Mechanisms of action of novel skin penetration enhancers: Phospholipid versus skin lipid liposomes

Ethosomes: A novel drug carrier

Ethosomal systems are newer lipid vesicular carriers that have been around for 20 years, but over that period they have grown significantly as a means of transdermal drug delivery. They have a sizable amount of ethanol in them. These nanocarriers carry medicinal substances with various physicochemical qualities throughout the skin and deep skin layers. Since they were created in 1996, ethosomes have undergone substantial investigation; new substances have been added to their original composition, creating new varieties of ethosomal systems. These innovative carriers, which can be added to gels, patches, and lotions, are prepared using several novel methods. In addition to clinical trials, many in vivo models are employed to assess the effectiveness of dermal/transdermal administration. This review focuses on different generation of ethosomes and their comparison with other conventional liposomes.

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In early December 2019, a large pneumonia epidemic occurred in Wuhan, China.

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COVID-19 therapy focuses on treating the disease's symptoms.

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Globally, numerous studies and researchers have recently started fighting this virus.

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This paper examines the main characteristics of coronavirus and the computational analyses necessary to avoid infection.

Single-dose pharmacokinetics and bioavailability of a novel extended duration transdermal buprenorphine solution in cats

A novel transdermal buprenorphine solution (TBS) was developed for evaluation in order to make available an extended duration opioid analgesic for cats. Healthy adult cats were administered a single TBS dose of 10 mg (1.57-4.35 mg/kg), 30 mg (4.72-13.0 mg/kg), or 50 mg (7.87-21.7 mg/kg) (4 cats per group) applied topically to the unclipped dorsal cervical skin and plasma buprenorphine concentrations were evaluated through 7 days. To determine the absolute bioavailability of TBS, healthy cats were administered single TBS dose of 20 mg (3.33-4.76 mg/kg) or 0.05 mg (0.008-0.011 mg/kg) IV buprenorphine (6 cats per group). The mean ± standard deviation maximum plasma buprenorphine concentrations (C_max ) were 10.5 ± 6.28, 18.6 ± 8.68, and 22.5 ± 4.47 ng/ml following 10, 30, and 50 mg doses, respectively, with the time of C_max occurrence (t_max ) typically occurring at 2-12 h post-dosing. Mean plasma buprenorphine terminal half-lives ranged between 78.3 and 91.2 h. Increasing the dose threefold and fivefold from the 10 mg dose increased the exposure by 2.8- and 3.6-fold, respectively, indicating that plasma buprenorphine exposure increased in a less than proportional manner at doses >30 mg. Transient sedation, mydriasis, and euphoria were observed within 4 h post-dosing. Mean rectal temperatures were increased 0.6-0.9°C greater than baseline (37.4-37.8°C) through 168 h post-dosing. The absolute bioavailability was 16.0% (90% CI: [11.8%-21.7%]). Flip-flop pharmacokinetics were observed with a terminal elimination half-life of 0.82 ± 0.13 and 64.9 ± 15.0 h for IV buprenorphine and 20 mg of TBS, respectively. A single administration of TBS over a range of doses resulted in extended plasma buprenorphine concentrations and opioid physiological and behavioral effects.

Lipid-Drug Conjugates and Nanoparticles for the Cutaneous Delivery of Cannabidiol

Lipid nanoparticles are currently used to deliver drugs to specific sites in the body, known as targeted therapy. Conjugates of lipids and drugs to produce drug-enriched phospholipid micelles have been proposed to increase the lipophilic character of drugs to overcome biological barriers. However, their applicability at the topical level is still minimal. Phospholipid micelles are amphiphilic colloidal systems of nanometric dimensions, composed of a lipophilic nucleus and a hydrophilic outer surface. They are currently used successfully as pharmaceutical vehicles for poorly water-soluble drugs. These micelles have high in vitro and in vivo stability and high biocompatibility. This review discusses the use of lipid-drug conjugates as biocompatible carriers for cutaneous application. This work provides a metadata analysis of publications concerning the conjugation of cannabidiol with lipids as a suitable approach and as a new delivery system for this drug.

