Rheological Properties and Composition Affecting the Skin Permeation of a Model of a Hydrophilic Drug in Lecithin Reverse Wormlike Micelles.

We investigated the effect of the rheological properties and composition of lecithin reverse wormlike micelles (LRWs) on the skin permeation of a model of a hydrophilic drug to determine whether LRWs support uniform hydrophilic drug/oil-based formulations and good drug penetrate into skin. Here, we prepared LRWs with D (-)-ribose (RI) or glycerol (GL) as polar compounds, liquid paraffin (LP) or isopropyl myristate (IPM) as oils, and 6-carboxyfluorescein (CF) as a model for a hydrophilic drug, and evaluated the rheological properties and skin penetration characteristics of the preparations. The LRWs showed moderate viscosity at 25 °C, a typical storage temperature, but decreasing viscosity at 32 °C, the surface temperature of human skin, suggesting that the LRWs would penetrate the microstructure of skin (e.g., wrinkles and hair follicles). The highest skin permeability of CF was observed when IPM was used as the oil, suggesting that both the stratum corneum and hair follicle routes are involved in drug permeation. The penetration of CF into hair follicles is influenced not only by the rheology of the formulation but also by the interaction between IPM and sebum in the hair follicles.

Preparation and Application of Decanoic Acid/Arginine Hydrogels to a Transdermal Formulation.

We prepared a supramolecular hydrogel composed of decanoic acid and arginine (C10/Arg gel) and evaluated its application to a transdermal formulation. C10/Arg gel adjusted to pH 7 with 1 M NaOH aq or 1 M HCl aq provided a translucent hydrogel with a lamellar liquid crystal structure in the concentration region of decanoic acid ≥12% and arginine ≤9%. Rheological measurements showed that C10/Arg gel is a viscoelastic material with both solid and liquid properties, with elasticity being dominant over viscosity in the low shear stress region. The skin permeability of hydrocortisone (HC) and indomethacin (IM) from C10/Arg gels was investigated in vitro using hairless mouse skin and compared to control formulation drug suspensions (IM or HC) in water. The cumulative permeation amount of HC and IM from the C10/Arg gel at 10 h after application was approximately 16 and 11 times higher than that of the control, respectively. On the other hand, the flux of IM decreased with increasing arginine concentration, likely due to the acid-base interaction between Arg and IM in C10/Arg gel. Adequate drug skin permeation enhancement by C10/Arg gel requires optimizing the gel composition for each specific drug.

Influence of Surfactant on the Skin Permeation of Methylisothiazolinone and Methylchloroisothiazolinone.

Patch tests are often used in safety evaluations to identify the substance causing skin irritation, but the same substance can sometimes give positive or negative results depending on the test conditions. Here, we investigated differences in the skin penetration of two test compounds under different application conditions. We studied the effects of the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant polysorbate 80 (PS) on skin penetration of the preservatives methylisothiazolinone (MT) and methylchloroisothiazolinone (MCT), which are used in cosmetics such as shampoos. The skin permeation of MT was enhanced by SDS but was unchanged by PS. Skin impedance decreased in the presence of SDS whereas PS had the same effect as the control aqueous solution, suggesting that SDS reduction of the barrier function of skin affects the permeation of MT, a hydrophilic drug. Application of a mixture of MCT and MT in the presence of SDS did not affect the skin permeation of MCT whereas the permeation of MT was enhanced by SDS, indicating that the skin permeation of MCT is less affected by SDS than is MT. Thus, attention should be paid to the possible effect of co-solutes, especially hydrophilic drugs.

A Consideration on Infinite and Finite Dosing in Skin Permeation Using Reconstructed Models.

