Inclusion complex of piroxicam with beta-cyclodextrin and incorporation in cationic microemulsion. In vitro drug release and in vivo topical anti-inflammatory effect

Topical formulations of piroxicam were evaluated by determination of their in vitro release and in vivo anti-inflammatory effect. The in vitro release assay demonstrated that the microemulsion (ME) systems provided a reservoir effect for piroxicam release. However, the incorporation of the ME into carboxyvinilic gel provoked a greater reduction in the release of piroxicam than the ME system alone. Anti-inflammatory activity was carried out by the cotton pellet granuloma inhibition bioassay. Topical anti-inflammatory effect of the piroxicam inclusion complex/ME contained in carboxyvinilic gel showed significant inhibition of the inflammation process (36.9%, P < 0.05). Subcutaneous administration of the drug formulations showed a significant effect on the inhibition of inflammation, 68.8 and 70.5%, P <0.05, when the piroxicam was incorporated in ME and in the combined system beta -cyclodextrin (B-CD)/ME, respectively, relative to the buffered piroxicam (42.2%). These results demonstrated that the ME induced prolonged effects, providing inhibition of the inflammation for 9 days after a single dose administration. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Rheological, Mechanical and Adhesive Properties of Surfactant-Containing Systems Designed as a Potential Platform for Topical Drug Delivery

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development and In Vitro Evaluation of Surfactant Systems for Controlled Release of Zidovudine

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Surfactant systems for nasal zidovudine delivery: structural, rheological and mucoadhesive properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Electrochemical study of o-toluidine blue impregnated in mesoporous silica channels

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Rhodamine 6G encapsuled mesoporous silica channels

We report the effect of solvent on the rhodamine 6G encapsuled into channels of mesoporous silica, synthesized by two-step process that gives intermediary stable hybrid micelles. Mesoporous materials have been obtained by the method that involves surfactant micelles (mainly cationic) and inorganic precursor of the structure to be obtained. MSU-X type mesoporous silica has been synthesized with polyethylene oxide surfactant as the directing-structure agent and tetraethyl orthosilicate Si(OEt)(4) as the silica source. The influence of the solvent on the encapsulation of rhodamine dye was systematically explored, specially its influence on the luminescence properties. Rhodamine 6G encapsuled into mesoporous silica channel was characterized by UV-Vis and luminescence spectroscopies, scanning electron microscopy, small angle x ray scattering and N(2) sorption-desorption. The pore size and the solvent effects into luminescence dye encapsuled into mesoporous silica channels are observed in the visible absorption and emission spectra of rhodamine 6G. The intense photo luminescence band of rhodamine 6G dye is in 500 to 600 nm region. The observed shift of the absorption and emission bands can be assigned to the effect of the solvents dielectric constant and pore size of mesoporous silica.

Estudos das interações de quitosana/CTAB/C12E8

Surfactant-polymer interactions are widely used when required rheological properties for specific applications, such as the production of fluids for oil exploration. Studies of the interactions of chitosan with cationic surfactants has attracted attention by being able to cause changes in rheological parameters of the systems making room for new applications. The commercial chitosan represents an interesting alternative to these systems, since it is obtained from partial deacetylation of chitin: the residues sites acetylated can then be used for the polymer-surfactant interactions. Alkyl ethoxylated surfactants can be used in this system, since these non-ionic surfactants can interact with hydrophobic sites of chitosan, modifying the rheology of solutions or emulsions resultants, which depends on the relaxation phenomenon occurring in these systems. In this work, first, inverse emulsions were prepared from chitosan solution as the dispersed phase and cyclohexane as the continuous phase were, using CTAB as a surfactant. The rheological analysis of these emulsions showed pronounced pseudoplastic behavior. This behavior was attributed to interaction of "loops" of chitosan chains. Creep tests were also performed and gave further support to these discussions. Subsequently, in order to obtain more information about the interaction of chitosan with non-ionic surfactants, solutions of chitosan were mixed with C12E8 and and carried out rheological analysis and dynamic light scattering. The systems showed marked pseudoplastic behavior, which became less evident when the concentration of surfactant was increased. Arrhenius and KWW equations were used to obtain parameters of the apparent activation energy and relaxation rate distribution, respectively, to which were connected to the content of surfactant and temperature used in this work

POLYETHYLENE GLYCOL ADDITION DOES NOT IMPROVE EXOGENOUS SURFACTANT FUNCTION IN AN EXPERIMENTAL MODEL of MECONIUM ASPIRATION SYNDROME

