Disposition of Nanoparticles and an Associated Lipophilic Permeant following Topical Application to the Skin

Methodologies to Evaluate the Hair Follicle-Targeted Drug Delivery Provided by Nanoparticles

Nanotechnology has been investigated for treatments of hair follicle disorders mainly because of the natural accumulation of solid nanoparticles in the follicular openings following a topical application, which provides a drug "targeting effect". Despite the promising results regarding the therapeutic efficacy of topically applied nanoparticles, the literature has often presented controversial results regarding the targeting of hair follicle potential of nanoformulations. A closer look at the published works shows that study parameters such as the type of skin model, skin sections analyzed, employed controls, or even the extraction methodologies differ to a great extent among the studies, producing either unreliable results or precluding comparisons altogether. Hence, the present study proposes to review different skin models and methods for quantitative and qualitative analysis of follicular penetration of nano-entrapped drugs and their influence on the obtained results, as a way of providing more coherent study protocols for the intended application.

Cationic micelles as nanocarriers for enhancing intra-cartilage drug penetration and retention

There is a tremendous unmet medical need for osteoarthritis (OA) treatment around the world, and pharmacological management is the most common option but presents a limited and short efficacy. Insufficient drug delivery to articular cartilage is the key cause. It is widely accepted that the complex structure of articular cartilage and the rapid clearance of joint liquids largely hinder drug penetration and retention in the cartilage. To address these obstacles, we designed and prepared a positively charged micellar system that can effectively deliver a model drug to the deep zone of the cartilage and prolong the drug retention time. In this work, a triblock copolymer composed of cationic poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) and poly(ε-caprolactone) (PCL), denoted as PDMAEMA-PCL-PDMAEMA, was synthesized. A triblock copolymer composed of brush poly[poly(ethylene glycol) methacrylate] (pPEGMA) and PCL, denoted as pPEGMA-PCL-pPEGMA, was prepared for comparison. The two types of triblock copolymers were self-assembled in an aqueous environment to form cationic and neutral micelles, respectively. A hydrophobic fluorescent dye as a model drug was loaded into micelle cores, and the dye-loaded micelles were evaluated for intra-cartilage penetration and retention using porcine knee cartilage explants. The PDMAEMA-PCL-PDMAEMA cationic micelles were found to significantly enhance the intra-cartilage penetration and retention capability due to the electrostatic interaction between the micelles and the negatively charged cartilage extracellular matrix. The confocal microscopy study showed that the cationic micelles could penetrate the full-thickness porcine cartilage explants (around 1.5 mm) within 24 hours. Up to 87% of the cationic micelles were taken up by porcine cartilage explants, and 71% of the absorbed micelles were retained in the tissue for at least 4 days. Although the pPEGMA-PCL-pPEGMA neutral micelles were able to penetrate the full-thickness cartilage, this type of micelle showed lower uptake (44%) and retention (44%) rates. This observation implied that the surface charge of micelles could play an important role in efficient intra-cartilage drug delivery. This study verified the feasibility and effectiveness of the PDMAEMA-PCL-PDMAEM cationic micelles in intra-cartilage drug delivery, showing that cationic micelles could be promising carriers for OA treatment.

Nanostructured Drug Delivery Systems for Targeting 5-α-Reductase Inhibitors to the Hair Follicle

Androgenetic alopecia is a multifactorial condition characterized by noticeable hair loss, affecting both men and women and representing a debilitating and chronic disorder that considerably affects the quality of life. Available topical treatments based on minoxidil or finasteride require repeated applications and are associated with a certain number of adverse effects. The challenges associated with current treatments pave the way for the research of new therapeutic strategies, more precise and selective, and capable of providing long-term results. In this context, the present review examines the new proposed formulation strategies to deliver 5-α-reductase inhibitors in order to obtain a targeted drug delivery, for improving drug retention at the site of action in the hair follicle, contemporaneously reducing drug systemic absorption, which is the cause of important adverse effects. In particular, the research will be focused on the several aspects that influence the performance of nanostructured drug delivery systems in creating a depot in the hair follicles, such as particle size, surface charge, excipients, and combined application with external stimuli (infrared radiation, mechanical massage, ultrasounds application).

Topical transdermal chemoprevention of breast cancer: where will nanomedical approaches deliver us?

