Ethosomes,binary ethosomes and transfersomes of terbinafine hydrochloride: A comparative study

The aim of this study was to compare the skin permeation of ethosomes, binary ethosomes and transfersomes of Terbinafine Hydrochloride (TH) under non-occlusive conditions. These lipid vesicles were prepared and characterized for shape, size, zeta-potential and entrapment efficiency. Franz diffusion cells and confocal laser scanning microscopy (CLSM) were used for the percutaneous absorption studies. The quantity of drug in the skin from ethosomes, binary ethosomes (the weight ratio of ethanol to propylene glycol 7:3, ethanol-PG = 7:3, w/w), and transfersomes was 1.26, 1.51 (p <0.05), 1.56 (p <0.01) times higher than that of TH from traditional liposomes (control). The skin deposition of the applied dose (DD%) of TH from ethosomes, binary ethosomes, and transfersomes was 3.34 (p < 0.05), 9.88 (p < 0.01), 2.52 times higher than that of TH from control. The results of CLSM experiments showed that penetration depth and fluorescence intensity of Rhodamine B from binary ethosomes was much greater than that from ethosomes and transfersomes. These results indicated the binary ethosomes (ethanol-PG = 7:3, w/w) most effectively permitted drug penetration through skin; transfersomes made drug easiest to accumulate in the skin. Ethosomes improved drug delivery with greater improvement in skin permeation than improvement in skin deposition.     

乙醇脂质体、二元醇脂质体及传递体对多奈哌齐经皮转运的对比性研究

目的:制备多奈哌齐乙醇脂质体、二元醇脂质体和传递体,并比较皮肤渗透性,从而进一步有效优化药物的经皮转运。方法:通过形态,粒径分布,Zeta电位值和包封率对多奈哌齐乙醇脂质体、二元醇脂质体及传递体进行了初步表征,运用Franz扩散池和共聚焦激光扫描电镜考察了3种囊泡的经皮转运情况。结果:当二元醇脂质体包封率最高(89.1±0.42)%时,乙醇-丙二醇=7∶3,且二元醇脂质体(乙醇-丙二醇为7∶3,W/W)在皮肤中24 h的累积渗透百分数分别是乙醇脂质体和传递体的3.9和5.4倍。结论:二元醇醇脂质体(乙醇-丙二醇为7∶3,W/W)时,有效地改善了药物在醇脂质体中的包封率,且显著增加的药物在皮肤中的累积量。     

Comparative study of liposomes,transfersomes and ethosomes as carriers for improving topical delivery of celecoxib

Topical administration of celecoxib proved to be an effective mean of preventing skin cancer development and improving anticancer drugs effectiveness in skin tumors treatment. The aim of this study was the development of an effective topical formulation of celecoxib, able to promote drug skin delivery, providing its in depth penetration through the skin layers. Three kinds of vesicular formulations have been investigated as drug carriers: liposomes containing a surfactant, or transfersomes and ethosomes, containing suitable edge activators. Firstly, the effect of membrane composition variations on the system performance has been evaluated for each vesicle type. Selected formulations were characterized for particle size, polydispersity index and encapsulation efficiency. The best formulations were subjected to ex vivo permeation studies through excised human skin. All vesicular formulations markedly (p < 0.001) improved the drug amount penetrated into the skin with respect to an aqueous suspension, from 2.0 to 6.5, up to 9.0 folds for liposomes, transfersomes and ethosomes, respectively. In particular, ethosomes containing Tween 20 as edge activator not only showed the best vesicle dimensions and homogeneity, and the highest encapsulation efficacy (54.4%), but also enabled the highest increase in drug penetration through the skin, probably due to the simultaneous presence in their composition of ethanol and Tween 20, both acting as permeation enhancers. Therefore, among the various vesicular formulations examined in the study, Tween 20-ethosomes can be considered the most promising one as carrier for topical celecoxib applications aimed to prevent skin cancer development and increase the anticancer drugs effectiveness against skin tumors.     

