An antisense oligonucleotide targeting TGF-ß2 inhibits lung metastasis and induces CD86 expression in tumor-associated macrophages.

BACKGROUND: The transforming growth factor (TGF)-ß pathway is a well-described inducer of immunosuppression and can act as an oncogenic factor in advanced tumors. Several preclinical and clinical studies show that the TGF-ß pathway can be considered a promising molecular target for cancer therapy. The human genome has three TGF-ß isoforms and not much is known about the oncogenic response to each of the isoforms. Here, we studied the antitumor response to ISTH0047, a recently developed locked nucleic acid-modified antisense oligonucleotide targeting TGF-ß2. MATERIALS AND METHODS: We have studied the anticancer response to ISTH0047 using gymnotic delivery in tumor cell cultures and in in vivo preclinical orthotopic mouse models for primary tumors (breast and kidney tumors) and lung metastasis. RESULTS: We observed that ISTH0047 is able to significantly reduce TGF-ß2 mRNA and protein levels without altering the levels of TGF-ß1 and TGF-ß3. ISTH0047 prevented lung metastasis in syngeneic orthotopic renal cell carcinoma (RENCA) and breast cancer (4T1) tumor models. In addition, using an orthotopic xenograft model of a lung cancer cell line (CRL5807) that mainly expresses TGF-ß2, we observed that ISTH0047 had an important effect on the lung microenvironment inhibiting the growth of lung lesions. ISTH0047 treatment re-educated macrophages in the lung parenchyma to express the tumor-suppressive factor, CD86. CONCLUSION: Overall, our data point to TGF-ß2 as a therapeutic target and ISTH0047 as a novel anticancer drug to prevent lung metastasis by impacting on the tumor niche, in part, through the induction of CD86 in tumor-associated macrophages.

New methodology for assessing the environmental burden of cement mortars with partial replacement of coal bottom ash and fly ash.

This paper assess the mechanical an environmental behaviour of cement mortars manufactured with addition of fly ash (FA) and bottom ash (BA), as partial cement replacement (10%, 25% and 35%). The environmental behaviour was studied by leaching tests, which were performed under several temperature (23 °C and 60 °C) and pH (5 and 10) conditions, and ages (1, 2, 4 and 7 days). Then, the accumulated amount of the different constituents leached was analysed. In order to obtain an environmental burden (EB) value of each cement mixture, a new methodology was developed. The EB value obtained is related to the amount leached and the hazardous level of each constituent. Finally, the integral study of compressive strength and EB values of cement mixtures allowed their classification. The results showed that mortars manufactured with ordinary Portland cement (OPC) and with coal BA had similar or even better environmental and mechanical behaviour than mortars with FA. Therefore, the partial replacement of cement by BA might be as suitable or even better as the replacement by FA.

In vivo and in vitro evaluation of topical formulations containing physiological lipid mixture for replacement of skin barrier function.

AIM: The aim of the study was to describe a new in vivo and in vitro approach of the efficacy evaluation of cosmetic emollients to better understand the link between the formulation and the activity of cosmetic products. METHODS: Two long term in vivo studies were carried out on nine healthy Caucasian volunteers mean age 40±12 years to evaluate the protecting and repairing effects of the two different barrier repair cosmetic formulations. The application of the formulations was repeated once a day during 7 days and biophysical parameters (TEWL and Skin Hydration) were measured before and after Sodium laureth sulphate exposure The in vitro study was carried out by freeze substitution transmission electron microscopy (FSTEM) on stratum corneum samples obtained by sections of fresh skin from young pigs, depleted with a solvent mixture and treated with the two products RESULTS: The in vivo results demonstrated that daily product application provided a reinforcement of the skin barrier with protecting and repairing effects from chemical injuries the extent of which was dependent on the formulation features (product A>product B) The role of the technical form on the lipid availability was confirmed by the in vitro evaluation tests. CONCLUSION: The results point out that a daily application of physiological lipid mixture containing emulsion can protect healthy skin and promote the reparing effect on unpaired barrier skin, reducing TEWL and maintaining hydration of the stratum corneum. The efficacy degree is higher when the cosmetic form promotes the availability of active ingredients increasing the product performance.

