Topical delivery enhancement with multilamellar liposomes into pilosebaceous units: I. In vitro evaluation using fluorescent techniques with the hamster ear model

Coenzyme Q10 phospholipidic vesicular formulations for treatment of androgenic alopecia: ex vivo permeation and clinical appraisal

INTRODUCTION

Coenzyme Q10 (CoQ10) is an antioxidant molecule with anti-aging activity on human hair, and because of its pharmaceutical limitations such as large molecular weight, high lipophilicity and poor water solubility, its therapeutic effectiveness has been hampered. Therefore, different vesicular nanocarriers were developed in the current work, for enhancement of the skin penetration of CoQ10 for treatment of androgenic alopecia.

AREAS COVERED

In order to overcome the poor skin penetration of CoQ10, it was formulated in liposomes, transfersomes, ethosomes, cerosomes and transethosomes using the thin-film hydration method. Results revealed that transethosomes were the carrier of choice for CoQ10, in which it displayed a particle size of 146 nm, zeta potential -55 mV and entrapment efficiency of 97.63%. Transethosomes also achieved the highest deposition percentage for CoQ10, exceeding 95% in the different skin layers. Upon clinical examination in patients suffering from androgenic alopecia, CoQ10 transethosomes displayed better clinical response than the administration of CoQ10 solution, which was further confirmed by dermoscopic examination.

EXPERT OPINION

Findings of this study further prove that loading antioxidants such as CoQ10 in nanocarriers maximizes their therapeutic efficiency, and opens many opportunities for their application in treatment of several other topical diseases.

Enhancing Permeation of Drug Molecules Across the Skin via Delivery in Nanocarriers: Novel Strategies for Effective Transdermal Applications

The transdermal route of administration provides numerous advantages over conventional routes i.e., oral or injectable for the treatment of different diseases and cosmetics applications. The skin also works as a reservoir, thus deliver the penetrated drug for more extended periods in a sustained manner. It reduces toxicity and local irritation due to multiple sites for absorption and owes the option of avoiding systemic side effects. However, the transdermal route of delivery for many drugs is limited since very few drugs can be delivered at a viable rate using this route. The stratum corneum of skin works as an effective barrier, limiting most drugs' penetration posing difficulty to cross through the skin. Fortunately, some non-invasive methods can significantly enhance the penetration of drugs through this barrier. The use of nanocarriers for increasing the range of available drugs for the transdermal delivery has emerged as a valuable and exciting alternative. Both the lipophilic and hydrophilic drugs can be delivered via a range of nanocarriers through the stratum corneum with the possibility of having local or systemic effects to treat various diseases. In this review, the skin structure and major obstacle for transdermal drug delivery, different nanocarriers used for transdermal delivery, i.e., nanoparticles, ethosomes, dendrimers, liposomes, etc., have been discussed. Some recent examples of the combination of nanocarrier and physical methods, including iontophoresis, ultrasound, laser, and microneedles, have also been discussed for improving the therapeutic efficacy of transdermal drugs. Limitations and future perspectives of nanocarriers for transdermal drug delivery have been summarized at the end of this manuscript.

Potential of Nanoparticles as Permeation Enhancers and Targeted Delivery Options for Skin: Advantages and Disadvantages

The topical route of administration has many advantages for the treatment of various skin disorders as well as cosmeceutical purposes. This route bypasses hepatic first-pass effect and systemic availability of many pharmaceuticals is limited to skin organelles such as hair follicles and so could avoid unwanted adverse reactions and increase the localized therapeutic effect. Despite such attributed advantages of the topical route, the most important challenge is skin barrier characteristics that should be overcome to obtain dermal or trans-dermal drug delivery. Different approaches have been recruited to overcome this barrier. In this review, different types of nanoparticles for skin permeation enhancement and targeted delivery to skin organelles are discussed. The potential mechanisms of each nanocarrier in permeation enhancement and dermal delivery are considered and finally, the most important advantages and disadvantages of each group are summarized.

An update on formulation strategies of benzoyl peroxide in efficient acne therapy with special focus on minimizing undesired effects

Benzoyl peroxide (BPO) in the form of over the counter monotherapeutics or prescription-only combinations is a key component of topical acne therapy, but its unfavourable side effect profile reduces the therapeutic value of this compound. Various galenic approaches have been pursued to resolve this ambivalence, but only a few have managed to enter the market. This article aims to give a comprehensive overview of the published experimental vehicle systems and to identify the fundamental rationales. With regard to the formulation, an increase in the tolerability of BPO can essentially be achieved by combining BPO with re-fattening and moisturizing substances, by incorporating it and controlling its release, as well as by targeted deposition of the active ingredient at the site of action, i.e. drug targeting. Recently, novel particulate formulations have been proposed that combine several of these design principles and are expected to bring new developments in this dynamic field of research.

Extracellular vesicles derived from Malassezia furfur stimulate IL-6 production in keratinocytes as demonstrated in in vitro and in vivo models

BACKGROUND

Malassezia is one of the commensal microorganisms colonized on human skin and has been shown to be related to several inflammatory cutaneous disorders. Previous studies indicated that Malassezia. sympodialis (M. sympodialis) can produce extracellular vesicles, however, the immunoregulatory function of Malassezia extracellular vesicles on keratinocytes has not been studied.