In vitro study of ethosome penetration in human skin and hypertrophic scar tissue

The purpose of this study is to characterize a novel transdermal delivery carrier, ethosomes containing 5-fluorouracil. The delivery of drugs from ethosomes in human hypertrophic scar (HS) and the mechanisms of action of ethosomes in human HS were investigated. Percutaneous ethosome permeation was evaluated in vitro in human HS and skin using a Franz's cell. The amount of 5-fluorouracil that permeated HS and skin after 24 hours was most abundant in ethosomes via HS (E-Scar), followed by hydroethanolic solution via HS (H-Scar), ethosomes via skin (E-Skin), and hydroethanolic solution via skin (H-Skin). The penetration of ethosomes in HS and skin was analyzed by ethosomes fluorescently labeled with rhodamine 6GO using confocal laser scanning microscopy. The fluorescence intensity after application for 24 hours was highest in E-Scar, followed by E-Skin, H-Scar, and H-Skin, which indicates the penetration of ethosomes in HS was greatest. In conclusion, we consider that ethosomes are a highly efficient carrier in HS.     

Nanocarriers to Enhance the Accumulation of Vitamin K1 into the Skin

Purpose

Vitamin K1 (VK1) is a molecule abundant in some species of leaf vegetables with beneficial effects in humans following administration on the skin. This work investigates the possibility to use formulations based on lipid vesicles, namely liposomes, transfersomes and ethosomes, suitable to be administered on the skin by nebulization and alternative to fat semisolid preparations present on the market.

Methods

Lipid vesicles encapsulating VK1 were prepared and characterized. Ex-vivo experiments on Franz cells were carried out to study the VK1 accumulation/permeation in/through the skin. Vesicles interaction with the skin was investigated by confocal laser scanning microscopy (CLSM) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy.

Results

All developed carriers were stable following long-term storage and were not altered following nebulization. In ex-vivo experiments, vesicles with the highest deformability index, namely transfersomes and ethosomes, led to an enhanced VK1 accumulation/permeation into/through the skin. Interestingly, the nebulization of the vesicles led to a further increase of VK1 accumulation into the skin.

Conclusions

In conclusion, to achieve a local effect of VK1 on the skin, the topical nebulization of VK1-containing transfersomes could offer a good compromise between a high VK1 penetration into the skin and a limited permeation through it.

     

Formulation and characterization of Phospholipon 90 G and tween 80 based transfersomes for transdermal delivery of eprosartan mesylate

The objective of the current study was to formulate the eprosartan mesylate loaded transfersomes using different proportions of Phospholipon^® 90?G and Tween^® 80 (95–75:5–25% w/w). The prepared transfersomes were characterized for their vesicles size, shape, polydispersity index, zeta potential, entrapment efficiency, in vitro skin permeation, confocal laser scanning microscopy, and in vivo skin irritation. Results revealed that the formulated transfersomes were negatively charged, spherical unilamellar structure of 71.18–85.66?nm with entrapment efficiency of 83.00–88.19%, and presented transdermal flux of 1.78–5.02?μg/cm²/h across rat skin. Confocal laser scanning microscopy confirmed that the formulated rhodamine 6?G loaded transfersomes could penetrate deeply and uniformly into rat skin. Additionally, in vivo skin irritation studies revealed that the prepared transfersomes were devoid of any skin irritation potential (erythema and edema). Results of this study revealed that the transfersomes prepared with Tween^® 80 could be used to enhance the transdermal delivery of eprosartan mesylate. In conclusion, transdermal transfersomes formulation may prove to be an encouraging drug carrier for eprosartan mesylate and other actives, particularly owing to their simple formulation and unsophisticated scale-up methods.     

Comparison of 5-aminolevulinic acid-encapsulated liposome versus ethosome for skin delivery for photodynamic therapy

Topical photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) is an alternative therapy for many non-melanoma skin cancers. The major limitation of this therapy, however, is the low permeability of ALA through the stratum corneum (SC) of the skin. The objective of the present work was to characterize ethosomes containing ALA and to enhance the skin production of protoporphyrin IX (PpIX), compared to traditional liposomes. Results showed that the average particle sizes of the ethosomes were less than those of liposomes. Moreover, the entrapment efficiency of ALA in the ethosome formulations was 8-66% depending on the surfactant added. The particle size of the ethosomes was still approximately <200 nm after 32 days of storage. An in vivo animal study observed the presence of PpIX in the skin by confocal laser scanning microscopy (CLSM). The results indicated that the penetration ability of ethosomes was greater than that of liposomes. The enhancements of all the formulations were ranging from 11- to 15-fold in contrast to that of control (ALA in an aqueous solution) in terms of PpIX intensity. In addition, colorimetry detected no erythema in the irradiated skin. The results demonstrated that the enhancement ratio of ethosome formulations did not significantly differ between the non-irradiated and irradiated groups except for PE/CH/SS, which may have been due to a photobleaching effect of the PDT-irradiation process.     