Despite the high incidence of breast cancer, there are few pharmacological prevention strategies for the high-risk population and those that are available have low adherence. Strategies that deliver drugs directly to the breasts may increase drug local concentrations, improving efficacy, safety and acceptance. The skin of the breast has been proposed as an administration route for local transdermal therapy, which may improve drug levels in the mammary tissue, due to both deep local penetration and percutaneous absorption. In this review, we discuss the application of nanotechnology-based strategies for the delivery of well established and new agents as well as drug repurposing using the topical transdermal route to improve the outcomes of preventive therapy for breast cancer.

Can mesoporous nanoparticles promote bioavailability of topical pharmaceutics?

When applied to skin, particulate matter has been shown to accumulate in hair follicles. In addition to follicles, the skin topography also incorporates trench-like furrows where particles potentially can accumulate; however, the furrows have not been as thoroughly investigated in a drug delivery perspective. Depending on body site, the combined follicle orifices cover up to 10% of the skin surface, while furrows can easily cover 20%, reaching depths exceeding 25 µm. Hence, porous particles of appropriate size and porosity could serve as carriers for drugs to be released in the follicles prior to local or systemic absorption. In this paper, we combine multiphoton microscopy, scanning electron microscopy, and Franz cell diffusion technology to investigate ex-vivo skin accumulation of mesoporous silica particles (average size of 400-600 nm, 2, and 7 µm, respectively), and the potential of which as vehicles for topical delivery of the broad-spectrum antibiotic metronidazole. We detected smaller particles (400-600 nm) in furrows at depths of about 25 µm, also after rinsing, while larger particles (7 µm) where located more superficially on the skin. This implies that appropriately sized porous particles may serve as valuable excipients in optimizing bioavailability of topical formulations. This work highlights the potential of skin furrows for topical drug delivery.

Supramolecular and Macromolecular Matrix Nanocarriers for Drug Delivery in Inflammation-Associated Skin Diseases

Skin is our biggest organ. It interfaces our body with its environment. It is an efficient barrier to control the loss of water, the regulation of temperature, and infections by skin-resident and environmental pathogens. The barrier function of the skin is played by the stratum corneum (SC). It is a lipid barrier associating corneocytes (the terminally differentiated keratinocytes) and multilamellar lipid bilayers. This intricate association constitutes a very cohesive system, fully adapted to its role. One consequence of this efficient organization is the virtual impossibility for active pharmaceutical ingredients (API) to cross the SC to reach the inner layers of the skin after topical deposition. There are several ways to help a drug to cross the SC. Physical methods and chemical enhancers of permeation are a possibility. These are invasive and irritating methods. Vectorization of the drugs through nanocarriers is another way to circumvent the SC. This mini-review focuses on supramolecular and macromolecular matrices designed and implemented for skin permeation, excluding vesicular nanocarriers. Examples highlight the entrapment of anti-inflammatory API to treat inflammatory disorders of the skin.

Stem Cells as a Target for the Delivery of Active Molecules to Skin by Topical Administration

Cutaneous stem cells, gained great attention in the field of regenerative medicine as a potential therapeutic target for the treatment of skin and hair disorders and various types of skin cancers. Cutaneous stem cells play a key role in several processes like the renovation of skin structures in the condition of homeostasis and after injuries, the hair follicle growth and the reconstruction and production of melanocytes. Thus, gaining effective access to skin stem cells for therapeutic interventions that often involve active molecules with non-favorable characteristics for skin absorption is a valuable achievement. The topical route with high patient compliance and several other benefits is gaining increasing importance in basic and applied research. However, the major obstacle for topical drug delivery is the effective barrier provided by skin against penetration of the vast majority of exogenous molecules. The research in this field is focusing more and more on new strategies to circumvent and pass this barrier effectively. In this article the existing approaches are discussed considering physical and chemical methods along with utilization of novel drug delivery systems to enhance penetration of drugs to the skin. In particular, attention has been paid to studies finalized to the delivery of molecules to cutaneous stem cells with the aim of transferring signals, modulating their metabolic program, inducing physiological modifications and stem cell gene therapy.