Tracking climate change in a dispersal-limited species: reduced spatial and genetic connectivity in a montane salamander.

Tropical montane taxa are often locally adapted to very specific climatic conditions, contributing to their lower dispersal potential across complex landscapes. Climate and landscape features in montane regions affect population genetic structure in predictable ways, yet few empirical studies quantify the effects of both factors in shaping genetic structure of montane-adapted taxa. Here, we considered temporal and spatial variability in climate to explain contemporary genetic differentiation between populations of the montane salamander, Pseudoeurycea leprosa. Specifically, we used ecological niche modelling (ENM) and measured spatial connectivity and gene flow (using both mtDNA and microsatellite markers) across extant populations of P. leprosa in the Trans-Mexican Volcanic Belt (TVB). Our results indicate significant spatial and genetic isolation among populations, but we cannot distinguish between isolation by distance over time or current landscape barriers as mechanisms shaping population genetic divergences. Combining ecological niche modelling, spatial connectivity analyses, and historical and contemporary genetic signatures from different classes of genetic markers allows for inference of historical evolutionary processes and predictions of the impacts future climate change will have on the genetic diversity of montane taxa with low dispersal rates. Pseudoeurycea leprosa is one montane species among many endemic to this region and thus is a case study for the continued persistence of spatially and genetically isolated populations in the highly biodiverse TVB of central Mexico.

[Functional evaluation and quality of life in megaprostheses implanted by musculoskeletal tumors in the lower limb]. / Evaluación funcional y calidad de vida en megaprótesis implantadas por tumores musculoesqueléticos en miembro inferior.

INTRODUCTION: radical resection is the surgical treatment of choice in musculoskeletal malignancies, which often settle in the pelvis and lower limbs. Megaprothesis reconstruction has been imposed in recent years as the gold standard in limb preservation surgery. MATERIAL AND METHODS: descriptive retrospective study series of cases, including 30 patients operated between 2011 and 2019 of musculoskeletal pelvic and lower limb tumors at our institution that underwent limb-sparing reconstruction with the megaprosthesis. Functional results according to the MSTS (Musculoskeletal Tumor Society) index and complication rate were analyzed. RESULTS: the average follow-up was 40.8 months (12-101.7). Nine patients (30%) underwent pelvic resections and reconstructions, 11 patients (36.7%) underwent hip reconstruction with megaprothesis due to femoral involvement, in three patients (10%) complete femur resection was performed, and seven patients (23.3%) underwent prosthetic reconstruction of the knee. The mean MSTS score was 72.5% (range: 40-95%), and the complication rate was 56.7% (17 patients), being de tumoral recurrence (29%) the main complication. CONCLUSION: tumor megaprothesis give satisfying functional results, allowing the patients to realize a relatively normal life after a lower limb-sparing surgery.

INTRODUCCIÓN: la resección amplia es el tratamiento quirúrgico de elección en los tumores malignos musculoesqueléticos, que con frecuencia asientan en la pelvis y en los miembros inferiores. La reconstrucción mediante megaprótesis se ha impuesto en los últimos años como primera opción en la cirugía de preservación de la extremidad. MATERIAL Y MÉTODOS: estudio retrospectivo descriptivo serie de casos, incluye 30 pacientes intervenidos entre 2011 y 2019 de tumores musculoesqueléticos de pelvis y miembro inferior. En todos ellos valoramos la tasa de complicaciones y los resultados funcionales mediante el índice MSTS (Musculoskeletal Tumor Society). RESULTADOS: se realizó un seguimiento de 40.8 meses (12-101.7). En nueve pacientes (30%) se realizaron resecciones y reconstrucciones pélvicas, a 11 pacientes (36.7%) se les implantaron megaprótesis de cadera por afectación femoral, en tres de los pacientes (10%) se realizó resección del fémur completo y en siete pacientes (23.3%) reconstrucción protésica de la rodilla. El resultado funcional medio de la escala MSTS fue de 72.5% (rango: 40-95%) y la tasa de complicaciones de 56.7% (17 pacientes), siendo la recurrencia tumoral (29%) la principal complicación. CONCLUSIÓN: la reconstrucción mediante megaprótesis ofrece buenos resultados funcionales a los pacientes dentro de la cirugía de resección radical, permitiendo realizar una vida relativamente normal.