Superiority of liquid crystalline cubic nanocarriers as hormonal transdermal vehicle: comparative human skin permeation-supported evidence

ABSTRACT

Objectives: The aim of this investigation was to explore the feasibility of various nanocarriers to enhance progesterone penetration via the human abdominal skin.

Methods: Four progesterone-loaded nanocarriers; cubosomes, nanoliposomes, nanoemulsions and nanomicelles were formulated and characterized regarding particle size, zeta potential, % drug encapsulation and in vitro release. Structural elucidation of each nanoplatform was performed using transmission electron microscopy. Ex vivo skin permeation, deposition ability and histopathological examination were evaluated using Franz diffusion cells.

Results: Each nanocarrier was fabricated with a negative surface, nanometric size (≤ 270 nm), narrow size distribution and reasonable encapsulation efficiency. In vitro progesterone release showed a sustained release pattern for 24 h following a non-Fickian transport diffusion mechanism. All nanocarriers exhibited higher transdermal flux relative to free progesterone. Cubosomes revealed a higher skin penetration with transdermal steady flux of 48.57.10^–2 ± 0.7 µg/cm² h. Nanoliposomes offered a higher percentage of skin progesterone deposition compared to other nanocarriers. Based on the histopathological examination, cubosomes and nanoliposomes were found to be biocompatible for transdermal application. Confocal laser scanning microscopy confirmed the ability of fluoro-labeled cubosomes to penetrate through the whole skin layers.

Conclusion: The elaborated cubosomes proved to be a promising non-invasive nanocarrier for transdermal hormonal delivery.     

Prevention of follicular penetration: barrier-enhancing formulations against the penetration of pollen allergens into hair follicles

The hair follicles could be a reservoir for topically applied substances. They are not only surrounded by a close network of blood capillaries, which makes them interesting for drug delivery, but they are also the host of dendritic cells, which are important for immunomodulation. Previously, pollen allergens were shown to penetrate into the hair follicles. The application of barrier-enhancing formulations might represent an effective strategy to prevent pollen protein penetration into the hair follicle. In the present study, porcine skin areas were pretreated with 4 barrier-enhancing emulsions. One skin area served as control and remained without pretreatment. Afterwards, fluorescein-isothiocyanate-labeled grass pollen proteins were applied to the porcine skin samples, and their penetration was investigated via fluorescent laser scanning microscopy. It was shown that the barrier-enhancing formulations were able to significantly reduce the penetration of exogenous proteins into the hair follicles, the extent of such reduction depending on the formulation.     

Magnesium ascorbyl phosphate vesicular carriers for topical delivery; preparation,in-vitro and ex-vivo evaluation,factorial optimization and clinical assessment in melasma patients

Ascorbic acid (vitamin C) is an antioxidant that is widely used in cosmetics in skincare products. Due to the excessive low stability of ascorbic acid in cosmetic formulations, the stabilized ascorbic acid derivative, magnesium ascorbyl phosphate (MAP) was formulated as vesicular carriers; ethosomes and niosomes. The aim was to deliver MAP at the intended site of action, the skin, for sufficient time with enhanced permeation to get an effective response. Ethosomes were formulated using a full 3² factorial design to study ethanol and phospholipid concentration effect on ethosomes properties. Niosomes were formulated using 2³ factorial designs to study the effect of surfactant type, surfactant concentration and cholesterol concentration on niosomes properties. The prepared formulations were evaluated for their Entrapment efficiency, particle size, polydispersity index, zeta potential and % drug permeated. The optimized ethosomal and niosomal formulations were incorporated into carbopol gel and evaluated for their permeation, skin retention and stability. A comparative split-face clinical study was done between the ethosomal and niosomal formulations for melasma treatment using Antera 3 D^® camera. The optimized ethosomal and niosomal gels showed comparable controlled permeation and higher skin retention over their ethosomes and niosomes formulations respectively. Magnesium ascorbyl phosphate ethosomal gel showed clinically and statistically significant melanin level decrease after one month while MAP niosomal gel showed clinically and statistically significant melanin level decrease after six months. A combination of MAP ethosomes and niosomes could be promising skincare formulations for melasma and hyperpigmentation short and long-term treatment.     

