Percutaneous Absorption Studies Research Articles

A sensitive LC–ESI-MS/MS method for the quantification of avobenzone in rat plasma and skin layers: Application to a topical administration study

This study describes the development of a sensitive high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method for the quantification of avobenzone in rat plasma and skin layers. Separations were performed on a Zorbax SB C8 column using a binary gradient mobile phase composed of acetonitrile and 0.1% formic acid in water. The assay achieved LLOQ of 0.5ng/ml for plasma, 5ng/ml for stratum corneum, and 10ng/ml for epidermis and dermis. This method was applied to a percutaneous absorption study of avobenzone in rats. At 12h following topical application of emulsion and lotion (applied amount of avobenzone 11.7mg/kg), avobenzone was found primarily in the stratum corneum (16.3-17.8%) followed by epidermis (2.0-3.4%) and dermis (0.11-0.15%). Avobenzone was not quantifiable in the plasma samples collected over a 12h sampling period. Given the excellent plasma assay sensitivity, this study provides evidence that the systemic absorption of avobenzone is insignificant, if any, after topical application.

Simultaneous determination of phenoxyethanol and its major metabolite, phenoxyacetic acid, in rat biological matrices by LC–MS/MS with polarity switching: Application to ADME studies

This study describes the development of a simple LC-ESI–MS/MS method with polarity switching for the simultaneous analysis of phenoxyethanol (PE) and its major metabolite, phenoxyacetic acid (PAA), in rat plasma, urine, and 7 different tissues. The assay was validated to demonstrate the linearity, precision, accuracy, LLOQ, recovery, and stability by using the matrix matched QC samples. The assay achieved the LLOQ of 10 and 20ng/mL of PE and PAA, respectively, for plasma samples and the LLOQ of 20 and 50ng/mL of PE and PAA, respectively, for urine and tissue samples. This method was successfully applied to the percutaneous absorption, distribution, metabolism, and excretion studies in rats. The absolute topical bioavailability of PE was 75.4% and 76.0% for emulsion and lotion, respectively. Conversion of PE to PAA was extensive, with the average AUCPAA-to-AUCPE ratio being 4.4 and 5.3 for emulsion and lotion, respectively. The steady-state tissue-to-plasma PE concentration ratio (Kp) was higher than unity for kidney, spleen, heart, brain, and testis and was lower (≤0.6) for lung and liver, while the metabolite Kp ratio was higher than unity for kidney, liver, lung, and testis and was lower (≤0.3) for other tissues. Findings of this study may be useful to evaluate the relationship between exposure and toxic potential of PE in risk assessment.

New easy handling and sampling device for bioavailability screening of topical formulations.

Biopharmaceutical assessment of topical drug formulations is widely carried out by using vertical diffusion cells (Franz type cell). Although Franz diffusion cell model is well designed for percutaneous absorption studies, the extent of drug penetration within the skin requires more adapted device. Recently, we have developed a new patented versatile, easy-to-use, and disposable diffusion cell called VitroPharma. In this study we have assessed the cutaneous bioavailability of caffeine as hydrophilic compound model using Franz diffusion cell and VitroPharma. The percutaneous absorption of caffeine assessed with Franz diffusion cell and VitroPharma was characterized by using (i) finite dose model and (ii) classical pharmacokinetic analysis. Furthermore, the follow-up of caffeine penetration within the skin was determined by sequential measurements of tissular drug concentration throughout the time of skin exposure with VitroPharma. However, classical experimental design using Franz diffusion cell involved unique determination of tissular concentration at the final point of skin exposure protocol. Finally, device equivalence between Franz diffusion cell and VitroPharma was claimed from percutaneous absorption data analysis. Concomitant assessment of dual penetration and permeation kinetics by using VitroPharma reinforced the understanding of skin drug delivery.