Skin efficacy of liposomes composed of internal wool lipids rich in ceramides.

Ceramides from intercellular lipids of skin stratum corneum are known to play an essential role in maintaining and structuring the lipid barrier of the skin. Internal wool lipids (IWL), which are also rich in ceramides, have a composition similar to that of the stratum corneum lipids. IWL extracted with chloroform/methanol azeotrope at the laboratory scale have been shown to be capable of forming liposomes with a stable bilayer structure. Furthermore, topical application of these IWL liposomes on intact and compromised skin has been demonstrated to improve barrier skin properties.In this study we evaluated the effect on human skin repair of different IWL extract compositions obtained by two extraction methodologies. The formation and characteristics of the liposomes prepared were greatly influenced by the IWL composition, primarily the sterol sulfate content. The IWL liposomes improved skin barrier integrity and increased skin hydration when applied onto intact skin. These improvements were slightly enhanced in the case of IWL liposomes that were richer in polar lipids.

Liposome formation with wool lipid extracts rich in ceramides.

Internal wool lipids (IWLs) are rich in cholesterol, free fatty acids, cholesteryl sulfate, and, mainly, ceramides. The repairing effect of these lipids structured as liposomes was demonstrated by reinforcing the skin-barrier integrity and increasing the water-holding capacity when applied onto the skin. This work was focused on the formation of liposomes with IWLs rich in ceramides, obtained at pilot plant level with organic solvent extraction by using methanol and acetone. The lipid composition of the two extracts was quantitatively analyzed. IWL extracts containing different amounts of sterol sulfate were used to form liposomes at physiologic p(H). Vesicle size distribution, polydispersity index, and zeta potential of all liposomes were determined to characterize them and to study their stability. The results obtained showed that IWL extract composition, which was different depending on the extraction methodologies used, greatly influences the characteristics of the liposomes formed. Vesicular size and polydispersity index liposomes were smaller when the extract composition contained a higher proportion of either free fatty acids or sterol sulfate. Moreover, liposome stability was improved when some amount of sterol sulfate was added to the composition of methanol and acetone extracts. This natural mixture with keratinaceous origin could have a special interest for cosmetic or dermopharmaceutical companies.

Lamellar rearrangement of internal lipids from human hair.

The internal lipids were extracted from untreated hair without surface lipids. Liposomes were formed with the internal lipids at different hydration levels to determine the organization of these lipids and the influence of the water content on the lamellar structure of the hair fibres by X-ray Scattering (SAXS). Two structures of hair lipids were observed at 4.5 and approximately 9.0 nm with a different behaviour as a function of water content: the largest bilayer being the one that showed a capacity to retain water inside its structure. SAXS was also applied directly to three samples: a packed swatch of hair fibres at 60% RH, fibres soaked in water and delipidized fibres. Only the lamella at 9.0 nm was slightly affected by water content. Moreover, there was a small diminution in intensity probably due to a high permeability of wet fibres which could give rise to a disorder of the lipid structure. These two lamellar rearrangements are probably made up of lipids with a different and specific hydrophilic/hydrophobic balance.

Cosmetic effectiveness of topically applied hydrolysed keratin peptides and lipids derived from wool.

