AOT water-in-oil microemulsions as a penetration enhancer in transdermal drug delivery of 5-fluorouracil

In vitro transdermal permeation of 5-fluorouracil (antineoplastic), a hydrophilic drug encapsulated in AOT/water/isopropylmyristate water-in-oil microemulsions (MEs), were studied using a modified Keshary and Chien diffusion cell. AOT (aerosol-OT or sodium bis(2-ethylhexyl) sulfosuccinate) is an anionic surfactant, which forms 'water-in-oil' ME in non-aqueous medium. The effect of water and AOT concentrations in MEs to the transdermal permeation of 5-fluorouracil through hairless mouse skin was investigated. MEs with 5:95 weight ratio of AOT:isopropylmyristate, containing 0.9, 1.8, 2.7 and 3.6% w/w of water have showed 1.68-, 2.36-, 3.58- and 3.77-fold increases in the skin flux of 5-fluorouracil (5-FU) respectively, compared to the aqueous solution of drug. The MEs with 5:95, 9:91 and 13:87 weight ratio of AOT:isopropyl myristate at fixed water content W0=15 (W0=[H2O]/AOT]) gave 3.58-, 5.04- and 6.3-fold enhancement of drug. In addition, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to examine the effect of ME on lipid alkyl chain, hydration level, and corneocyte cells of the stratum corneum (SC). Results reveal that the ME interacts with a component of the SC and perturbs its architectural structure. The extent of perturbation in the SC depends on the concentration of water and AOT in the ME. Preliminary dermal toxicity studies indicate that the AOT/water/isopropylmyristate ME be safe for the transdermal permeation of 5-FU.     

Bicellar systems as modifiers of skin lipid structure

The characterization of different bicellar aggregates and the effects of these systems on the stratum corneum (SC) microstructure have been studied. Dynamic light scattering (DLS) and freeze fracture electron microscopy (FFEM) techniques showed that both of the systems studied, dimyristoyl-phosphatidylcholine/dihexanoyl-phosphocholine (DMPC/DHPC) and dipalmitoyl-phosphocholine (DPPC)/DHPC, were formed by small discoidal aggregates at room temperature (20°C). Treating skin with DMPC/DHPC bicelles does not affect the SC lipid microstructure, whereas bicellar systems formed by DPPC and DHPC can promote the formation of new structures in the SC lipid domains. This indicates the passage of lipids from bicelles through the SC layers and also a possible interaction of these lipids with the SC lipids. Given the absence of surfactant in the bicellar composition and the small size of these structures, the use of these smart nano-systems offers great advantages over other lipid systems for dermatological purposes. Bicelles could be promising applications as drug carriers through the skin. This contribution, based on the new biological use of bicelles, may be useful to scientists engaged in colloid science and offers a new tool for different applications in skin and cosmetic research.     

Fish Skin as a Model Membrane to Study Transmembrane Drug Delivery with Cyclodextrins

The possibility of using fish skin as model membrane tostudy drug permeation and penetration enhancement by cyclodextrins was investigated.The permeability of the skin from four species of fish, Anarhichas lupus (catfish),Pleuronectes platessa (Plaice), Hippoglossus hippoglossus (Halibut)and Anarhichas minor (Spotted catfish), was compared in a Franz diffusion cell set-up using 1% hydrocortisone aqueous solution as a donor phase. The drug fluxthrough fish skin was more than 100 times faster than the flux through hairless mouse skin and more than 10 000 times faster than through snake skin. Catfishskin was most easily accessible and was therefore used for further study. The octanol-water partition coefficient did not affect the transmembrane flux of small molecules whereas the aqueous diffusion coefficient could be correlated with the flux.The hydrocortisone flux of from aqueous hydroxypropyl--cyclodextrin solutions, which were saturated with the drug, increased with increasing cyclodextrinconcentration. From these and other observations it was concluded that small moleculesare transported through fish skin in aqueous channels. The properties of thesechannels resemble the properties of the aqueous diffusion layer present in human andanimal skin and other types of biological membranes. Previous studies have shown thatcyclodextrins will enhance drug delivery by increasing aqueous diffusion rate. Catfish skin can therefore be a good model membrane to study penetration enhancementby cyclodextrins.     