INTRODUCTION: When vitamin derivatives penetrate the epidermis, they release active compound such as ascorbic acids (AsA) and tocopherols via enzymatic digestion of chemical modifiers. To determine the transdermal penetration of the derivatives, the total permeation of both the derivatives and their active compounds that released from the derivatives should be considered. In this study, we established a skin penetration test method using a cultured, reconstructed skin model with active epidermal enzymes. And we analyzed two vitamin derivatives with different chemical properties: magnesium ascorbyl phosphate (APM) and sodium tocopheryl phosphate (TPNa), both of which has been confirmed their skin permeation in the reconstructed models and the digestion to AsA and α-tocopherol by the epidermal enzymes, respectively. METHODS: We prepared the 1% of water solution containing either APM or TPNa. Then, we tested the cumulative permeation of the derivatives at 2 application volumes, 25 µL/cm2 (finite dosing) and 85 µL/cm2 (infinite dosing), on cultured reconstructed skin and observed the permeation of the permeants every 2 h up to 24 h. RESULTS: When the applied formula was used to assess the evaporation rate to determine an end point of the test system, all the water evaporated in 6 h in finite model and in 8 h in infinite model. Both models showed that the cumulative permeation of the active compounds increased and a constant flux until 8 h after application; however, the flux decreased thereafter, indicating that the decreased flux depended on an end point of the test system. This indicated that our test system can analyze the permeation of the vitamin derivatives within 8 h before reaching the end point. CONCLUSION: Using an infinite model of this system, we assessed the cumulative permeation of vitamin derivatives within 8 h using a reconstructed skin model.

A comprehensive review on transethosomes as a novel vesicular approach for drug delivery through transdermal route.

Drug delivery through transdermal route is one of the effective methods for the application of drugs. It overcomes many drawbacks which are encountered with the oral route. Moreover, many drugs are not able to pass through the stratum corneum, which is the main barrier for the transdermal drug delivery. Formation of ultra-deformable vesicles (UDVs) is a novel technique for the transdermal applications of the drugs. Transethosomes (TEs), ethosomes, and transferosomes are all part of the UDV. Because of the presence of increased concentrations of ethanol, phospholipids, and edge activators, TEs provide improved drug permeation through the stratum corneum. Because of the elasticity of TEs, drug penetration into the deeper layer of skin also increases. TEs can be prepared using a variety of techniques, including the cold method, hot method, thin film hydration method, and the ethanol injection method. It increases patient adherence and compliance because it is a non-invasive procedure of administering drugs. Characterization of the TEs includes pH determination, size and shape, zeta potential, particle size determination, transition temperature, drug content, vesicle stability, and skin permeation studies. These vesicular systems can be utilized to deliver a variety of medications transdermally, including analgesics, antibiotics, antivirals, and anticancer and arthritis medications. This review aims to describe vesicular approaches that had been used to overcome the barrier for the transdermal delivery of drug and also describes brief composition, method of preparation, characterization tests, mechanism of penetration of TEs, as well as highlighted various applications of TEs in medicine.

Investigating the Anti-Inflammatory Properties and Skin Penetration Ability of Cornelian Cherry (Cornus mas L.) Extracts.

Plant extracts can be a valuable source of biologically active compounds in many cosmetic preparations. Their effect depends on the phytochemicals they contain and their ability to penetrate the skin. Therefore, in this study, the possibility of skin penetration by phenolic acids contained in dogwood extracts of different fruit colors (yellow, red, and dark ruby red) prepared using different extractants was investigated. These analyses were performed using a Franz chamber and HPLC-UV chromatography. Moreover, the antioxidant properties of the tested extracts were compared and their impact on the intracellular level of free radicals in skin cells was assessed. The cytotoxicity of these extracts towards keratinocytes and fibroblasts was also analyzed and their anti-inflammatory properties were assessed using the enzyme-linked immunosorbent assay (ELISA). The analyses showed differences in the penetration of individual phenolic acids into the skin and different biological activities of the tested extracts. None of the extracts had cytotoxic effects on skin cells in vitro, and the strongest antioxidant and anti-inflammatory properties were found in dogwood extracts with dark ruby red fruits.

Chondroitin Sulfate for Cartilage Regeneration, Administered Topically Using a Nanostructured Formulation.