Nanoparticles for topical drug delivery: Potential for skin cancer treatment

Nanoparticles offer new opportunities for the treatment of skin diseases. The barrier function of the skin poses a significant challenge for nanoparticles to permeate into the tissue, although the barrier is partially compromised in case of injury or inflammation, as in the case of skin cancer. This may facilitate the penetration of nanoparticles. Extensive research has gone into developing nanoparticles for topical delivery; however, relatively little progress has been made in translating them to the clinic for treating skin cancers. We summarize the types of skin cancers and practices in current clinical management. The review provides a comprehensive outlook of the various nanoparticle technologies tested for topical therapy of skin cancers and summarizes the obstacles that impede its progress from the bench-to-bedside. The review also aims to provide an understanding of the pathways that govern nanoparticle penetration into the skin and a critical analysis of the approaches used to study nanoparticle interactions within the tissue.

Recent advances in follicular drug delivery of nanoparticles

Introduction: The improvement of percutaneous absorption represents a clear dermatopharmaceutical aim. Recently, the hair follicle was recognized to be an important penetration pathway. Especially nanoparticles show an enhanced intrafollicular penetration and can be utilized to target specific cell populations within the hair follicle.Areas covered: The present review briefly summarizes the recent advances in follicular drug delivery of nanoparticles. Moreover, the particularities of the hair follicle as a penetration pathway are summarized which include its structure and specific barrier properties. Recently, the mechanism of the follicular penetration process has been clarified.In the meantime, different strategies have been developed to successfully improve follicular drug delivery of nanoparticles. One approach is to equip the nanocarriers with a triggered release system enabling them to release their drug load at the right time and place.Expert opinion: Follicular drug delivery with smart nanocarrier-based drug delivery systems represents a promising approach to increase the percutaneous absorption of topically applied substances. Although technical achievements and efficacy proofs concerning an increased penetration of substances are already available, the practical implementation into clinical application still represents an additional challenge and should be in the focus of interest in future research.

A practical framework for implementing Quality by Design to the development of topical drug products: Nanosystem-based dosage forms

Skin has been increasingly recognized as an important drug administration route with topical formulations, offering a targeted approach for the treatment of several dermatological disorders. The effectiveness of this route is hampered by its natural barrier, the stratum corneum (SC), and hence, different strategies have been investigated to improve percutaneous drug transport. The design of nanodelivery systems, aiming at solving skin delivery issues, have been largely explored, due to their potential to revolutionize dermal therapies, improving therapeutic effectiveness and reducing side effects. Apart from nanosystem benefits, the fulfilment of the reproducibility requirements and quality standards still limit their industrial production. The optimization of nanosystem formulation and manufacturing process is complex, usually involving a large number of variables. Therefore, a science- and risk-oriented approach, such as Quality by Design (QbD) will provide a comprehensive and noteworthy knowledge, yielding high quality drug products without extensive regulatory burden. This review aims to set up the basis for QbD development approach, encompassing preliminary and systematic risk assessments, with critical process parameters (CPPs) and critical material attributes (CMAs) identification, of different nanosystems potentially used in dermal therapies.

Nanomaterials for transdermal drug delivery: beyond the state of the art of liposomal structures

A wide range of biomedical materials have been proposed to meet the different needs for controlled oral or intravenous drug delivery. The advantages of oral delivery such as self-administration of a pre-determined drug dose at defined time intervals makes it the most convenient means for the delivery of small molecular drugs. It fails however to delivery therapeutic macromolecules due to rapid degradation in the stomach and size-limited transport across the epithelium. The primary mode of administration of macromolecules is presently via injection. This administration mode is not without limitations, as the invasive nature of injections elicits pain and decreases patients' compliance. Alternative routes for drug delivery have been looked for, one being the skin. Delivery of drugs via the skin is based on the therapeutics penetrating the stratum corneum (SC) with the advantage of overcoming first-pass metabolism of drugs, to deliver drugs with a short-half-life time more easily and to eliminate frequent administrations to maintain constant drug delivery. The transdermal market still remains limited to a narrow range of drugs. The low permeability of the SC to water-soluble and macromolecular drugs poses significant challenges to transdermal administration via passive diffusion through the skin, as is the case for all topically administered drug formulations intended to bring the therapeutic into the general circulation. To widen the scope of drugs for transdermal delivery, new procedures to enhance skin permeation to hydrophilic drugs and macromolecules are under development. Next to the integration of skin enhancers into pharmaceutical formulations, nanoparticles based on lipid carriers have been widely considered and reviewed. While being briefly reviewed here, the main focus of this article is on current advancements using polymeric and metallic nanoparticles. Next to these passive technologies, the handful of active technologies for local and systemic transdermal drug delivery will be discussed and put into perspective. While passive approaches dominate the literature and the transdermal market, active delivery based on microneedles or iontophoresis approaches have shown great promise for transdermal drug delivery and have entered the market, in the last decade. This review gives an overall idea of the current activities in this field.