OBJECTIVE

To investigate the extracellular vesicular production capability of Malassezia. furfur (M. furfur) and examine their immunoregulatory effects both in vitro and in vivo.

METHODS

Extracellular vesicles derived from M. furfur were isolated by sequential ultracentrifugation procedure. Their structure and diameter were determined by negative stain TEM and NTA, respectively. Confocal microscopy was used to visualize the internalization of these nanoparticles into HaCaT cells and mice epidermal keratinocytes. The expressions of inflammatory cytokines were screened using PCR Array assay and validated in vitro by qPCR and ELISA assays. In vivo cytokine production was measured by the IHC method. The role of NF-κB in such process was evaluated in HaCaT cells by western blot assay.

RESULTS

Our results showed that M. furfur produced ovoid-shaped nanoparticles, which could be then internalized into HaCaT cells, as well as mice epidermal keratinocytes. IL-6 expression was significantly enhanced in response to extracellular vesicular stimulation both in vitro and in vivo, in which process the activation of NF-κB was involved.

CONCLUSION

M. furfur has the ability to release extracellular vesicles, which can be internalized into keratinocytes and promote the production of IL-6 with the involvement of NF-κB dependent pathway. Such findings reveal some important new insights into Malassezia pathogenesis and therapy.

Characterization of silver particles in the stratum corneum of healthy subjects and atopic dermatitis patients dermally exposed to a silver-containing garment

Silver is increasingly being used in garments to exploit its antibacterial properties. Information on the presence of silver nanoparticles (AgNPs) in garments and their in vivo penetration across healthy and impaired skin from use is limited. We investigated the presence of AgNPs in a silver containing garment and in the stratum corneum (SC) of healthy subjects (CTRLs) and individuals with atopic dermatitis (AD). Seven CTRLs and seven AD patients wore a silver sleeve (13% Ag w/w) 8 h/day for five days on a forearm and a placebo sleeve on the other forearm. After five days, the layers of the SC were collected by adhesive tapes. The silver particles in the garment and SC were characterized by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) and atomic force microscopy (AFM). AFM and SEM revealed the presence of sub-micrometre particles having a broad range of sizes (30-500 nm) on the surface of the garment that were identified as silver. On the SC tapes collected from different depths, aggregates with a wide range of sizes (150 nm-2 μm) and morphologies were found. Most aggregates contained primarily silver, although some also contained chlorine and sulfur. There was no clear difference in the number or size of the aggregates observed in SC between healthy and AD subjects. After use, AgNPs and their aggregates were present in the SC at different depths of both healthy subjects and AD patients. Their micrometre size suggests that aggregation likely occurred in the SC.

Topical anesthesia

Topical anesthetics are being widely used in numerous medical and surgical sub-specialties such as anesthesia, ophthalmology, otorhinolaryngology, dentistry, urology, and aesthetic surgery. They cause superficial loss of pain sensation after direct application. Their delivery and effectiveness can be enhanced by using free bases; by increasing the drug concentration, lowering the melting point; by using physical and chemical permeation enhancers and lipid delivery vesicles. Various topical anesthetic agents available for use are eutectic mixture of local anesthetics, ELA-max, lidocaine, epinephrine, tetracaine, bupivanor, 4% tetracaine, benzocaine, proparacaine, Betacaine-LA, topicaine, lidoderm, S-caine patch™ and local anesthetic peel. While using them, careful attention must be paid to their pharmacology, area and duration of application, age and weight of the patients and possible side-effects.

Nanodelivery Systems as New Tools for Immunostimulant or Vaccine Administration: Targeting the Fish Immune System

Fish disease treatments have progressed significantly over the last few years and have moved from the massive use of antibiotics to the development of vaccines mainly based on inactivated bacteria. Today, the incorporation of immunostimulants and antigens into nanomaterials provide us with new tools to enhance the performance of immunostimulation. Nanoparticles are dispersions or solid particles designed with specific physical properties (size, surface charge, or loading capacity), which allow controlled delivery and therefore improved targeting and stimulation of the immune system. The use of these nanodelivery platforms in fish is in the initial steps of development. Here we review the advances in the application of nanoparticles to fish disease prevention including: the type of biomaterial, the type of immunostimulant or vaccine loaded into the nanoparticles, and how they target the fish immune system.

Visualizing dermal permeation of sodium channel modulators by mass spectrometric imaging

Determining permeability of a given compound through human skin is a principal challenge owing to the highly complex nature of dermal tissue. We describe the application of an ambient mass spectrometry imaging method for visualizing skin penetration of sodium channel modulators, including novel synthetic analogs of natural neurotoxic alkaloids, topically applied ex vivo to human skin. Our simple and label-free approach enables successful mapping of the transverse and lateral diffusion of small molecules having different physicochemical properties without the need for extensive sample preparation.

Liposomes in topical photodynamic therapy

INTRODUCTION

Topical photodynamic therapy (PDT) refers to topical application of a photosensitizer onto the site of skin disease which is followed by illumination and results in death of selected cells. The main problem in topical PDT is insufficient penetration of the photosensitizer into the skin, which limits its use to superficial skin lesions. In order to overcome this problem, recent studies tested liposomes as delivery systems for photosensitizers.