Meconium (MEC) is a potent inactivator of pulmonary surfactant. The authors studied the effects of polyethylene glycol addition to the exogenous surfactant over the lung mechanics and volumes. Human meconium was administrated to newborn rabbits. Animals were ventilated for 20 minutes and dynamic compliance, ventilatory pressure, and tidal volume were recorded. Animals were randomized into 3 study groups: MEC group (without surfactant therapy); S100 group (100 mg/kg surfactant); and PEG group (100 mg/kg porcine surfactant plus 5% PEG). After ventilation, a pulmonary pressure-volume curve was built. Histological analysis was carried out to calculate the mean alveolar size (Lm) and the distortion index (DI). Both groups treated with surfactant showed higher values of dynamic pulmonary compliance and lower ventilatory pressure, compared with the MEC group (P .05). S100 group had a larger maximum lung volume, V30, compared with the MEC group (P .05). Lm and DI values were smaller in the groups treated with surfactant than in the MEC group (P .05). No differences were observed between the S100 and PEG groups. Animals treated with surfactant showed significant improvement in pulmonary function as compared to nontreated animals. PEG added to exogenous surfactant did not improve lung mechanics or volumes.

The 434(G > C) polymorphism in the eosinophil cationic protein gene and its association with tissue eosinophilia in oral squamous cell carcinomas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structure and Applications of a Rhamnolipid Surfactant Produced in Soybean Oil Waste

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vesicle-micelle transition in mixtures of dioctadecyldimethylammonium chloride and bromide with nonionic and zwitterionic surfactants

We have investigated the effect of mixing spontaneously formed dispersions of the cationic vesicle-forming dioctadecyldimethylammonium chloride and bromide (DODAX, with X being anions Cl- (C) or Br- (B)) with solutions of the micelle-forming nonionic ethylene oxide surfactants penta-, hepta-, and octaethyleneglycol mono-n-dodecyl ether, C12En (n = 5, 7, and 8), and the zwitterionic 3-(N-hexadecyl-N,N-dimethylammonio)propane sulfonate (HPS). We used for this purpose differential scanning calorimetry (DSC), turbidity, and steady-state fluorescence spectroscopy to investigate the vesicle-micelle (V-M) transition yielded by adding C12En and HPS to 1.0 mM vesicle dispersions of DODAC and DODAB. The addition of these surfactants lowers the gel-to-liquid crystalline phase transition temperature (T-m) of DODAC and DODAB, and the transition becomes less cooperative, that is, the thermogram transition peak shifts to lower temperature and broadens to disappear when the V-M transition is complete, the vesicle bilayer becomes less organized, and the T., decreases, in agreement with measurements of the fluorescence quantum yield of trans-diphenylpolyene (t-DPO) fluorescence molecules incorporated in the vesicle bilayer. Turbidity data indicate that the V-M transition comes about in three stages: first surfactants are solubilized into the vesicle bilayer; after saturation, the vesicles are ruptured, and, finally, the vesicles are completely solubilized and only mixed micelles are formed. The critical points of bilayer saturation and vesicle solubilization were obtained from the turbidity and fluorescence curves, and are reported in this communication. The solubility of DODAX is stronger for C12En than it is for HPS, meaning that C12En solubilizes DODAX more efficiently than does HPS. The surfactant solubilization depends slightly on the counterion, and varies according to the sequence C12E5 > C12E7 > C12E8 > HPS.

Vesicle-to-micelle transition in dioctadecyldimethylammonium bromide and dioctadecyldimethylammonium chloride dispersions induced by octaethylene glycol n-dodecyl monoether. An isothermal titration calorimetry study

We have used isothermal titration calorimetry to investigate the vesicle-to-micelle transition in dioctadecyldimethylammonium bromide (DODAB) and chloride (DODAC) vesicle dispersions induced by the nonionic surfactant octaethylene glycol n-dodecyl monoether (C12E8) at room temperature. Small and giant unilamellar vesicles were prepared by sonication and without sonication, respectively, of the pure cationic surfactants at low concentrations in water. The titration of 1.0 mM DODAX (X = Cl- and Br-) by a concentrated micellar solution of C12E8 shows that the enthalpy of interaction (DeltaH(obs)) of C12E8 in micellar form with DODAX is always endothermic. The titration curves are understood on the basis of superposition of the enthalpies of partitioning of C12E8 into the bilayer, of micelle formation and of vesicle-to-micelle transformation. The enthalpy, DeltaH(obs), initially increases owing to the incorporation of C12E8 into the vesicle bilayer until the C12E8/DODAX saturation ratio (R-sat) is reached, then DeltaH(obs) decreases, in different ways for DODAB and DODAC, owing to degradation of vesicles and formation of mixed micelles and intermediary structures up to the C12E8/DODAX solubilization ratio, R-sol. Above R-sol only mixed micelles exist. The surfactant solubilization takes place in three stages. All the critical ratios are lower for DODAB than for DODAC, meaning that C12E8 solubilizes more strongly in DODAB for example, R-sat is 0.8 for DODAB and 1.2 for DODAC. Sonication has no significant effect on the transition.