Novel imidazole fluorescent poly(ionic liquid) nanoparticles for selective and sensitive determination of pyrogallol

This paper reports novel imidazole fluorescent poly(ionic liquid) nanoparticles (FPILNs) of poly(1-[(4-methyphenyl)methyl]-3-vinyl-imidazolium bromide (poly([MVI]Br) for selective and sensitive determination of pyrogallol. An imidazole ionic liquid of 1-[(4-methyphenyl)methyl]-3-vinyl-imidazolium bromide ([MVI]Br) was synthesized and used as the only monomer to obtain poly([MVI]Br) possessing phenyl fluorophores using a radical polymerization technique. The obtained poly([MVI]Br) can form nanoparticles in water. Scanning electron microscopy and dynamic light scattering results revealed majority of poly([MVI]Br) FPILNs with diameters ranging from 40 to 400nm. Although [MVI]Br showed weak fluorescence intensity, poly([MVI]Br) FPILNs exhibited strong fluorescence intensity with a quantum yield of 0.192, which is attributed to the presence of significant number of phenyl fluorophores and rigid construction. The selective and sensitive determination of pyrogallol was achieved through fluorescence quenching of poly([MVI]Br) FPILNs, and the quenching was attributed to the oxidation of poly([MVI]Br) FPILNs by O₂˙¯ produced by pyrogallol autoxidation. The poly([MVI]Br) FPILNs-based sensor demonstrated a good linear relationship between the extent of fluorescence quenching and the concentration of pyrogallol in a range of 0.05 - 10.0μM, achieving a detection limit of 0.01μM. Furthermore, the poly([MVI]Br) FPILNs-based assay detected pyrogallol in environmental water samples, suggesting its potential to be applied for practical purposes.

A Review of the Structure, Preparation, and Application of NLCs, PNPs, and PLNs

Nanostructured lipid carriers (NLCs) are modified solid lipid nanoparticles (SLNs) that retain the characteristics of the SLN, improve drug stability and loading capacity, and prevent drug leakage. Polymer nanoparticles (PNPs) are an important component of drug delivery. These nanoparticles can effectively direct drug delivery to specific targets and improve drug stability and controlled drug release. Lipid–polymer nanoparticles (PLNs), a new type of carrier that combines liposomes and polymers, have been employed in recent years. These nanoparticles possess the complementary advantages of PNPs and liposomes. A PLN is composed of a core–shell structure; the polymer core provides a stable structure, and the phospholipid shell offers good biocompatibility. As such, the two components increase the drug encapsulation efficiency rate, facilitate surface modification, and prevent leakage of water-soluble drugs. Hence, we have reviewed the current state of development for the NLCs’, PNPs’, and PLNs’ structures, preparation, and applications over the past five years, to provide the basis for further study on a controlled release drug delivery system.

Hyaluronan polymeric micelles for topical drug delivery

Nanosized materials offer promising strategy for topical drug delivery due to their enhancing effect on drug percutaneous transport across the stratum corneum barrier. In this work, polymeric micelles made from hydrophobized hyaluronic acid (HA) were probed for skin delivery. Compared to non-polymeric micelle solutions containing similar drug amount, in vitro skin penetration analysis indicated 3 times larger deposition of drug in the epidermis and 6 times larger drug deposition in the dermis after 5h of topical treatment in Franz diffusion cells. The drug deposition was further increased with prolonged time of topical treatment. Laser confocal microscopy revealed the accumulation of both, the HA forming the vehicle and the payload, in the epidermis and dermis. Although fluorescent labeling of the HA would suggest co-transport of the HA and the drug, loading FRET pair dyes in the micellar core clearly demonstrated gradual micelle disruption with increasing skin depth. Transcellular penetration was the predominant pathway for the loaded drug. The HA polymeric micelles also demonstrated increased bioactivity of loaded compound in vitro and in vivo. In addition, the loaded micelles were found to be stable in cream formulations and thus they have great potential for topical applications for cosmetic and pharmaceutical purposes.