Design of solid lipid nanoparticles for caffeine topical administration

Context: Solid lipid nanoparticles (SLN) are drug carriers possessing numerous features useful for topical application. A copious scientific literature outlined their ability as potential delivery systems for lipophilic drugs, while the entrapment of a hydrophilic drug inside the hydrophobic matrix of SLN is often difficult to obtain.Objective: To develop SLN intended for loading caffeine (SLN-CAF) and to evaluate the permeation profile of this substance through the skin once released from the lipid nanocarriers. Caffeine is an interesting compound showing anticancer and protective effects upon topical administration, although its penetration through the skin is compromised by its hydrophilicity.Materials and methods: SLN-CAF were formulated by using a modification of the quasi-emulsion solvent diffusion technique (QESD) and characterized by PCS and DSC analyses. In vitro percutaneous absorption studies were effected using excised human skin membranes (i.e. Stratum Corneum Epidermis or SCE).Results: SLN-CAF were in a nanometric range (182.6 ± 8.4 nm) and showed an interesting payload value (75% ± 1.1). DSC studies suggest the presence of a well-defined system and the successful drug incorporation. Furthermore, SLN-CAF generated a significantly faster permeation than a control formulation over 24 h of monitoring.Discussion and conclusions: SLN-CAF were characterized by valid dimensions and a good encapsulation efficiency, although the active to incorporate showed a hydrophilic character. This result confirms the suitability of the formulation strategy employed in the present work. Furthermore, the in vitro evidence outline the key role of lipid nanoparticles in enhancing caffeine permeation through the skin.

Water sorption evaluation of stratum corneum

• Porcine skin is a well-accepted and readily available model of the human skin barrier. • Skin function is largely dependent on stratum corneum water balance. • Moisture absorption/desorption isotherm curves for human and porcine SC were studied. • Great influence of the stratum corneum thickness on the permeability properties. Skin function is largely dependent on SC water balance. Animal skin is frequently used as an alternative to human skin in percutaneous absorption studies. Porcine skin is a well-accepted and readily available model of the human skin barrier. It is important to assess how similar porcine skin water permeability is to that of human skin to confirm the validity of the model. Moisture absorption/desorption isotherm curves for human and porcine SC were obtained. The apparent diffusion coefficients of porcine SC calculated were slightly smaller than that of human SC. Besides, when SC thickness was considered, diffusion coefficients were obtained, with porcine SC having a significant higher permeability. The higher thickness of the porcine SC compensates its higher diffusion per thickness unit, leading to similar apparent diffusion coefficients, thus indicating the suitability of the porcine SC for the skin permeation studies.

Development, characterization & in vitro skin permeation of rutin ethosomes as a novel vesicular carrier

Objective : The aim of the present study was to formulate and characterize rutin ethosomes and to evaluate the rutin ethosomes to enhance its skin permeation rate as compared to parent drug, rutin. Materials and Methods : Rutin ethosomes were formulated by cold method and optimized using 2 3 factorial design by design expert software (version 8.0). The optimized rutin ethosomes were characterized for particle size distribution, vesicular shape using scanning electron microscopy, zeta potential, entrapment efficiency and short term stability studies. A specially designed franz diffusion cell was used for the percutaneous absorption studies of optimized rutin ethosomes using pig ear skin and the results were analysed using DD solver 8 software. Results and Discussion : The entrapment efficiency of optimized ethosomes prepared using phospholipid concentration of 2.5 g with 30 ml ethanol for 12.5 minutes, was found to be maximum i.e. 73.9 %. Lipid vesicular system of rutin exhibited a negative zeta potential of -46.0 mV indicating a high degree of stability for rutin ethosomes. In vitro drug permeation studies of pure rutin and rutin ethosomes suggested that rutin ethosomes were better able to permeate across pig ear skin at the end of 120 minutes than pure rutin. Therefore, rutin ethosomes were better able to facilitate permeation of rutin deeply into the pig ear skin when compared with pure rutin. Conclusion : Rutin ethosomal formulation has tremendous potential to serve as a topical drug delivery system due to its enhanced rate of permeation.

Bicellar systems as vehicle for the treatment of impaired skin

This study assesses the potential usefulness of bicellar systems to retard the penetration of drugs into damaged skin. The active compound used in this study was diclofenac diethylamine (DDEA). Initially, physicochemical characterisation of the DDEA bicellar systems was performed at different temperatures by small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) techniques. Subsequently, in vitro percutaneous absorption of bicellar systems into in vitro damaged skin was studied.SAXS results indicated a slight decrease in the width of their bilayers with increasing temperature, with no apparent stacking in those systems. WAXS patterns were compatible with an orthorhombic lateral packing of the nanoaggregates. The thermogram obtained by DSC indicated a decrease in gel-to-liquid crystalline transition temperature (Tm) when the drug was included into bicellar systems. A retardation effect for DDEA was detected by in vitro percutaneous absorption studies when DDEA was vehiculised in the bicellar systems with respect to an aqueous solution of the drug. It seems that the use of bicellar systems as a vehicle for topical application of DDEA on skin with an impaired barrier function may inhibit the penetration of DDEA to the systemic level. Such systems may consequently repair stratum corneum barrier function to some extent. The use of these systems could be considered a new alternative strategy to treat topically pathological skin with different drugs.