In the pharmaceutical sector, solid lipid nanoparticles (SLN) are vital for drug delivery incorporating a lipid core. Chondroitin sulfate (CHON) is crucial for cartilage health. It is often used in osteoarthritis (OA) treatment. Due to conflicting results from clinical trials on CHON's efficacy in OA treatment, there has been a shift toward exploring effective topical systems utilizing nanotechnology. This study aimed to optimize a solid lipid nanoparticle formulation aiming to enhance CHON permeation for OA therapy. A 3 × 3 × 2 Design of these experiments determined the ideal parameters: a CHON concentration of 0.4 mg/mL, operating at 20,000 rpm speed, and processing for 10 min for SLN production. Transmission electron microscopy analysis confirmed the nanoparticles' spherical morphology, ensuring crucial uniformity for efficient drug delivery. Cell viability assessments showed no significant cytotoxicity within the tested parameters, indicating a safe profile for potential clinical application. The cell internalization assay indicates successful internalization at 1.5 h and 24 h post-treatment. Biopharmaceutical studies supported SLNs, indicating them to be effective CHON carriers through the skin, showcasing improved skin permeation and CHON retention compared to conventional methods. In summary, this study successfully optimized SLN formulation for efficient CHON transport through pig ear skin with no cellular toxicity, highlighting SLNs' potential as promising carriers to enhance CHON delivery in OA treatment and advance nanotechnology-based therapeutic strategies in pharmaceutical formulations.

Formulation of Polymeric Micelles to Increase the Solubility and Photostability of Caffeic Acid.

Caffeic acid (CA), a hydrophobic polyphenol with various pharmacological activities, exhibits a low aqueous solubility and sensitivity to light. In order to improve its chemical properties and overcome the limits in its application, the compound was loaded in P123 micelles (MCs) prepared using two polymer concentrations (10 and 20% w/w, MC10 and MC20). The micelles were characterised in terms of the size distribution, zeta potential, drug encapsulation efficiency, rheology, and cumulative drug release. Micellar formulations exhibited sizes in the range of 11.70 and 17.70 nm and a good polydispersion, indicating the formation of relatively small-sized micelles, which is favourable for drug delivery applications. Additionally, the stability and antioxidant profiles of the free CA and the CA loaded in micelles were studied. The results obtained on the free CA showed the formation of photodegradation products endowed with higher DPPH scavenging activity with respect to the pure compound. Instead, it was found that the incorporation of CA into the micelles significantly increased its solubility and decreased the photodegradation rate. Overall, the results indicate the successful formation of P123 micelles loaded with CA, with promising characteristics such as a small size, good encapsulation efficiency, sustained release profile, and improved light stability. These findings suggest the potentiality of these micelles as a delivery system for CA, thus enhancing its bioavailability.

Kombucha as a Potential Active Ingredient in Cosmetics-An Ex Vivo Skin Permeation Study.

Kombucha is a non-alcoholic beverage, that is increasingly used in the cosmetic industry. The available literature reports the positive effects of kombucha on the skin, in particular its antioxidant action. However, there is a lack of information on skin permeation and the accumulation of active ingredients showing such effects. Skin aging is largely dependent on oxidative stress, therefore in our study we assessed the ex vivo permeation of two types of kombucha (green and black tea) through porcine skin. The antioxidant activity (DPPH, ABTS, FRAP methods) and total polyphenol content of these extracts were determined before and after permeation testing. Moreover, the content of selected phenolic acids as well as caffeine was assessed. Skin permeation was determined using a Franz diffusion cell. The antioxidant activity of both Kombuchas was found to be high. In addition, gallic acid, chlorogenic acid, protocatechuic acid, coumaric acid, m-hydroxybenzoic acid, and caffeine were identified. A 24-h ex vivo study showed the permeation of some phenolic acids and caffeine and their accumulation in the skin. Our results confirm the importance of studying the skin permeation of what are still little known ingredients in cosmetic preparations. Evaluation of the accumulation of these ingredients can guarantee the efficacy of such preparations.

Preformulation evaluation of selumetinib for topical application: skin distribution and photodegradation analysis using MALDI imaging and LC-MS/MS.

Understanding drug behavior within the skin, especially for photosensitive compounds, is crucial for developing effective and safe topical therapies. This study employs Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) and Liquid Chromatography-Mass Spectrometry (LC-MS/MS) to investigate the skin permeation and photostability of selumetinib, a MEK inhibitor used in treating type 1 neurofibromatosis (NF1). The highest amounts of selumetinib in the skin sections were obtained when using the gel formulation, suggesting that it is to be preferred to cream formulations to achieve higher permeation of the drug. Our study also revealed that selumetinib is amenable to photodegradation in ex vivo skin explants, and yields one main degradation product, whose degradation is likely triggered by hydrogen abstraction. MALDI-MSI results showed selumetinib and its degradation product concentrate in skin appendages, indicating these structures might serve as drug reservoirs, potentially prolonging retention and efficacy. This study demonstrates that combining MALDI-MSI with LC/MS-MS can highly contribute to the characterization of the fate of photosensitive compounds in the skin, an essential prerequisite to the development of compound-specific photoprotective measures. It will also pave the way for innovative topical delivery strategies for NF1 treatment.