Nanostructured lipid carriers for enhanced in vitro and in vivo schistosomicidal activity of praziquantel: effect of charge

WHO considers praziquantel (PZQ) as the drug of choice for treatment of Schistosoma mansoni infection but this requires high dose due to poor solubility and first pass metabolism. The aim of this work was to optimize nanostructured lipid carriers (NLCs) for enhanced PZQ oral delivery. The optimization involved testing the effect of surface charge of NLCs. NLCs comprised precirol ATO as solid lipid with oleic acid, Span 60 and Tween 80 as liquid components. Dicetyl phosphate and stearyl amine were the negative and positive charging agents, respectively. NLCs were prepared by microemulsification technique and were characterized. The schistosomicidal activity of PZQ loaded NLCs was monitored in vitro and in vivo using infected mice. PZQ showed high entrapment efficiency in all types of NLCs (ranged from 93.97 to 96.29%) with better PZQ loading in standard NLCs. This was clarified by thermal analysis which reflected displacement of PZQ by charging agents. In vitro schistosomicidal study revealed the superiority of PZQ loaded positively charged NLCs (LC50 and LC95 equal 0.147 and 0.193 µg/ml respectively) with traditional and negatively charged NLCs being inferior to simple PZQ solution after short incubation period. Scanning electron micrographs showed that PZQ loaded positively charged NLCs resulted in more intense ultrastructural changes in worms. The superiority of positively charged NLCs was confirmed by in vivo assessment as they showed better improvement in histopathological features of the liver of the infected mice compared with other formulations. The study introduced positively charged NLCs as promising carriers for oral delivery of PZQ.

Pharmacokinetic and Pharmacodynamic Evaluation of Resveratrol Loaded Cationic Liposomes for Targeting Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. The destructive nature of the disease makes it difficult for clinicians to manage the condition. Hence, there is an urgent need to find new alternatives for HCC, as the role of conventional cytotoxic drugs has reached a plateau to control HCC associated mortality. Antioxidant compounds of plant origin with potential anti-tumor effect have been recognized as alternate modes in cancer treatment and chemoprevention. Resveratrol (RS) is a model natural nonflavonoid drug known for its anti-cancer activity. However, its clinical application is limited due to its poor bioavailability. The current research work aims to formulate, optimize, and characterize RS loaded cationic liposomes (RLs) for specific delivery in HCC. The optimized liposomes formulation (RL5) was spherical with a vesicle size (VS) of 145.78 ± 9.9 nm, ζ potential (ZP) of 38.03 ± 9.12 mV, and encapsulation efficiency (EE) of 78.14 ± 8.04%. In vitro cytotoxicity studies in HepG2 cells demonstrated an improved anti-cancer activity of RL5 in comparison with free RS. These outcomes were supported by a cell uptake study in HepG2 cells, in which RL5 exhibited a higher uptake than free RS. Furthermore, confocal images of HepG2 cells after 3 and 5 h of incubation showed higher internalization of coumarin 6 (C6) loaded liposomes (CL) as compared to those of the free C6. Pharmacokinetic and pharmacodynamic (prophylactic and therapeutic treatment modalities) studies were performed in N-nitrosodiethylamine (NDEA-carcinogen) induced HCC in rats. Pharmacokinetic evaluation of RL5 demonstrated increased localization of RS in cancerous liver tissues by 3.2- and 2.2-fold increase in AUC and Cmax, respectively, when compared to those of the free RS group. A pharmacodynamic investigation revealed a significant reduction in hepatocyte nodules in RL5 treated animals when compared to those of free RS. Further, on treatment with RL5, HCC-bearing rats showed a significant decrease in the liver marker enzymes (alanine transaminase, alkaline phosphatase, aspartate transaminase, total bilirubin levels, γ-glutamyl transpeptidase, and α-fetoprotein), in comparison with that of the disease control group. Our findings were supported by histopathological analysis, and we were first to demonstrate that NDEA induced detrimental effect on rat livers was successfully reversed with the treatment of RL5 formulation. These results implied that delivery of RS loaded cationic liposomes substantially controlled the severity of HCC and that they can be considered as a promising nanocarrier in the management of HCC.