Development of a Novel Penetration-Enhancing Agent for Hair Products

HAIRCARECUBETM (HCC) is a new additive for hair products that allows the active ingredient to penetrate into the hair. During the course of percutaneous absorption studies, we discovered that lyotropic liquid crystal promotes the skin’s absorptiveness to medicines. We conducted a study to determine whether or not lyotropic liquid crystal could be applied as a penetration-enhancing agent in hair, and as a result we have succeeded in developing HCC. In place of hair dye, we used fluorescein-HCC to evaluate hair permeability, and strong fluorescence was observed as deep as the core of the hair. Moreover, the strength of the fluorescence was dependent on HCC concentration. This result did not change under acidic or basic conditions. In addition, the same trends were observed when using an oxidative hair dye. Furthermore, when HCC was used together with hydrolyzed keratin, which repairs hair damage, a stronger restorative effect was observed. These results confirmed that HCC has the effect of promoting the permeation of pigments and other active ingredients into hair. HCC is expected to be very useful as an additive for developing functional cosmetic hair products.

Transdermal Drug Delivery In Vitro Using Diffusion Cells

The assessment of percutaneous absorption of molecules is a very important step in the evaluation of any dermal or transdermal drug delivery system. In order to perform percutaneous drug absorption studies, it is essential that the methods are standardized and that the integrity of the skin is monitored and maintained to ensure that the data obtained are valid and relevant. Reproducible data on percutaneous absorption in humans are as well required to predict the systemic risk from dermal exposure to chemicals, such as hazardous substances at the workplace, agrochemicals and cosmetic ingredients. In vitro and animal models provide important tools for screening a series of drug formulations, evaluation of skin permeation enhancing properties and mechanism of action of the carrier systems and estimation of rank of skin transport for a series of drug molecules. In this review, we have summarized in vitro testing of skin absorption using static Franz-type diffusion cells.

In vitro study of percutaneous absorption of aluminum from antiperspirants through human skin in the Franz™ diffusion cell

Aluminum salts such as aluminum chlorohydrate (ACH) are known for use as an active antiperspirant agent that blocks the secretion of sweat. A local case report of hyperaluminemia in a woman using an aluminum-containing antiperspirant for 4years raises the problem of transdermal absorption of aluminum (Al). Only a very limited number of studies have shown that the skin is an effective barrier to transdermal uptake of Al. In accordance with our analytical procedure, the aim of this study with an in vitro Franz™ diffusion cell was to measure aluminum uptake from three cosmetic formulations of antiperspirant: the base for an “aerosol” (38.5% of ACH), a “roll-on” emulsion (14.5% ACH), and a “stick” (21.2%), by samples of intact and stripped human skin (5 donors). The Al assays were performed by Zeeman Electrothermal Atomic Absorption Spectrophotometry (ZEAAS). Following contacts lasting 6, 12 and 24h, the Al assays showed only insignificant transdermal absorption of Al (≤0.07% of the quantity of Al deposited) and particularly low cutaneous quantities that varied according to the formulations (1.8μg/cm² for “aerosol base” and “stick” — 0.5μg/cm² for the “roll-on”). On stripped skin, for which only the “stick” formulation was tested, the measured uptake was significantly higher (11.50μg/cm² versus 1.81μg/cm² for normal skin). These results offer reassurance as regards to the use of antiperspirants for topical application of ACH-containing cosmetic formulations on healthy skin over a limited time span (24h). On the other hand, high transdermal Al uptake on stripped skin should compel antiperspirant manufacturers to proceed with the utmost caution.