Revolutionizing Knee Osteoarthritis Treatment: Innovative Self-Nano-Emulsifying Polyethylene Glycol Organogel of Curcumin for Effective Topical Delivery.

In the current study, self-nano-emulsifying (SNE) physically cross-linked polyethylene glycol (PEG) organogel (SNE-POG) as an innovative hybrid system was fabricated for topical delivery of water-insoluble and unstable bioactive compound curcumin (CUR). Response surface methodology (RSM) based on Optimal Design was utilized to evaluate the formulation factors. Solid fiber mechanism with homogenization was used to prepare formulations. Pharmaceutical evaluation including rheological and texture analysis, their mathematical correlations besides physical and chemical stability experiments, DSC study, in vitro release, skin permeation behavior, and clinical evaluation were carried out to characterize and optimize the SNE-OGs. PEG 4000 as the main organogelator, Poloxamer 188 (Plx188) and Ethyl Cellulose (EC) as co-gelator/nanoemulsifier agents, and PEG 400 and glycerin as solvent/co-emulsifier agents could generate SNE-POGs in PS range of 356 to 1410 nm that indicated organic base percentage and PEG 4000 were the most detrimental variables. The optimized OG maintained CUR stable in room and accelerated temperatures and could release CUR sustainably up to 72 h achieving high flux of CUR through guinea pig skin. A double-blind clinical trial confirmed that pain scores, stiffness, and difficulty with physical function were remarkably diminished at the end of 8 weeks compared to the placebo (71.68% vs. 7.03%, 62.40% vs. 21.44%, and 45.54% vs. 8.66%, respectively) indicating very high efficiency of system for treating knee osteoarthritis. SNE-POGs show great potential as a new topical drug delivery system for water-insoluble and unstable drugs like CUR that could offer a safe and effective alternative to conventional topical drug delivery system.

Development of engineered transferosomal gel containing meloxicam for the treatment of osteoarthritis.

OBJECTIVE: .In this study, we investigated the potential of meloxicam (MLX) developed as transferosomal gel as a novel lipidic drug delivery system to address osteoarthritis (OTA), a degenerative joint disease that causes pain and stiffness. By incorporating meloxicam into a transferosomal gel, our aim was to provide a targeted and efficient delivery system capable of alleviating symptoms and slowing down the progression of OTA. MATERIAL AND METHODS: Classical lipid film hydration technique was utilized to formulate different transferosomal formulations. Different transferosomal formulations were prepared by varying the molar ratio of phospholipon-90H (phosphodylcholine) to DSPE (50:50, 60:40, 70:30, 80:20, and 90:10) and per batch, 80mg of total lipid was used. The quality control parameters such as entrapment efficiency, particle size and morphology, polydispersity and surface electric charge, in vitro drug release, ex vivo permeation and stability were measured. RESULTS: The optimized transferosomal formulations revealed a small vesicle size (121±12nm) and greater MLX entrapment (68.98±2.3%). Transferosomes mediated gel formulation MLX34 displayed pH (6.3±0.2), viscosity (6236±12.3 cps), spreadability (13.77±1.77 gm.cm/sec) and also displayed sustained release pattern of drug release (81.76±7.87% MLX released from Carbopol-934 gel matrix in 24h). MLX34 revealed close to substantial anti-inflammatory response, with ∼81% inhibition of TNF-α in 48h. Physical stability analysis concluded that refrigerator temperature was the preferred temperature to store transferosomal gel. CONCLUSION: MLX loaded transferosomes containing gel improved the skin penetration and therefore resulted into increased inhibition of TNF-α level.

New lipophilic organic nitrates: candidates for chronic skin disease therapy.