Diffusion and sorption of methanol and water in Nafion using time-resolved Fourier transform infrared-attenuated total reflectance spectroscopy

Direct methanol fuel cells (DMFCs) are promising portable power sources. However, their performance diminishes significantly because of high methanol crossover (flux) in the polymer electrolyte membrane (e.g., Nafion 117) at the desired stoichiometric methanol feed concentration. In this study, the diffusion and sorption of methanol and water in Nafion 117 were measured using time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. This technique is unique because of its ability to measure multicomponent diffusion and sorption within a polymer on a molecular level in real time as function of concentration. Both the effective mutual diffusion coefficients and concentrations of methanol and water in Nafion 117 were determined with time-resolved FTIR-ATR spectroscopy as a function of methanol solution concentration. The methanol flux, calculated from FTIR-ATR, matched that determined from a conventional technique (permeation cell) and increased by almost 3 orders of magnitude over the methanol solution concentration range studied (0.1-16 M). Furthermore, the data obtained in this study reveal that the main contribution to the increase in methanol flux is due to methanol sorption in the membrane.     

Green Electrospun Silk Fibroin Nanofibers Loaded with Cationic Ethosomes for Transdermal Drug Delivery

Transdermal drug delivery system(TDDS) facilitates the controlled release of active ingredients penetrating through the skin, avoiding the liver first pass effect. Electrospinning is a simple process to fabricate ultrafine fibers with a higher specific surface area, making them excellent candidates for drug delivery. In current work, a novel silk fibroin(SF) nanofiber loaded with cationic ethosomes(CEs) was prepared via green electrospinning. The data of Fourier transform infrared spectroscopy(FTIR) and laser scanning confocal microscopy(LSCM) confirmed the existence of CEs in the SF nanofibers. The morphology of the nanofibers was not significantly affected by the incorporation of CEs as shown by scanning electron microscopy(SEM) images. The CEs-loaded SF nanofibrous patch (CEs-SFnP) showed good cytocompatibility as proved by both cell counting Kit-8(CCK-8) assay and SEM. Using doxorubicin hydrochloride(Dox) as a model drug, the transdermal performance of CEs-SFnP was evaluated through Franz diffusion cell against mouse skin. The results indicated that CEs-SFnP can effectively deliver drug into the skin, with a much higher permeation rate than the normal nanofibers without CEs. The as-spun CEs-SFnP in this study could find promising applications in TDDS.     

The effect of internal lipids on the water sorption kinetics of keratinised tissues

Water has a large influence on the properties of keratinised tissues. The water diffusion properties of keratinised tissues are known to be governed by the cell membrane complex, which is mainly composed of internal lipids. The main aim of this work was to characterise the differences in the water sorption and desorption behaviour of human hair and stratum corneum (SC) both with and without internal lipids. Absorption and desorption curves were obtained using a thermogravimetric balance equipped with a controlled humidity chamber. The results demonstrate that the role of the intercellular lipids in the SC is more marked than in hair, which is likely due to the greater amount of lipids present in its structure. Therefore, lipid structures in the SC are essential both to prevent changes in the water-holding capacity of the skin and to maintain the water permeability of the SC.     

Transdermal drug transfer from a polymer device: study of the polymer and the process

Special polymer devices containing a drug are able to deliver the drug to the patient through transdermal delivery. Two points are of interest: the nature of the polymer device, and the process of drug delivery. The polymer device considered in this paper is able to maintain a constant drug concentration on the patient's skin surface. The process of drug delivery is studied through in vitro and in vivo tests. In vitro tests show that the skin plays the role of a membrane, with a steady state for the drug transfer following a non-steady state. The parameters of diffusion through the skin are thus calculated from this test. In vivo tests are described by a process of drug transfer consisting of two stages: the stages of absorption into, and elimination out of, the blood. The polymer device plays a major role, as it should maintain a constant concentration of drug on the skin.     

