Controlled nail delivery of a novel lipophilic antifungal agent using various modern drug carrier systems as well as in vitro and ex vivo model systems

Novel Discoveries and Clinical Advancements for Treating Onychomycosis: A Mechanistic Insight

Onychomycosis continues to be the most challenging disease condition for pharmaceutical scientists to develop an effective drug delivery system. Treatment challenges lie in incomplete cure and high relapse rate. Present compilation provides cumulative information on pathophysiology, diagnostic techniques, and conventional treatment strategies to manage onychomycosis. Novel technologies developed for successful delivery of antifungal molecules are also discussed in brief. Multidirectional information offered by this article also unlocks the panoramic view of leading patented technologies and clinical trials. The obtained clinical landscape recommends the use of advanced technology driven approaches, as a promising way-out for treatment of onychomycosis. Collectively, present review warrants the application of novel technologies for the successful management of onychomycosis. This review will assist readers to envision a better understanding about the technologies available for combating onychomycosis. We also trust that these contributions address and certainly will encourage the design and development of nanocarriers-based delivery vehicles for effective management of onychomycosis.

Linalool-Incorporated Synergistically Engineered Modified Liposomal Nanocarriers for Enhanced Transungual Delivery of Terbinafine against Onychomycosis

This work investigates the synthesis of linalool-containing invasomes for terbinafine (TBF-IN) in order to increase the solubility, bioavailability, and nail permeability of terbinafine (TBF) for transungual administration. TBF-IN was created utilising the thin-film hydration technique, and with the Box-Behnken design (BBD), optimisation was carried out. TBF-INopt were investigated for vesicle size, zeta potential, PDI (Polydispersity index), entrapment efficiency (EE) and in vitro TBF release. In addition, nail permeation analysis, TEM (transmission electron microscopy), and CLSM (confocal scanning laser microscopy) were performed for further evaluation. The TBF-INopt exhibited spherical as well as sealed vesicles with a considerably small size of 146.3 nm, an EE of 74.23 per cent, a PDI of 0.1612, and an in vitro release of 85.32 per cent. The CLSM investigation revealed that the new formulation had better TBF nail penetration than the TBF suspension gel. The antifungal investigation demonstrated that the TBF-IN gel has superior antifungal activity against Trichophyton rubrum and Candida albicans compared to the commercially available terbinafine gel. In addition, an investigation of skin irritation using Wistar albino rats indicates that the TBF-IN formulation is safe for topical treatment. This study confirmed that the invasomal vesicle formulation is an effective vehicle for the transungual delivery of TBF for the treatment of onychomycosis.

Poly(pseudo)rotaxanes formed by mixed micelles and α-cyclodextrin enhance terbinafine nail permeation to deeper layers

This work aimed to develop water-based formulations for onychomycosis topical treatment using micelles of small pegylated surfactants associated with α-cyclodextrin (αCD) to deliver terbinafine to the nail. Kolliphor® RH40 (RH40) and Gelucire® 48/16 (GEL) single and mixed micelles (RH40:GEL 1:1) were prepared. αCD was added to the surfactants dispersions to form poly(pseudo)rotaxanes (PPR). Formulations were characterized in terms of drug solubilization (3 to 34-fold increase), particle size (9–11 nm) and Z-potential (+0.3 − +1.96 mV), blood compatibility (non-hemolytic), rheological behavior (solid-like viscoelastic properties after 5–10% αCD addition), drug release and interaction with the nail plate. GEL micelles and surfactant-10% αCD PPRs notably hydrated the nail plate. The high viscosity of PPR led to a slower drug release, except for RH40:GEL +10% αCD that surprisingly released terbinafine faster. The RH40:GEL +10% αCD formulation delivered twice more amount of terbinafine to deeper regions of nail plate compared to other formulations. The results evidenced the potential of PPR formed by small pegylated surfactants as a water-based formulation for nail drug delivery.

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RH40, GEL and their mixed micelles increased 3-fold and 34-fold TB solubility in water and citrate buffer, respectively.

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Addition of αCD (5–10%) led to PPR formation and viscoelastic supramolecular gels without decrease in TB solubilization.

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PPR formulations with 10% αCD enhanced nail plate hydration, increasing its porosity.

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Compared to mixed micelles, PRP showed slower release rate but promoted TB accumulation in deeper regions of hooves.