Organic nitrates are widely used, but their chronic efficacy is blunted due to the development of tolerance. The properties of new tolerance free organic nitrates were studied. Their lipophilicity profile and passive diffusion across polydimethylsiloxane membrane and pig ear-skin, and their efficacy in tissue regeneration using HaCaT keratinocytes were evaluated. The permeation results show that these nitrates have a suitable profile for NO topical administration on the skin. Furthermore, the derivatives with higher NO release exerted a pro-healing effect on HaCaT cells. This new class of organic nitrates might be a promising strategy for the chronic treatment of skin pathologies.

Design of an Ante-enhancer with an Azone-Mimic Structure using Ionic Liquid.

PURPOSE: Laurocapram (Azone) was broadly examined as a representative enhancer of skin penetration in the 1980s. However, it was not approved for treatment because it caused skin irritation following its penetration into the epidermis through the stratum corneum. In the present study, a so-called ante-enhancer with an Azone-mimic structure was designed based on an ante-drug with negligible systemic toxic effects following its permeation through the skin. METHODS: The ante-enhancer was designed using ionic liquid technology: an ionic liquid-type ante-enhancer (IL-Azone) with an Azone-mimic structure was prepared from ε-caprolactam and myristic acid as cationic and anionic substances, respectively. The enhancing effects of IL-Azone on the permeation by the following model drugs through pig skin were examined: isosorbide 5-mononitrate (ISMN), antipyrine (ANP), and fluorescein isothiocyanate dextran (FD-4). Skin irritation by IL-Azone was assessed using the Draize method. RESULTS: The primary irritation index (P.I.I.) of IL-Azone by the Draize method was markedly lower than that of Azone (6.9). Although the ability of IL-Azone to enhance skin penetration was not as high as Azone, IL-Azone moderately increased skin permeation by the model compounds tested (ISMN: 4.7 fold, ANP: 4.5 fold, FD-4: 4.0 fold). CONCLUSIONS: These results suggest the usefulness of designing a skin penetration enhancer using ionic liquid technology. Further trials on the ionic liquid design with an Azone-mimic structure using other cations and anions may lead to the development of better ante-enhancers.

Drug permeation enhancement, efficacy, and safety assessment of azelaic acid loaded SNEDDS hydrogel to overcome the treatment barriers of atopic dermatitis.

Atopic dermatitis is one of the most widespread chronic inflammatory skin conditions that can occur at any age, though the prevalence is highest in children. The purpose of the current study was to prepare and optimize the azelaic acid (AzA) loaded SNEDDS using Pseudo ternary phase diagram, which was subsequently incorporated into the Carbopol 940 hydrogel for the treatment of atopic dermatitis. The composition was evaluated for size, entrapment efficiency, in vitro, ex vivo, and in vivo studies. The polydispersity index of the optimized preparation was found to be less than 0.5, and the size of the distributed globules was found to be 151.20 ± 3.67 nm. The SNEDDS hydrogel was characterized for pH, viscosity, spreadability, and texture analysis. When compared to the marketed formulation, SNEDDS hydrogel was found to have a higher rate of permeation through the rat skin. In addition, a skin irritation test carried out on experimental animals showed that the SNEDDS formulation did not exhibit any erythematous symptoms after a 24-h exposure. In conclusion, the topical delivery of AzA through the skin using SNEDDS hydrogel could prove to be an effective approach for the treatment of atopic dermatitis.

Development, validation and application of a gas chromatography method for the determination of dillapiole from Piper aduncum essential oil in skin permeation samples.

The essential oil extracted from the leaves of Piper aduncum has antifungal, insecticidal and antibacterial activity. Studies with its main compound, dillapiole (DIL) revealed antibacterial and anti-inflammatory potential. Despite all this bioactivity, there is no updated report on the development and validation of analytical and bioanalytical methodology to quantify DIL in skin samples. A selective, precise, accurate and adequate method for the determination of DIL in solutions, porcine ear skin samples and receptor fluid was developed and validated by headspace extraction-gas chromatography with flame ionization detection (HS-GC-FID). HS-GC-FID was applied to determine DIL in Franz cell permeation and retention studies using porcine ear skin samples. In the HS-GC-FID method, matrix-related interferences were not observed at the peak of the DIL retention time. The results showed a high recovery (>97%) after the extraction procedure, allowing the quantification of DIL in complex matrices. In vitro permeation/retention for DIL showed cumulative amounts permeated in the order: receptor fluid (21.98 ± 1.19 µg/cm2 ) > epidermis (15.40 ± 1.20 µg/cm2 ) > dermis (9.52 ± 1.13 µg/cm2 ). HS-GC-FID was successfully validated and the results point to DIL transdermal permeation and to the potential to develop pharmaceutical formulations for skin delivery to treat inflammation or infections.