BACKGROUND/PURPOSE: Skin moisturisation, elasticity, feel and appearance can all be improved through the topical application of protein hydrolysates. Recent studies suggest that supplementing intercellular lipids of the stratum corneum can enhance the functioning of the skin. METHODS: In this study, a hydrolysed keratin peptide (molecular weight <1000 Da) was prepared from wool and tested on skin in two different formulations: an aqueous solution and an internal wool lipids (IWL) liposome suspension. In vivo long-term studies were performed to evaluate the water barrier function of the skin after topical application of different formulations. During the treatment period, hydration and elasticity were determined. A sorption-desorption test was also performed to assess the hygroscopic properties and water-holding capacity of the different treated skin sites. RESULTS: Significant differences were found between the control and treated sites, with the treated areas showing an increase in hydration and elasticity as a result of keratin peptide application. Measurements also indicated that the keratin formulations reinforce the skin barrier integrity, improving its water-holding capacity. CONCLUSION: A combination of the keratin peptide with the IWL showed beneficial effects, indicating that this combination is suitable for designing new cosmetics products.

[Aneurysmal bone cyst located on the acetabular roof in an 11-year-old male]. / Quiste óseo aneurismático localizado en el techo acetabular en un varón de 11 años.

The aneurysmal bone cyst is a benign rare tumor, which usually develops during childhood and its more often found in limbs. The most accepted treatment consists in curetagge and filling with graft. However, certain locations may be inaccesible for surgery and represent therapeutical challenges. We present the case of an 11 year-old male patient with limping and right hip pain without any traumatic nor infectious record. In the image studies with CT and MRI a lytic and expansive lession was found in the upper part of the right acetabulum and right iliac wing, all of which suggested an aneurysmal bone cyst with an associated acetabular fracture. A biopsy was performed which confirmed the diagnosis. He was treated with a CT-guided embolization and, due to its size, curetagge and allograft filling afterwards. He was asymptomatic after1 year of follow-up.

El quiste óseo aneurismático es una tumoración benigna poco común, de aparición en la infancia generalmente y a nivel de extremidades. El tratamiento más habitual consiste en el curetaje y relleno con injerto. No obstante, localizaciones poco accesibles a la cirugía suponen un reto terapéutico. Se presenta el caso de un paciente de 11 años con cojera y dolor en cadera derecha sin antecedente traumático ni infeccioso. En los estudios de imagen con TAC y RM se evidencia una lesión lítica expansiva que ocupa todo el techo del acetábulo y pala ilíaca derecha, sugestiva de un quiste óseo aneurismático presentando fractura acetabular asociada. Se realizó una biopsia que confirmó el diagnóstico. Se trató mediante embolización guiada por angiografía debido al gran volumen y alto riesgo de fractura, después del curetaje y relleno con aloinjerto evolucionó satisfactoriamente y el paciente se encuentra asintomático al año de la intervención.

Wool peptide derivatives for hand care.

Hands experience much greater wear and tear during normal daily routines compared with most other parts of the body, and thereby demand specific needs from cosmetics targeted at hand care. Keratin proteins are the major structural component of the outer layers of the skin. In this work a novel keratin fraction from wool, which has high cystine content present in the S-sulphonated form, has been developed to target hand care applications. In vivo long-term studies were performed to evaluate the water-holding capacity and elasticity of hand skin following topical application of keratins. Moreover, protection of healthy skin against detergent-induced dermatitis was evaluated after topical application of the keratin-active formulation. Significant results in the measured biophysical parameters were found, which indicated an improvement in the skin's water-holding capacity, hydration, and elasticity for volunteers with dry skin as a result of the keratin peptide treatment. Results also indicated that the keratin peptide treatment can prevent some of the damaging effects associated with surfactant exposure.

[Surgical treatment of malignant primary tumors of the pelvis on Ennekings zone II]. / Tratamiento quirúrgico de los tumores primarios malignos de pelvis de la zona II de Enneking.