Comparative Ungual Drug Uptake Studies: Equine Hoof Membrane vs. Human Nail Plate

Human nail diseases, mostly caused by fungal infections, are common and difficult to treat. The development and testing of new drugs and drug delivery systems for the treatment of nail diseases is often limited by the lack of human nail material for permeation studies. Animal material is frequently used, but there are only few comparative data on the human nail plate, and there is neither a standardized test design nor a nail bed analogue to study drug uptake into the nail. In this study, a new permeation device was developed for permeation studies, and the permeation behavior of three model substances on the human nail plate and a model membrane from the horse hoof was investigated. A linear correlation was found between drug uptake by the human nail plate and the uptake by the equine hoof. The developed and established permeation device is suitable for investigations of ungual drug transport and enables the use of different membrane diameters and the use of a gel-based nail bed analog. The hydrogel-based acceptor medium used ensures adequate stabilization and hydration of the nail membrane.

Quality by Design Guided Development of Polymeric Nanospheres of Terbinafine Hydrochloride for Topical Treatment of Onychomycosis Using a Nano-Gel Formulation

Superficial fungal diseases of the skin and nails are an increasingly common occurrence globally, requiring effective topical treatment to avoid systemic adverse effects. Polymeric nanoparticles have demonstrated sustained and effective drug delivery in a variety of topical formulations. The aim of this project was to develop polymeric antifungal nanospheres containing terbinafine hydrochloride (TBH) to be loaded into a hydrogel formulation for topical nail drug delivery. A quality by design (QbD) approach was used to achieve optimized particles with the desired quality target product profile (QTPP). Polyvinyl alcohol (PVA) at 2% w/v and a drug to polymer ratio of 1:4, together with a robust set of processes and material attributes, resulted in nanoparticles of 108.7 nm with a polydispersity index (PDI) of 0.63, 57.43% recovery, and other desirable characteristics such as zeta potential (ZP), particle shape, aggregation, etc. The nanospheres were incorporated into a carbomer-based gel, and the delivery of TBH through this formulation was evaluated by means of in vitro drug release testing (IVRT) and ex vivo nail permeation study. The gel containing the TBH nanospheres demonstrated a slower and controlled drug release profile compared with the control gel, in addition to a more efficient delivery into the nail. These antifungal nanospheres can be utilized for topical therapy of a multitude of superficial fungal infections.

Investigation on utility of some novel terpenes on transungual delivery of fluconazole for the management of onychomycosis

BACKGROUND

Onychomycosis, the most prevailing affliction of the nail, accounts for approximately 90% of the toenail infection worldwide. Owing to this infection, the affected patients experience reduced quality of their life as its awful appearance undermines their daily activities and social interactions. Onychomycosis is notoriously strenuous to cure. Systemic therapy, though effective, possess severe complication of toxicities, contra-indication, and drug-drug interaction. Albeit topical therapy is favorable to its localized effect, its potency relates to the effective concentration of the antifungal drugs achieved at the infection site. An approach to accomplish this goal would be acquiring benefits from the terpenes as penetration enhancers from natural sources. This investigation aimed to study the effectiveness of six terpenes, namely safranal, lavandulol, rose oxide, 3-methyl-2-butene-1-ol, linalool, and limonene, as potential penetration enhancers for improved nail permeation of fluconazole through the human nail.

METHODS

Ex vivo permeation experiments were carried out by soaking the nail clippings of human volunteers in control and working solutions containing fluconazole (5 mg/ml) per se and fluconazole (5 mg/ml) with 6% of each terpene, including safranal, lavandulol, rose oxide, 3-methyl-2-butene-1-ol, linalool, and limonene, respectively, for 48 hours. The amount of fluconazole in nail clippings was quantified using an HPLC method.

RESULTS

Statistical analysis showed that fluconazole transungual permeation was influenced by the studied terpenes in the following order: safranal > lavandulol acetate > limonene > rose oxide (P-value > 0.05) while the other terpenes showed no significant difference with the control group and safranal represents as the most effective permeation enhancer for the transungual delivery of fluconazole.

CONCLUSION

It is concluded that the safranal can be successfully used as a safe and potential permeation enhancer to enhance the transungual delivery of fluconazole for the treatment of onychomycosis.

