Stratum Corneum Lipid Liposomes Research Articles

Quality by Design (QbD) enabled and Box-Behnken design assisted approach for formulation of tranexamic acid loaded stratum corneum lipid liposomes

Tranexamic acid, a highly hydrophilic drug, is used for treatment of hyperpigmentation but topical delivery of drug is limited by poor permeation across lipidic stratum corneum membrane. Stratum corneum lipid liposomes have lipidic composition similar to that of stratum corneum layer that aids in efficient topical delivery of drugs. For quantitative analysis of drug, a LC-MS/MS based approach was successfully developed. In this study a QbD based approach was applied to optimize tranexamic acid loaded stratum corneum lipid liposomes by working on elements of QTPPs, CQAs, CMAs, CPPs and risk assessment. A 33 Box-Behnken design was used for correlation between independent variables (lipid: cholesterol ratio, RPM of magnetic stirrer and number of cycles of probe sonication) and dependent variables (encapsulation efficiency and mean particle size). A robust model was achieved, which had potential of being explored for the identification of design space. Both the responses (CQAs) were later overlayed to find the optimality region and an optimized batch was thus obtained having encapsulation of 35.78% and mean particle size of 93.5 nm. The final optimized batch as per desirability was studied further for in vitro drug release and that showed a complete release (101.65%) within 6 h that followed a zero-order drug release kinetics. The study concludes a reliable and robust formulation model for stratum corneum lipid liposomes with reduced failure and variability. Study also focuses on encapsulation of tranexamic acid (hydrophilic drug) in lipidic carrier systems. This paper lays the groundwork for future preclinical and clinical studies of stratum corneum lipid liposomes containing tranexamic acid for topical administration.

Stratum corneum lipid liposomes for investigating skin penetration enhancer effects

Knowledge of the mechanism of action of skin penetration enhancers is essential to formulators for optimizing formulations and to maximize the efficacy of enhancers. To obtain information about the effects of penetration enhancers as a fast initial screening, investigations have been performed to identify possible correlations of the biological effectiveness of penetration enhancers with their interaction with a well-defined model system consisting of skin mimic lipid bilayers, as determined by calcein release experiments using stratum corneum lipid liposomes (SCLLs). We aimed to investigate the enhancing effects of different concentrations of two chemical penetration enhancers, Kolliphor RH40 and Transcutol on SCLLs. The results obtained by SCLL-based techniques were compared with conventional ex vivo penetration studies in case of Kolliphor RH40 to evaluate the potential of SCLLs as an alternative tool for screening various types and concentrations of penetration enhancers. As a result, calcein leakage assay performed with SCLL was considered to be a good model for the skin penetration enhancing effect. This method could be used as a time-saving and sensitive alternative in vitro screening technique in the early stage of the development of dermal formulations.

Stratum corneum lipid liposome-encapsulated panomycocin: preparation, characterization, and the determination of antimycotic efficacy against Candida spp. isolated from patients with vulvovaginitis in an in vitro human vaginal epithelium tissue model.

In this study, a liposomal lyophilized powder formulation of panomycocin was developed for therapeutic purposes against vulvovaginal candidiasis which affects 80% of women worldwide. Panomycocin is a potent antimycotic protein secreted by the yeast Wickerhamomyces anomalus NCYC 434. This study involved the preparation of panomycocin-loaded stratum corneum lipid liposomes (SCLLs), characterization of the SCLLs, and determination of antimycotic efficacy of the formulation against Candida albicans and Candida glabrata clinical vaginal isolates in a human vaginal epithelium tissue model. The encapsulation and loading efficiencies of SCLLs were 73% and 76.8%, respectively. In transmission electron microscopy images, the SCLLs appeared in the submicron size range. Dynamic light scattering analyses showed that the SCLLs had uniform size distribution. Zeta potential measurements revealed stable and positively charged SCLLs. In Fourier transform infrared spectroscopy analyses, no irreversible interactions between the encapsulated panomycocin and the SCLLs were detected. The SCLLs retained >98% of encapsulated panomycocin in aqueous solution up to 12 hours. The formulation was fungicidal at the same minimum fungicidal concentration values for non-formulated pure panomycocin when tested on an in vitro model of vaginal candidiasis. This is the first study in which SCLLs and a protein as an active ingredient have been utilized together in a formulation. The results obtained in this study led us to conduct further preclinical trials of this formulation for the development of an effective topical anti-candidal drug with improved safety.