The effect of chain length on the melting temperature and size of dialkyldimethylammonium bromide vesicles

Differential scanning calorimetry (DSc) and dynamic light scattering (DLS) were used to obtain the gel to liquid-crystalline phase transition temperature (T-m) and the apparent hydrodynamic radius (R-h) of spontaneously formed cationic vesicles of dialkyldimethylammonium bromide salts (CnH2n+1)(2)(CH3)(2)N+center dot Br-, with varying chain lengths. The preparation of cationic vesicles from aqueous solution of these surfactants, for n = 12, 14, 16 and 18 (DDAB, DTDAB, DHDAB and DODAB, respectively), requires the knowledge of the surfactant gel to liquid-crystalline phase transition temperature, or melting temperature (T-m) since below this temperature these surfactants are poorly or not soluble in water. That series of cationic surfactants has been widely investigated as vesicle-forming surfactants, although C-12 and C-18, DDAB and DODAB are by far the most investigated from this series. The dependence of T-m of these surfactants on the number n of carbons in the surfactant tails is reported. The T-m obtained by DSC increases non-linearly with n, and the vesicle apparent radius R-h is about the same for DHDAB and DODAB, but much smaller for DDAB. (c) 2006 Elsevier B.V.. All rights reserved.

The effect of sodium chloride on the formation of W/O microemulsions in soy bean oil/surfactant/water systems and the solubilization of small hydrophilic molecules

Partial pseudoternary phase diagrams were constructed for soy bean oil (SBO)/surfactant/NaCl aqueous solution systems, at 25 degrees C, using the anionic sodium bis(2-ethylhexyl) sulfosuccinate (ACT) and zwiterionic phosphatidylcholine (PC) or mixtures of these surfactants. The isotropic single phase of water-in-oil (W/O) microemulsions (MEs) is shown in the phase diagram and their viscosity reported. ME samples containing small amount of surfactant exhibit slightly higher viscosity than pure SBO, and were used in the solubilization of small water soluble molecules. NaCl enhances the area of the ME phase and MEs with different surfactant composition exhibit different induction time as obtained from tests of oxidative stability, and so are the MEs enriched with ascorbic acid, folic acid and FeSO4, with the latter exhibiting lower stability. The so prepared enriched soy bean oil has potential application in food industry since the surfactants are food grade. (C) 2007 Elsevier B.V. All rights reserved.

Thermotropic phase behavior in aqueous mixtures of dioctadecyldimethylammonium bromide and alkyltrimethylammonium bromide surfactant series studied by differential scanning calorimetry

The effect of the micelle-forming surfactant series alkyltrimethylammonium bromide (C(n)TAB, n = 12, 14, 16 and 18) on the thermotropic phase behavior of dioctadecyldimethylammonium bromide (DODAB) vesicles in water was investigated by differential scanning calorimetry at constant 5.0 mM total surfactant concentration and varying individual surfactant concentrations. The pre-, post- and main transition temperatures (T-s, T-p and T-m), melting enthalpy (Delta H) and peak width of the main transition (Delta T-1/2) are reported as a function of the surfactant molar fraction. No clear dependence of these parameters on the C(n)TAB chain length was found. At 5 mM, neat DODAB in water exhibits two transition temperatures, T-s = 32.1 and T-m = 42.7 degrees C, as obtained from the DSC upscans, but not a clear T-p. For every n, except n = 12, T-s vanishes as CnTAB concentration increases and approaches CMC. T-m behaves differently for different n, the longer C(14)TAB and C(16)TAB decrease, while C(18)TAB increases T-m with increasing concentration. The data indicate that changes in T-m, T-s, T-p and Delta H of the transition are related not only to the extent of C(n)TAB affinity to DODAB but also to the surfactant chain length. Accordingly, C18TAB yields a more compact bilayer, thus increasing T-m, while C(14)TAB and C(1G)TAB yield a less organized bilayer and reduce T-m. C(12)TAB does not much affect T-s and T-m, although it yields T-p approximate to 51.6 degrees C. (C) 2008 Elsevier B.V. All rights reserved.