Impact of Cosmetic Lotions on Nanoparticle Penetration through ex vivo C57BL/6 Hairless Mouse and Human Skin: A Comparison Study

Understanding the interactions of nanoparticles (NPs) with skin is important from a consumer and occupational health and safety perspective, as well as for the design of effective NP-based transdermal therapeutics. Despite intense efforts to elucidate the conditions that permit NP penetration, there remains a lack of translatable results from animal models to human skin. The objectives of this study are to investigate the impact of common skin lotions on NP penetration and to quantify penetration differences of quantum dot (QD) NPs between freshly excised human and mouse skin. QDs were mixed in 7 different vehicles, including 5 commercial skin lotions. These were topically applied to skin using two exposure methods; a petri dish protocol and a Franz diffusion cell protocol. QD presence in the skin was quantified using Confocal Laser Scanning Microscopy. Results show that the commercial vehicles can significantly impact QD penetration in both mouse and human skin. Lotions that contain alpha hydroxyl acids (AHA) facilitated NP penetration. Lower QD signal was observed in skin studied using a Franz cell. Freshly excised human skin was also studied immediately after the sub-cutaneous fat removal process, then after 24 hours rest ex vivo. Resting human skin 24 hours prior to QD exposure significantly reduced epidermal presence. This study exemplifies how application vehicles, skin processing and the exposure protocol can affect QD penetration results and the conclusions that maybe drawn between skin models.

Synergetic skin targeting effect of hydroxypropyl-β-cyclodextrin combined with microemulsion for ketoconazole

The objective was to develop a ternary skin targeting system for ketoconazole (KET) using a combined strategy of microemulsion (ME) and cyclodextrin (HP-β-CD), i.e., KET-CD-ME, which exploits both virtues of cyclodextrin complex and ME to obtain the synergetic effect. KET-CD-ME was formulated using Labrafil M 1944 CS as oil phase, Solutol HS 15 as surfactant, Transcutol P as cosurfactant, and HP-β-CD solution as aqueous phase. The formulation of KET-CD-ME was optimized and the optimal formulation was characterized in terms of particle size, size distribution, pH value, and viscosity. Long term stability experiment showed that HP-β-CD could increase the physical stability of ternary system and KET chemical stability. Percutaneous permeation of KET from KET-CD-ME in vitro through rat skin was investigated in comparison with KET microemulsion (KET-ME), KET HP-β-CD inclusion solution (KET-CD), KET aqueous suspension, and commercial KET cream; the results showed that the combination of ME with HP-β-CD exhibited significantly synergistic effect on KET deposition within the skin (29.38 ± 1.79 μg/cm(2)) and a slightly synergistic effect on KET penetration through the skin (11.3 μg/cm(2)/h). The enhancement of the combination on skin deposition was further visualized by confocal laser scanning microscope (CLSM). In vitro sensitivity against Candida parapsilosis test indicated that KET-CD-ME enhanced KET antifungal activity mainly owing to the solubilization of HP-β-CD on KET in the ternary system. Moreover, the interactions between HP-β-CD and KET in the ternary system were elucidated through microScale thermophoresis (MST) and 2D (1)H NMR spectroscopy. The profiles from MST confirmed the host-guest interactions of HP-β-CD with KET in the ternary system and a deep insight into the interactions between KET and HP-β-CD were obtained by means of 2D (1)H NMR spectroscopy. The results indicate that the ternary system of ME combination with HP-β-CD may be a promising approach for skin targeting delivery of KET.

Facile preparation of biocompatible and robust fluorescent polymeric nanoparticles via PEGylation and cross-linking

Novel cross-linked copolymers of PEG-IM-PhNH2 are successfully synthesized through PEGylation via radical polymerization of 2-isocyanatoethyl methacrylate and poly(ethylene glycol) monomethyl ether methacylate and subsequent cross-linking with an amino-terminated aggregation-induced emission fluorogen. Such obtained amphiphilic copolymers can self-assemble to form uniform fluorescent polymeric nanoparticles (FPNs) and be utilized for cell imaging. These cross-linked FPNs are demonstrated good water dispersibility with ultralow critical micelle concentration (∼ 0.002 mg mL(-1)), uniform morphology (98 ± 2 nm), high red fluorescence quantum yield, and excellent biocompatibility. More importantly, this novel strategy of fabricating cross-linked FPNs paves the way to the future development of more robust and biocompatible fluorescent bioprobes.