氮酮对鼠角质层角蛋白作用的光谱证据

应用13CNMR和ATR-FTIR为测试手段,探讨角蛋白的分子运动自由度与堆积结构,以及氮酮对鼠角质层角蛋白的作用.经氮酮处理后,角蛋白主侧链碳的自旋晶格弛豫时间t1从7.9,8.2和2.1s分别减小到5.4,3.6和1.6s,表明氮酮作用加快了角蛋白所有碳的运动,获得了氮酮对鼠角质层角蛋白作用的确凿证据.同时,ATR-FTIR结果显示,经氮酮处理后,角蛋白的酰胺吸收峰带的峰位从1544.7cm^-1向低波数位移到1541.4cm^-1.结果表明氮酮可使部分角蛋白从α-螺旋型结构向β-折叠型结构和无规则卷曲型结构转变,导致角蛋白的堆积结构疏松,增大了角蛋白碳运动的自由度     

Development of different temoporfin-loaded invasomes—novel nanocarriers of temoporfin: Characterization, stability and in vitro skin penetration studies

A previous study revealed that the invasome dispersion containing 3.3% (w/v) ethanol and 1% (w/v) of the terpene mixture (cineole:citral:d-limonene = 45:45:10, v/v = standard mixture) could significantly enhance skin penetration of the highly hydrophobic photosensitizer temoporfin (mTHPC). Invasomes enhanced mTHPC-deposition in stratum corneum (SC) compared to liposomes without terpenes and conventional liposomes, and they were efficient in delivering mTHPC to deeper skin layers [J. Control. Release 127 (2008) 271–280]. The aim of this study was to develop new mTHPC-loaded invasomes in order to further enhance the drug penetration. The ratio between d-limonene, citral and cineole was varied in the standard terpene mixture and also single terpenes were used. As a result new mTHPC-loaded invasome dispersions were prepared, characterized and investigated for stability and in vitro penetration of mTHPC into abdominal human skin using Franz diffusion cells.Invasomes were of a small particle size (<150 nm), high homogeneity (<0.3), mostly unilamellar and spherical, but also deformed vesicles were detected. Invasomes containing 1% (w/v) cineole provided the highest skin penetration enhancement of mTHPC, i.e. they provided high amounts of mTHPC in the SC and deeper skin layers, indicating that also incorporation of a single terpene into invasomes could provide efficient nanocarriers of mTHPC. These invasomes could be considered as a promising tool for delivering the photosensitizer mTHPC to the skin.However, in contrast to most invasomes, being effective nanocarriers of mTHPC, there were also formulations less effective than liposomes containing 3.3% (w/v) ethanol and one formulation was less efficient than conventional liposomes.     

Celecoxib determination in different layers of skin by a newly developed and validated HPLC‐UV method

A simple, rapid and sensitive analytical procedure for the measurement of celecoxib (CXB) levels in skin samples after in vitro penetration studies was developed and validated. In vitro permeability studies in porcine skin were performed for quantification of CXB at different layers of skin, the stratum corneum (SC) and epidermis plus dermis (EP + D) as well as in the acceptor solution (AS) to assess CXB permeation through skin. CXB was quantified by HPLC using a C₁₈ column and UV detection at 251 nm. The mobile phase was methanol–water 72:28 (v/v) and the flow‐rate was 0.8 mL/min. The CXB retention time was 5 min. The assay was linear for CBX in the concentration range of 0.1–3.0 μg/mL in the AS (drug permeated through skin) and 5.0–50.0 μg/mL for drug retained in SC and [EP + D] in vitro. The linear correlation coefficients for the different calibration curves were equal or greater than 0.99. Intra‐ and inter‐assay variabilities were below 8.0%. Extraction of CXB from skin samples showed recoveries higher than 95.0% after 15 min of ultrasonic sound and centrifugation at 2500 rpm for 3 min. The method was considered appropriate for the assay of CXB in skin samples, after in vitro cutaneous penetration studies. Copyright © 2011 John Wiley & Sons, Ltd.     

