Showing papers by "Joke A. Bouwstra published in 1996"

Preparation and Characterization of Nonionic Surfactant Vesicles

Abstract: Nonionic surfactant vesicles (NSVs) were prepared from polyoxyethylene alkyl ether surfactants (CnEOm) and sugar ester surfactants. The relationship between the hydrophilic–lipophilic balance (HLB), gel–liquid transition temperature (Tc) of the surfactants, and vesicle formation was examined. For spontaneous vesicle formation both an HLB between 7.5 and 10.5 and aTcbelow the experimental temperature were necessary. Surfactants with a suitable HLB, but with a highTc, were able to form vesicles upon sonication. Cholesterol (CHOL) encapsulation facilitated vesicle formation. The minimum amount of cholesterol necessary to form vesicles and the maximum amount that could be encapsulated were related to the HLB and theTc. Addition of cholesterol and dicetylphosphate decreased the size of NSVs. Cholesterol decreased the floating and increased the sedimentation behavior of vesicles. Dicetylphosphate stabilized the suspensions and minimized the aggregation behavior of sugar ester vesicles. The capacity of the NSVs to encapsulate carboxyfluorescein and triamcinolone acetonide was not influenced by the physical state of the bilayers. Heating CnEOmvesicles without cholesterol to 40°C or higher resulted in an increase in size, in contrast to vesicles with a CHOL/SURF molar ratio of 0.67. This is probably the explanation for the decrease in size with increasing CHOL content in the NSVs.

Diffusion of estradiol from non-ionic surfactant vesicles through human stratum corneum in vitro

Abstract: L'effet de l'encapsulation de l'estradiol dans des vesicules de surfactifs non ioniques sur la diffusion a travers le stratum corneum humain a ete etudie in vitro. Les vesicules de surfactifs non ioniques ont ete preparees a partir d'ethers alkyliques de polyxoyethylene (C n EO m ) et d'ester de saccharose (Wasag-7 et Wasag-15) avec du cholesterol, du phosphate de dicetyle et la quantite maximale d 'estradiol qui pouvait etre incorporee. Un tampon phosphate sature en estradiol a servi de temoin. Une application occlusive a l'etat de gel des vesicules C 18 EO 7 /cholesterol, Wasag-7 ou Wasag-15/cholesterol/phosphate de dicetyle dans le tampon phosphate augmente le flux d'estradiol d'un facteur 1,5 a 2,4. L'application occlusive a l'etat liquide des vesicules C 12 EO 7 /cholesterol (1/0,43) et C 12 EO 7 /cholesterol (1/0, 18) dans le tampon phosphate augmente le flux d'un facteur 4,8 et 9,5 respectivement. Le pretraitement occlusif avec des vesicules vides C 12 EO 7 /cholesterol (1/0,18) suivi du tampon phosphate sature en estradiol conduit a un flux augmente 2, 9 fois. Les micelles C 12 EO 7 chargees d'estradiol ne manifestent aucun effet. L'application occlusive de vesicules C 12 EO 7 /cholesterol (1/0, 43) et Wasag-7/cholesterol/phosphate de dicetyle sur une toile de Silastic et du stratum corneum avec la toile de Silastic face au compartiment donneur conduit a un flux d'estradiol de 1,8 a 2,2 fois plus fort. L'augmentation du flux d'estradiol est en relation avec la flexibilite de la bicouche et l'encapsulation de l'estradiol dans les vesicules.

The use of vibratome sections for the ruthenium tetroxide protocol: a key for optimal visualization of epidermal lipid bilayers of the entire human stratum corneum in transmission electron microscopy.

Abstract: In this paper we describe a preparative procedure which allows maximal visualization of all lipid bilayers in the human stratum corneum (SC). We used 50-μm-thick vibratome sections of paraformaldehyde/glutaraldehyde-fixed human skin. The sections were post-fixed in 1% osmium tetroxide and 0.5% ruthenium tetroxide. The vibratome sections were dehydrated only in 70% ethanol in order to prevent dissolution of the lipids. Lipid bilayers, including the alternating electron-dense and electron-lucent lamellae, were visible between all cell layers of the SC. In addition, this preparative procedure also appeared to be excellent for the ultrastructural preservation of lamellar bodies.

Visualization and electron diffraction on cryosections of stratum corneum: a utopia?

Abstract: The skin acts as an effective barrier to protect the body against penetration of substances from the environment and against desiccation The main barrier function resides in the stratum corneum, and more specifically in the intercellular lipid domains Several techniques have been used to elucidate the local lipid crystal arrangements in these domains, but they either needed an extensive pretreatment of the skin with the risk of damaging the native structure, or were not suited to obtain local structure information as bulk quantities of stratum corneum were required In this paper a method of performing local structure analysis (electron diffraction) on cryo-fixed specimens is described Therefore a cold chain procedure was used to obtain cryosections of stratum corneum On these sections visualization and electron diffraction at low temperature were carried out Using a so-called tape sandwich method, cryosections were prepared in which corneocytes and lipid matrix could easily be distinguished Moreover, detailed cellular components such as desmosomes and intracellular lipid domains were observed However, probably due to the limited amount of intercellular lipids in the stratum corneum, electron diffraction on cryosections did not result in diffraction patterns that were undoubtedly originating from the intercellular lipids In the electron diffraction patterns of a skin lipid model system reflections were present that were indicative of hexagonal and orthorhombic sublattices The d-spacings of these reflections were similar to the spacings of the high-intensity reflections of the X-ray diffraction pattern of the same mixture This showed agreement between a bulk and a local technique, X-ray and electron diffraction