Development of a topical adapalene-solid lipid nanoparticle loaded gel with enhanced efficacy and improved skin tolerability

The present investigation substantiates the efficacy of adapalene loaded solid lipid nanoparticles (Ada-SLNs) in ameliorating the skin irritation potential of adapalene owing to its altered skin distribution.

Fluorescent polymeric nanoparticles with ultra-low CMC for cell imaging

Fluorescent polymeric nanoparticles (FPNs) with ultra-low critical micelle concentration were facilely fabricated through radical polymerization and ring-opening crosslinking, and utilized for cell imaging.

Downregulation of immunological mediators in 2,4-dinitrofluorobenzene-induced atopic dermatitis-like skin lesions by hydrocortisone-loaded chitosan nanoparticles

Background

Atopic dermatitis is a chronic, noncontiguous, and exudative disorder accompanied by perivascular infiltration of immune mediators, including T-helper (Type 1 helper/Type 2 helper) cells, mast cells, and immunoglobulin E. The current study explores the immunomodulatory and histological effects of nanoparticle (NP)-based transcutaneous delivery of hydrocortisone (HC).

Methods

In this study, HC, the least potent topical glucocorticoid, was administered transcutaneously as chitosan NPs. The pharmacological and immunological effects of the NP-based HC delivery on the alleviation of 2,4-dinitrofluorobenzene-induced atopic dermatitis (AD)-like skin lesions were evaluated using the NC/Nga mouse model.

Results

In vivo Dino-Lite^® microscopic assessment revealed that the NP-based formulation displayed a remarkable ability to reduce the severity of the pathological features of AD (dermatitis index, 3.0). The AD suppressive activity of the NP-based topical formulation was expected owing to the interruption of a series of immunopathological events, including the production of immunoglobulin E, release of histamine, and expression of prostaglandin-E₂ and vascular endothelial growth factor-α in the sera and skin of the tested animals. Analysis of the cytokine expression in AD-like skin lesions further revealed that the NP-based formulation inhibited the pathological expression of interleukin (IL)-4, IL-5, IL-6, IL-13, IL-12p70, interferon-γ, and tumor necrosis factor-α in serum and skin homogenates of NC/Nga mice. Further, our histological findings indicated that the NP-based formulation inhibited fibroblast infiltration and fragmentation of elastic fibers, further supporting the clinical importance of these formulations in maintaining the integrity of elastic connective tissues.

Conclusion

The current investigation suggests that NP-mediated transcutaneous delivery of HC could be considered an effective therapeutic approach to manage dermatitis.

Delivery and targeting of nanoparticles into hair follicles

It has been demonstrated that nanoparticles used for follicular delivery provide some advantages over conventional pathways, including improved skin bioavailability, enhanced penetration depth, prolonged residence duration, fast transport into the skin and tissue targeting. This review describes recent developments using nanotechnology approaches for drug delivery into the follicles. Different types of nanosystems may be employed for management of follicular permeation, such as polymeric nanoparticles, metallic nanocrystals, liposomes, and lipid nanoparticles. This review systematically introduces the mechanisms of follicles for nanoparticulate penetration, highlighting the therapeutic potential of drug-loaded nanoparticles for treating skin diseases. Special attention is paid to the use of nanoparticles in treating appendage-related disorders, in particular, nanomedical strategies for treating alopecia, acne, and transcutaneous immunization.

Nanomedicine strategies for targeting skin inflammation

Topical treatment of skin diseases is an attractive strategy as it receives high acceptance from patients, resulting in higher compliance and therapeutic outcomes. Recently, the use of variable nanocarriers for dermal application has been widely explored, as they offer several advantages compared with conventional topical preparations, including higher skin penetration, controlled and targeted drug delivery and the achievement of higher therapeutic effects. This article will focus on skin inflammation or dermatitis as it is one of the most common skin problems, describing the different types and causes of dermatitis, as well as the typical treatment regimens. The potential use of nanocarriers for targeting skin inflammation and the achievement of higher therapeutic effects using nanotechnology will be explored.