High-Throughput Screening of Potential Skin Penetration-Enhancers Using Stratum Corneum Lipid Liposomes: Preliminary Evaluation for Different Concentrations of Ethanol.

In this study, we developed a technique for high-throughput screening (HTS) of skin penetration-enhancers using stratum corneum lipid liposomes (SCLLs). A fluorescent marker, sodium fluorescein (FL), entrapped in SCLLs was prepared to provide a preliminary evaluation of the effect of different concentrations of ethanol on the disruption effect of SCLLs, which is an alternative for skin penetration-enhancing effects. In addition, SCLLs containing a fluorescent probe (DPH, TMA-DPH, or ANS) were also prepared and utilized to investigate SCLL fluidity. The results using SCLL-based techniques were compared with conventional skin permeation and skin impedance test using hairless rat skin. The obtained correlations were validated between FL leakage, SCLL fluidity with various probes, or skin impedance and increases in the skin permeation enhancement ratio (ER) of caffeine as a model penetrant. As a result, FL leakage and SCLL fluidity using ANS were considered to be good indices for the skin penetration-enhancing effect, suggesting that the action of ethanol on the SC lipid and penetration-enhancing is mainly on the polar head group of intercellular lipids. In addition, this screening method using SCLL could be utilized as an alternative HTS technique for conventional animal tests. Simultaneously, the method was found to be time-saving and sensitive compared with a direct assay using human and animal skins.

Potential of Stratum Corneum Lipid Liposomes for Screening of Chemical Skin Penetration Enhancers.

The evaluation of effective skin chemical penetration enhancers (CPEs) is a crucial process in the development of transdermal and dermal formulations with the capacity to overcome the stratum corneum barrier. In the present study, we aimed to investigate the potential of stratum corneum lipid liposomes (SCLLs) as an alternative tool for the screening of various types and concentrations of CPEs. SCLLs were prepared using a thin-film hydration technique, and two types of fluorescent probes (sodium fluorescein [FL] or 1,6-diphenyl-1,3,5-hexatriene [DPH] were entrapped separately into SCLLs (FL-SCLL and DPH-SCLL, respectively). FL leakage from SCLLs as well as the fluidity of DPH-SCLLs were determined after incubating with various types of CPEs as a function of their concentrations. The obtained results showed a concentration-dependent relationship for most CPEs both for FL leakage and the fluidity of SCLLs. When observing these data in detail, however, the concentration profiles could be classified into five main categories depending on the mode of action of the CPEs. These results strongly suggest the usefulness of SCLLs for high-throughput screening of effective CPEs as well as the understanding of their possible mode of action, especially in the early stage of skin formulation development.

Effect of glycation focusing on the process of epidermal lipid synthesis in a reconstructed skin model and membrane fluidity of stratum corneum lipids.

ABSTRACTWe previously reported that epidermal glycation causes an increase in saturated fatty acid (FA) content in a differentiated reconstructed skin model and HaCaT cells. However, the relationship between ceramides (CERs) and glycation and their effects on stratum corneum (SC) barrier function was not elucidated. In this study, we investigated the effect of glycation on lipid content in 6-day-old cultured reconstructed skin. We used the EPISKIN RHE 6D model and induced glycation using glyoxal. In addition to transepidermal water loss, content of CERs, cholesterol and FA in the reconstructed epidermal model were analyzed by high performance thin layer chromatography. Expression of genes related to ceramide metabolism was determined by real time RT-PCR. Membrane fluidity of stratum corneum lipid liposomes (SCLL) that mimic glycated epidermis was analyzed using an electron spin resonance technique. It was found that FA was significantly increased by glycation. CER[NS], [AP], and cholesterol were decreased in glycated epidermis. Expression of ceramide synthase 3 (CERS3) was significantly decreased while fatty acid elongase 3 was increased by glyoxal in a dose dependent manner. Membrane fluidity of SCLL mimicking the lipid composition of glycated epidermis was increased compared with controls. Therefore, disruption of CER and FA content in glycated epidermis may be regulated via CERS3 expression and contribute to abnormal membrane fluidity.