Improving Transungual Permeation Study Design by Increased Bovine Hoof Membrane Thickness and Subsequent Infection

Ungual formulations are regularly tested using human nails or animal surrogates in Franz diffusion cell experiments. Membranes sometimes less than 100 µm thick are used, disregarding the higher physiological thickness of human nails and possible fungal infection. In this study, bovine hoof membranes, healthy or infected with Trichophyton rubrum, underwent different imaging techniques highlighting that continuous pores traversed the entire membrane and infection resulted in fungal growth, both superficial, as well as in the membrane’s matrix. These membrane characteristics resulted in substantial differences in the permeation of the antifungal model substance bifonazole, depending on the dosage forms. Increasing the thickness of healthy membranes from 100 µm to 400 µm disproportionally reduced the permeated amount of bifonazole from the liquid and semisolid forms and allowed for a more pronounced assessment of the effects by excipients, such as urea as the permeation enhancer. Similarly, an infection of 400-µm membranes drastically increased the permeated amount. Therefore, the thickness and infection statuses of the membranes in the permeation experiments were essential for a differential readout, and standardized formulation-dependent experimental setups would be highly beneficial.

Enhanced nail delivery of voriconazole-loaded nanomicelles by thioglycolic acid pretreatment: A study of protein dynamics and disulfide bond rupture

This work aimed to select an effective penetration enhancer (PE) for nail pretreatment, develop voriconazole (VOR)-loaded nanomicelles, and evaluate their ability to deliver VOR to the nail. A complete analysis of nail protein dynamics, bond rupture, and microstructure was performed. Alternative methods as electron paramagnetic resonance (EPR) and the Ellman's reagent (DTNB) assay were also evaluated. Nanomicelles were produced and characterized. The PE hydrated the hooves, following the order: urea ≈ cysteine ≈ glycolic acid < thioglycolic acid (TGA) < NaOH. SEM images and methylene blue assay showed enlarged pores and roughness of porcine hooves after incubation with NaOH and TGA. EPR was demonstrated to be the most sensitive technique. DTNB assay quantified higher thiol groups for samples treated with TGA (p < 0.05). A stratigraphic analysis with Raman spectroscopy demonstrated that hooves treated with TGA presented a higher SH/SS ratio at the edges, affecting protein secondary structure. In vitro permeation studies demonstrated significant VOR permeation (29.44 ± 6.13 µg/cm²), 10-fold higher than previous studies with lipid nanoparticles. After TGA pretreatment, VOR permeation was further enhanced (3-fold). TGA pretreatment followed by VOR-loaded nanomicelles demonstrates a promising approach for onychomycosis treatment. The novel methods for protein analysis were straightforward and helpful.

Potential of Naftifine Application for Transungual Delivery

Naftifine is used to treat fungal skin infections as it inhibits dermatophytes, which are the cause of onychomycosis. However, naftifine's ability to permeate the human nail barrier has not been investigated, thus, the antimycotic potential is not clearly established. This work aims to evaluate the effect of penetration enhancing factors on the accumulation of naftifine hydrochloride through human nail clippings. Naftifine polymeric nail lacquers with Eudragit RL100 were developed as a suitable delivery system. Low penetration of naftifine into nail has been determined as less than 10% of applied drug dose accumulated in the nail layers. Incorporation of thioglycolic acid into formulations resulted in increased accumulation of antifungal agent in the nail layers by 100% compared with a control group. Salicylic acid did not effect naftifine accumulation in the human nail. The permeation of naftifine through the nail increased by threefold when the thioglycolic acid-containing formulation was applied and the nail was pretreated with a fractional CO2 laser. Structural changes of the nail barrier, induced by fractional CO2 laser, were visualized by microscopy. The results suggest, that naftifine nail penetration could be significantly increased when physical and chemical enhancing factors are applied.