AREAS COVERED

This paper reviews the use of different types of liposomes for encapsulating photosensitizers for topical PDT. Liposomes should enhance the photosensitizers' penetration into the skin, while decreasing its absorption into systemic circulation. Only few photosensitizers have currently been encapsulated in liposomes for topical PDT: 5-aminolevulinic acid (5-ALA), temoporfin (mTHPC) and methylene blue.

EXPERT OPINION

Investigated liposomes enhanced the skin penetration of 5-ALA and mTHPC, reduced their systemic absorption and reduced their cytotoxicity compared with free drugs. Their high tissue penetration should enable the treatment of deep and hyperkeratotic skin lesions, which is the main goal of using liposomes. However, liposomes still do not attract enough attention as drug carriers in topical PDT. In vivo studies of their therapeutic effectiveness are needed in order to obtain enough evidence for their potential clinical use as carriers for photosensitizers in topical PDT.

Nanoparticles and microparticles for skin drug delivery

Skin is a widely used route of delivery for local and systemic drugs and is potentially a route for their delivery as nanoparticles. The skin provides a natural physical barrier against particle penetration, but there are opportunities to deliver therapeutic nanoparticles, especially in diseased skin and to the openings of hair follicles. Whilst nanoparticle drug delivery has been touted as an enabling technology, its potential in treating local skin and systemic diseases has yet to be realised. Most drug delivery particle technologies are based on lipid carriers, i.e. solid lipid nanoparticles and nanoemulsions of around 300 nm in diameter, which are now considered microparticles. Metal nanoparticles are now recognized for seemingly small drug-like characteristics, i.e. antimicrobial activity and skin cancer prevention. We present our unpublished clinical data on nanoparticle penetration and previously published reports that support the hypothesis that nanoparticles >10nm in diameter are unlikely to penetrate through the stratum corneum into viable human skin but will accumulate in the hair follicle openings, especially after massage. However, significant uptake does occur after damage and in certain diseased skin. Current chemistry limits both atom by atom construction of complex particulates and delineating their molecular interactions within biological systems. In this review we discuss the skin as a nanoparticle barrier, recent work in the field of nanoparticle drug delivery to the skin, and future directions currently being explored.

Treatment of vitiligo with khellin liposomes, ultraviolet light and blister roof transplantation

BACKGROUND

Various surgical and non-surgical methods are available to treat vitiligo. Surgical techniques such as epidermal blister graft transplantation may be effective for the re-pigmentation of stable, but refractory vitiligo areas. Khellin has phototherapeutic properties that are similar to those of the psoralens, but with substantially lower phototoxic effects and DNA mutation effects. Its penetration into the hair follicles is enhanced by encapsulating it into liposomes. Subsequent activation of the khellin with UV light stimulates the melanocytes in the hair follicles.

OBJECTIVE

The first objective was to evaluate the additional value of combining blister roof transplantation (BRT) with khellin in liposomes and ultraviolet light (KLUV) in the treatment of recalcitrant vitiligo patches. The second objective was to assess patients' satisfaction.

MATERIALS AND METHODS

Nineteen patients with vitiligo lesions which did not respond to KLUV treatment for at least a year were treated with BRT followed by KLUV. The transplantation was performed by creating blisters with a suction device, preparing the target site with Erbium laser ablation and the actual transplantation. Locations where randomly assigned. A blinded observer established the results.

RESULTS

Seventy-five percent of the patients were satisfied with the cosmetic result. All of the patients would recommend the treatment to other vitiligo patients. More than 75% re-pigmentation of the vitiligo areas was noted in 47% of the patients according to the blinded evaluation of photographs taken before and after the treatment.

Eradication of drug resistant Staphylococcus aureus by liposomal oleic acids

Staphylococcus aureus (S. aureus) represents a major threat to a broad range of healthcare and community associated infections. This bacterium has rapidly evolved resistance to multiple drugs throughout its antibiotic history and thus it is imperative to develop novel antimicrobial strategies to enrich the currently shrinking therapeutic options against S. aureus. This study evaluated the antimicrobial activity and therapeutic efficacy of oleic acid (OA) in a liposomal formulation as an innate bactericide against methicillin-resistant S. aureus (MRSA). In vitro studies showed that these OA-loaded liposomes (LipoOA) could rapidly fuse into the bacterial membranes, thereby significantly improving the potency of OA to kill MRSA compared with the use of free OA. Further in vivo tests demonstrated that LipoOA were highly effective in curing skin infections caused by MRSA bacteria and preserving the integrity of the infected skin using a mouse skin model. Moreover, a preliminary skin toxicity study proved high biocompatibility of LipoOA to normal skin tissues. These findings suggest that LipoOA hold great potential to become a new, effective, and safe antimicrobial agent for the treatment of MRSA infections.

Rational design of a topical androgen receptor antagonist for the suppression of sebum production with properties suitable for follicular delivery

A novel nonsteroidal androgen receptor antagonist, (R)-4-(1-benzyl-4,4-dimethyl-2-oxopyrrolidin-3-yloxy)-2-(trifluoromethyl)benzonitrile (1), for the topical control of sebum production is reported. This compound, which is potent, selective, and efficacious in the clinically validated golden Syrian hamster ear animal model, was designed to be delivered to the pilosebaceous unit, the site of action, preferentially by the follicular route.

Can drug-bearing liposomes penetrate intact skin?