Enhancement of Skin Penetration of Hydrophilic and Lipophilic Compounds by pH-sensitive Liposomes.

Enhance skin penetration of hydrophilic and lipophilic compounds using liposomes that are responsible to the pH of the skin surface. pH-sensitive liposomes were prepared by a thin layer and freeze-thaw method with dioleoyl phosphatidyl ethanolamine and cholesteryl hemisuccinate. Liposomal fusion with stratum corneum lipid liposomes was measured using fluorescence resonance energy transfer. Particle diameter and zeta potential of the liposomes after fusion were measured by dynamic light scattering and electrophoresis. Under neutral pH conditions, the diameter of the pH-sensitive liposomes was 130 nm and their zeta potential was -70 mV. In weakly acidic conditions, the diameter was larger than 3,000 nm and the zeta potential was -50 mV. In contrast, the particle diameter and the zeta potential of the non-pH-sensitive liposomes remained constant under various pH conditions. A skin penetration study was performed on hairless mice skin using vertical diffusion cells, showing that the fusion ability of pH-sensitive liposomes was higher than that of non-pH-sensitive liposomes. In the skin penetration study was carried out using hydrophilic (calcein) and lipophilic (N-(7-nitrobenz- 2-oxa-1,3-diazol-4yl)-PE) (NBD-PE) model compounds which were applied to the skin with pH-sensitive liposomes as carrier. The fluorescent compounds contained within the pH-sensitive liposomes permeated the skin more effectively than those within non-pH-sensitive liposomes, and this ability was further enhanced with the lipophilic compound. These studies suggest that pH-sensitive liposomes have potential as an important tool for delivery of compounds into the skin.

Physicochemical Analysis of Liposome Membranes Consisting of Model Lipids in the Stratum Corneum

Lamellar lipid layers in the stratum corneum (SC), the outermost layer of the skin, act as a primary permeability barrier to protect the body. The roles of SC lipid composition and membrane structure in skin barrier function have been extensively investigated using ex-vivo SC samples and reconstructed SC lipids in the form of multi-lamellar lipids or liposomes. The primary lipids, especially ceramide, have been found to be highly important. Atopic dermatitis (AD) is a well-known chronic inflammatory skin disease with immunologic and epidermal abnormalities of the permeability barrier; therefore, a comparison of SC lipids in AD skin with those in normal skin is a promising method to explore the mechanisms of skin barrier function. Here, we focused on the effect of sphingoids (ceramide metabolites and a minor component of the SC lipids) and their content/species on skin barrier function. A significant difference in the leakage ratio was observed between model SC lipid liposomes with a different sphingolipid ratio (sphingosine/sphinganine), with a value of 5.43 for normal skin vs. 14.3 for AD skin. This result shows a good concordance with AD mouse experiments. Therefore, an alteration in the composition of minor SC lipids resulting from a ceramide metabolic abnormality can affect the membrane integrity (i.e., skin barrier function). Small angle X-ray scattering (SAXS) measurements revealed no distinct differences in the SAXS pattern between the 3 models, with all models forming a rigid membrane (i.e., a nearly hydrated solid). According to increasing the temperature, the peaks indicated that the lamellar structures decreased in all models and that the lateral packing of lipids decreased, which suggested annealing or melting of the gel to a liquid crystal, although no distinct phase transition was observed through fluorescence anisotropy measurements. Hence, we assume that the altered sphingoid composition triggers local membrane structural changes (i.e., formation of domains or clusters).