Ex vivo nail infection as an effective preclinical method for screening of new topical antifungals

Onychomycosis are fungal nail infections comprising of about 50% of onychopathies and are commonly caused by dermatophytes. The treatment of this dermatomycosis requires a long period of time and is associated with high rates of recurrence. In view of the need to evaluate the antifungal performance of promising preclinical compounds, we developed, in this study, a practical and accessibleex vivo model for establishing a Trichophyton rubrum onychomycosis framework using porcine hooves. This model has as its main advantage the similar structural and three-dimensional characteristics that the porcine hooves have with the human nail. The proposed model allowed to evaluate the antifungal activity of a new antifungal compound and a reference drug (terbinafine), both already incorporated into a nail lacquer for topical use. Treatments with compound 3-selenocyanate-indole (Se4a) and with terbinafine incorporated into this nail lacquer completely inhibited fungal growth, corresponding to the profile of in vitro activity observed against T. rubrum. This study concludes that the ex vivo porcine hoof model is an effective alternative method for preclinical screening of drugs or new topical compounds developed to combat onychomycosis. Further studies are needed to compare the permeability of porcine hooves with human nails permeability.

Mechanistic Insights of Formulation Approaches for the Treatment of Nail Infection: Conventional and Novel Drug Delivery Approaches

Onychomycosis is a chronic disorder that is difficult to manage and hard to eradicate with perilous trends to relapse. Due to increased prevalence of HIV, use of immunosuppressant drugs and lifestyle-related factors, population affected with fungal infection of nail (Onychomycosis) happens to increase extensively in last two decades. Modalities available for the treatment of onychomycosis include systemically administered antifungals, mechanical procedures, and topical drug therapy. But the efficacy of the most of approaches to deliver drug at targeted site, i.e., deep-seated infected nail bed is limited due to compact and highly keratinized nail structure. A series of advanced formulation approaches, such as transfersomes, liposomes, nano/micro emulsion, nail lacquers etc., have been attempted to improve the drug penetration into nail plate more efficiently. The manuscript reviews these formulation approaches with their possible mechanisms by which they improve the drug penetration.Comparative analysis of available treatment modalities for onychomycosis has been provided with pros and cons of each alternatives. Additionally, ongoing research about the application of biological materials such as modified cationic antimicrobial peptides (AMPs), plant-derived proteins, and synthetic antimicrobial peptidomimetics have also been explored.

Preparation and in vivo evaluation of a highly skin- and nail-permeable efinaconazole topical formulation for enhanced treatment of onychomycosis

Onychomycosis is a progressive fungal infection of the nails that involves the deeper nail layer and nail bed. It is important to maintain sufficient drug concentration in the diseased tissues after topical application. In this study, a stable topical delivery system for efinaconazole (EFN) was designed to enhance absorption potential through the skin and nail plate by incorporating ethanol, diethylene glycol monoethyl ether (Transcutol P) and isopropyl myristate, and cyclomethicone into the topical solution as a delivery vehicle, permeation enhancers, and a wetting agent, respectively. In addition, the stability of EFN in the formulation was significantly improved by adding butylated hydroxytoluene, diethylenetriamine pentaacetic acid, and citric acid as an antioxidant, chelating agent, and pH-adjusting agent, respectively, without discoloration. The optimum EFN formulation (EFN-K) showed 1.46-fold greater human skin permeation than that of the reference control (commercial 10% EFN topical solution). Furthermore, after a 24-hour incubation, the amount of infiltrated EFN from EFN-K in the human nail plate was 4.11-fold greater than that of the reference control, resulting in an 89.7% increase in nail flux at 7 days after treatment. EFN-K significantly accelerated structural recovery of the keratin layer in a Trichophyton mentagrophytes-infected guinea pig onychomycosis model, decreasing the mean viable fungal cell count by 54.3% compared to the vehicle-treated group after once-daily treatment for 4 weeks. Thus, the accelerated skin and nail penetration effect of EFN-K is expected to achieve good patient compliance, and improve the complete cure rate of onychomycosis.

Potential of Chemical and Physical Enhancers for Transungual Delivery of Amorolfine Hydrochloride

Topical monotherapy of nail infection is limited by poor drug permeability into the human nail plate. Numerous substances and methods are applied to improve the antifungal agent delivery across the nail plate. This work aimed to evaluate the effect of chemical and physical enhancers on the accumulation and permeation of amorolfine hydrochloride through human nail clippings. Polymeric nail lacquers with Eudragit E100 were developed as a potentially suitable delivery system for amorolfine hydrochloride. Incorporating thioglycolic acid and urea into formulations provided increased accumulation of antifungal agent in nail layers of up to 100% and 57%, respectively. Structural changes of nail barrier, induced by fractional CO₂ laser, were visualized by microscopy. The permeation of amorolfine hydrochloride through the nail increased twofold when thioglycolic acid-containing formulation was applied and the nail was pretreated with a fractional CO₂ laser. The results suggest that this novel combination of enhancers has the potential to be an effective option for topical drug delivery through the nail, and increased the efficacy of treatment.