Confocal Raman microspectroscopy for skin characterization: a comparative study between human skin and pig skin

The present paper provides a spectral comparison between abdominal human skin (Transkin) and pig ear skin using confocal Raman microspectroscopy at 660 nm. Pig ear skin is usually utilized as a substitute for human skin for active ingredients assessment in dermatological and cosmetics fields. Herein, the comparison is made at the level of the stratum corneum (SC), the SC/epidermis junction and the viable epidermis. The 660 nm excitation source appears to be the most appropriate wavelength for such skin characterization. From Raman signatures of both skin types, a tentative assignment of vibrations was performed in the fingerprint and the high wavenumber spectral regions. Significant differences were highlighted for lipid content in in-depth spectra and for hyaluronic acid (HA) and carotenoid in SC spectra. Marked tissular variability was also revealed by certain Raman vibrations. These intrinsic molecular data probed by confocal Raman microspectroscopy have to be considered for further applications such as cutaneous drug permeation.     

Epilobium angustifolium L. Essential Oil—Biological Activity and Enhancement of the Skin Penetration of Drugs—In Vitro Study

Epilobium angustifolium L. is a popular medicinal plant found in many regions of the world. This plant contains small amounts of essential oil whose composition and properties have not been extensively investigated. There are few reports in the literature on the antioxidant and antifungal properties of this essential oil and the possibility of applying it as a potential promoter of the skin penetration of drugs. The essential oil was obtained by distillation using a Clavenger type apparatus. The chemical composition was analyzed by the GC-MS method. The major active compounds of E. angustifolium L. essential oil (EOEa) were terpenes, including α-caryophyllene oxide, eucalyptol, β-linalool, camphor, (S)-carvone, and β-caryophyllene. The analyzed essential oil was also characterized by antioxidant activity amounting to 78% RSA (Radical Scavenging Activity). Antifungal activity against the strains Aspergillus niger, A. ochraceus, A. parasiticum, and Penicillium cyclopium was also determined. The largest inhibition zone was observed for strains from the Aspergillus group. The EOEa enhanced the percutaneous penetration of ibuprofen and lidocaine. After a 24 h test, the content of terpene in the skin and the acceptor fluid was examined. It has been shown that the main compounds contained in the essential oil do not penetrate through the skin, but accumulate in it. Additionally, FTIR-ATR analysis showed a disturbance of the stratum corneum (SC) lipids caused by the essential oil application. Due to its rich composition and high biological activity, EOEa may be a potential candidate to be applied, for example, in the pharmaceutical or cosmetic industries. Moreover, due to the reaction of the essential oil components with SC lipids, the EOEa could be an effective permeation enhancer of topically applied hydrophilic and lipophilic drugs.     

Design of original bioactive formulations based on sugar-surfactant/non-steroidal anti-inflammatory catanionic self-assemblies: a new way of dermal drug delivery

A new kind of catanionic assembly was developed that associates a sugar-based surfactant with a non-steroidal anti-inflammatory drug (NSAID). Three different assemblies using indomethacin, ibuprofen and ketoprofen as NSAIDs were easily obtained in water by an acid-base reaction. These assemblies formed new amphiphilic entities because of electrostatic and hydrophobic effects in water and led to the spontaneous formation of vesicles. These catanionic vesicles were then tested as potential NSAID delivery systems for dermatological application. The anti-inflammatory activity was evaluated in vivo, and this study clearly showed an improved therapeutic effect for NSAIDs that were formulated as catanionic vesicles. These vesicles ensured a slower diffusion of the NSAID through the skin. This release probably increased the time of retention of the NSAID in the targeted strata of the skin. Thus, the present study suggests that this catanionic bioactive formulation could be a promising dermal delivery system for NSAIDs in the course of skin inflammation treatment.     