Nano-formulation for topical treatment of precancerous lesions: skin penetration, in vitro, and in vivo toxicological evaluation

With the aim of improving the topical delivery of the antineoplastic drug 5-fluorouracil (5FU), it was loaded into ultradeformable liposomes composed of soy phosphatidylcholine and sodium cholate (UDL-5FU). The liposome populations had a mean size of 70 nm without significant changes in 56 days, and the ultradeformable formulations were up to 324-fold more elastic than conventional liposomes. The interaction between 5FU and the liposomal membrane was studied by three methods, and also release profile was obtained. UDL-5FU did penetrate the stratum corneum of human skin. At in vitro experiments, the formulation was more toxic on a human melanoma-derived than on a human keratinocyte-derived cell line. Cells captured liposomes by metabolically active processes. In vivo toxicity experiments were carried out in zebrafish (Danio rerio) larvae by studying the swimming activity, morphological changes, and alterations in the heart rate after incubation. UDL-5FU was more toxic than free 5FU. Therefore, this nano-formulation could be useful for topical application in deep skin precancerous lesions with advantages over current treatments. This is the first work that assessed the induction of apoptosis, skin penetration in a Saarbrücken penetration model, and the toxicological effects in vivo of an ultradeformable 5FU-loaded formulation.

Chemical Enhancer: A Simplistic Way to Modulate Barrier Function of the Stratum Corneum

Human skin could be a prime target to deliver drugs into the human body as it is the largest organ of human body. However, the main challenge of delivering drug into the skin is the stratum corneum (SC), the outer layer of epidermis, which performs the main barrier function of the skin. Scientists have developed several techniques to overcome the barrier properties of the skin, which include other physical and chemical techniques. The most common and convenient technique is to use special formulation additives (chemical enhancers, CEs) which either drags the drug molecule along with it or make changes in the SC structure, thereby allowing the drug molecule to penetrate in to the SC. The main focus is to deliver drugs in the certain layers of the skin (for topical delivery) or ensuring proper percutaneous absorption (for transdermal delivery). However, skin drug delivery is still very challenging as different CEs act in different ways on the skin and they have different types of interaction with different drugs. Therefore, proper understanding on the mechanism of action of CE is mandatory. In this article, the effect of several CEs on skin has been reviewed based on the published articles. The main aim is to compile the recent knowledge on skin-CE interaction in order to design a topical and transdermal formulation efficiently. A properly designed formulation would help the drug either to deposit into the target layer or to cross the barrier membrane to reach the systemic circulation.

Stratum corneum lipid liposomes for investigating skin penetration enhancer effects

Knowledge of the mechanism of action of skin penetration enhancers is essential to formulators for optimizing formulations and to maximize the efficacy of enhancers. To obtain information about the effects of penetration enhancers as a fast initial screening, investigations have been performed to identify possible correlations of the biological effectiveness of penetration enhancers with their interaction with a well-defined model system consisting of skin mimic lipid bilayers, as determined by calcein release experiments using stratum corneum lipid liposomes (SCLLs). We aimed to investigate the enhancing effects of different concentrations of two chemical penetration enhancers, Kolliphor RH40 and Transcutol on SCLLs. The results obtained by SCLL-based techniques were compared with conventional ex vivo penetration studies in case of Kolliphor RH40 to evaluate the potential of SCLLs as an alternative tool for screening various types and concentrations of penetration enhancers. As a result, calcein leakage assay performed with SCLL was considered to be a good model for the skin penetration enhancing effect. This method could be used as a time-saving and sensitive alternative in vitro screening technique in the early stage of the development of dermal formulations.

The aim of this work was to investigate the applicability of stratum corneum lipid liposomes as in vitro skin models for studying skin penetration enhancer effect of Kolliphor RH40 and Transcutol.

Potential of Stratum Corneum Lipid Liposomes for Screening of Chemical Skin Penetration Enhancers

The evaluation of effective skin chemical penetration enhancers (CPEs) is a crucial process in the development of transdermal and dermal formulations with the capacity to overcome the stratum corneum barrier. In the present study, we aimed to investigate the potential of stratum corneum lipid liposomes (SCLLs) as an alternative tool for the screening of various types and concentrations of CPEs. SCLLs were prepared using a thin-film hydration technique, and two types of fluorescent probes (sodium fluorescein [FL] or 1,6-diphenyl-1,3,5-hexatriene [DPH] were entrapped separately into SCLLs (FL-SCLL and DPH-SCLL, respectively). FL leakage from SCLLs as well as the fluidity of DPH-SCLLs were determined after incubating with various types of CPEs as a function of their concentrations. The obtained results showed a concentration-dependent relationship for most CPEs both for FL leakage and the fluidity of SCLLs. When observing these data in detail, however, the concentration profiles could be classified into five main categories depending on the mode of action of the CPEs. These results strongly suggest the usefulness of SCLLs for high-throughput screening of effective CPEs as well as the understanding of their possible mode of action, especially in the early stage of skin formulation development.