Lipid Nanoparticles as Carrier for Octyl-Methoxycinnamate: In Vitro Percutaneous Absorption and Photostability Studies

The aim of the present study was the evaluation of lipid nanoparticles (solid lipid nanoparticles, SLN, and nanostructured lipid carriers, NLC) as potential carriers for octyl-methoxycinnamate (OMC). The release pattern of OMC from SLN and NLC was evaluated in vitro, determining its percutaneous absorption through excised human skin. Additional in vitro studies were performed in order to evaluate, after UVA radiation treatment, the spectral stability of OMC-loaded lipid nanoparticles. From the obtained results, ultrasonication method yielded both SLN and NLC in the nanometer range with a high active loading and a particle shape close to spherical. Differential scanning calorimetry data pointed out the key role of the inner oil phase of NLC in stabilizing the particle architecture and in increasing the solubility of OMC as compared with SLN. In vitro results showed that OMC, when incorporated in viscosized NLC dispersions (OMC-NLC), exhibited a lower flux with respect to viscosized SLN dispersions (OMC-SLN) and two reference formulations: a microemulsion (OMC-ME) and a hydroalcoholic gel (OMC-GEL). Photostability studies revealed that viscosized NLC dispersions were the most efficient at preserving OMC from ultraviolet-mediated photodegradation.

Regenerated keratin membrane to match the in vitro drug diffusion through human epidermis

This work aimed to develop membranes made of regenerated keratin and ceramides (CERs) to match the barrier property of the human stratum corneum in in vitro percutaneous absorption studies. The membrane composition was optimized on the basis of the in vitro drug diffusion profiles of ibuprofen, propranolol and testosterone chosen as model drugs on the basis of their different diffusion and solubility properties. The data were compared to those obtained using human epidermis.The ATR-FTIR and SEM analyses revealed that CERs were suspended into the regenerated keratin matrix, even if a partial solubilization occurred. It resulted in the membranes being physically stable after exposure to aqueous buffer and/or mineral oil and the fluxes of ibuprofen and propranolol from these vehicles through membranes and human skin were of the same order of magnitude. The best relationship with human epidermis data was obtained with 180μm-thick membrane containing 1% ceramide III and 1% ceramide VI. The data on the testosterone diffusion were affected by the exposure of the membrane to a water/ethanol solution over a prolonged period of time, indicating that such an organic solvent was able to modify the supermolecular organization of keratin and CERs.The keratin/CER membranes can represent a simplified model to assay the in vitro skin permeability study of small molecules.

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.

In vivo study of percutaneous absorption of 4-chloroaniline using microdialysis in the rat.

The present work was undertaken to study the percutaneous absorption of 4-chloroaniline (parachloroaniline, PCPA, CAS 106-47-8), a chemical intermediate in pesticide manufacture, using in vivo microdialysis in the rat. The results of the microdialysis study showed that PCPA was able to cross the skin (Tmax = 3 h and area under the curve (AUC) = 332.1 ng.h/ml) and rapidly enter the systemic circulation (Tmax = 3.3 +/- 0.6 h). It could be also shown that PCPA was partly metabolised during its percutaneous absorption. The analysis of cutaneous dialysate samples using gas chromatography/mass spectrometry (GC-MS) showed that the metabolite was 4-chloracetanilide. Taken together, the data obtained showed that contact with the skin is a danger for exposed persons.

Bicellar systems as a new colloidal delivery strategy for skin

The presented work evaluates the use of bicellar systems as new delivery vectors for controlled release of compounds through the skin. Two different active principles were introduced into the bicellar systems: diclofenac diethylamine (DDEA) and flufenamic acid (Ffa). Bicellar systems are discoidal aggregates formed by long and short alkyl chain phospholipids. Characterization of the bicellar systems by dynamic light scattering (DLS) and cryogenic transmission electron microscopy (Cryo-TEM) showed that particle size decreased when DDEA was encapsulated and increased when Ffa was included in the bicellar systems. Percutaneous absorption studies demonstrated a lower penetration of DDEA and Ffa through the skin when the drugs were included in the bicellar systems than when the drugs were applied in an aqueous solution (DDEA) and in an ethanolic solution (Ffa); the reduction in penetration was more pronounced with Ffa. These bicellar systems may have retardant effects on percutaneous absorption, which result in a promising strategy for future drug or cosmetic delivery applications.

