Bicellar systems to modify the phase behaviour of skin stratum corneum lipids

Bicellar systems are a fascinating category of versatile lipid assemblies that comprise bilayered disk-shaped nanoaggregates formed in water by long and short alkyl chain phospholipids. Bicelles bridge the gap between micelles and lipid vesicles by combining the attractive properties of both systems. These structures have recently been proposed in dermatological, cosmetic and pharmaceutical applications. Two new binary bicellar systems composed of cholesterol sulphate (SCHOL) and long-chain phospholipids (dimyristoyl- phosphatidylcholine, DMPC, or dipalmitoyl-phosphatidylcholine, DPPC) are characterised herein by differential scanning calorimetry, fluorescence spectroscopy, X-ray scattering and microscopy. Additionally, a comparative study on skin treated with the new SCHOL systems (DMPC/SCHOL and DPPC/SCHOL) and classic DHPC systems (DMPC/DHPC and DPPC/DHPC) was performed. These studies were conducted to determinate how deeply bicelles penetrate into the skin and the extension of their effect on the phase behaviour of stratum corneum (SC) lipids using attenuated total reflectance-Fourier transform infrared spectroscopy and two-photon excitation fluorescence microscopy. Our results show that SCHOL modified the typical discoidal morphology and the phase behaviour of the systems, inducing coexistence of two phases, liquid-ordered and ripple phases. The effect of the systems on SC lipids depends on their composition and is related to the fluidity of the SC lipid alkyl chains. Thus, systems with DMPC induced more disorder in SC lipids than systems with DPPC, and SCHOL did not modify the lipid arrangement. Perdeuterated systems in the infrared spectroscopy technique supported a different distribution in the tissue for every system. DMPC systems were primarily at the first layers of the SC, whereas DPPC systems were more widely distributed. Systems with SCHOL had enhanced distribution and penetration of bicellar systems throughout the SC. This journal is © 2012 the Owner Societies

Structural phase transitions involved in the interaction of phospholipid bilayers with octyl glucoside

6 pages, 2 figures.-- PMID: 7813457 [PubMed].-- Available online Mar 3, 2005.The transitional stages induced by the interaction of the nonionic surfactant octyl glucoside (OcOse) on phosphatidylcholine liposomes were studied by means of transmission electron microscopy (TEM), light scattering and permeability changes. A linear correlation was observed between the effective surfactant/lipid molar ratio (Re; three-stage model proposed for liposome solubilization) and the OcOse concentration in the initial and final interaction stages, despite showing almost a constant value during bilayer saturation. The bilayer/aqueous phase partition coefficient (K) decreased in the subsolubilizing interaction steps and increased during solubilization. Thus, whereas a preferential distribution of surfactant monomers in the aqueous phase with respect to the lipid bilayers took place in the initial interaction steps, a larger association of OcOse molecules with these lipids in bilayers occurred during solubilization. The initial steps of bilayer saturation (50-70% permeability) were attained for a lower free surfactant (Sw) than that for its critical micellar concentration (cmc). When Sw reached the OcOse cmc, solubilization started to occur (Resat). Large unilamellar vesicles began to form as the OcOse exceeded 60 mol/100 mol, exhibiting for 65 mol/100 mol (50% permeability) vesicles of approximately 400 nm. TEM pictures for 100% permeability (72 mol/100 mol) and Resat still showed unilamellar vesicles, albeit that the Resat TEM picture showing traces of smaller structures. Exceeding surfactant amounts led to a decrease in static light scattering; the vesicle-size curve began to show a bimodal distribution. The TEM picture showed tubular structures together with bilayer fragments. Thereafter, the open structures were gradually affected by the surfactant and the scattered intensity gradually decreased to a constant low value.This work was supported by funds from DGICYT (Direccidn General de Investigacidn CientGca y Te'cnica; Prog. no. PB91-0065), Spain.Peer reviewe

Vesicle-micelle structural transition of phosphatidylcholine bilayers and Triton X-100