High-Throughput Screening of Potential Skin Penetration-Enhancers Using Stratum Corneum Lipid Liposomes: Preliminary Evaluation for Different Concentrations of Ethanol

In this study, we developed a technique for high-throughput screening (HTS) of skin penetration-enhancers using stratum corneum lipid liposomes (SCLLs). A fluorescent marker, sodium fluorescein (FL), entrapped in SCLLs was prepared to provide a preliminary evaluation of the effect of different concentrations of ethanol on the disruption effect of SCLLs, which is an alternative for skin penetration-enhancing effects. In addition, SCLLs containing a fluorescent probe (DPH, TMA-DPH, or ANS) were also prepared and utilized to investigate SCLL fluidity. The results using SCLL-based techniques were compared with conventional skin permeation and skin impedance test using hairless rat skin. The obtained correlations were validated between FL leakage, SCLL fluidity with various probes, or skin impedance and increases in the skin permeation enhancement ratio (ER) of caffeine as a model penetrant. As a result, FL leakage and SCLL fluidity using ANS were considered to be good indices for the skin penetration-enhancing effect, suggesting that the action of ethanol on the SC lipid and penetration-enhancing is mainly on the polar head group of intercellular lipids. In addition, this screening method using SCLL could be utilized as an alternative HTS technique for conventional animal tests. Simultaneously, the method was found to be time-saving and sensitive compared with a direct assay using human and animal skins.

Biomimetic Lipid-Based Nanosystems for Enhanced Dermal Delivery of Drugs and Bioactive Agents

Clinical utility of conventional oral therapies is limited by their inability to deliver therapeutic molecules at the local or targeted site, causing a variety of side effects. Transdermal delivery has made a significant contribution in the management of skin diseases with enhanced therapeutic activities over the past two decades. In the modern era, various biomimetic and biocompatible polymer-lipid hybrid systems have been used to augment the transdermal delivery of therapeutics such as dermal patches, topical gels, iontophoresis, electroporation, sonophoresis, thermal ablation, microneedles, cavitational ultrasound, and nano or microlipid vesicular systems. Nevertheless, the stratum corneum still represents the main barrier to the delivery of vesicles into the skin. Lipid based formulations applied to the skin are at the center of attention and are anticipated to be increasingly functional as the skin offers many advantages for the direction of such systems. Accordingly, this review provides an overview of the development of conventional to advanced biomimetic lipid vesicles for skin delivery of a variety of therapeutics, with special emphasis on recent developments in this field including the development of transferosomes, niosomes, aquasomes, cubosomes, and other new generation lipoidal carriers.

Enhancing the in vivo transdermal delivery of gold nanoparticles using poly(ethylene glycol) and its oleylamine conjugate

In this study, we investigated the effect of (ethylene glycol) (PEG) and PEG-oleylamine (OAm) functionalization on the skin permeation property of gold nanoparticles (GNS) in vivo. Chemisorption of polymers onto GNS was verified by a red shift in the ultraviolet-visible spectrum as well as by a change in the nanoparticle surface charge. The physicochemical properties of pristine and functionalized nanoparticles were analyzed by ultraviolet-visible spectroscopy, zeta potential analyzer, and transmission electron microscopy. Transmission electron microscopy revealed that the interparticle distance between nanoparticles increased after GNS functionalization. Comparing the skin permeation profile of pristine and functionalized GNS, the follicular deposition of GNS increased twofold after PEG-OAm functionalization. Moreover, PEG- and PEG-OAm-functionalized nanoparticles were able to overcome the skin barrier and deposit in the deeper subcutaneous adipose tissue. These findings demonstrate the potential of PEG- and PEG-OAm-functionalized GNS in serving a multitude of applications in transdermal pharmaceuticals.