INTRODUCTION: Surgical treatment of malignant bone tumors of the pelvis with periacetabular involvement is constantly evolving. Even though acetabular reconstructions improve quality of life without impairing cancer control, they are not complication free. Our purpose is to describe the functional outcomes and surgical complications of different reconstructive techniques for Enneking zone II tumors. MATERIAL AND METHODS: Fifteen patients underwent surgery for malignant pelvic bone tumors between 2002 and 2012. Seven patients were retrospectively evaluated according to the Enneking and Dunham classification and were found to have periacetabular involvement, as follows: 3 were type II; 1 types I + II; 2 types II + III, and one types I + II + III. Five patients had a standard chondrosarcoma and 2 osteosarcoma. Patients included 4 males and 3 females; mean age was 43 years. The minimum follow-up period was 12 months (mean 6.14 years). All of them underwent cancer resection with periacetabular reconstruction: massive osteochondral allograft in 3 patients, structural allograft and hip arthroplasty in 2 patients, and prosthesis with iliac anchoring in 2. They were clinically, radiologically and functionally evaluated with the MSTS scale (1993). RESULTS: The mean MSTS score 6 months after surgery was 20.71 (69%). Five patients (71.4%) had surgical complications: 2 dislocations of the native femoral head on the allograft; one aseptic prosthetic dislodgement, and 2 deep infections. All patients had free intraoperative borders. CONCLUSIONS: Acetabular reconstructions after oncologic resection for malignant bone tumors seem to provide good functional outcomes. However, only selected cases should undergo surgeries associated with a high complication rate.

El tratamiento quirúrgico de los tumores óseos malignos de pelvis con afectación periacetabular está en continua evolución. Las reconstrucciones acetabulares mejoran la calidad de vida sin perjudicar el control oncológico; sin embargo, no están exentas de complicaciones. Nuestro objetivo es describir los resultados funcionales y las complicaciones quirúrgicas de diferentes técnicas reconstructivas de la zona II de Enneking.

Changes in phosphatidylcholine liposomes caused by a mixture of Triton X-100 and sodium dodecyl sulfate.

The mechanisms governing the interaction of equimolecular mixtures of Triton X-100 (Tx-100) and sodium dodecyl sulfate (SDS) with phosphatidylcholine liposomes were investigated. Permeability alterations were determined as a change in 5(6)-carboxyfluorescein released from the interior of vesicles and bilayer solubilization as a decrease in the static light-scattered by liposome suspensions. At subsolubilizing level, a maximum bilayer/water partitioning of surfactant mixture was reached at 30% CF release, which correlated with the increased presence of SDS in the bilayers. However, transition stages between 70% CF release and 100% light-scattering corresponded to the increased presence of Tx-100 in these structures. These findings may be correlated with the reduced deleterious effects caused by this mixture in different tissues versus pure SDS, given that the presence of Tx-100 may modulate the level of SDS partitioning in the human stratum corneum. At subsolubilizing level, the mixture showed higher affinity with bilayers than those reported for single components, whereas at solubilizing level this affinity was slightly lower and higher than those reported for Tx-100 and SDS respectively. A direct relationship was established in the initial interaction steps between the growth of vesicles, the leakage of entrapped CF and the effective molar ratio of surfactant to phospholipid in bilayers (Re). This dependence was also detected during solubilization, where the decrease in the vesicle size and in the scattered light of the system depended on the Re parameter and hence on the bilayer composition. The fact that the free surfactant concentration at subsolubilizing and solubilizing levels showed respectively lower and similar values than the critical micelle concentration (c.m.c.) of the surfactant mixture indicates that permeability alterations and solubilization were determined respectively by the action of surfactant monomer and by the formation of mixed micelles. This finding supports the generally admitted assumption, for single surfactants, that the concentration of free surfactant must reach the c.m.c. for solubilization to occur and highlights the influence of the negative synergism of this surfactant mixture on the free surfactant concentration needed to saturate or solubilize liposomes.

Different stratum corneum lipid liposomes as models to evaluate the effect of the sodium dodecyl sulfate.