Chemical enhancer solubility in human stratum corneum lipids and enhancer mechanism of action on stratum corneum lipid domain

Previously, chemical enhancer-induced permeation enhancement on human stratum corneum (SC) lipoidal pathway at enhancer thermodynamic activities approaching unity in the absence of cosolvents (defined as Emax) was determined and hypothesized to be related to the enhancer solubilities in the SC lipid domain. The objectives of the present study were to (a) quantify enhancer uptake into SC lipid domain at saturation, (b) elucidate enhancer mechanism(s) of action, and (c) study the SC lipid phase behavior at Emax. It was concluded that direct quantification of enhancer uptake into SC lipid domain using intact SC was complicated. Therefore a liposomal model of extracted human SC lipids was used. In the liposome study, enhancer uptake into extracted human SC lipid liposomes (EHSCLL) was shown to correlate with Emax. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC) were used to evaluate lipid phase alterations in enhancer-treated intact SC. IR spectra demonstrated an increase in the lipid domain fluidity and DSC thermograms indicated a decrease in the phase transition temperature with increasing Emax. These results suggest that the enhancer mechanism of action is through enhancer intercalation into SC intercellular lipids and subsequent lipid lamellae fluidization related to enhancer lipid concentration.

Preparation and characterization of ceramide-based liposomes with high fusion activity and high membrane fluidity

Liposomes are useful vesicles that deliver drugs effectively to various organs. For transdermal applications, liposomes with high membrane fluidity, high fusion activity, and comprising stratum corneum lipid have been used for drug delivery. With the aim to increase drug distribution to the skin, we developed new liposomes with three characteristics: high membrane fluidity, high fusion activity to the stratum corneum lipid liposomes (SCLL), and lipid compositions based on stratum corneum lipids. New liposomes were prepared based on SCLL. First, lipid compositions of SCLL were optimized. Second, the alkyl chain length of ceramides and fatty acids, and the saturation degree of fatty acids were altered. As a result, liposomes with the highest membrane fluidity and fusion activity to SCLL were composed of C-8 ceramide/cholesterol/linolenic acid/cholesterol sulfate = 45/5/5/45 (w/w%), and named C8L. C8L had 1.54-times greater membrane fluidity and 6.57-times greater fusion activity to SCLL than SCLL. Transmission electron microscopy revealed that C8L had a spherical structure. The surface charge and the particle size were approximately −47.7 mV and 184 nm, respectively. Thus, in the future, C8L will be used to facilitate drug delivery to the skin.

A Liposome Permeability Model for Stratum Corneum Lipid Bilayers Based on Commercial Lipids

The objective was to evaluate stratum corneum lipid liposomes (SCLLs) prepared from commercial lipids as a convenient model system for studying the mechanisms of chemical permeation enhancers. Liposomes prepared from extracted stratum corneum lipids (ESCLLs) were used as a control. Three different types of SCLLs were prepared by sonication or extrusion from mixtures of commercial ceramides, cholesterol, free fatty acids, and cholesterol 3-sulfate (SCLL-I-III; 55/25/15/5 weight ratio). Absolute mannitol permeabilities were 5- to 20-fold lower in SCLLs than in ESCLLs. 1-alkyl-2-pyrrolidone enhancers produced the same enhancement factor for mannitol efflux in sonicated SCLLs (SCLL-I) as reported previously for the ESCLLs. Enhancer-induced changes at graded depths were further monitored in SCLL-I vesicles using fluorescence spectroscopy with n-(9-anthroyloxy) fatty acid fluorescent probes. Lipid packing order, as determined from rotational correlation times derived from steady-state anisotropy and lifetime data, was found to be higher in SCLL-I than in ESCLLs. 1-alkyl-2-pyrrolidones were found to increase the fluidity of the bilayers to approximately the same extent at intermediate depths (C6-C9) as previously reported for the ESCLLs. The present results demonstrate that the sonicated SCLL model may be useful for studying the mechanisms of action of transdermal permeation enhancers.