Poloxamer 407-based intranasal thermoreversible gel of zolmitriptan-loaded nanoethosomes: formulation, optimization, evaluation and permeation studies

Zolmitriptan is the drug of choice for migraine, but low oral bioavailability (<50%) and recurrence of migraine lead to frequent dosing and increase in associated side effects. Increase in the residence time of drug at the site of drug absorption along with direct nose to brain targeting of zolmitriptan can be a solution to the existing problems. Hence, in the present investigation, thermoreversible intranasal gel of zolmitriptan-loaded nanoethosomes was formulated by using mucoadhesive polymers to increase the residence of the drug into the nasal cavity. The preparation of ethosomes was optimized by using 3(2) factorial design for percent drug entrapment efficiency, vesicle size, zeta potential, and polydispersity index. Optimized formulation E6 showed the vesicle size (171.67 nm) and entrapment efficiency (66%) when compared with the other formulations. Thermoreversible gels prepared by using poloxamer 407 showed the phase transition temperature at 32-33 °C which was in line with the nasal physiological temperature. The optimized ethosomes were loaded into the thermoreversible mucoadhesive gel optimized by varying concentrations of poloxamer 407, carbopol 934, HPMC K100, and evaluated for gel strength, gelation temperature, mucoadhesive strength, in vitro drug release, and ex vivo drug permeation, where G3 and G6 were found to be optimized formulations. In vitro drug release was studied by different kinetic models suggested that G3 (n = 0.582) and G6 (n = 0.648) showed Korsemeyer-Peppas (KKP) model indicating non-Fickian release profiles. A permeation coefficient of 5.92 and 5.9 µg/cm(2) for G3 and G6, respectively, revealed very little difference in release rate after 24 h between both the formulations. Non-toxic nature of the gels on columnar epithelial cells was confirmed by histopathological evaluation.

Semi-solid fluorinated-DPPC liposomes: Morphological, rheological and thermic properties as well as examination of the influence of a model drug on their skin permeation

The goal of this study was to investigate the influence of an incorporated model drug on the skin permeation of the vehicle itself as it may affect the microstructure and properties of the applied formulation via molecular interactions. For this purpose, we performed skin permeation studies using liposomes prepared with F-DPPC, a monofluorinated analog of dipalmitoylphosphatidylcholine (DPPC), with and without sodium fluorescein (SoFl) serving as model drug. Interestingly, the liposome preparation with F-DPPC yielded semi-solid opalescent systems. Hence, a thorough characterization was accomplished beforehand by electron microscopy imaging, rheological and thermoanalytical experiments. Freeze-fracture electron microscopy images confirmed the existence of globular shaped vesicles in the F-DPPC preparations and oscillatory rheological measurements proved the viscoelastic properties of F-DPPC and F-DPPC+SoFl liposomes in contrast to the viscous characteristics of DPPC liposomes. Thermoanalytical measurements revealed an increased phase transition temperature Tm of about 50 °C for F-DPPC and F-DPPC+SoFl liposomes compared to pure DPPC liposomes with a Tm of about 43° C. The similar Tm of F-DPPC+SoFl and F-DPPC liposomes as well as the similar skin permeation of the vehicle compound F-DPPC compared to its drug-free counterpart suggest an incorporation of sodium fluorescein into the aqueous core of F-DPPC liposomes.

The infant skin barrier: can we preserve, protect, and enhance the barrier?

Infant skin is different from adult in structure, function, and composition. Despite these differences, the skin barrier is competent at birth in healthy, full-term neonates. The primary focus of this paper is on the developing skin barrier in healthy, full-term neonates and infants. Additionally, a brief discussion of the properties of the skin barrier in premature neonates and infants with abnormal skin conditions (i.e., atopic dermatitis and eczema) is included. As infant skin continues to mature through the first years of life, it is important that skin care products (e.g., cleansers and emollients) are formulated appropriately. Ideally, products that are used on infants should not interfere with skin surface pH or perturb the skin barrier. For cleansers, this can be achieved by choosing the right type of surfactant, by blending surfactants, or by blending hydrophobically-modified polymers (HMPs) with surfactants to increase product mildness. Similarly, choosing the right type of oil for emollients is important. Unlike some vegetable oils, mineral oil is more stable and is not subject to oxidation and hydrolysis. Although emollients can improve the skin barrier, more studies are needed to determine the potential long-term benefits of using emollients on healthy, full-term neonates and infants.