Using liposomes to deliver drugs to and through human skin is controversial, as their function varies with type and composition. Thus they may act as drug carriers controlling release of the medicinal agent. Alternatively, they may provide a localized depot in the skin so minimizing systemic effects or can be used for targeting delivery to skin appendages (hair follicles and sweat glands). Liposomes may also enhance transdermal drug delivery, increasing systemic drug concentrations. With such a multiplicity of functions, it is not surprising that mechanisms of liposomal delivery of therapeutic agents to and through the skin are unclear. Accordingly, this article provides an overview of the modes and mechanisms of action of different vesicles as drug delivery vectors in human skin. Our conclusion is that vesicles, depending on the composition and method of preparation, can vary with respect to size, lamellarity, charge, membrane fluidity or elasticity and drug entrapment. This variability allows for multiple functions ranging from local to transdermal effects. Application to dissimilar skins (animal or human) via diverse protocols may reveal different mechanisms of action with possible vesicle skin penetration reaching different depths, from surface assimilation to (rarely) the viable tissue and subsequent systemic absorption.

Photodynamic therapy of acne vulgaris using 5-aminolevulinic acid 0.5% liposomal spray and intense pulsed light in combination with topical keratolytic agents

BACKGROUND

Increasing antibiotic resistance of Propionibacterium acnes and growing awareness on the side effects of topical and systemic drugs in the treatment of acne vulgaris by physicians and patients have paved the way for a search into new efficacious and safe treatment modalities such as photodynamic therapy (PDT). Although the efficacy of PDT using 20% 5-aminolevulinic acid (ALA) cream has been established, phototoxic side effects limit its use. The 5-ALA concentration can be lowered by a factor of 40 by changing the vehicle of 5-ALA from a moisturizing cream to liposome encapsulation.

OBJECTIVES

Assessment of the efficacy and the safety of PDT using 5-ALA 0.5% in liposomal spray and intense pulsed light (IPL) in combination with topical peeling agents (Li-PDT-PC) in acne vulgaris.

MATERIALS AND METHODS

32 patients suffering from acne participated in this randomized, prospective, single blind study. All patients were treated with Li-PDT-PC. During the study nine patients were additionally treated with topical or systemic antibiotics (Li-PDT-PC-AT). These patients were removed from the study although their results were recorded. Results After a mean period of 7.8 months and a mean number of 5.7 treatments the mean total number of lesions dropped from 34.6 lesions to 11.0 lesions, resulting in a mean improvement of 68.2%. Side effects were minimal. Additionally, an intention to treat analysis was conducted.

CONCLUSION

Photodynamic therapy of acne vulgaris using 5-ALA 0.5% liposomal spray and IPL in combination with topical peeling agents is safe and efficacious, even in patients with acne recalcitrant to standard therapy.

The antimicrobial activity of liposomal lauric acids against Propionibacterium acnes

This study evaluated the antimicrobial activity of lauric acid (LA) and its liposomal derivatives against Propionibacterium acnes (P. acnes), the bacterium that promotes inflammatory acne. First, the antimicrobial study of three free fatty acids (lauric acid, palmitic acid and oleic acid) demonstrated that LA gives the strongest bactericidal activity against P. acnes. However, a setback of using LA as a potential treatment for inflammatory acne is its poor water solubility. Then the LA was incorporated into a liposome formulation to aid its delivery to P. acnes. It was demonstrated that the antimicrobial activity of LA was not only well maintained in its liposomal derivatives but also enhanced at low LA concentration. In addition, the antimicrobial activity of LA-loaded liposomes (LipoLA) mainly depended on the LA loading concentration per single liposomes. Further study found that the LipoLA could fuse with the membranes of P. acnes and release the carried LA directly into the bacterial membranes, thereby killing the bacteria effectively. Since LA is a natural compound that is the main acid in coconut oil and also resides in human breast milk and liposomes have been successfully and widely applied as a drug delivery vehicle in the clinic, the LipoLA developed in this work holds great potential of becoming an innate, safe and effective therapeutic medication for acne vulgaris and other P. acnes associated diseases.

Fluorescence detection and diagnosis of non-melanoma skin cancer at an early stage

BACKGROUND

The occurrence of non-melanoma skin cancer (NMSC), including actinic keratosis (AK) is increasing all over the world. The detection and diagnosis of NMSC is not optimal in clinical practice. Complementary methods for detection and accurate demarcation of NMSC at an early stage are needed in order to limit the damage caused by tumours.

OBJECTIVE

The purpose of the present study was to use a large area skin fluorescence detection system to detect early NMSCs (clinical visible as well as non-visible lesions) in the face, neck, chest, back and hands of patients treated with UV and outdoor workers.

METHODS

Fluorescence detection with a purpose-made digital camera and software (Dyaderm combined with 5-aminolevulinic acid (5-ALA) encapsulated in liposomes.

RESULTS

In 93 consecutively referred patients positive skin fluorescence was detected in 61 patients. After histological examination the positive fluorescence appeared to be correlated to benign lesions in 28 patients (sebaceous gland hyperplasia in 22 patients) and to (pre-) malignant lesions in 33 patients (actinic keratosis in 29, BCC in 3 and SCC in 1 patient). False negative fluorescence was found in only one lesion. In five patients the FD technique used in this study appeared to be more sensitive for the identification of (pre-) malignant lesions than the clinical examination. This is in contrast with FD techniques used in previous studies.