Transdermal Delivery of Tea Catechins by Electrically Assisted Methods

Tea polyphenols, including (+)-catechin, (–)-epicatechin, and (–)-epigallocatechin-3-gallate (EGCG), have been shown to possess potent antioxidant and chemopreventive activities. The aim of this study was to assess the effects of electroporation, iontophoresis, and their combination on the transdermal delivery of tea catechins across porcine skin. The permeation characteristics were investigated using various analogues of catechins, pH values, and modes of electroporation and iontophoresis. The mechanisms by which these catechins were transported via the skin were elucidated by examining the electric conductivity, transepidermal water loss (TEWL), and fusion of stratum corneum lipid liposomes (SCLL). The isomers, (+)-catechin and (–)-epicatechin, showed different behaviors of skin permeation and local skin deposition with the electrically assisted methods. The results suggest evidence of selective skin absorption of (–)-epicatechin over (+)-catechin. A synergistic effect was detected for (+)-catechin but not for (–)-epicatechin after application of electroporation followed by iontophoresis. The presence of a gallic acid ester in the structure of EGCG significantly increased the skin uptake of catechins. However, a negligible amount of or no EGCG molecules permeated across the skin. The mechanisms involved in the enhancement of electroporation may be the skin reservoir effect and an increase in skin permeability. The TEWL profiles suggest that in addition to the force of electrorepulsion, the skin hydration effect and structural alterations may also have contributed to the enhancement by iontophoresis. Electroporation did not influence the skin barrier function, although the skin permeability increased according to the SCLL fusion study.

Mechanisms of action of novel skin penetration enhancers: Phospholipid versus skin lipid liposomes

Employing thermal analysis, we investigated the mechanism of action of novel enhancers and probed phospholipid (PL) versus stratum corneum lipid (SCL) liposomes as model membranes. The enhancers included octyl salicylate (OS), padimate O (PADO) and 2-(1-nonyl)-1,3-dioxolane (ND). The negative controls were the empty liposomes. Positive controls employed dimethylsulfoxide (DMSO) and Azone™ (AZ). For PL liposomes, DMSO sharpened the transitions. AZ abolished the pre-transition, broadened the main transition and linearly reduced its transition temperature ( T m). OS or PADO reduced T m and size of pre-transition, broadened the main transition and decreased its T m (non-linearly). ND abolished the pre-transition but increased T m of the main endotherm, suggesting retardation rather than enhancement. The results of SCL correlated with PL liposomes except for ND. In SCL liposomes, ND reduced T m and broadened the peaks indicating lipid disruption, which indicated its enhancing effects. In conclusion, OS, PADO and ND can enhance drugs by disrupting intercellular lipid domain but they differ from AZ in terms of the relationship between efficacy and concentration. Although PL liposomes are simple model membranes with sharp transitions which give detailed information about the effects of enhancers, they can provide misleading results. Simultaneous use of other models like SCL liposomes is recommended.

In vitro percutaneous absorption of all- trans retinoic acid applied in free form or encapsulated in stratum corneum lipid liposomes

The objective of this study was to design an all- trans retinoic acid (RA) topical release system that modifies drug diffusion parameters in the vehicle and the skin in order to reduce systemic absorption and the side-effects associated with topical application of the drug to skin. Three cases of application of hydrogels containing RA either in free form or encapsulated in stratum corneum lipid liposomes (SCLLs) have been considered. For this purpose, we have evaluated the RA in formulations with combinations of Carbopol ® Ultrez™ 10 (U10) and hyaluronic acid (HA) for percutaneous absorption. In vitro permeability experiments with [ 3H]- t-RA were carried out using a Franz-type diffusion cell in abdominal rat skin samples. Accumulation of the drug in the surface and skin layers was evaluated by both the tape stripping method and a dissection technique, and subsequently, all the radiolabelled samples were analyzed by liquid scintillation counting. The results show that RA encapsulation not only prolongs drug release but also promotes drug retention by the viable skin. At the same time, interaction between RA and HA has an obstructive effect on diffusion, which contributes to the formation of a reservoir of the latter.