Bicelles: lipid nanostructured platforms with potential dermal applications

Bicelles emerge as promising membrane models, and because of their attractive combination of lipid composition, small size and morphological versatility, they become new targets in skin research. Bicelles are able to modify skin biophysical parameters and modulate the skin's barrier function, acting to enhance drug penetration. Because of their nanostructured assemblies, bicelles have the ability to penetrate through the narrow intercellular spaces of the stratum corneum of the skin to reinforce its lipid lamellae. The bicelle structure also allows for the incorporation of different molecules that can be carried through the skin layers. All of these characteristics can be modulated by varying the lipid composition and experimental conditions. The remarkable versatility of bicelles is their most important characteristic, which makes their use possible in various fields. This system represents a platform for dermal applications. In this review, an overview of the main properties of bicelles and their effects on the skin are presented.

Polymeric micelles of PEG-PE as carriers of all-trans retinoic acid for stability improvement

The topical application of all-trans retinoic acid (ATRA) is an effective treatment for several skin disorders, including photo-aging. Unfortunately, ATRA is susceptible to light, heat, and oxidizing agents. Thus, this study aimed to investigate the ability of polymeric micelles prepared from polyethylene glycol conjugated phosphatidylethanolamine (PEG-PE) to stabilize ATRA under various storage conditions. ATRA entrapped in polymeric micelles with various PEG and PE structures was prepared. The critical micelle concentrations were 97-243 μM, depending on the structures of the PEG and PE molecules. All of the micelles had particle diameters of 6-20 nm and neutral charges. The highest entrapment efficiency (82.7%) of the tested micelles was exhibited by ATRA in PEG with a molecular weight of 750 Da conjugated to dipalmitoyl phosphatidylethanolamine (PEG(750)-DPPE) micelles. The PEG(750)-DPPE micelle could significantly retard ATRA oxidation compared to ATRA in 75% methanol/HBS solution. Up to 87% of ATRA remained in the PEG(750)-DPPE micelle solution after storage in ambient air for 28 days. This result suggests that PEG(750)-DPPE micelle can improve ATRA stability. Therefore, ATRA in PEG(750)-DPPE micelle is an interesting alternative structure for the development of cosmeceutical formulations.

Cavamax W7 composite ethosomal gel of clotrimazole for improved topical delivery: development and comparison with ethosomal gel

The present research work was aimed to formulate clotrimazole encapsulated Cavamax W7 composite ethosomes by injection method for improved delivery across epidermis. 3(2) factorial design was used to design nine formulations (F1-F9) and compared with ethosomal formulations (F10-F12). F9 with vesicle size of 202.8 ± 4.8 nm, highest zeta potential (-83.6 ± 0.96 mV) and %EE of 98.42 ± 0.15 was selected as optimized composite ethosome and F12 as reference ethosomal formulation. As revealed by transmission electron microscopy F9 vesicles were more condensed, uniformly spherical in shape than F12 vesicles. Vesicular stability studies indicated F9 to be more stable as compared to F12. Both F9 and F12 were incorporated in carbopol 934 gel base to get G1-G8 gel formulations and evaluated for in vitro skin permeability. Cavamax W7 composite ethosomal optimized gel (G5) showed higher in vitro percent cumulative drug permeation (88.53 ± 2.10%) in 8 h and steady state flux (J(ss)) of 3.39 ± 1.45 μg/cm(2)/min against the J(ss) of 1.57 ± 0.23 μg/cm(2)/min for ethosomal gel (G1) and 1.13 ± 0.06 μg/cm(2)/min for marketed formulation. The J(ss) flux of G5 was independent of amount of drug applied/unit area of skin. In vivo confocal laser scanning microscopic study of G5 depicted uniform and deeper penetration of rhodamine B (marker) in epidermis from Cavamax W7 composite ethosomal gel in comparison to G1. Finally, G5 demonstrated better (p < 0.05) antifungal activity against Candida albicans and Aspergillus niger than G1 thus, signifying that Cavamax W7 composite ethosomes present a superior stable and efficacious vesicular system than ethosomal formulation for topical delivery of clotrimazole.