Enhanced cutaneous bioavailability of dehydroepiandrosterone mediated by nano-encapsulation

Polymeric nanocarriers, especially nanospheres (NSs) and nanocapsules (NCs), can promote the penetration of their cargo through the skin barrier, towards improved cutaneous bioavailability. Dehydroepiandrosterone (DHEA), an endogenous hormone exhibiting poor aqueous solubility, was shown to be effective in modulating skin-aging processes following topical application. In this study, we designed adequate DHEA preparations, in an attempt to enable local delivery of the active ingredient to the viable skin layers. In addition, the potential efficiency of DHEA NCs on dermal collagen synthesis was evaluated. Cryo-TEM observations and thermal analysis indicated that DHEA was successfully incorporated within a stable NC-based delivery system. Moreover, higher [(3)H]-DHEA levels were recorded in the viable skin layers following different incubation periods of NCs on excised pig skin specimens as compared to DHEA oil solution (free molecule). Furthermore, significantly higher (4-fold) skin flux values were observed for the DHEA NCs as compared to the values elicited by the oil control solution. Finally, collagen synthesis in human skin organ culture, assessed by the incorporation of [(3)H]-proline, was up to 42% higher for DHEA NCs 48h post-topical application than for the untreated specimens. Overall, these results suggest that poly lactic-co-glycolic acid (PLGA)-based NCs have promising potential to be used topically for various skin disorders.

Zinc oxide nanoparticle removal from wounded human skin

Aim: Nanoparticle removal from skin is relevant given the concern over topical nanoparticle toxicity. Zinc oxide nanoparticles (ZnO-NPs) are commonly used in sunscreens and their use is currently debated. This study explores the penetration and removal of ZnO-NPs from injured skin. Materials & methods:Ex vivo/in vivo human skin was tape-stripped and/or microneedled followed by ZnO-NP application. After 2 h, treated skin was washed three-times using soapy water. Multiphoton tomography assessed the ZnO-NP signal before and after washing. Results: Washing once removed over 85 and 83% of ZnO-NP signal from ex vivo intact and tape-stripped skin, respectively (p < 0.05) but only 28% (p = 0.5) was removed from puncture sites. A similar trend was found in vivo with removal of 85 and 93% of ZnO-NP signal from intact and tape-stripped skin, respectively (p < 0.05). Conclusion: Washing is effective for the removal of ZnO-NPs from superficial layers of intact and tape-stripped skin, but not from puncture wounds.

Original submitted 5 July 2012; Revised submitted 3 October 2012; Published online 7 March 2013

Basic considerations in the dermatokinetics of topical formulations

Assessing the bioavailability of drug molecules at the site of action provides better insight into the efficiency of a dosage form. However, determining drug concentration in the skin layers following topical application of dermatological formulations is a great challenge. The protocols followed in oral formulations could not be applied for topical dosage forms. The regulatory agencies are considering several possible approaches such as tape stripping, microdialysis etc. On the other hand, the skin bioavailability assessment of xenobiotics is equally important for topical formulations in order to evaluate the toxicity. It is always possible that drug molecules applied on the skin surface may transport thorough the skin and reaches systemic circulation. Thus the real time measurement of molecules in the skin layer has become obligatory. In the last two decades, quite a few investigations have been carried out to assess the skin bioavailability and toxicity of topical/dermatological products. This review provides current understanding on the basics of dermatokinetics, drug depot formation, skin metabolism and clearance of drug molecules from the skin layers following application of topical formulations.

Polymeric nanoparticles-based topical delivery systems for the treatment of dermatological diseases

Human skin not only functions as a permeation barrier (mainly because of the stratum corneum layer) but also provides a unique delivery pathway for therapeutic and other active agents. These compounds penetrate via intercellular, intracellular, and transappendageal routes, resulting in topical delivery (into skin strata) and transdermal delivery (to subcutaneous tissues and into the systemic circulation). Passive and active permeation enhancement methods have been widely applied to increase the cutaneous penetration. The pathology, pathogenesis, and topical treatment approaches of dermatological diseases, such as psoriasis, contact dermatitis, and skin cancer, are then discussed. Recent literature has demonstrated that nanoparticles-based topical delivery systems can be successful in treating these skin conditions. The studies are reviewed starting with the nanoparticles based on natural polymers especially chitosan, followed by those made of synthetic, degradable (aliphatic polyesters), and nondegradable (polyacrylates) polymers; emphasis is given to nanospheres made of polymers derived from naturally occurring metabolites, the tyrosine-derived nanospheres (TyroSpheres™). In summary, the nanoparticles-based topical delivery systems combine the advantages of both the nanosized drug carriers and the topical approach, and are promising for the treatment of skin diseases. For the perspectives, the penetration of ultra-small nanoparticles (size smaller than 40 nm) into skin strata, the targeted delivery of the encapsulated drugs to hair follicle stem cells, and the combination of nanoparticles and microneedle array technologies for special applications such as vaccine delivery are discussed.