CONCLUSION

Diagnostic skin fluorescence using liposomal encapsulated 5-ALA and a specialised computerised detection and visualisation system offers the possibility for detection of NMSC at an early, pre-clinical stage. The technique is well suited to examine large areas of skin. It also identifies areas of most interest for performing confirmatory skin biopsies, as well as pre-operative assessment of boundaries of skin malignancies, and finally, the technique is applicable in the control and follow-up of skin cancer treatment.

Lipid vesicles for skin delivery of drugs: reviewing three decades of research

Since liposomes were first shown to be of potential value for topical therapy by Mezei and Gulasekharam in 1980, studies continued towards further investigation and development of lipid vesicles as carriers for skin delivery of drugs. Despite this long history of intensive research, lipid vesicles are still considered as a controversial class of dermal and transdermal carriers. Accordingly, this article provides an overview of the development of lipid vesicles for skin delivery of drugs, with special emphasis on recent advances in this field, including the development of deformable liposomes and ethosomes.

Enhancement of follicular delivery of finasteride by liposomes and niosomes

Finasteride is indicated orally in the treatment of androgenetic alopecia and some other pilosebaceous unit (PSU) disorders. We wished to investigate whether topical application of finasteride-containing vesicles (liposomes and niosomes) could enhance drug concentration at the PSU, as compared to finasteride hydroalcoholic solution (HA). Liposomes consisted of phospholipid (dimyristoyl phosphatidylcholine (DMPC) or egg lecithin):cholesterol:dicetylphosphate (8:2:1, mole ratio). Niosomes were comprising non-ionic surfactant (polyoxyethylene alkyl ethers (Brij series) or sorbitan monopalmitate):cholesterol:dicetylphosphate (7:3:1, mole ratio). Vesicles were prepared by the film hydration technique and characterized with regard to the size, drug entrapment efficiency and gel-liquid transition temperature (T(c)). In vitro permeation of (3)H-finasteride through hamster flank skin was faster from hydroalcoholic solution (0.13 microg/cm(2)h) compared to vesicles (0.025-0.058 microg/cm(2)h). In vivo deposition of (3)H-finasteride vesicles in hamster ear showed that liquid-state vesicle, i.e. those made of DMPC or Brij97:Brij76 (1:1), were able to deposit 2.1 or 2.3% of the applied dose to the PSU, respectively. This was significantly higher than drug deposition by gel-state vesicles (0.35-0.51%) or HA (0.76%). Both in vitro permeation and in vivo deposition studies, demonstrated the potentials of liquid-state liposomes and niosomes for successful delivery of finasteride to the PSU.

The hair follicle and its stem cells as drug delivery targets

The hair follicle is a skin appendage with a complex structure containing many cell types that produce highly specialised proteins. The hair follicle is in a continuous cycle: anagen is the hair growth phase, catagen the involution phase and telogen is the resting phase. The follicle offers many potential therapeutic targets. Hoffman and colleagues have pioneered hair-follicle-specific targeting using liposomes to deliver small and large molecules, including genes. They have also pioneered ex vivo hair-follicle targeting with continued expression of the introduced gene following transplantation. Recently, it has been discovered that hair follicle stem cells are highly pluripotent and can form neurons, glial cells and other cell types, and this has suggested that hair follicle stem cells may serve as gene therapy targets for regenerative medicine.

Novel Drug Delivery Systems: Potential in Improving Topical Delivery of Antiacne Agents

Acne is the most common cutaneous disorder of multifactorial origin with a prevalence of 70-85% in adolescents. The majority of the acne sufferers exhibit mild to moderate acne initially, which progresses to the severe form in certain cases. Topical therapy is employed as first-line treatment in mild acne, whereas for moderate and severe acne, systemic therapy is required in addition to topical therapy. Currently, several topical agents are available that affect at least one of the main pathogenetic factors responsible for the development of acne. Although topical therapy has an important position in acne treatment, side effects associated with various topical antiacne agents and the undesirable physicochemical characteristics of certain important agents like tretinoin and benzoyl peroxide affect their utility and patient compliance. Novel drug delivery strategies can play a pivotal role in improving the topical delivery of antiacne agents by enhancing their dermal localization with a concomitant reduction in their side effects. The current review emphasizes the potential of various novel drug delivery strategies like liposomes, niosomes, aspasomes, microsponges, microemulsions, hydrogels and solid lipid nanoparticles in optimizing and enhancing the topical delivery of antiacne agents.

Follicular targeting--a promising tool in selective dermatotherapy

The penetration of topically applied compounds varies considerably in the different regions of the human body. The presence of hair follicles significantly contributes to this effect by an increase in surface area and a disruption of the epidermal barrier towards the lower parts of the hair follicle. The human hair follicle, hereby, serves not only as a reservoir, but also as a major entry point for topically applied compounds. Topical delivery of active compounds to specific targets within the skin may help reduce side-effects caused by unspecific reactions, and may help develop new strategies in the prevention and treatment of skin diseases. Various drug carrier and drug delivery systems are currently being investigated. The aim of these investigational efforts is to direct topically applied compounds to the different types of hair follicles and, ideally, to specific compartments and cell populations within the hair follicles. Follicular targeting offers opportunities for new developments, not only in hair therapy and in the treatment of hair follicle associated diseases but also in gene therapy and immunotherapy.