The stability of stratum corneum (SC) liposomes against the action of surfactants has been revised. To this end, two types of vesicles were used; vesicles formed with the lipid and protein material extracted from SC, and lipid mixtures approximating the SC composition. In this case, the proportion of ceramides (Cer) and cholesteryl sulfate (Chol-sulf) was varied and the relative proportion of the other lipids remained constant. The increasing presence of these two lipids increased the resistance of liposomes against the action of the anionic surfactant sodium dodecyl sulfate (SDS). The rise in the cell-to-cell cohesion that occurred in recessive X-linked ichthyosis due to the accumulation of Chol-sulf could be associated in part to the enhanced stability of (Chol-sulf)-enriched bilayers. It is noteworthy that the surfactant partitioning between bilayers and the aqueous phase increased and decreased, respectively, as the proportion of Cer and Chol-sulf increased. This effect may be attributed to the variations in both the electrostatic interactions lipid-surfactant (electrostatic repulsion between the sulfate groups of both Chol-sulf and SDS), and the hydrophilic lipophilic balance of the lipid mixtures, in which Cer is replaced by the major polar lipid of the mixture (Chol-sulf). The fact that the free surfactant concentration was always smaller than its critical micelle concentration indicates that the permeability alterations were mainly ruled by the action of surfactant monomers, in agreement with the results reported for sublytic interactions of this surfactant with PC liposomes.

Liposomes as alternative vehicles for sun filter formulations.

The aim of our study was to determine the influence of several types of liposomes with a different lipid composition on the percutaneous absorption of one conventional sun filter with a lipophilic character (ethyl hexyl methoxycinnamate) using both in vitro and in vivo methodologies. Three different liposomes were prepared with unsaturated and saturated phosphatidylcholine (PC, HPC), and with a wool lipid mixture (IWL) with a composition similar to that of the stratum corneum lipids. Results showed that the liquid crystalline state associated with PC liposomes plays a key role in enhancing skin penetration. when liposomes with a composition and structural organization similar to that of the stratum corneum lipids (HPC and IWL) are used, the skin penetration is retarded, suggesting a certain reinforcement of the stratum corneum barrier. These two types of liposomes could be regarded as alternatives to conventional oil/water emulsions in the formulations of lipidic sun filters. Finally, an acceptable correlation was obtained using both in vitro and in vivo methodologies to evaluate the corresponding skin absorption profile.

Direct formation of mixed micelles in the solubilization of phospholipid liposomes by Triton X-100.

The vesicle to micelle transition which results in the interaction of the Triton X-100 surfactant with phosphatidylcholine vesicles was studied by means of dynamic light scattering (at different reading angles) and by freeze-fracture electron microscopy techniques. Vesicle solubilization was produced by the direct formation of mixed micelles without the formation of complex intermediate aggregates. Thus, vesicle to micelle transformation was mainly governed by the progressive formation of mixed micelles within the bilayer. A subsequent separation of these micelles from the liposome surface (vesicle perforation by the formation of surfactant-stabilized holes on the vesicle surface) led to a complete solubilization of liposomes.

Transmission electron microscopy and light scattering studies on the interaction of a nonionic/anionic surfactant mixture with phosphatidylcholine liposomes.

The interaction of an equimolecular mixture of nonylphenol polyethoxylated [NP(EO)10] and sodium dodecyl sulfate (SDS) surfactants with phosphatidylcholine (PC) liposomes was studied by means of transmission electron microscopy (TEM) and changes in the mean particle size (quasielastic light scattering; QELS) and in the static light scattering (SLS) of the system during liposome solubilization. A good correlation was found between the TEM diameter of particles and the mean hydrodynamic diameter (HD) determined by QELS. The aggregates resulting in this interaction were dependent on the surfactant concentration in the system. Thus, an initial vesicle growth occurred when the surfactant concentration was 15.98 mol%, together with the formation of a very small percentage of smaller particles. Additional surfactant amounts (28.32 mol%) led first to the formation of largest vesicles (HD 418 nm) and second to a fall in the vesicle diameter and in the SLS of the system. Thus, for 38.27 mol%, the TEM picture still showed the presence of vesicles, albeit with signs of disintegration. When additional amounts of surfactant were added to the system, the size curve started to show a bimodal distribution. Thus, for 51.81 mol% surfactant concentration, a sharp curve appeared at 51 nm, corresponding to the formation of small particles and TEM pictures clearly showed vesicle disintegration with formation of tubular structures. It is noteworthy that additional surfactant amounts (from 52 to 60 mol%) led to the formation of unclosed multilayered structures together with smaller aggregates. The gradual increase in the proportion of these smaller aggregates (mixed micelles) led to the complete solubilization of liposomes.