Fabrication of Alginate-Based O/W Nanoemulsions for Transdermal Drug Delivery of Lidocaine: Influence of the Oil Phase and Surfactant

Transdermal drug delivery of lidocaine is a good choice for local anesthetic delivery. Microemulsions have shown great effectiveness for the transdermal transport of lidocaine. Oil-in-water nanoemulsions are particularly suitable for encapsulation of lipophilic molecules because of their ability to form stable and transparent delivery systems with good skin permeation. However, fabrication of nanoemulsions containing lidocaine to provide an extended local anesthetic effect is challenging. Hence, the aim of this study was to address this issue by employing alginate-based o/w nanocarriers using nanoemulsion template that is prepared by combined approaches of ultrasound and phase inversion temperature (PIT). In this study, the influence of system composition such as oil type, oil and surfactant concentration on the particle size, in vitro release and skin permeation of lidocaine nanoemulsions was investigated. Structural characterization of lidocaine nanoemulsions as a function of water dilution was done using DSC. Nanoemulsions with small droplet diameters (d < 150 nm) were obtained as demonstrated by dynamic light scattering (DLS) and cryo-TEM. These nanoemulsions were also able to release 90% of their content within 24-h through PDMS and pig skin and able to the drug release over a 48-h. This extended-release profile is highly favorable in transdermal drug delivery and shows the great potential of this nanoemulsion as delivery system.     

Quantification of topically delivered 5-aminolevulinic acid by lontophoresis across ex vivo human stratum corneum

Iontophoretic transport of the prodrug 5-aminolevulinic acid (ALA), which is used for photodynamic therapy (PDT), across human stratum corneum (SC) was studied quantitatively in vitro. The experiments were carried out in a three-compartment iontophoresis cell consisting of two electrode chambers equipped with Ag-AgCl electrodes, each separated from a central acceptor chamber by a sheet of SC, supported by a dialysis membrane, to mimic the side-by-side configuration normally used in vivo. Acceptor fluid samples were collected every hour for a period of 30 h in a fraction collector and analyzed by high-performance liquid chromatography-fluorometry after derivatization of the ALA. The iontophoretic ALA flux was studied as a function of the applied current density and the ALA concentration in the donor solution (1, 2.5 or 10% ALA). Depending on the ALA concentration in the donor cell, iontophoresis enhances the flux from close to the detection limit of 0.23 nmol cm(-2) h(-1) at zero current density (passive diffusion) to several hundred or thousand nanomoles per square centimeter per hour at current densities ranging from 100 to 1000 microA cm(-2). For example, interpolating our data we find that with an ALA concentration of 2% in the donor chamber, a current density of 0.255 mA cm(-2) transports 0.065 micromol cm(-2) ALA across the SC in 10 min (conditions of Rhodes et al. (1997), J. Invest. Dermatol. 108, 87-91). For passive diffusion we find that a 5 h topical application of 20% ALA results in the transport of 0.05 micromol cm(-2). Thus, the amount of ALA that passively diffuses through the SC in several hours, leading to therapeutic levels of protoporphyrin IX (PpIX) in the epidermis, can be delivered by iontophoresis in 10 min or less. However, because the formation of sufficient PpIX also requires several hours and also because the SC overlying skin lesions such as basal cell carcinoma (BCC) is not intact, the clinical benefit of topical ALA delivery by iontophoresis for PDT of BCC is yet to be established.     

Characterization of porcine skin as a model for human skin studies using infrared spectroscopic imaging

Porcine skin is often considered a substitute for human skin based on morphological and functional data, for example, for transdermal drug diffusion studies. A chemical, structural and temporal characterization of porcine skin in comparison to human skin is not available but will likely improve our understanding of this porcine skin model. Here, we employ Fourier transform infrared (FT-IR) spectroscopic imaging to holistically measure chemical species as well as spatial structure as a function of time to characterize porcine skin as a model for human skin. Porcine skin was found to resemble human skin spectroscopically and differences are elucidated. Cryo-prepared fresh porcine skin samples for spectroscopic imaging were found to be stable over time and small variations are observed. Hence, we extended characterization to the use of this model for dynamic processes. In particular, the capacity and stability of this model in transdermal diffusion is examined. The results indicate that porcine skin is likely to be an attractive tool for studying diffusion dynamics of materials in human skin.     