Skin penetration and deposition of carboxyfluorescein and temoporfin from different lipid vesicular systems: In vitro study with finite and infinite dosage application

The aim of the present research is to evaluate the influence of different lipid vesicular systems as well as the effect of application mode on skin penetration and deposition behaviors of carboxyfluorescein (hydrophilic model drug) and temoporfin (lipophilic model drug). All of the lipid vesicular systems, including conventional liposomes, invasomes and ethosomes, were prepared by film hydration method and characterized for particle size distribution, ζ-potential, vesicular shape and surface morphology, in vitro human skin penetration and skin deposition. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) defined that all of lipid vesicles had almost spherical structures with low polydispersity (PDI < 0.2) and nanometric size range (z-average no more than 150 nm). In addition, all lipid vesicular systems exhibited a negative zeta potential. In vitro skin penetration and deposition experiments demonstrated that, in the case of CF with finite dose application (10 μl/cm2) and infinite dose application (160 μl/cm2), lipid vesicular systems, especially ethosomes and invasomes, compared with non-vesicular systems, can significantly improve the delivery of hydrophilic drug such as carboxyfluorescein into skin deep layers or across the skin. While in the case of mTHPC with finite and infinite dose application, most of drug accumulation was observed in the skin superficial layer for both lipid vesicular systems and non-vesicular systems. The results also revealed that the factors influencing the drug skin distribution concern the physicochemical characteristics of the drug, the choice of the vehicle formulation and the application mode applied.     

尼美舒利醇质体的体外经皮渗透特性及皮肤刺激性

目的:考察醇质体作为尼美舒利经皮给药载体的体外渗透性及刺激性。方法:采用注入法制备尼美舒利醇质体,采用Franz扩散池和鼠皮进行体外渗透实验,HPLC测定药物浓度并计算药物稳态透皮速率、12 h累积释放量及皮内滞留量;采用小鼠皮肤红斑平均积分考察尼美舒利醇质体刺激性。结果:测得尼美舒利醇质体的稳态经皮渗透速率和12 h累积释放量分别是(16.28±1.68)μg.(cm2.h)-1,(195.38±19.89)μg/cm2,与脂质体相比提高了1.9倍(P<0.05);而醇质体的皮内滞留量为(318.67±38.57)μg/cm2,仅是脂质体的1.07倍(P>0.05)。皮肤刺激性实验显示,NIM醇质体的红斑指数与生理盐水的差异并不明显(P>0.05)。结论:尼美舒利醇质体的经皮渗透性和皮肤刺激性都优于脂质体,是一种有效的经皮给药制剂。     

Nanosized ethosomes-based hydrogel formulations of methoxsalen for enhanced topical delivery against vitiligo: formulation optimization,in vitro evaluation and preclinical assessment

The present investigation aimed for the development and characterization of ethosomes-based hydrogel formulations of methoxsalen for enhanced topical delivery and effective treatment against vitiligo. The ethosomes were prepared by central composite design (CCD) and characterized for various quality attributes like vesicle shape, size, zeta potential, lamellarity, drug entrapment and drug leaching. The optimized ethosomes were subsequently incorporated int Carbopol® 934 gel and characterized for drug content, rheological behavior, texture profile, in vitro release, ex vivo skin permeation and retention, skin photosensitization and histopathological examination. Ethosomes were found to be spherical and multilamellar in structures having nanometric size range with narrow size distribution, and high encapsulation efficiency. Ethosomal formulations showed significant skin permeation and accumulation in the epidermal and dermal layers. The fluorescence microscopy study using 123 Rhodamine exhibited enhanced permeation of the drug-loaded ethosomes in the deeper layers of skin. Also, the developed formulation showed insignificant phototoxicity and erythema vis-à-vis the conventional cream. The results were cross-validated using histopathological examination of skin segments. In a nutshell, the ethosomes-based hydrogel formulation was found to be a promising drug delivery system demonstrating enhanced percutaneous penetration of methoxsalen with reduced phototoxicity and erythema, thus leading to improved patient compliance for the treatment against vitiligo.     