Ethosomes as dermal/transdermal drug delivery systems: applications, preparation and characterization.

Transdermal drug delivery systems (TDDSs) have gained substantial attention during the last decade. TDDS are versatile delivery systems in which active components are delivered to skin for local effects or systemic delivery of active pharmaceutical through the skin. Overcoming stratum corneum is the most challenging step of delivering drugs through the skin. Lipid-based vesicular delivery systems due to the capability of the delivery of both hydrophilic and hydrophobic drugs are becoming more popular during the recent years. Ethosomes are innovative, biocompatible, biodegradable and non-toxic form of lipid-based vesicles that efficiently enable to entrap drugs of various physicochemical properties. These are other forms of liposome which contain high amounts of ethanol in their structure that enabling ethosomes to efficiently penetrate through deeper layers of skin. Ethosomes have various compositions based on their type but are mainly composed of phospholipids, ethanol, water and the active components. Ethosomes are easily manufactured and they are superior compared to liposomes in terms of different aspects due to the presence of ethanol. The purpose of this review is to thoroughly focus on various aspects of ethosomes, including mechanism of penetration, advantages and disadvantages, characterisation and applications.

Novel Hyaluronic Acid ethosomes based gel formulation for topical use with reduced toxicity, better skin permeation, deposition, and improved pharmacodynamics.

Hyaluronic Acid (HA) has been applied as an anti-ageing molecule in the form of topical products. Current topical commercial formulations of HA face the limitations of very small and stagnant skin permeation, thereby demanding enduring administration of the formulation to sustain its action. In this study, Lipid-based nanocarriers in the form of ethosomes were formulated in a 1% w/w HA strength and were extensively evaluated in vitro, ex-vivo, and in vivo parameters along with a comparison to it's commercial counterpart. The optimised ethosomes-based HA gel formulation revealed required pH (6.9 ± 0.2), small globule size (1024 ± 9 nm), zeta potential of -6.39 ± 0.2 mV, and 98 ± 1.1% HA content. The ex vivo skin permeation and deposition potenwere conferred on synthetic membrane Strat-M, Human cadaver skin, mice skin, rat skin, and pig skin, and both parameters were found to be much higher in comparison to the commercial topical formulation. Skin deposition capacity of the optimised HA formulation was further confirmed by Scan Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) and it was observed that the developed ethosomal gel formulation got deposited more on the treated skin. The in vivo anti-ageing effect of optimised ethosomal gel on rats was found to be greater when compared to commercial formulation of HA and the developed carrier-based system proved to deliver the HA molecule in very small amounts into the systemic circulation. The results endorse the ethosomal carrier-based formulation of HA as a attractive technique for better local bioavailability of HA.

Exploring Nanocarriers as Treatment Modalities for Skin Cancer.

Cancer is a progressive disease of multi-factorial origin that has risen worldwide, probably due to changes in lifestyle, food intake, and environmental changes as some of the reasons. Skin cancer can be classified into melanomas from melanocytes and nonmelanoma skin cancer (NMSC) from the epidermally-derived cell. Together it constitutes about 95% of skin cancer. Basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (CSCC) are creditworthy of 99% of NMSC due to the limited accessibility of conventional formulations in skin cancer cells of having multiple obstacles in treatment reply to this therapeutic regime. Despite this, it often encounters erratic bioavailability and absorption to the target. Nanoparticles developed through nanotechnology platforms could be the better topical skin cancer therapy option. To improve the topical delivery, the nano-sized delivery system is appropriate as it fuses with the cutaneous layer and fluidized membrane; thus, the deeper penetration of therapeutics could be possible to reach the target spot. This review briefly outlooks the various nanoparticle preparations, i.e., liposomes, niosomes, ethosomes, transferosomes, transethosomes, nanoemulsions, and nanoparticles technologies tested into skin cancer and impede their progress tend to concentrate in the skin layers. Nanocarriers have proved that they can considerably boost medication bioavailability, lowering the frequency of dosage and reducing the toxicity associated with high doses of the medication.