Raman Microspectroscopy as a Tool to Elucidate the Efficacy of Topical Formulations Containing Curcumin

The success of the onychomycosis treatment is directly associated with factors such as the choice of the medication, the administration route, and the pharmaceutical formulation. Photodynamic therapy (PDT) is an emerging and promising technique indicated for onychomycosis treatment. For this application, the main challenge is the efficient delivery of the photosensitizer (PS). Curcumin is widely used as a PS, however it is an unstable molecule and it is a challenge to develop a formulation with good penetration into the nail plate, maintaining the stability of curcumin. In this study, the molecular mechanisms underlying the efficacy of two topical formulations containing curcumin used in a clinical trial for onychomycosis treatment were analyzed by Raman microspectroscopy. It is shown that curcumin is present in both formulations in aggregated and non-aggregated states, and in aggregates it is present in different conformations, depending on the interaction with the solvent. This proves to be critical for efficient and uniform PS delivery to the nail and its complete use during the treatment. These analyses are showing how promising Raman microspectroscopy is in understanding the molecular mechanisms of the efficiency of photosensitizers and are helping to improve the development of pharmaceutical formulations.

Recent Patents on Permeation Enhancers for Drug Delivery Through Nails

The human nail is a unique barrier with a keratinized constitution that favors protection and fine touch. However, many disorders can affect the nail, among them, are the onychomycosis and psoriasis. Systemic oral therapy has been applied to treat these diseases, even presenting disadvantages, including side effects, drug interactions, contraindications, toxicity, high cost and low patient compliance. A great option to succeed in dealing with the problems associated with oral therapy is the topical administration of drugs. However, nail composition, low diffusion through ungual route and reduced tissue bioavailability for topical treatments are limiting factors. These drawbacks can be overcome by promoting penetration through the nails by employing penetration enhancers. The review focuses on patents that highlight permeation enhancers applied to nail drug delivery for the treatment of onychomycosis and psoriasis. Literature and patent searches were conduced regarding the topic of interest. The substantial literature and patent search revealed that permeation enhancers, especially chemicals, are great strategies for promoting the ungual delivery of drugs. Nail topical therapy containing permeation enhancers is an attractive option for delivering localized treatments.

Fusarium oxysporum is an onychomycosis etiopathogenic agent

AIM

To evaluate and characterize the etiopathogenesis of the fusarial onychomycosis in an ex vivo study through fragments of sterile human nail, without the addition of any nutritional source.

MATERIALS & METHODS

The infection and invasion of Fusarium oxysporum in the nail were evaluated by scanning electron microscopy (SEM), CFU, matrix, histopathology and Fourier Transform Infrared Spectrometer coupled to an equipment with diamond accessory (FTIR-ATR).

RESULTS

F. oxysporum infected and invaded across the nail, regardless of application face. However, the dorsal nail surface was the strongest barrier, while the ventral was more vulnerable to infection and invasion process. The fungal-nail interaction resulted in the formation of a dense biofilm.

CONCLUSION

F. oxysporum infect and invade the healthy human nail, resulting in biofilm formation. Therefore, F. oxysporum is likely a primary onychomycosis agent.

Chemical and physical strategies in onychomycosis topical treatment: A review

Onychomycosis is a fungal infection of the fingernails or toenails caused by dermatophytes, nondermatophytes, moulds, and yeasts. This condition affects around 10-30% people worldwide, negatively influencing patients' quality of life, with severe outcomes in some cases. Since the nail unit acts as a barrier to exogenous substances, its physiological features hampers drug penetration, turning the onychomycosis treatment a challenge. Currently, there are several oral and topical therapies available; nevertheless, cure rates are still low and relapse rates achieves 10-53%. Also, serious side effects may be developed due to long-term treatment. In light of these facts, researchers have focused on improving topical treatments, either by modifying the vehicle or by using some physical technique to improve drug delivery trough the nail plate, hence increasing therapy effectiveness. Therefore, the aim of this paper is to explain these novel alternative approaches. First, the challenges for drug ungual penetration are presented. Then, the chemical and physical strategies developed for overcoming the barriers for drug penetration are discussed. We hope that the information gathered may be useful for the development of safer and more effective treatments for onychomycosis.