8 pages, 5 figures, 2 tables.-- PMID: 7980461 [PubMed].-- PMCID: PMC1137632.The structural transition stages induced by the interaction of the non-ionic surfactant Triton X-100 on phosphatidylcholine unilamellar vesicles were studied by means of static and dynamic light-scattering, transmission-electron-microscopy (t.e.m.) and permeability changes. A linear correlation was observed between the effective surfactant/lipid molar ratios (Re) ('three-stage' model proposed for the vesicle solubilization) and the surfactant concentration throughout the process. However, this correlation was not noted for the partition coefficients of the surfactant between the bilayer and the aqueous medium (K). Thus a sharp initial K increase was observed until a maximum value was achieved for permeability alterations of 50% (initial step of bilayer saturation). Further surfactant additions resulted in a fall in the K values until 100% of bilayer permeability. Additional amounts of surfactant led to an increase in K until bilayer solubilization. Hence, a preferential incorporation of surfactant molecules into liposomes governs the initial interaction steps, leading to the initial stage of bilayer saturation with a free surfactant concentration that was lower than its critical micelle concentration (c.m.c.). Additional amounts of surfactant increased the free surfactant until the c.m.c. was reached, after which solubilization started to occur. Thus the initial step of bilayer saturation was achieved for a smaller surfactant concentration than that for the Resat, although this concentration was the minimum needed for solubilization to start. Large unilamellar vesicles began to form as the surfactant exceeded 15 mol% (50% bilayer permeability), the maximum vesicle growth being attained for 22 mol% (400 nm). Thereafter, static light-scattering started to decrease gradually, this fall being more pronounced after 40 mol%. The t.e.m. picture for 40 mol% (Resat.) showed unilamellar vesicles, although with traces of smaller structures. From 50 mol% the size distribution curves began to show a bimodal distribution. The t.e.m. pictures for 50-64 mol% revealed tubular structures, together with open bilayer fragments. Thereafter, increasing amounts of surfactant (65-69 mol%) led to planar multilayered structures which gradually tended to form concentric and helicoidal conformations. The scattered intensity decreased to a low constant value at more than 71-72 mol%. However, the surfactant concentration for the Re(sol) (72.6 mol %) still presented traces of aggregated structures, albeit with mono-modal size-distribution curves (particle size of 50 nm). This vesicle size corresponded to the liposome solubilization via mixed-micelle formation.This work was supported by funds from DGICYT (Direccion General de lnvestigación Científica y Técnica) (Prog. no PB91 - 0065), Spain.Peer reviewe

Procedimiento de tintura de lana con colorantes dispersos utilixando liposomas como vehículo dispersante

Fecha de presentación nacional 19.05.1993.-- Titular: Consejo Superior de Investigaciones Científicas (CSIC).Procedimiento de tintura de lana utilizando liposomas como vehículo dispersante. Se re ere a la utilización de liposomas multilamelares como vehículos de colorantes dispersos tales como C.I. Disperse Violet 1 (A) y C.I. Disperse Orange 1 (B) en la tintura de la lana. Comprende, asimismo, aspectos cinéticos relacionados con la adsorción y fijación del colorante por medio de liposomas multilamelares a diferentes concentraciones tanto de phospholípido como de colorante sobre muestras de lana no tratada o previamente cloradas. Este proceso conduce a un agotamiento controlado del colorante sobre la lana, directamente relacionado con la proporción relativa de ambos componentes en los liposomas. El óptimo agotamiento de la tintura se obtiene para unas proporciones en peso colorante/fosfolípido de 0.25 y 0.29 para los colorantes (A y B). Las cantidades totales de colorante unido a las fibras de lana siguen una tendencia similar a la observada para el proceso de agotamiento. Sin embargo, las muestras de lana clorada p sentaron un ligero descenso en la cantidad total de colorante fijado a medida que el contenido en ácido cisteínico de la lana clorada aumenta.Peer reviewe

