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

Influence of the temperature in the adsorption of sodium dodecyl sulfate on phosphatidylcholine liposomes

8 pages, 4 figures.-- PMID: 12787940 [PubMed].-- Printed version published Jun 2003.The influence of the temperature on the adsorption of monomeric and micellar solutions of the anionic surfactant sodium dodecyl sulfate (SDS) on phosphatidylcholine (PC) liposomes was investigated using the fluorescent probe 2-(p-toluidinyl)-naphthalene-6-sodium sulfonate (TNS). The number of adsorbed molecules was quantified by measuring changes in the electrostatic potential (Ψo) of the liposomes/probe during an incubation with SDS at varying temperatures. At low surfactant concentrations (from 0.05 to 0.25 mM), the increase in temperature reduced the number of surfactant molecules incorporated per vesicle regardless of the incubation time, whereas at high surfactant concentrations (from 0.50 to 1.0 mM) the incubation time has an opposite effect on this process. Thus, after 10 s, the surfactant adsorption decreased with temperature, yet it increased progressively with time. The adsorption was linear with temperature below critical micellar concentration (CMC) of SDS and this linear tendency did not change above CMC. This suggests an adsorption of SDS monomers regardless of the surfactant concentration.This work was supported by funds from M.C.Y.T., Prog. No. 2001 1188-CO2-02, Spain.Peer reviewe

Preparation and characterization of a supramolecular hydrogel made of phospholipids and oleic acid with a high water content

A hydrogel formed with phospholipids and fatty acids would be of great interest in the medical field due to the biological relevance that these molecules have in living organisms. However, the tendency of phospholipid mixtures to form vesicular or micellar aggregates at high water content hinders the formation of this type of hydrogels. In this study, a highly hydrated hydrogel (95% water) was formed with hydrogenated phosphatidylcholine and oleic acid. The preparation method involved a freeze-heating cycle of the aqueous lipid mixture, favouring the supramolecular aggregation of these molecules into a microscopic spongey morphology. Confocal fluorescence imaging showed that the microstructure of the hydrogel is made from the aggregation of giant multilamellar vesicles (5-20 µm diameter) while transmission electron microscopy revealed the existence of nanosized unilamellar vesicles (150 nm diameter) coexisting with lipid lamellae. Despite this type of aggregation, X-ray scattering experiments performed on the hydrogel show almost no correlation between lipid membranes. In terms of rheological properties, the material shows a prevalent elastic behaviour and a low structural strength consequence of non-covalent interactions. With such properties and composition, this structured but easily deformable material might become a useful tool for biomedical applications.The authors would like to acknowledge Jaume Caelles from the SAXS-WAXS service at IQAC for X-ray measurements and Lidia Delgado from CCITUB for cryo-TEM sample preparation. Rheology assays were performed by Susana Vílchez at the Nanostructured Liquid Characterization Unit of CSIC and CIBER-BBN. Authors are also grateful to Lipoid GmbH for kindly providing Phospholipon® 90H and to MINECO for funding this work with the RTC-2016-4957-1 project.We acknowledge support of the publication fee by the CSIC Open Access Support Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe

Structural Versatility of Bicellar Systems and Their Possibilities as Colloidal Carriers

Bicellar systems are lipid nanostructures formed by long- and short-chained phospholipids dispersed in aqueous solution. The morphological transitions of bicellar aggregates due to temperature, composition and time variations have been revised in this work. To this end, two bicellar systems have been considered; one formed by dimyristoyl-phosphatidylcholine (DMPC) and dihexanoyl- phosphatidylcholine (DHPC) and another formed by dipalmitoyl-phosphatidylcholine (DPPC) and DHPC. The relationship between the magnetic alignment, the morphology of the aggregates and the phase transition temperature (Tm) of lipids is discussed. In general terms, the non-alignable samples present rounded objects at temperature below the Tm. Above this temperature, an increase of viscosity is followed by the formation of large elongated aggregates. Alignable samples presented discoidal objects below the Tm. The best alignment was achieved above this temperature with large areas of lamellar stacked bilayers and some multilamellar vesicles. The effect of the inclusion of ceramides with different chain lengths in the structure of bicelles is also revised in the present article. A number of physical techniques show that the bicellar structures are affected by both the concentration and the type of ceramide. Systems are able to incorporate 10% mol of ceramides that probably are organized forming domains. The addition of 20% mol of ceramides promotes destabilization of bicelles, promoting the formation of mixed systems that include large structures. Bicellar systems have demonstrated to be morphologically stable with time, able to encapsulate different actives and to induce specific effects on the skin. These facts make bicellar systems good candidates as colloidal carriers for dermal delivery. However, water dilution induces structural changes and formation of vesicular structures in the systems; stabilization strategies have been been explored in recent works and are also updated here.This work was supported by funds from CICYT (CTQ 2010-16964) and from Generalitat de Catalunya (2009 SGR 1212). M. Cócera is funded by the JAE-DOC program from CSIC (co-funded by FSE)

Bicelas encapsuladas en liposomas y su aplicación en sistemas diluídos

[EN] The aim ofthe invention is to preserve the morphology of bicelles in high-water-content environments. For this purpose, the invention relates to a liposome comprising, in the internal aqueous solution thereof, at least one bicelle. The bicelle concentration in said solution is between 5 and 25 % dry weight in relation to the end liposome. The invention also relates to the use of the liposomes for the encapsulation of active principIes, as well as to the use thereof as a drug or to produce a cosmetic product. The invention further relates to the method for obtaining said liposomes.[ES] La presente invención tiene como fInalidad preservar la morfología de las bicelas en ambientes con alto contenido en agua, por ello, la invención se refIere a un liposoma que comprende, en su solución acuosa interna, al menos, una bicela. La concentración de bicelas en dicha solución es de entre el 5 y 25% en peso seco con respecto al liposoma fInal. La invención también se refIere al uso de dichos liposomas para el encapsulado de principios activos, así como a su uso como medicamento o para la elaboración de un producto cosmético. Además, la presente invención se refIere al método de obtención de dichos liposomas.Peer reviewedConsejo Superior de Investigaciones Científicas (España)A1 Solicitud de patente con informe sobre el estado de la técnic