Efficiency of emulsifier-free emulsions in delivering caffeine and α-tocopherol to human skin.

OBJECTIVE: Increasing consumer demand for natural and environmentally friendly products is driving the cosmetic industry to seek greener and safer processes. High-frequency ultrasound technology (HFUT) stabilizes emulsions without adding emulsifying surfactants (ES). In this work, the formulation characteristics of an HFUT-treated emulsion and a Reference emulsion were compared for both caffeine and α-tocopherol. METHODS: A comparison was made between ES-free emulsions and the Reference emulsions based on droplet size, viscosity, pH and rheology behaviour for both active cosmetic ingredients. The permeation of caffeine and the skin retention of α -tocopherol were studied in vitro using Franz diffusion cells on human skin biopsies, considered the gold standard for permeation assays. RESULTS: The formulations developed were stable and showed suitable droplet size distribution. In the case of ES-free emulsions, the average droplet size was inferior to 1.5 µm regardless of the polarity of the active. All formulations presented a shear-thinning pseudoplastic behaviour, an attribute usually desired for cosmetic products. The skin permeation studies showed that in the case of caffeine (model hydrophilic molecule), the ES-free emulsion presented a delivery capacity similar to that of the Reference emulsion. However, for α-tocopherol (highly lipophilic model molecule), differences were observed in the distribution of the active in the stratum corneum with an advantage for the Reference emulsion, probably due to the impact of surfactants on the SC lipids. CONCLUSION: This work demonstrates that HFUT is a reliable tool that is able to prepare stable ES-free emulsions loaded with hydrophilic or lipophilic active ingredients. Skin permeation studies confirm that the emulsions produced by HFUT promote the delivery of the actives to the human skin. In the case of α-tocopherol, the delivery efficiency was lower than with the Reference emulsion, especially in the SC layers, due to the absence of surfactants. Nevertheless, the ES-free emulsion still represents a good compromise between efficacy and the need for green cosmetics in the market.

OBJECTIF: La demande croissante des consommateurs pour des produits naturels et respectueux de l'environnement encourage l'industrie cosmétique à développer des procédés plus écologiques et plus sûrs. La technologie des ultrasons à haute fréquence (HFUT) permet de stabilizer les émulsions sans ajouter de tensioactifs émulsionnants (ES). Dans ce travail, les caractéristiques d'une émulsion traitée par HFUT et d'une émulsion de référence ont été comparées. La caféine et l'α-tocophérol ont été utilisés comme actifs modèles. MÉTHODES: Les émulsions sans ES et les émulsions de référence on été comparées en termes de taille des gouttelettes, de viscosité, de pH et de comportement rhéologique pour les deux actifs. La perméation de la caféine et la rétention cutanée de l'α-tocophérol ont été étudiées in vitro sur des biopsies de peau humaine, en utilisant des cellules de diffusion de Franz, le 'gold standard' des tests de perméation. RÉSULTATS: Les formulations développées sont stables et présentent une distribution appropriée de la taille des gouttelettes. La taille moyenne des gouttelettes des émulsions sans ES est inférieure à 1.5 µm, quelle que soit la polarité de l'actif. Toutes les formulations présentent un comportement rhéofluidifiant adapté à un usage cosmétique. Les études de perméation cutanée montrent que l'émulsion sans ES contenant de la caféine (molécule modèle hydrophile) présente une capacité de délivrance similaire à celle de l'émulsion de référence. Dans le cas de l'α-tocophérol (molécule modèle lipophile), des différences ont été observées dans la distribution de l'actif dans le stratum corneum (SC) avec un avantage pour l'émulsion de référence, probablement lié à l'interaction entre les tensioactifs et les lipides du SC. CONCLUSION: Ce travail démontre que le traitement par HFUT permet de préparer des émulsions stables sans ES, quelle que soit la polarité des actifs cosmétiques à véhiculer. Les études de perméation cutanée confirment que les émulsions produites par HFUT permettent la diffusion cutanée des actifs dans la peau humaine. Même si dans le cas de l'α-tocophérol la quantité accumulée était plus faible, l'émulsion traitée par HFUT propose un bon compromis entre efficacité et éco-responsabilité.