Lipid nanoparticles for skin penetration enhancement—correlation to drug localization within the particle matrix as determined by fluorescence and parelectric spectroscopy

With topical treatment of skin diseases, the requirement of a high and reproducible drug uptake often still is not met. Moreover, drug targeting to specific skin strata may improve the use of agents which are prone to cause local unwanted effects. Recent investigations have indicated that improved uptake and skin targeting may become feasible by means of nanoparticular systems such as solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC) and nanoemulsions (NE). Here we describe techniques to characterize drug loading to carrier systems and skin penetration profiles by using the lipophilic dye nile red as a model agent. Since the mode of drug association with the particle matrix may strongly influence the efficiency of skin targeting, parelectric spectroscopy (PS) was used to differentiate between matrix incorporation and attachment to the particle surface and fluorescence spectroscopy (FS) to solve dye distribution within NLC particles. Nile red was incorporated into the lipid matrix or the covering tensed shell, respectively, of SLN and NLC with all the lipids studied (Compritol, Precirol, oleic acid, Miglyol). In NLC, the dye was enriched in the liquid phase. Next, nile red concentrations were followed by image analysis of vertical sections of pigskin treated with dye-loaded nanoparticular dispersions and an oil-in-water cream for 4 and 8 h in vitro. Following the SLN dispersions, dye penetration increased about fourfold over the uptake obtained following the cream. NLC turned out less potent (<threefold increase) and penetration appeared even reduced when applying a NE. In contrast to previous studies with glucocorticoids attached to the surface of SLN, a targeting effect was not detected here. Therefore, drug targeting appears to be more strictly related to the mode of interaction of drug and particle than penetration enhancement.

Liposomes and niosomes as topical drug delivery systems

The skin acts as a major target as well as a principle barrier for topical/transdermal (TT) drug delivery. The stratum corneum plays a crucial role in barrier function for TT drug delivery. Despite major research and development efforts in TT systems and the advantages of these routes, low stratum corneum permeability limits the usefulness of topical drug delivery. To overcome this, methods have been assessed to increase permeation. One controversial method is the use of vesicular systems, such as liposomes and niosomes, whose effectiveness depends on their physicochemical properties. This review focuses on the effect of liposomes and niosomes on enhancing drug penetration, and defines the effect of composition, size and type of the vesicular system on TT delivery.

Tea Tree Oil Concentration in Follicular Casts After Topical Delivery: Determination by High-Performance Thin Layer Chromatography Using a Perfused Bovine Udder Model

Tea tree oil, a popular antimicrobial agent is recommended for the treatment of acne vulgaris, a disease of the pilosebaceous unit. Tea tree oil formulations (colloidal bed, microemulsion, multiple emulsion, and liposomal dispersion containing 5% w/w tea tree oil) were applied to bovine udder skin. The follicular uptake of tea tree oil upon application was determined by a cyanoacrylate method. Tea tree oil was determined by quantifying terpinen-4-ol content using high-performance thin layer chromatography. The accumulation of tea tree oil in the follicular casts was 0.43 +/- 0.01, 0.41 +/- 0.009, 0.21 +/- 0.006, and 0.16 +/- 0.005 percentage by weight (milligram oil/gram of sebum plug) for microemulsion, liposomal dispersion, multiple emulsion, and colloidal bed, respectively. This is the first study of its kind to quantify tea tree oil concentration in the follicles.

Enhanced transfollicular delivery of adriamycin with a liposome and iontophoresis

To find a better way to deliver drugs into hair follicles, we tried two approaches: single topical application using various liposomes; and iontophoresis combined with topical application of ionic liposome. After delivery of adriamycin (ADR) to wax-depilated rat skin, the transport of the drug was examined under fluorescence microscopy. Most liposomal ADR showed more effective transdermal and transfollicular penetration than free ADR. Among tested liposomes, the non-ionic GDL liposome (GDL/CH/POE-10 = glycerol dilaulate/cholesterol/polyoxyethylene-10) was the most selective to hair follicles against skin, while the cationic liposome (GDL/CH/POE-10/DOTAP, dioleoyl trimethylammonium propane) containing monocationic DOTAP was less selective; however, it was better at improving the delivery amount and penetration of ADR into the follicles and skin. The DMPC/DMPG (7/3) formulation of anionic PC liposome (DMPC/DMPG = dimyristoyl-phosphocholine/-phospoglycerol) showed results similar to the cationic liposome. The DMPC/DMPG (3/7) formulation yielded poor results, however, probably because of its increased viscosity and anionic property. Although ADR delivery was enhanced by liposomal formulations, topical applications had some limitations in delivery capacity and speed. To accelerate delivery, iontophoresis was combined with the cationic liposome at positive 0.2-0.4 mA/cm(2) for 20-30 min. The resulting delivery of ADR through follicular routes was excellent. This combination method diffused ADR 3.0-fold more efficiently, rapidly and deeply than single topical application of cationic liposomal ADR. This system also achieved a 3.5-fold higher diffusive follicular delivery than a free ADR/iontophoresis combination. Furthermore, it was demonstrated that the tetracationic lipid DOSPER and hydrophile spermine could serve as a cationic additive instead of the monocationic DOTAP in the liposome. These results suggest that the combinative system of the topically applied cationic liposome followed by iontophoresis has a significant synergistic effect on the transfollicular delivery of ADR.

