Organogels from water-in-oil microemulsions

Luisi, Pier Luigi; Scartazzini, Roger; Haering, Gabriel; Schurtenberger, Peter

doi:10.1007/bf01411679

Cited by 167 publications

(106 citation statements)

References 24 publications

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“…Dos diagramas de fases encontrados na literatura, 13,23 somente o diagrama de fases com iso-octano foi realizado com uma concentração de AOT próxima a desenvolvida neste trabalho, concentração de AOT = 0,14 mol/L. Neste diagrama, 13 Luisi e colaboradores mostraram a existência de quatro regiões distintas nos seus experimentos, [AOT] = 0,1 e 0,14 mol/L. A distribuição das diversas regiões do organo-gel de iso-octano são diferentes das regiões do diagrama de fase do organo-gel de heptano.…”

Section: Resultsunclassified

“…Através dos diagramas de fase do organo-gel de iso-octano pode-se comparar o efeito da concentração do surfactante, AOT. Observa-se que aumentando a concentração de AOT, ocorre um aumento na área que forma o gel 13 .…”

Section: Resultsunclassified

“…O organo-gel ou MBG do inglês, microemulsion based gels, é formado pela solubilização de gelatina em uma microemulsão água em óleo, para a formação de géis transparentes [13][14] . A formação do organo-gel foi primeiramente descrita em 1986, [15][16] e sua caracterização física/estrutural tem sido alvo de vários estudos [17][18][19][20][21] .…”

Section: Introductionunclassified

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Organo-gel de heptano: diagrama de fases e aplicações sintéticas

Queiroz

Nascimento

1999

Quím. Nova

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Recebido em 1/4/98; aceito em 12/8/98 ORGANO-GEL OF HEPTANE: PHASES DIAGRAM AND SYNTHETIC APPLICATIONS. The phase diagram formation of microemulsion-based gels composed of an anionic surfactant aerosol-OT sodium bis (2-ethylhexyl)-sulphosuccinate), water, gelatin and an organic solvent is presented for heptane. The stability of this organo-gel, when an enzyme is immobilized is discussed in terms of its reutilization in various esters synthesis.Keywords: microemulsion-based gels; phase diagram; enzyme immobilization. ARTIGO INTRODUÇÃOAs enzimas são empregadas como catalisadores em muitos processos sintéticos em meio aquoso, mas o uso é restrito pela baixa solubilidade em água de substratos e produtos 1 . Este problema pode ser solucionado imobilizando a enzima em suportes, permitindo assim sua aplicação em meio orgânico. Existem diferentes métodos para realizar conversões enzimáticas em solventes orgânicos 2-3 . Enzimas solubilizadas em microemulsão água em óleo 4-6 ou em organo-gel têm sido amplamente investigadas do ponto de vista quantitativo [7][8][9][10][11] .As microemulsões água em óleo são fluidas sob condições normais, e consistem de gotas esféricas de água de dimensões nanométricas polidispersas em um meio contendo óleo, estabilizadas por uma monocamada de surfactante na interface água-óleo. São termodinamicamente estáveis e podem ser formadas apenas com a mistura de seus componentes 12 .O organo-gel ou MBG do inglês, microemulsion based gels, é formado pela solubilização de gelatina em uma microemulsão água em óleo, para a formação de géis transparentes [13][14] . A formação do organo-gel foi primeiramente descrita em 1986, 15-16 e sua caracterização física/estrutural tem sido alvo de vários estudos [17][18][19][20][21] .As mudanças que ocorrem na estrutura do organo-gel variam de acordo com a quantidade de seus componentes (água, óleo, surfactante e gelatina), permitindo obter diagramas de fases, também conhecidos como "regiões de estabilidade". Estes, por sua vez, possibilitam estudar a relação dos componentes do organo-gel no processo de gelatinização, para se obter organo-géis com rigidez e estabilidade diversas 22 . Este artigo, mostra o diagrama de fases para um organo-gel de heptano, sua eficiência como suporte para a imobilização de palatase M e sua estabilidade em sucessivas sínteses do laurato de 1-pentila. EXPERIMENTAL MateriaisA enzima utilizada neste trabalho foi palatase M 1000L (Novo Nordisk A/S), com atividade de 1000 LU/g (LU é a quantidade de enzima que libera um micromol de ácido butírico por minuto a partir de tributirina, em pH = 7,0, T = 30 o C, 4,8 % (w/v) de tributirina e 0,0095% (w/v) de goma arábica).O surfactante di-(2-etilhexil) sulfosuccinato de sódio (Aerosol-OT, AOT) (D-0885 lote 120H0456) e gelatina em pó (tipo A: Bloom 300) usados na preparação do organo-gel foram obtidos da Sigma. Os solventes e os reagentes (grau analítico) foram obtidos das seguintes fontes: Merck (ácido láurico), Grupo Química (heptano, hexano), Vetec (1-pentanol). A sílica para coluna (28-200 me...