Optimized Ciclopirox-Based Eudragit RLPO Nail Lacquer: Effect of Endopeptidase Enzyme as Permeation Enhancer on Transungual Drug Delivery and Efficiency Against Onychomycosis

The aims of our investigation were to develop and optimize ciclopirox (CPX) nail lacquer using nonbiodegradable Eudragit RLPO (E-RLPO) as a film former and to assess its penetration efficiency across the human nail plate. Preliminary trials such as hydration enhancement factor (HEF), a retained drug in the nail plate, and SEM were studied to select the optimized permeation enhancer to be incorporated in the optimized lacquer formulation. A 3³ full factorial design was built up to study the effect of three different factors, concentration of E-RLPO (10, 20, and 30%), Tween 80 (0.25, 0.5, and 1%), and triacetin (0, 10, and 30% of polymer weight). The studied responses were the drying time, water resistance, viscosity, and drug release up to 4 h. An ex vivo permeation study for the optimized formulations was carried out. The preliminary study aided the selection of 5% papain (endopeptidase enzyme) as a penetration enhancer; it showed the highest HEF of 15.27%, the highest amount of drug retained in the nail plate (886.2 μg/g). An ex vivo permeation study guided the selection of F4B (flux value of 3.79 μg/cm²/h) as optimized formulation. The optimized lacquer formula showed threefold increases in the permeation than the marketed CPX lacquer (Batrafen®). Confocal laser scanning microscopy revealed the higher intensity of the Rhodamine B dye across the nail plate in the case of the formula containing papain than the marketed formula without papain. Conclusively, an efficient and stable nail lacquer was developed for potential transungual delivery of CPX to target the drug to the nail bed and ensure efficiency against onychomycosis.

Voriconazole-loaded nanostructured lipid carriers (NLC) for drug delivery in deeper regions of the nail plate

Voriconazole-loaded nanostructured lipid carriers (VOR-NLC) were developed and drug penetration evaluated in porcine hooves in vitro. Synergistic effect of urea (Ur), selected among other known chemical enhancers according to hoof hydration potential, was also evaluated. VOR-NLC presented a high encapsulation efficiency (74.52±2.13%), approximate mean diameter of 230nm and were positively charged (+27.32±2.74mV). Stability studies indicated they were stable under refrigeration (4±2°C) for up to 150days. SEM images revealed hooves treated with VOR-NLC and VOR-NLC-Ur suffered a disturbance on the surface depicting high roughness and porosity. Permeation data showed a substantial VOR amount retained in superficial hooves sections independent of the formulation used (2.42±0.26; 2.52±0.36 and 2.41±0.60μg/cm² for unloaded VOR, VOR-NLC and VOR-NLC-Ur, respectively, p>0.05). Still, successive extractions, revealed the amount of VOR retained in deeper regions was significantly higher when VOR-NLC or VOR-NLC-Ur was used (0.17±0.04, 0.47±0.14 and 0.36±0.07μg/cm² for unloaded VOR, VOR-NLC and VOR-NLC-Ur, respectively, p<0.05). Such results indicate NLC are promising formulations for the management of onychomycosis. Further studies in diseased nail plates are necessary.

Effect of Film-Forming Polymers on Release of Naftifine Hydrochloride from Nail Lacquers

The successful topical therapy of onychomycosis depends on effective drug release and penetration into nail, which can be achieved by using an adequately developed delivery system. This study evaluated and compared effect of film-forming polymers Eudragit RL100, Eudragit RS100, and ethyl cellulose on naftifine hydrochloride release from experimental nail lacquer formulations. Quality of formulations was evaluated by determining drying time and water resistance. Interactions between active pharmaceutical ingredient and excipients were investigated using microcalorimetry and FT-IR. Optimization of nail lacquer formulations was performed by naftifine hydrochloride release testing. Release of naftifine hydrochloride increased with increasing concentration of Eudragit RL100. Plasticizer triacetin affected the release of naftifine hydrochloride, when Eudragit RS100 polymer was used. Ethyl cellulose polymer was determined to be not applicable for naftifine hydrochloride nail lacquer formulations. Two compositions of nail lacquers were optimized and could be used in further development of transungual delivery systems.