Determination of pharmaceutical compounds in skin by imaging matrix-assisted laser desorption/ionisation mass spectrometry

Matrix-assisted laser desorption/ionisation (MALDI) quadrupole time-of-flight mass spectrometry (Q-TOFMS) has been used to detect and image the distribution of a xenobiotic substance in skin. Porcine epidermal tissue was treated with 'Nizoral', a medicated shampoo containing ketoconazole (+/-)-1-acetyl-4-[p-[[(2R,4S)-2-(2,4-dichlorophenyl)-2-(imidazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]piperazine) as active ingredient. Following incubation for 1 h at 37 degrees C all excess formulation was washed from the surface. A cross-section of the drug-treated tissue was then blotted onto a cellulose membrane, precoated in matrix (alpha-cyano-4-hydroxycinnamic acid (CHCA)), by airspray deposition. In separate experiments the tissue surface was treated with Nizoral within a triangular former, and subsequently blotted onto a matrix-coated membrane. Sample membranes were then mounted into the recess of specialised MALDI targets with adhesive tape. All samples were analysed by MALDI-TOFMS using an Applied Biosystem 'Q-star Pulsar i' hybrid Q-TOF mass spectrometer fitted with an orthagonal MALDI ion source and imaging software. Detection of the protonated molecule was readily achievable by this technique. Treatment of the tissue within a template gave rise to images depicting the expected distribution of the drug, demonstrating that this technique is capable of producing spatially useful data. Ion images demonstrating the permeation of the applied compound into the skin were achieved by imaging a cross-sectional imprint of treated tissue. A calibration graph for the determination of ketoconazole was prepared using the sodium adduct of the matrix ion as an internal standard. This enabled construction of a quantitative profile of drug in skin. Conventional haematoxylin and eosin staining and microscopy methods were employed to obtain a histological image of the porcine epidermal tissue. Superimposing the mass spectrometric and histological images appeared to indicate drug permeation into the dermal tissue layer.

Liposomes et peau : passé, présent, futur

tAmong various approaches to intra- and percutaneous administration of drugs, e.g. application of patches, ointments, iontophoresis, electroporation, the use of lipid vesicles like liposomes and niosomes presents numerous advantages. They are not toxic or invasive, may deliver hydrophobic and/or hydrophilic molecules, and the size of the transported molecule is not a limiting factor. Liposomes are obtained with natural amphiphilic lipids whereas niosomes are composed of synthetic amphiphilic molecules. These microscopic vesicles contain from one to several concentric lipid bi-layers with intercalated aqueous compartments. Trans-epidermal penetration of the vesicles is proportional to the "fluidity" of their lipids and their negative charge. Several drugs and cosmetics in this gallenic form are already commercially available and successfully used, presenting a better dose/effect ratio and provoking less side-effects.

Liposomes increase skin penetration of entrapped and non-entrapped hydrophilic substances into human skin: a skin penetration and confocal laser scanning microscopy study

Liposomes have been extensively studied and suggested as a vehicle for topical drug delivery systems. However, the mechanism by which liposomes deliver drugs into intact skin is not fully understood. In the present study, we have tried to understand the mechanism of transport of hydrophilic drugs into the skin using liposomes. The effect of separation of the non-entrapped, hydrophilic fluorescent compound, carboxyfluorescein (CF), from liposomally entrapped CF was investigated by measuring the penetration of CF across human skin under non-occlusive conditions in vitro using Franz diffusion cells. The fluorescent dye, CF, was incorporated into the liposomes and applied onto the skin. After a 6 and 12h incubation period, the amount of CF in the epidermal membrane and the full thickness skin was determined by fluorescence spectroscopy or by confocal laser scanning microscopy (CLSM). The liposomal formulation containing CF both inside and outside the vesicles showed statistically enhanced penetration of CF into the human stratum corneum (SC) as compared to the formulations containing CF only outside of the liposomes and CF in Tris buffer. The CLSM results revealed that the formulation in which CF was present outside the liposomes showed bright fluorescence intensity in the SC and very weak fluorescence in the viable epidermis. However, the CF in Tris buffer failed to show any fluorescence in the viable epidermis. The results indicated that phospholipid vesicles not only carry the entrapped hydrophilic substance, but also the non-entrapped hydrophilic substance into the SC and possibly into the deeper layers of the skin.

Drug delivery routes in skin: a novel approach

The role of hair follicles in transdermal delivery remains difficult to elucidate due partly to animal model complications. This paper explores a novel technique employing two human skin membranes to differentiate shunt route delivery from bulk transepidermal input. The method monitors penetration through epidermal membranes and compares this with delivery through a sandwich of stratum corneum and epidermis, with the corneum forming a top membrane. As orifices of shunts occupy only 0.1% of the area, there is negligible chance that shunts in the membranes will superimpose. The top layer blocks shunts available in the bottom layer. If shunts are important, delivery through sandwiches will be much reduced compared with that through epidermis, allowing for increased double membrane thickness. Experiments with penetrants under passive, iontophoretic and electroporation conditions illustrated the value of the method. A Monte Carlo simulation suggested that any failure of membrane adherence would not affect conclusions drawn.