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Section: Resultsunclassified

Section: Introductionunclassified

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Organo-gel de heptano: diagrama de fases e aplicações sintéticas

Queiroz

Nascimento

1999

Quím. Nova

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“…The main reason for the formation of electrospun phospholipid fibers is that, with the increase of the phospholipid concentration, a transition occurs from single molecules to micelles, then to the formation of rod-like structures, and finally a creation of elongated aggregates that can be electrospun. 10 Isooctane is thus a suitable solvent to electrospun phospholipids, since it is known to promote the formation of elongated cylindrical reverse micelles 18 and supramolecular structures of lecithin solutions.…”

Section: Nanomechanics Of Electrospun Phospholipid Fibermentioning

confidence: 99%

Nanomechanics of electrospun phospholipid fiber

Mendes

Nikogeorgos

Lee

et al. 2015

Applied Physics Letters

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Electrospun asolectin phospholipid fibers were prepared using isooctane as a solvent and had an average diameter of 6.1 ± 2.7 μm. Their mechanical properties were evaluated by nanoindentation using Atomic Force Microscopy, and their elastic modulus was found to be approximately 17.2 ± 1 MPa. At a cycle of piezo expansion-retraction (loading-unloading) of a silicon tip on a fiber, relatively high adhesion was observed during unloading. It is proposed that this was primarily due to molecular rearrangements at the utmost layers of the fiber caused by the indentation of the hydrophilic tip. The phospholipid fibers were shown to be stable in ambient conditions, preserving the modulus of elasticity up to 24 h.

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“…These reverse worms become tangled in the oil and form a three-dimensional (3D) network throughout the solution, turning the solution into an gel-like solution (also called a lecithin organogel). [1][2][3][4][5][6] In this reverse micellar system the polar substance is the key ingredient for the formation of reverse worms. We have also identified other key ingredients that can be used as substitutes for water in the preparation of reverse worms in n-decane, such as urea, 7) sucrose fatty acid esters, 8) D-ribose, 9) 2-deoxy-D-ribose, 9) polyglycerols, 10) ascorbic acid, 11) and multivalent carboxylic acids.…”

mentioning

confidence: 99%

Skin Permeation of Testosterone from Viscoelastic Lecithin Reverse Wormlike Micellar Solution

Imai

Hashizaki

Yanagi

et al. 2016

Biological & Pharmaceutical Bulletin

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We evaluated testosterone-containing lecithin reverse wormlike micelles (reverse worms) composed of a polar substance/lecithin/isopropyl myristate for transdermal application. Water, D-ribose, or tetraglycerol were used as the polar substance and were key ingredients for forming the reverse worms. Using the reverse worms, 1 wt% of testosterone could be stably solubilized. When using D-ribose as polar substance, the maximum zero-shear viscosity of the reverse worms solution was higher than that of systems using water or tetraglycerol as the polar substance. The mechanism of skin permeation of testosterone from reverse worms solution was elucidated using skin permeation experiments with hairless mouse skin. When the structure of the reverse worms transitioned to lamellar liquid crystals at the skin/formulation interface, testosterone became supersaturated in the formulations. The structural transition occurred in systems using water or D-ribose as the polar substance, increasing the flux of testosterone. The flux of testosterone from reverse worms solution thus depends on the type of polar substance used.Key words reverse wormlike micelle; lecithin organogel; skin permeation; rheology; phase diagram; hairless mouse skin Recent advances in drug dosage forms have led to improved quality of life for patients. The transdermal dosage form, in particular, represents one of the most important drug delivery methods. Transdermal dosage forms enable avoidance of the hepatic first-pass effect, which can be problematic with oral administration. Another advantage of transdermal dosage forms is that they are easy to apply and remove from the skin. Based on these advantages, transdermal dosage forms have been adopted for a variety of medications.We investigated the possibility of using lecithin reverse wormlike micelle (called reverse worms) comprised of a polar substance/lecithin/oil as the vehicle for transdermal therapeutic application of testosterone (TES). Lecithin is an amphiphilic molecule composed of both hydrophilic and hydrophobic groups. In general, lecithin forms spherical or ellipsoidal reverse micelles when added alone to oil. When trace amounts of a polar substance (e.g., water) 1) are added to this solution, the polar substance can attach to the phosphate groups of the lecithin molecules via hydrogen bonding, widening the gap between the head groups of neighboring lecithin molecules. Thus, the value of the critical packing parameter decreases and the interface curvature of the molecular assembly subsequently induces the formation of reverse worms. As a result, phase transition from reverse spherical micelles to reverse worms takes place. These reverse worms become tangled in the oil and form a three-dimensional (3D) network throughout the solution, turning the solution into an gel-like solution (also called a lecithin organogel). [1][2][3][4][5][6] In this reverse micellar system the polar substance is the key ingredient for the formation of reverse worms. We have also identified other key ingredients that can be...

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Organogels from water-in-oil microemulsions

Cited by 167 publications

References 24 publications

Organo-gel de heptano: diagrama de fases e aplicações sintéticas

Organo-gel de heptano: diagrama de fases e aplicações sintéticas

Nanomechanics of electrospun phospholipid fiber

Skin Permeation of Testosterone from Viscoelastic Lecithin Reverse Wormlike Micellar Solution

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