Structural and component mining of nails using bioengineering techniques

The human nail is one of the challenging membranes for the scientists to target and to improve the clinical efficacy of ungual formulations. The understanding of nail physiology, impact of hydration on its properties and presence of trace elements in nails as biomarkers has been explored by various researchers in clinical studies. Despite the importance of biophysical techniques for the assessment of structure and physiology of nail, minimum literature analyses biophysical, biochemical and bioanalytical approaches. However, nowadays scientists in bioengineering field are keen in developing non-invasive, reliable and reproducible techniques for the assessment of different anatomical and functional parameters of nails for testing of ungual products.

Onychomycosis: Potential of Nail Lacquers in Transungual Delivery of Antifungals

Onychomycosis constitutes the most common fungal infection of the nail (skin beneath the nail bed) that affects the finger as well as toe nails. It is an infection that is initiated by yeasts, dermatophytes, and nondermatophyte molds. Nail lacquers are topical solutions intended only for use on fingernails as well as toenails and have been found to be useful in the treatment of onychomycosis. Thus, in the present review an attempt has been made to focus on the treatment aspects of onychomycosis and the ungual delivery of antifungals via nail lacquer. Several patents issued on nail lacquer till date have also been discussed. Penetration efficiency was assessed by several researchers across the human nail plate to investigate the potentiality of nail lacquer based formulations. Various clinical trials have also been conducted in order to evaluate the safety and efficacy of nail lacquers in delivering antifungal agents. Thus, it can be concluded that nail lacquer based preparations are efficacious and stable formulations. These possess tremendous potential for clinical topical application to the nail bed in the treatment of onychomycosis.

Transungual permeation: current insights

Nail disorders are beyond cosmetic concern; besides discomfort in the performance of daily chores, they disturb patients psychologically and affect their quality of life. Fungal nail infection (onychomycosis) is the most prevalent nail-related disorder affecting a major population worldwide. Overcoming the impenetrable nail barrier is the toughest challenge for the development of efficacious topical ungual formulation. Sophisticated techniques such as iontophoresis and photodynamic therapy have been proven to improve transungual permeation. This article provides an updated and concise discussion regarding the conventional approach and upcoming novel approaches focused to alter the nail barrier. A comprehensive description regarding preformulation screening techniques for the identification of potential ungual enhancers is also described in this review while highlighting the current pitfalls for the development of ungual delivery.

Progressive development in experimental models of transungual drug delivery of anti-fungal agents

Pre-clinical development comprises of different procedures that relate drug discovery in the laboratory for commencement of human clinical trials. Pre-clinical studies can be designed to recognize a lead candidate from a list to develop the procedure for scale-up, to choose the unsurpassed formulation, to determine the frequency, and duration of exposure; and eventually make the foundation of the anticipated clinical trial design. The foremost aim in the pharmaceutical research and industry is the claim of drug product quality throughout a drug's life cycle. The particulars of the pre-clinical development process for different candidates may vary; however, all have some common features. Typically in vitro, in vivo or ex vivo studies are elements of pre-clinical studies. Human pharmacokinetic in vivo studies are often supposed to serve as the 'gold standard' to assess product performance. On the other hand, when this general assumption is revisited, it appears that in vitro studies are occasionally better than in vivo studies in assessing dosage forms. The present review is compendious of different such models or approaches that can be used for designing and evaluation of formulations for nail delivery with special reference to anti-fungal agents.

Transungual delivery: deliberations and creeds

Although considered as trifling illness, nail diseases have a reasonably high occurrence and a noteworthy impact on the patients' quality of life. Furthermore, there is a need to improve the topical treatment for nail diseases to avoid drug interactions and to reduce side effects associated with oral therapy. Topical drug delivery to the nails has established amplified consideration lately. Strategies (such as chemical enhancers, formulation strategies, physical and mechanical methods) are being investigated in order to improve drug permeability across the nail plate. The rationale of this review is to present contemporary information on the structure of human nail along with its comparison with animal hooves. Precincts of nail permeability have been briefly discussed with respect to factors like permeant's molecular size, hydrophilicity, charge and the nature of the vehicle. These factors affect drug uptake and permeation through the nail. Formulations like nail lacquers which mimic cosmetic varnish and colloidal carriers along with nail substitutes that can be utilized for transungual delivery have also been discussed.