Mechanisms of Penetration Enhancement and Transport Utilizing Skin Keratine Liposomes for the Topical Delivery of Licochalcone A

Keratin liposomes have emerged as a useful topical drug delivery system given theirenhanced ability to penetrate the skin, making them ideal as topical drug vehicles. However, the mechanisms of the drug penetration enhancement of keratin liposomes have not been clearly elucidated. Therefore, licochalcone A(LA)-loaded skin keratin liposomes (LALs) were prepared to investigate their mechanisms of penetration enhancement on the skin and inB16F10 cells. Skin deposition studies, differential scanning calorimetry (DSC), attenuated total reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), and skin distribution and intracellular distribution studies were carried out to demonstrate the drug enhancement mechanisms of LALs. We found that the optimal application of LALs enhanced drug permeation via alterations in the components, structure, and thermodynamic properties of the stratum corneum (SC), that is, by enhancing the lipid fluidization, altering the skin keratin, and changing the thermodynamic properties of the SC. Moreover, hair follicles were the main penetration pathways for the LA delivery, which occurred in a time-dependent manner. In the B16F10 cells, the skin keratin liposomes effectively delivered LA into the cytoplasm without cytotoxicity. Thus, LAL nanoparticles are promising topical drug delivery systems for pharmaceutical and cosmetic applications.     

Enhanced transdermal delivery of indomethacin-loaded PLGA nanoparticles by iontophoresis

Nanoparticles effectively deliver therapeutic agent by penetrating into the skin. Indomethacin (IM) and coumarin-6 were loaded in PLGA nanoparticles with an average diameter of 100 nm. IM and coumarin-6 were chosen as a model drug and as a fluorescent marker, respectively. The surfaces of the nanoparticles were negatively charged. Permeability of IM-loaded PLGA nanoparticles through rat skin was studied. Higher amount of IM was delivered through skin when IM was loaded in nanoparticles than IM was free molecules. Also, iontophoresis was applied to enhance the permeability of nanoparticles. When iontophoresis with 3 V/cm was applied, permeability of IM was much higher than that obtained by simple diffusion of nanoparticles through skin. The combination of charged nanoparticle system with iontophoresis is useful for effective transdermal delivery of therapeutic agents.     

Nano-formulations for transdermal drug delivery: A review

The different applications of nano-formulations (vesicles or nanoparticles and nanoemulsions) have been widely studied. Here, the classification, characteristics, transdermal mechanism, and application of the most popular nano-formulations in transdermal drug delivery system are reviewed.     

Perturbation of human skin due to application of high voltage

Electroporation is believed to be the effect that greatly enhances the transport of water-soluble molecules across the stratum corneum (SC) by application of short high voltage pulses. However, electroporation was originally a phenomenon investigated at the level of cell and model membranes, which is only partially comparable to the complicated structure of the stratum corneum. Here, we show, that electroporation is accompanied by other effects, which may be primarily involved in creation of new pathways and altering existing pathways, respectively. Experimental evidence shows that the dramatic increase in skin permeability is due to synergistic effect of electric field and heating by high local current density. Heating starts at small spots, not related to a visible skin structure and results in a propagating heat front. The phase transition of the SC lipids plays a major role in skin permeability during the pulse. The permeability after a high voltage pulse correlates well with the surface area showing a permanent low electrical resistance after pulsing. The main transport of water-soluble molecules is facilitated by the electric field due to the electrophoretic driving force in conjunction with the high permeability due to the breakdown of the multilamellar system of the SC lipids.