Lipid nanocarriers as skin drug delivery systems: Properties,mechanisms of skin interactions and medical applications

During the past decades, lipid nanocarriers are gaining momentum with their multiple advantages for the management of skin diseases. Lipid nanocarriers enable to target the therapeutic payload to deep skin layers or even to reach the blood circulation making them a promising cutting-edge technology.Lipid nanocarriers refer to a large panel of drug delivery systems. Lipid vesicles are the most conventional, known to be able to carry lipophilic and hydrophilic active agents. A variety of lipid vesicles with high flexibility and deformability could be obtained by adjusting their composition; namely ethosomes, transfersomes and penetration enhancer lipid vesicles which achieve the best results in term of skin permeation. Others are designed with the objective to perform higher encapsulation rate and higher stability, such as solid lipid nanoparticles and nanostructured lipid nanocarriers.In this review, we attempted to give an overview of lipid based nanocarriers developed with the aim to enhance dermal and transdermal drug delivery. A special focus is put on the nanocarrier composition, behavior and interaction mechanisms with the skin. Recent applications of lipid-based nanocarriers for the management of skin diseases and other illnesses are highlighted as well.     

Melatonin loaded ethanolic liposomes: physicochemical characterization and enhanced transdermal delivery.

The current investigation aims to evaluate the transdermal potential of novel ethanolic liposomes (ethosomes) bearing Melatonin (MT), an anti-jet lag agent associated with poor skin permeation and long lag time. MT loaded ethosomes were prepared and characterized for vesicular shape and surface morphology, vesicular size, entrapment efficiency, stability, in vitro skin permeation and in vivo skin tolerability. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Dynamic Light Scattering (DLS) defined ethosomes as spherical, unilamellar structures having low polydispersity (0.032+/-0.011) and nanometric size range (122+/-3.5 nm). % Entrapment efficiency of MT in ethosomal carrier was found to be 70.71+/-1.4. Stability profile of prepared system assessed for 120 days revealed very low aggregation and growth in vesicular size (7.6+/-1.2%). MT loaded ethosomal carriers also provided an enhanced transdermal flux of 59.2+/-1.22 microg/cm2/h and decreased lag time of 0.9 h across human cadaver skin. Fourier Transform-Infrared (FT-IR) data generated to assess the fluidity of skin lipids after application of formulation revealed a greater mobility of skin lipids on application of ethosomes as compared to that of ethanol or plain liposomes. Skin permeation profile of the developed formulation further assessed by confocal laser scanning microscopy (CLSM) revealed an enhanced permeation of Rhodamine Red (RR) loaded formulations to the deeper layers of the skin (240 microm). Further, a better skin tolerability of ethosomal suspension on rabbit skin suggested that ethosomes may offer a suitable approach for transdermal delivery of melatonin.     

根皮素醇质体的制备、表征及对体外透皮吸收的影响

目的：制备根皮素醇质体,考察醇质体作为根皮素经皮给药载体的可行性。方法：乙醇注入法制备根皮素醇质体。采用包封率和粒径为考察指标,正交试验优化大豆磷脂用量、胆固醇用量、乙醇体积及水浴温度。测定根皮素醇质体粒径分布、多分散指标和Zeta电位,采用Franz扩散池比较根皮素及其醇质体体外透皮特征。结果：根皮素醇质体最佳处方工艺：磷脂用量为220 mg、胆固醇用量为14 mg、乙醇体积为5 mL、水浴温度为40℃,根皮素醇质体平均包封率为（83.09±1.24）%,载药量为（4.86±0.89）%,粒径为（162.19±5.88） nm,PDI为（0.067±0.011）;Zeta电位为（-15.09±2.16） mV。根皮素以醇质体形式给药后单位累积透过量提高了3.43倍,且渗透过程符合零级动力学。结论：醇质体具有包封率高,粒径分布均匀等特点,可提高根皮素的渗透速率和经皮渗透量,值得进一步研究。     

局部用辣椒碱传递体的制备及体内外评价

目的制备辣椒碱传递体，并评价其体内外皮肤渗透性。方法采用高剪切分散乳化均质机制备辣椒碱传递体，并对其大小与结构、包封率、释放度、体外皮肤渗透性和在大鼠组织的分布进行评价。结果辣椒碱传递体结构为小单室泡囊，平均粒径150.6 nm。包封率随脂质浓度增加而增加，当脂质浓度为8%时，包封率为96.7%。体外累积释放量随接受液中乙醇浓度的提高而增加，不同基质大鼠腹部皮肤体外辣椒碱累积透皮量为：传递体>霜剂和混悬液。不同种类皮肤辣椒碱累积透皮量为：小鼠>大鼠>人，人体皮肤辣椒碱累积透皮量为：表皮膜>真皮层和完整皮肤。辣椒碱注射液对大鼠腹腔多次注射体内分布为：骨头>血液>皮肤>肌肉，辣椒碱传递体大鼠腿部局部多次给药，体内分布为：骨头>皮肤>血液>肌肉。结论辣椒碱传递体包封率达到药典的规定(>80%)，辣椒碱传递体可以增加辣椒碱的皮肤透过性，皮肤种类及皮肤的不同层次影响辣椒碱传递体的皮肤透过性。多次注射及局部给药，辣椒碱在骨头及肌肉的分布类似，但在血液及皮肤的分布有所不同。     

