymerisation. Subcutaneous administration of insulin-loaded nanocapsules to diabetic rats demonstrated that the bioactivity of insulin was largely retained following this method of preparing peptide-loaded nanocapsules and that the pharmacodynamic response was dependent on the amount of monomer used for polymerisation. The intragastric administration of insulin-loaded nanocapsules dispersed in the biocompatible microemulsion resulted in a significantly greater reduction in blood glucose levels of diabetic rats than an aqueous insulin solution or insulin formulated in the same microemulsion. This study demonstrates that the formulation of peptides within PBCA nanocapsules that are administered dispersed in a microemulsion can facilitate the oral absorption of encapsulated peptide. Such a system can be prepared in-situ by the interfacial polymerisation of a water-in-oil biocompatible microemulsion. [source] In this issue: Biotechnology Journal 8/2010BIOTECHNOLOGY JOURNAL, Issue 8 2010Article first published online: 12 AUG 2010 Biocatalyst microemulsions Pavlidis et al., Biotechnol. J. 2010, 5, 805,812 Enzymes maintain their catalytic activity when hosted in aqueous nanodroplets like reverse micelles. Researchers from Ioannina, Greece, propose the use of water-in-ionic liquid microemulsionbased organogels (w/IL MBGs) as novel supports for the immobilization of lipase B from Candida antarctica and lipase from Chromobacterium viscosum. These novel lipase-containing w/IL MBGs can be effectively used as solid phase biocatalysts in various polar and non-polar organic solvents or ILs, exhibiting up to 4.4-fold higher esterification activity compared to water-in-oil microemulsion-based organogels. The immobilized lipases retain their activity for several hours at 70°C, while their half life time is up to 25-fold higher compared to that observed in w/IL microemulsions Biocatalyst cryogelation Bieler et al., Biotechnol. J. 2010, 5, 881,885 Entrapment of biocatalysts in hydrogel beads allows stable operation in otherwise deteriorating solvents. Doing this by cryogelation is a gentle method to extend the scope of biocatalysis. To foster the use of this versatile method, researchers from Aachen, Germany, devised an automated injector for the production of PVA/PEG-enzyme immobilisates. The device consists of a thermostated reservoir connected to a programmable injector nozzle and an agitated receiving bath for the droplets. This lab-scale production unit yields up to 1500 beads with immobilized enzyme per minute with a narrow size distribution and good roundness. Biocatalyst membrane reactor Lyagin et al., Biotechnol. J. 2010, 5, 813,821 Screening of biocatalysts, substrates or conditions in the early stages of bioprocess development requires an enormous number of experiments and is a tedious, expensive and time-consuming task. Currently available screening systems can only be operated in batch or fed-batch mode, which can lead to severe misinterpretations of screening results. Researchers from Berlin, Germany, now developed a novel screening system that enables continuous feeding of substrates and continuous removal of products. A prototype based on the membrane reactor concept was designed and operated for a model reaction, the hydrolysis of cellulose. [source] Water-in-ionic liquid microemulsion-based organogels as novel matrices for enzyme immobilizationBIOTECHNOLOGY JOURNAL, Issue 8 2010Ioannis V. Pavlidis Abstract The use of water-in-ionic liquid microemulsion-based organogels (w/IL MBGs) as novel supports for the immobilization of lipase B from Candida antarctica and lipase from Chromobacterium viscosum was investigated. These novel lipase-containing w/IL MBGs can be effectively used as solid phase biocatalysts in various polar and non-polar organic solvents or ILs, exhibiting up to 4.4-fold higher esterification activity compared to water-in-oil microemulsion-based organogels. The immobilized lipases retain their activity for several hours at 70°C, while their half life time is up to 25-fold higher compared to that observed in w/IL microemulsions. Fourier-transform infrared spectroscopy data indicate that immobilized lipases adopt a more rigid structure, referring to the structure in aqueous solution, which is in correlation with their enhanced catalytic behavior observed. [source] Scattering vector dependence of the small-angle scattering from mixtures of hydrogenated and deuterated organic solventsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000Lise Arleth In connection with a contrast variation small angle neutron scattering (SANS) study of water-in-oil microemulsions, mixtures of hydrogenated and deuterated n -decane and similar mixtures of iso-octane have been measured as backgrounds. For the pure deuterated and hydrogenated solvents the spectra were flat but for all the mixtures the large molecular size of the alkanes give rise to a scattering vector dependence in the small angle scattering region. An explanation of this can be given based on the scattering contributions which have been identified for mixtures of water. The intensity is proportional to x(x, 1) where x is the volume fraction of deuterated molecules. Using the analogy to scattering from polymer blends of hydrogenated and deuterated chains, the scattering spectra are analysed using the model for random gaussian coils. For the solvent mixtures investigated in the present study, the radius of gyration was determined to be 3.8 Å for decane and 2.9 Å for iso-octane, independent of the fraction of deuterated molecules. [source] | ||||||||||