Predicting skin permeability from complex vehicles

It is now widely accepted that vehicle and formulation components influence the rate and extent of passive chemical absorption through skin. Significant progress, over the last decades, has been made in predicting dermal absorption from a single vehicle; however the effect of a complex, realistic mixture has not received its due attention. Recent studies have aimed to bridge this gap by extending the use of quantitative structure-permeation relationship (QSPR) models based on linear free energy relationships (LFER) to predict dermal absorption from complex mixtures with the inclusion of significant molecular descriptors such as a mixture factor that accounts for the physicochemical properties of the vehicle/mixture components. These models have been compiled and statistically validated using the data generated from in vitro or ex vivo experimental techniques. This review highlights the progress made in predicting skin permeability from complex vehicles.

Antidermatitic perspective of hydrocortisone as chitosan nanocarriers: an ex vivo and in vivo assessment using an NC/Nga mouse model

The aim of this study to administer hydrocortisone (HC) percutaneously in the form of polymeric nanoparticles (NPs) to alleviate its transcutaneous absorption, and to derive additional wound-healing benefits of chitosan. HC-loaded NPs had varied particle sizes, zeta potentials, and entrapment efficiencies, when drug-to-polymer mass ratios increased from 1:1 to 1:8. Ex vivo permeation analysis showed that the nanoparticulate formulation of HC significantly reduced corresponding flux [∼24 µg/(cm(2) h)] and permeation coefficient (∼4.8 × 10(-3) cm/h) of HC across the full thickness NC/Nga mouse skin. The nanoparticulate formulation also exhibited a higher epidermal (1610 ± 42 µg/g of skin) and dermal (910 ± 46 µg/g of skin) accumulation of HC than those associated with control groups. An in vivo assessment using an NC/Nga mouse model further revealed that mice treated with the nanoparticulate system efficiently controlled transepidermal water loss [15 ± 2 g/(m(2) h)], erythema intensity (232 ± 12), dermatitis index (mild), and thickness of skin (456 ± 27 µm). Taken together, histopathological examination predicted that the nanoparticulate system showed a proficient anti-inflammatory and antifibrotic activity against atopic dermatitic (AD) lesions. Our results strongly suggest that HC-loaded NPs have promising potential for topical/transdermal delivery of glucocorticoids in the treatment of AD.

Effect of microneedle treatment on the skin permeation of a nanoencapsulated dye

OBJECTIVES

The aim of the study was to investigate the effect of microneedle (MN) pretreatment on the transdermal delivery of a model drug (Rhodamine B, Rh B) encapsulated in polylactic-co-glycolic acid (PLGA) nanoparticles (NPs) focusing on the MN characteristics and application variables.

METHODS

Gantrez MNs were fabricated using laser-engineered silicone micro-mould templates. PLGA NPs were prepared using a modified emulsion-diffusion-evaporation method and characterised in vitro. Permeation of encapsulated Rh B through MN-treated full thickness porcine skin was performed using Franz diffusion cells with appropriate controls.

KEY FINDINGS

In-vitro skin permeation of the nanoencapsulated Rh B (6.19 ± 0.77 µg/cm²/h) was significantly higher (P < 0.05) compared with the free solution (1.66 ± 0.53 µg/cm²/h). Mechanistic insights were supportive of preferential and rapid deposition of NPs in the MN-created microconduits, resulting in accelerated dye permeation. Variables such as MN array configuration and application mode were shown to affect transdermal delivery of the nanoencapsulated dye.

CONCLUSIONS

This dual MN/NP-mediated approach offers potential for both the dermal and transdermal delivery of therapeutic agents with poor passive diffusion characteristics.