Topical delivery and photodynamic evaluation of a multivesicular liposomal Rose Bengal

We investigated the pharmaceutical and physicochemical properties of different multivesicular liposome (MVL) formulations for the delivery of Rose Bengal (RB) into skin layers for topical photodynamic therapy. The drug content, uniformity, spreadability and release kinetics of the optimum hydrogel formulation were studied. Skin penetration of the prepared gels was studied in albino mice using fluorescence microscopy and the photodynamic properties were evaluated. The loading efficiency of MVL ranged from 56% to 79%. In vitro RB release from MVL followed Higuchi's diffusion mechanism and the amount of RB released after 2 h from the optimum MVL (comprising D,L-dipalmitoylphosphatidyl choline, cholesterol and tripalmitin at a molar ratio of 1:0.7:0.1, respectively) was 2.5-fold higher than from the other MVL formulations. The type and concentration of phospholipids did not significantly (p > 0.05) affect vesicle size but significantly (p < 0.05) increased the encapsulation capacity and thermal properties. RB in hydrogel was spreadable and uniformly distributed. Fluorescence microscopy 30 min after topical application to the skin of mice showed that RB loaded into MVL was significantly (p < 0.05) more distributed into the dermal layers than free RB which accumulated in the epidermis. This finding was confirmed by the presence of superficial necrotic cells in histological sections of skin treated with free RB and the presence of RB in the deep dermal layers of sections of skin treated with the MVL-RB formulation and irradiated for 10 min with light of wavelength 550 nm from a light emitting diode at 80 mW. MVL hydrogel is a promising topical delivery system which allows successful delivery of RB into skin layers for different photodynamic therapies in dermatology.

Therapeutic and cosmeceutical potential of ethosomes: An overview

The main disadvantage of transdermal drug delivery is the poor penetration of most compounds into the human skin. The main barrier of the skin is located within its uppermost layer, the stratum corneum (SC). Several approaches have been developed to weaken this skin barrier. One of the approaches for increasing the skin penetration of drugs and many cosmetic chemicals is the use of vesicular systems, such as, liposomes and ethosomes. Ethosomes are phospholipid-based elastic nanovesicles containing a high content of ethanol (20-45%). Ethanol is known as an efficient permeation enhancer and has been added in the vesicular systems to prepare elastic nanovesicles. It can interact with the polar head group region of the lipid molecules, resulting in the reduction of the melting point of the stratum corneum lipid, thereby increasing lipid fluidity and cell membrane permeability. The high flexibility of vesicular membranes from the added ethanol permits the elastic vesicles to squeeze themselves through the pores, which are much smaller than their diameters. Ethosomal systems are much more efficient in delivering substances to the skin in the terms of quantity and depth, than either conventional liposomes or hydroalcoholic solutions. The scope of this small review is to introduce the novel concept of ethosomes and to describe some approaches and mechanisms of stimulating topical and transdermal products with ethosomes.

A novel transdermal delivery system for the anti-inflammatory lumiracoxib: influence of oleic acid on in vitro percutaneous absorption and in vivo potential cutaneous irritation

Transdermal delivery of non-steroidal anti-inflammatory drugs may be an interesting strategy for delivering these drugs to the diseased site, but it would be ineffective due to low skin permeability. We investigated whether oleic acid (OA), a lipid penetration enhancer in poloxamer gels named poloxamer-based delivery systems (PBDS), can improve lumiracoxib (LM) delivery to/through the skin. The LM partition coefficient (K) studies were carried out in order to evaluate the drug lipophilicity grade (K(octanol/buffer)), showing values >1 which demonstrated its high lipophilicity. Both in vitro percutaneous absorption and skin retention studies of LM were measured in the presence or absence of OA (in different concentrations) in PBDS using porcine ear skin. The flux of in vitro percutaneous absorption and in vitro retention of LM in viable epidermis increased in the presence of 10.0% (w/w) OA in 25.0% (w/w) poloxamer gel. In vivo cutaneous irritation potential was carried out in rabbits showing that this formulation did not provide primary or cumulative cutaneous irritability in animal model. The results showed that 25.0% poloxamer gel containing 10.0% OA is potential transdermal delivery system for LM.