Subsolubilizing alterations caused by alkyl glucosides in phosphatidylcholine liposomes.

The subsolubilizing alterations caused by a series of alkyl glucosides (alkyl chain lengths ranging from C8 to C12) in unilamellar phosphatidylcholine (PC) liposomes were investigated. The surfactant to phospholipid molar ratios (RE) and the normalized bilayer/aqueous phase partition coefficients (K) were determined by monitoring the increase of the fluorescence intensity of liposome suspensions due to the 5(6)-carboxyfluorescein (CF) released from the interior of vesicles to the bulk aqueous phase. Given that the free surfactant concentrations was always lower than the critical micelle concentration (CMC) of the surfactant tested we may assume that the surfactant-liposome interactions were mainly ruled by the action of surfactant monomers. In general terms, the decrease in the surfactant alkyl chain length (or the rise in the surfactant CMC) resulted in an increase in the ability of these surfactants to alter the permeability of liposomes and, inversely, in an abrupt decrease in their affinity with these bilayers structures. The overall balance of these opposite tendencies shows that at the two interaction levels studied (50 and 100% of CF release) the nonyl and the octyl glucoside showed, respectively, the highest ability to alter the release of the CF trapped in bilayers (lowest RE values), whereas the dodecyl glucoside showed the highest degree of partitioning into liposomes or affinity with these bilayer structures (highest K values).

Alterations in stratum corneum lipid liposomes due to the action of triton X-100. Influence of the level of ceramides on this process.

The role played by the ceramides (Cer) in the interaction of Triton X-100 (T(X-100)) with liposomes modeling the stratum corneum (SC) lipid composition was studied. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous phase partition coefficients (K) were determined at sublytic level by monitoring the changes in the fluorescence intensity of liposomes due to the 5(6)-carboxyfluorescein (CF) released from the interior of vesicles. Higher and lower Cer proportions than those existing in the SC (40%) led respectively to a fall and to a rise in the surfactant ability to alter these liposomes. However, the surfactant partitioning between bilayers and water (bilayer affinity with vesicles) exhibited a maximum for 40% Cer. Thus, at low Cer proportions the ability of T(X-100) molecules to alter these bilayers was maximum despite their reduced partitioning into bilayers, in line with the reported interaction of the anionic surfactant model sodium dodecyl sulfate with these vesicles. These findings underline the fragility of these bilayers as an effective barrier and could explain in part the reported dependencies of low level of Cer in skin lipids and function barrier abnormalities. The fact that the free surfactant concentration needed to achieve the two interaction levels investigated was lower than the surfactant CMC indicates that permeability alterations were mainly ruled by the action of surfactant monomers, regardless of Cer proportion in bilayers.

Influence of cholesterol on liposome fluidity by EPR. Relationship with percutaneous absorption.

The influence of liposome composition on bilayer fluidity and its effect on the percutaneous absorption into the skin were investigated. Liposomes formed with saturated or unsaturated phospholipids (H-PC or PC) with varying amounts of cholesterol were prepared and their penetration behaviour into the stratum corneum was followed up by means of the stripping method. The order and dynamics of the hydrophobic domain of the vesicles were studied using electron paramagnetic resonance (EPR) methodology. Phospholipid composition and the amount of cholesterol exert a considerable influence on the penetration behaviour of the probe encapsulated in the liposomes. This behaviour is closely related to the fluidity characteristics of these liposomes studied by EPR. Therefore, a penetration mechanism of the vesicles into the skin, based on the incorporation of lipids into the skin lipids and on fluidity behaviour, is suggested.