Mechanism of the synergic effects of calcium chloride and electroporation on the in vitro enhanced skin permeation of drugs

We have already reported the substantial synergic effects of CaCl 2 and electroporation (EP) on in vitro skin permeation of calcein and FITC dextrans. In the present paper, we investigated the mechanisms for these effects by considering changes in lamellar structure and barrier recovery time of the biggest skin barrier, the stratum corneum, by this combined treatment. The change in skin lamellar structure was evaluated by lipid mobility in the stratum corneum using ATR–FTIR, calcein release from stratum corneum-lipid liposomes (SCLL), in vitro skin permeation of calcein and transepidermal water loss (TEWL). The ATR–FTIR measurement, in vitro skin permeation and changes in TEWL were also used for examining the barrier recovery time. The CH stretching band of skin lipids produced with EP was blue-shifted when compared to that without EP. Asymmetric CH stretching was highest with EP in CaCl 2 solution. Little release of calcein was observed from SCLL without EP, whereas higher releases were observed after EP with or without NaCl or CaCl 2. Particularly high calcein release (>20%) was observed over 60 min with EP in CaCl 2 solution. The in vitro permeation study of calcein was conducted through excised hairless rat skin that was pretreated with EP before skin excision. Permeation rate was highest in skin excised immediately after in vivo EP, and this rate decreased with time after EP treatment. TEWL recovered to control levels within 2 h after EP in distilled water or NaCl solution, whereas high TEWL was maintained after EP in CaCl 2 solution. These results suggest that at least lamellar destruction of stratum corneum must be related to the enhanced skin permeation of drugs by the combination of CaCl 2 and EPF. On the other hand, a prolonged enhancing effect on the skin permeation of calcein by this combination may be due to a high lamellar destruction and/or delayed barrier repair of stratum corneum.

Mechanism of the synergic effects of calcium chloride and electroporation on the in vitro enhanced skin permeation of drugs

We have already reported the substantial synergic effects of CaCl2 and electroporation (EP) on in vitro skin permeation of calcein and FITC dextrans. In the present paper, we investigated the mechanisms for these effects by considering changes in lamellar structure and barrier recovery time of the biggest skin barrier, the stratum corneum, by this combined treatment. The change in skin lamellar structure was evaluated by lipid mobility in the stratum corneum using ATR–FTIR, calcein release from stratum corneum-lipid liposomes (SCLL), in vitro skin permeation of calcein and transepidermal water loss (TEWL). The ATR–FTIR measurement, in vitro skin permeation and changes in TEWL were also used for examining the barrier recovery time. The CH stretching band of skin lipids produced with EP was blue-shifted when compared to that without EP. Asymmetric CH stretching was highest with EP in CaCl2 solution. Little release of calcein was observed from SCLL without EP, whereas higher releases were observed after EP with or without NaCl or CaCl2. Particularly high calcein release (>20%) was observed over 60 min with EP in CaCl2 solution. The in vitro permeation study of calcein was conducted through excised hairless rat skin that was pretreated with EP before skin excision. Permeation rate was highest in skin excised immediately after in vivo EP, and this rate decreased with time after EP treatment. TEWL recovered to control levels within 2 h after EP in distilled water or NaCl solution, whereas high TEWL was maintained after EP in CaCl2 solution. These results suggest that at least lamellar destruction of stratum corneum must be related to the enhanced skin permeation of drugs by the combination of CaCl2 and EPF. On the other hand, a prolonged enhancing effect on the skin permeation of calcein by this combination may be due to a high lamellar destruction and/or delayed barrier repair of stratum corneum.

Dodecyl maltoside as a solubilizing agent of stratum corneum lipid liposomes

The lytic interactions of the nonionic surfactant dodecyl maltoside (DM) with liposomes formed by a mixture of lipids modeling the stratum corneum (SC) lipid composition were investigated. To this end, the surfactant to lipid molar ratios (Re) and the normalized bilayer/aqueous phase partition coefficients (K) were determined by monitoring the changes in the static light-scattering (SLS) of the system during solubilization. The fact that the free surfactant concentration was always similar to its critical micelle concentration indicates that the liposome solubilization was mainly ruled by formation of mixed micelles. In addition, the linear dependence established between the level of SLS and Re indicates a progressive incorporation of DM in the liposomes as well as the progressive formation of mixed micelles. DM showed in all cases lower bilayer activity (higher Re values) and greater affinity with vesicles (higher K values) than those reported for its interaction with phosphatidylcholine (PC) liposomes. Thus, whereas the SC lipid liposomes were more resistant to the action of this surfactant, its degree of partitioning into SC bilayers was higher throughout the solubilization process than that exhibited in PC vesicles. Comparison of the present Re values with those reported for the lytic interaction of dodecyl glucoside (DG) with SC liposomes reveals that in the case of DM the bilayer activity was more than three times higher than that for DG in spite of the identical alkyl chain length.