Selective photothermolysis of the sebaceous glands for acne treatment

BACKGROUND AND OBJECTIVES

The purpose of this study is to evaluate the efficacy of a long pulse diode laser (Cynosure, Inc.) to target and destroy enlarged sebaceous glands that are preloaded with Indocyanine green (ICG) chromophore.

STUDY DESIGN/MATERIALS AND METHODS

This study was designed in three phases. First, preliminary studies were performed to determine the ability of ICG to penetrate into enlarged sebaceous glands. Once penetration of the sebaceous gland was confirmed, the second phase was to determine the necessary parameters for the diode laser to effectively target the ICG loaded glands. This was done using laser-tissue interaction analysis. The final phase was done with patients that had active acne on their back to determine if selective destruction of the sebaceous glands could be achieved and also to assess the safety and efficacy of this novel treatment for acne.

RESULTS

Fluorescence microscopy of biopsy samples show evidence of ICG penetration into the sebaceous glands. Histological examination of biopsy samples from the treated areas finds selective necrosis of the sebaceous glands. Preliminary clinical results demonstrate a decrease in acne noted in the treatment area at 3, 6, and 10 months follow-up.

CONCLUSIONS

ICG and diode laser treatment is a new approach for the treatment of acne based on experimentally observed selective photothermolysis of the sebaceous glands.

Penetration and distribution of three lipophilic probes in vitro in human skin focusing on the hair follicle

Fluorescent model substances of increasing lipophilicity (Oregon Green) 488, Bodipy, FL C5 and Bodipy 564/570 C5) were selected to enable the visualization in the skin using confocal laser scanning microscopy. After measuring the penetration for 18 h, the nonfixed human scalp skin was imaged from the bottom parallel to the stratum corneum and in a cross-section view perpendicular to the skin surface. The images were evaluated by calculating relative accumulation values for different penetrants. The studies indicate that the penetrated amount is highest for Bodipy FL C5 (medium lipophilicity) and lowest for Bodipy 564/570 C5 (high lipophilicity) whereas Bodipy 564/570 C5 (high lipophilicity) reveals the highest relative accumulation in parts of the hair follicle compared to Oregon Green 488 (low lipophilicity). The addition of 30% (v/v) ethanol to the donor phase of substance with a low lipophilicity increases the follicular delivery. From our results we conclude that delivery to the hair follicle can be improved by increasing the drugs lipophilicity and optimizing the composition of the donor phase. However, no conclusion can be drawn about the actual route of transport to the hair follicle.

Skin hydration and possible shunt route penetration in controlled estradiol delivery from ultradeformable and standard liposomes

Human skin delivery of estradiol from ultradeformable and traditional liposomes was explored, comparing occlusive and open application, with the aim of examining the role of skin hydration. Partially hydrated epidermis was used for open hydration, but fully hydrated membranes were used for occluded studies. In addition, we developed a novel technique to investigate the role of shunt route penetration in skin delivery of liposomal estradiol. This compared delivery through epidermis with that through a stratum corneum (SC)/epidermis sandwich from the same skin with the additional SC forming the top layer of the sandwich. This design was based on the fact that orifices of shunts only occupy 0.1% of skin surface area and thus for SC/epidermis sandwiches there will be a negligible chance for shunts to superimpose. The top SC thus blocks most shunts available on the bottom membrane. If shunts play a major role then the delivery through sandwiches should be much reduced compared with that through epidermis, taking into consideration the expected reduction owing to increased membrane thickness. After open application, both ultradeformable and traditional liposomes improved estradiol skin delivery, with the ultradeformable liposomes being superior. Occlusion reduced the delivering efficiency of both vesicle types, supporting the theory that a hydration gradient provides the driving force. Shunt route penetration was found to play only a very minor role in liposomal delivery. In conclusion, full hydration of skin reduces estradiol delivery from liposomes and the shunt route is not the main pathway for this delivery.

Controls of hair follicle cycling

Nearly 50 years ago, Chase published a review of hair cycling in which he detailed hair growth in the mouse and integrated hair biology with the biology of his day. In this review we have used Chase as our model and tried to put the adult hair follicle growth cycle in perspective. We have tried to sketch the adult hair follicle cycle, as we know it today and what needs to be known. Above all, we hope that this work will serve as an introduction to basic biologists who are looking for a defined biological system that illustrates many of the challenges of modern biology: cell differentiation, epithelial-mesenchymal interactions, stem cell biology, pattern formation, apoptosis, cell and organ growth cycles, and pigmentation. The most important theme in studying the cycling hair follicle is that the follicle is a regenerating system. By traversing the phases of the cycle (growth, regression, resting, shedding, then growth again), the follicle demonstrates the unusual ability to completely regenerate itself. The basis for this regeneration rests in the unique follicular epithelial and mesenchymal components and their interactions. Recently, some of the molecular signals making up these interactions have been defined. They involve gene families also found in other regenerating systems such as fibroblast growth factor, transforming growth factor-beta, Wnt pathway, Sonic hedgehog, neurotrophins, and homeobox. For the immediate future, our challenge is to define the molecular basis for hair follicle growth control, to regenerate a mature hair follicle in vitro from defined populations, and to offer real solutions to our patients' problems.