Barrier function of intact and impaired skin: percutaneous penetration of caffeine and salicylic acid

Normally, percutaneous absorption tests are carried out using skin biopsies for an apparent and acceptable physiological condition. However, under different pathological conditions, the stratum corneum (SC) barrier function is impaired. The barrier function of the SC was assessed by correlation between the number of repeated applications of tape strips on the skin and its transepidermal water loss (TEWL), as well as by in vitro percutaneous absorption studies of different compounds, using Franz diffusion cells and porcine skin previously stripped. A progressive diminution of the skin barrier function has been detected by TEWL both in vitro and in vivo as the number of skin tape strips increases. On the other hand, the percutaneous absorption of the compounds tested increases in a different way as the number of strips increases. Salicylic acid increases linearly depending on the barrier disturbance. However, percutaneous absorption of caffeine exponentially increased with barrier disturbance. Our results indicate that the barrier impairment of skin always increases the penetration behavior of a given compound; however, the hydrophilic-lipophilic balance of the compounds or formulations used could greatly modify its penetration profile, especially when a modified skin is used. This in vitro protocol may be useful to simulate the percutaneous absorption profile of some drugs applied onto skin with an impaired SC barrier function and could be used to avoid, to some extent, the use of in vivo experimental animal models in the dermopharmaceutical field.

Novel dithranol phospholipid microemulsion for topical application: development, characterization and percutaneous absorption studies

The objective of this study was to develop and characterize a novel dithranol-containing phospholipid microemulsion systems for enhanced skin permeation and retention. Based on the solubility of dithranol, the selected oils were isopropyl myristate (IPM) and tocopherol acetate (TA), and the surfactants were Tween 80 (T80) and Tween 20 (T20). The ratios of cosurfactants comprising of phospholipids and ethanol (1 : 10) and surfactant to co-surfactant (1 : 1 and 2.75 : 1) were fixed for the phase diagram construction. Selected microemulsions were evaluated for globule size, zeta potential, viscosity, refractive index, per cent transmittance, stability (freeze thaw and centrifugation), ex vivo skin permeation and retention. The microemulsion systems composed of IPM and T80 with mean particle diameter of 72.8 nm showed maximum skin permeation (82.23%), skin permeation flux (0.281 mg/cm2/h) along with skin retention (8.31%) vis-à-vis systems containing TA and T20. The results suggest that the developed novel lecithinized microemulsion systems have a promising potential for the improved topical delivery of dithranol.

The in-vitro percutaneous absorption of glycerol trioleate through hairless mouse skin.

The chemical composition of the aqueous receptor fluid in one-chambered diffusion cells used for in-vitro percutaneous absorption studies has been shown to significantly affect the apparent extent of absorption of the triglyceride, glycerol trioleate. Using murine skin samples it was found that the addition of albumin to the receptor fluid resulted in an increase in the apparent extent of absorption, while the presence of the bacteriostatic agent thiomersal resulted in a decrease. The viability of the skin samples had no effect on absorption. It was determined that the chemical species in the receptor fluid was the free fatty acid. Albumin presumably bound the fatty acid, thereby creating a sink which enabled the fatty acid to partition from the skin into the receptor fluid.

Percutaneous absorption of indomethacin from pluronic F127 gels in rats.

Thermally reversible gels of the poly(oxyethylene)-poly (oxypropylene)-(polyoxyethylene) triblock copolymer, Pluronic F127, were evaluated as vehicles for the percutaneous administration of drugs using indomethacin as a model drug. In-vivo percutaneous absorption studies using a rat model suggest that a 20% w/w aqueous gel of Pluronic F127 may be of practical use as a base for topical administration of the drug. The addition of isopropyl myristate or (+)-limonene to the gel formulation significantly improved percutaneous absorption, particularly when the gel was applied using an occlusive dressing technique.

Dimeric Cinnamoylamide Derivatives as Inhibitors of Melanogenesis

Dimeric cinnamoylamide derivatives were synthetized and tested as inhibitors of tyrosinase activity and melanin formation. The most active dimeric cinnamoylamide derivatives was dimeric compound of p-coumaric acid (compound 1) that inhibited tyrosinase activity more efficiently than p-coumaric acid. It also inhibited melanin production by B16 melanoma cell line and normal human melanocytes more efficiently than kojic acid. We next investigated the potential mutagenic and skin sensitization effect of compound 1. Compound 1 was found to induce no mutagenic activity, no irritation and no delayed contact hypersensitivity at the maximum concentration of 10%. In vitro percutaneous absorption studies exhibited that compound 1 could diffuse across the skin till its site of action. All these results lead us to propose that compound 1 may be a safe and effective candidate for treating skin hyperpigmentation related disorders.