Sublytic Alterations Caused by the Nonionic Surfactant Dodecyl Maltoside in Stratum Corneum Lipid Liposomes

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTSublytic Alterations Caused by the Nonionic Surfactant Dodecyl Maltoside in Stratum Corneum Lipid LiposomesM. Cócera, O. López, L. Coderch, J. L. Parra, and A. de la MazaView Author Information Departamento de Tecnologías de Tensioactivos, Instituto de Investigaciones Químicas y Ambientales de Barcelona (I.I.Q.A.B.), Consejo Superior de Investigaciones Científicas (C.S.I.C.), Calle Jorge Girona 18-26, 08034 Barcelona, Spain Cite this: Langmuir 2002, 18, 1, 297–300Publication Date (Web):December 6, 2001Publication History Received17 May 2001Revised26 September 2001Published online6 December 2001Published inissue 1 January 2002https://doi.org/10.1021/la010733cCopyright © 2002 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views87Altmetric-Citations3LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (49 KB) Get e-AlertsSUBJECTS:Hydrophilicity,Lipids,Molecules,Surfactants,Vesicles Get e-Alerts

Influence of the hydrophobic tail of alkyl glucosides on their ability to solubilize stratum corneum lipid liposomes

The lytic interactions of a series of alkyl glucosides (alkyl chain lengths ranging from C8 to C12) with liposomes formed by a mixture of lipids modeling the stratum corneum (SC) lipid composition were investigated. The surfactant-to-lipid molar ratios (Re) and the normalized bilayer/aqueous phase partition coefficients (K) were determined by monitoring the changes in the static light-scattering (SLS) of the system during solubilization. The fact that the free surfactant concentrations were always similar to their critical micelle concentrations indicates that the liposome solubilization was mainly ruled by the formation of mixed micelles. At the two interaction levels studied (100 and 0% SLS) the nonyl glucoside showed the highest ability to saturate and to solubilize liposomes (lowest Re values), whereas the dodecyl glucoside showed the highest degree of partitioning into liposomes or affinity with these structures (highest K values). Comparison of the data for octyl glucoside with that reported for the interaction of this surfactant with phosphatidylcholine (PC) liposomes shows that whereas the SC lipid liposomes were more resistant to the action of this surfactant (higher Re values), its degree of partitioning into SC bilayers was both in the saturation and solubilization of liposomes similar to that exhibited in PC vesicles (similar K values).

Solubilization of stratum corneum lipid liposomes by Triton X-100. Influence of the level of cholesteryl sulfate in the process

The interaction of Triton X-100 (T X-100) with stratum corneum (SC) lipid liposomes varying the proportion of cholesteryl sulfate (Chol-sulf) was investigated. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous phase surfactant partition coefficients ( K) were determined by monitoring the changes in the static light scattering of the system during solubilization. The fact that the free surfactant concentration was always similar to its critical micelle concentration (CMC) indicates that the liposome solubilization was mainly ruled by the formation of mixed micelles. The T X-100 ability to saturate and to solubilize SC liposomes decreased as the proportion of Chol-sulf in bilayers increased until a minimum was reached for a Chol-sulf proportion of 10%. Inversely, the surfactant partitioning into liposomes (or affinity with these bilayers) increased as the proportion of Chol-sulf increased until a maximum was reached at the same Chol-sulf proportion. Hence, when the Chol-sulf proportion in bilayers was 10% (the same that existing in the intercellular SC lipids) the ability of T X-100 molecules to interact with liposomes exhibits a minimum despite their enhanced partitioning into liposomes. These effects may be related to the reported dependencies between the level of Chol-sulf in the intercellular lipids and the abnormalities in the skin properties as the barrier function.