Anti-inflammatory effects of locally applied enzyme-loaded ultradeformable vesicles on an acute cutaneous model

Superoxide dismutase (SOD) and catalase (CAT) are active scavengers of reactive oxygen species and were incorporated into ultradeformable vesicles with the aim of increasing enzyme bioavailability (skin delivery). These special very adaptable vesicles have been formulated and optimized for enzyme transport in order to penetrate into or across the intact skin barrier. Anti-inflammatory activity of SOD-loaded, CAT-loaded and of SOD- and CAT-loaded ultradeformable vesicles applied epicutaneously was measured using different protein doses on the skin, on an arachidonic acid-induced mouse ear oedema. The biological anti-oedema activity is a measurement of drug-targeting potentiation in the organ. Delivery by means of deformable vesicles was compared to conventional vesicles or the absence of an enzyme carrier mediated transport. This was done at various times following prophylactic application of the test formulations. Positive reference groups were treated epicutaneously with several low molecular weight non-steroidal anti-inflammatory drugs (NSAIDs). The latter included indomethacin (3 mg kg(-1)), etofenamate (30 mg kg(-1)) and piroxicam (1 mg kg(-1)) and reduced the oedema by 94 +/- 4%, 81 +/- 4% and 42 +/- 5%, respectively, if measured 30 min after ear treatment with a NSAID. Of the enzyme-loaded carriers tested, only the enzyme-loaded ultradeformable vesicles reduced the swelling of ears significantly: SOD (90 microg kg(-1)), CAT (250 microg kg(-1)) and SOD (90 microg kg(-1)) plus CAT (250 microg kg(-1)) reduced the oedema by 70 +/- 12%, 65 +/- 10% and 61 +/- 19%, respectively, at t = 30 min. Aqueous enzyme solutions and empty carriers had no such effect. The combination of two enzymes resulted in no increased therapeutic effect, but the results are inconclusive since only two dose combinations were tested. The results presented in this study suggest that antioxidant enzymes delivered by means of ultradeformable lipid vesicles can serve as a novel region-specific treatment of inflammation.

Simultaneous measurements of K+ and calcein release from liposomes and the determination of pore size formed in a membrane

The changes induced by biologically active substances in the permeability to K+ and calcein of liposomes composed of egg phosphatidylcholine and cholesterol were measured simultaneously in order to rapidly screen the sizes of pores formed in a membrane, using different sized markers. The substances examined in the present study were classified into three types based on differences in the rates at which K+ and calcein were released. The first type released only K+, and included gramicidin A. The second type predominantly released K+, preceding the release of calcein, and included amphotericin B and nystatin. The third type, including antimicrobial peptides, such as gramicidin S, alamethicin, and melittin, and several membrane-active drugs, like celecoxib (non-steroidal anti-inflammatory drug), 1-dodecylazacycloheptan-2-one (named azone; skin permeation enhancer), and chlorpromazine (tranquilizer), caused the release of K+ and calcein simultaneously. Thus, the sizes of pores formed in a liposomal membrane increased in the following order: types one, two, and three. We determined the size more precisely by conducting an osmotic protection experiment, measuring the release of calcein in the presence of osmotic protectants of different sizes. The radii of pores formed by the second type, amphotericin B and nystatin, were 0.36 - 0.46 nm, while the radii of pores formed by the third type were much larger, 0.63 - 0.67 nm or more. The permeability changes induced by substances of the third type are discussed in connection with a transient pore formed in a lipid packing mismatch taking place during the phase transition of dipalmitoylphosphatidylcholine liposomes.

Bioadhesive monolayer film for the in vitro transdermal delivery of sumatriptan

The work presented here aims to develop a bioadhesive monolayer film containing sumatriptan as adjuvant for the treatment of headache pain in a severe migraine attack. Permeation experiments were performed from the films prepared and from the respective solution, to evaluate the relevant permeation parameters. The effect of the penetration enhancers Transcutol, 2-pyrrolidone, and polyethylene glycol 600 was evaluated. The results obtained show that Transcutol and 2-pyrrolidone decreased sumatriptan permeation from solution, whereas a modest increase was produced by polyethylene glycol 600. The enhancers produced the same effects when they were included in the film. Compared to solution, the film showed a higher sumatriptan flux in the early times of the experiment. When the film was applied in occlusive conditions the profiles were much higher, indicating the importance of patch drying. Concerning skin retention, the bioadhesive film produced a reduction of the amount of sumatriptan remaining in the skin, but this can be advantageous in the control of drug input, since it reduces the reservoir effect in the skin and allows for an immediate interruption of drug input when the patch is removed.