SOLUBILIZATION OF PHOSPHOLIPID BILAYERS CAUSED BY SURFACTANTS

leads to the rupture of such structures and the solubilization of the phospholipid components. In this paper, solubilization is regarded as a decrease in light scattering of liposome suspensions. To this end, in accordance with the nomenclature, adopted by Lichtenberg, three parameters were considered as corresponding to the effective surfactantllipid molar ratios (Re) at which light scattering starts to decrease, Re,,; reaches 50% of the original value, Rem; and shows no further decrease, Resol. These parameters corresponded to the Re at which the surfactant (i) saturated the liposomes, (ii) resulted in a 50% solubilization of vesicles and (iii) led to a total solubilization of liposomes. The surfactants tested were the nonionic surfactant octylphenol ethoxylated with 10 units of ethylene oxide or Wton X-100 (OP-lOEO), two anionic surfactants, sodium dodecyl sulfate and sodium dodecyl ether sulfate, and an amphoteric surfactant dodecyl betaine (D-Bet). Unilamellar liposomes formed by egg phosphatidylcholine containing increasing amounts of phosphatidic acid were used. The Re parameters were the lowest for D-Bet, followed by OP-lOEO, whereas the anionic surfactants always showed the highest values regardless of the electrical charge of the lipid bilayers. These parameters seem also to be inversely related to the critical micelle concentration (CMC) of the surfactant, except for OP-1OEO. Moreover, the CMC values of the surfactantllipid systems at 0.5 mM lipid concentration corresponded in al1 cases to the surfactant concentration at which liposomes were saturated by surfactants. As a consequence, this ratio can be regarded as an interesting parameter associated with the mixed micelle formation in liposome solubilization

Solubilization of liposomes formed by lipids modeling the stratum corneum caused by alkyl pyridinium surfactants

The interactions of a series of alkyl pyridinium surfactants (alkyl chain lengths C-10 (DePB), C-12 (DoPB) and C-14 (TePB)) with liposomes modeling the stratum corneum (SC) lipid composition (40'% ceramides, 25%) cholesterol, 25'% palmitic acid and 10'!4/;c, holesteryl sulfate) were investigated. The surfactant:lipid molar ratios (Re) and the bilayer-aqueous phase partition coefficients (K) were determined by monitoring the changes in the static light scattering of the system during solubilization. The fact that the free concentration was always similar to the surfactant critical micelle concentration (CMC) indicates that liposome solubilization was mainly ruled by formation of mixed micelles. The Re and K values fell as the surfactant alkyl chain length decreased or their CMC increased. Thus, the higher the surfactant CMC the higher the surfactant ability to saturate or solubilize SC liposomes and the lower its degree of partitioning into liposomes. The balance of these two tendencies shows that the TePB and DoPB had respectively the highest power of saturation and solubilization of SC structures in terms of total surfactant amounts needed to produce these effects. Different trends in the interaction of these surfactants with SC liposomes were observed when comparing the Re and K values with those reported for PC ones. Thus, whereas SC liposomes were more resistant to the surfactant action, the degree of partitioning of these surfactants into these liposomes was higher in al1 cases

Unilamellar lipid bilayers including cholesterol in wool Chlorination: stability of chlorine liposomes and application on wool

We studied the application of unilamellar liposomes of a defined size (200 nm) containing cholesterol as vehicles for oxidative reagents in wool chlorination. To this end, we first studied the interaction between liposomes and chlorine in order to determine the physicochemical stability of these systems in the presence of this oxidative agent. We assessed physical stability by measuring both the mean vesicle size distribution of the vesicle suspensions and the changes in the ahsorbance of these systems, which are directly related to the aggregation or solubilization of liposomes. Our stndy of chemical stability was based on the lipid peroxidation index of liposomes at different chlorine concentrations at pH value 6.5. As regards the oxidative effects caused by the chlorine treatments of wool applied directly or by means of liposomes at pH 1.5, we investigated the extent of cysteic acid formation groups in wool fibers. Increasing amounts of cholestcrol in the lipid bilayers of liposomes enhaiice both the physicochemical stability of ihese systems and the inhibitor). ability of cvsteic acid formation when samples have been treated with chlorine-liposome systems