Pentapeptide modified ethosomes for enhanced skin retention and topical efficacy activity of indomethacin

Challenges associated with topical analgesics and anti-inflammatory drugs include poor drug penetration and retention at the desired lesion site. Therefore, improving these challenges would help to reduce the toxic and side effects caused by drug absorption into the systemic circulation and improve the therapeutic efficacy of topical therapeutic drugs. Pentapeptide (KTTKS) is a signal peptide in skin tissue, it can be recognized and bound by signal recognition particles. In the current study, we successfully prepared novel indomethacin (IMC) loaded KTTKS-modified ethosomes (IMC-KTTKS-Es), and the physicochemical properties and topical efficacy were investigated. Results showed that the prepared IMC-KTTKS-Es displayed a particle size of about 244 nm, a negative charge, good deformability, and encapsulation efficiency (EE) exceeding 80% for IMC, with a sustained release pattern. In vitro percutaneous permeation studies revealed that the skin retention was increased after the drug was loaded in the IMC-KTTKS-Es. Confocal laser scanning microscopy also showed improved skin retention of IMC-KTTKS-Es. In addition, IMC-KTTKS-Es showed improved topical analgesic and anti-inflammatory activity with no potentially hazardous skin irritation. This study suggested that the IMC-KTTKS-Es might be an effective drug carrier for topical skin therapy with a good safety profile.     

Nanoparticles for skin penetration enhancement--a comparison of a dendritic core-multishell-nanotransporter and solid lipid nanoparticles

Nanosized particles are of growing interest for topical treatment of skin diseases to increase skin penetration of drugs and to reduce side effects. Effects of the particle structure and size were studied loading nile red to dendritic core-multishell (CMS) nanotransporters (20-30 nm) and solid lipid nanoparticles (SLNs, 150-170 nm). Interaction properties of CMS nanotransporters with the dye molecules--attachment to the carrier surface or incorporation in the carrier matrix--were studied by UV/Vis and parelectric spectroscopy. Pig skin penetration was studied ex vivo using a cream for reference. Interactions of SLN and skin were followed by scanning electron microscopy, internalisation of the particles by viable keratinocytes by laser scanning microscopy. Incorporating nile red into a stable dendritic nanoparticle matrix, dye amounts increased eightfold in the stratum corneum and 13-fold in the epidermis compared to the cream. Despite SLN degradation at the stratum corneum surface, SLN enhanced skin penetration less efficiently (3.8- and 6.3-fold). Viable human keratinocytes showed an internalisation of both nanocarriers. In conclusion, CMS nanotransporters can favour the penetration of a model dye into the skin even more than SLN which may reflect size effects.     

Interaction of liposome formulations with human skin in vitro

The interaction of liposome formulations consisting of Phospholipon 80 and sphingomyelin with human skin was investigated. These formulations were shown previously to have a composition-dependent effect on the penetration of Heparin into the skin. Fluorescence labelled phosphatidylethanolamine (PE-NBD) was incorporated in the liposomes and the depth in which the fluorescent phospholipid label enters into epidermal membrane and full thickness skin was studied by confocal laser scanning microscopy (CLSM). Confocal sections parallel to the surface of the skin were recorded in heat separated epidermis. An even distribution of phospholipid in the lipid matrix of the stratum corneum surrounding the corneocytes was observed with Phospholipon 80 but not when sphingomyelin was included in the formulation. The addition of Heparin which formed a coating around the liposomes, caused a strong localization of fluorescence within the epidermis. For full thickness skin, mechanical cross sections of skin were made and optical sections were recorded parallel to the plane of cut. Phospholipid penetrated and was distributed fairly homogeneously in the lower dermis layers within 30 min of application regardless of liposome composition and the presence of Heparin. This rather quick penetration process seemed to follow distinct pathways along the epidermis and the upper dermis, notably the hair follicle route. Thus, a strong and in some respects composition-dependent interaction of phospholipids with skin is evident. These observations, however, are limited to the level of phospholipid molecules, rather than of entire liposomes interacting with skin.