Human nail plate modifications induced by onychomycosis: implications for topical therapy

Design, Development, and Evaluation of Constant Voltage Iontophoresis for the Transungual Delivery of Efinaconazole

The efficacy of topical antifungal therapy in onychomycosis has been hindered by the failure of the antimycotic to permeate the nail plate. This research aims to design and develop a transungual system for the effective delivery of efinaconazole utilizing constant voltage iontophoresis. Seven prototype drug-loaded hydrogel formulations (E1-E7) were prepared to assess the influence of solvent (ethanol) and cosolvent (Labrasol^®) on transungual delivery. Optimization was performed to evaluate the effect of three independent variables; voltage, solvent-to-cosolvent ratio, and penetration enhancer (PEG 400) concentration on critical quality attributes (CQAs), such as drug permeation and loading into the nail. The selected hydrogel product was characterized for pharmaceutical properties, efinaconazole release from the nail, and antifungal activity. Preliminary data indicates ethanol, Labrasol^®, and voltage influence the transungual delivery of efinaconazole. Optimization design indicates a significant impact by applied voltage (p-0.0001) and enhancer concentration (p-0.0004) on the CQAs. Excellent correlation between selected independent variables and CQAs was confirmed by the high desirability value (0.9427). A significant (p < 0.0001) enhancement in the permeation (~78.59 µg/cm²) and drug loading (3.24 µg/mg) was noticed in the optimized transungual delivery with 10.5 V. FTIR spectral data indicates no interaction between the drug and excipients, while the DSC thermograms confirmed the amorphous state of the drug in the formulation. Iontophoresis produces a drug depot in the nail that releases above the minimum inhibitory concentration level for an extended period, potentially reducing the need for frequent topical treatment. Antifungal studies further substantiate the release data and have shown remarkable inhibition of Trichophyton mentagrophyte. Overall, the promising results obtained here demonstrate the prospective of this non-invasive method for the effective transungual delivery of efinaconazole, which could improve the treatment of onychomycosis.

Treatment of nail clippings with ethyl alcohol improves the efficacy of Raman spectroscopy in the diagnosis of Trichophyton rubrum onychomycosis

The purpose of this work was to enhance the diagnostic accuracy of nail Raman spectroscopy for fungal nail infections, specifically onychomycosis caused by Trichophyton rubrum. The study assessed the different ethyl alcohol retention rates between control and infected nails after soaking nail clippings in ethanolic solutions and drying. Results revealed that ethyl alcohol completely evaporated from infected nail samples, while significant amounts were still present in control samples. Principal component analysis (PCA) was applied to discriminate control from infected nails and showed superior group separation when nails were treated with ethyl alcohol. PCA loadings plot attributed the efficient classification to the ν_s (CCO) Raman vibrational mode of ethyl alcohol. As Raman spectroscopy can detect minute concentration changes of ethyl alcohol in nails and the deterioration caused by onychomycosis accelerates its evaporation, a simple and rapid method for detecting T. rubrum onychomycosis is proposed.

Chitosan Nanoparticles Loaded Poloxamer 407 Gel for Transungual Delivery of Terbinafine HCl

The current study aimed to develop chitosan nanoparticles (CSNP) loaded poloxamer 407 (P407) gel formulation for transungual delivery of terbinafine HCl (TBN). TBN-CSNP were prepared by nanoprecipitation method and optimized by face-centered central composite design (FCCCD). Optimized TBN-CSNP formulation exhibited a spherical shape with hydrodynamic diameter; zeta potential and entrapment efficiency (EE) of 229 ± 5 nm; 37 ± 1.5 mV; and 75 ± 2% respectively. The solid state of TBN and its compatibility with formulation ingredients were confirmed through XRD and FTIR analysis respectively. TBN-CSNP loaded P407 gel exhibited pseudoplastic rheological behavior having a spreadability of 11 ± 2 g·cm/s. The washability study showed that 40 ± 2% of the gel was eroded after washing 12 times. Drug release from TBN-CSNP- and TBN-CSNP-loaded gel was 84 ± 5% and 57 ± 3%, respectively. The cumulative quantity of TBN permeated from TBN-CSNP-loaded P407 gel and TBN-loaded P407 gel was 25 ± 8 and 27 ± 4 µg/cm2, respectively. The nail uptake study showed that 3.6 ± 0.7 and 2.1 ± 0.3 µg of rhodamine was uptaken by the nail following 2 h topical application of TBN-CSNP loaded P407 gel and TBN loaded P407 gel, respectively. Hence, the developed CSNP-based P407 gel formulation can be a potential carrier for transungual delivery of TBN to topically treat onychomycosis.

Understanding the excretion rates of methylmercury and inorganic mercury from human body via hair and fingernails

Effective biomarkers are necessary to better understand the human mercury (Hg) exposure levels. However, mismatched biomarker sampling method causes extra uncertainty in assessing the risk of Hg exposure. To compare the differences between hair and fingernail, and further understand the excretion rates of methylmercury (MeHg) and inorganic mercury (IHg) via hair and fingernails, the total mercury (THg), MeHg, and IHg concentrations in paired hair and fingernail samples were investigated through paired samples collected from two typical mining areas, Wanshan mercury mine area (WMMA) and Hezhang zinc smelting area (HZSA). The positive correlation in THg, MeHg, and IHg concentrations (p <0.01) between hair and fingernail samples indicated that those two biomarkers can be corrected in application of assessing human Hg exposure. Compared to fingernails, the hair was suggested to be a more sensitive biomarker as the concentration of THg, MeHg and IHg were 2 ∼ 4 times higher than those in fingernails. Furthermore, the amounts of THg, MeHg, and IHg excreted via hair were 70 ∼ 226 times higher than that excreted via fingernails, and the hair plays a more important role than fingernails in the excretion of Hg from human bodies. Present study therefore provides some new insights to better understand the fate of human assimilated Hg.

Comparative Analysis of Type I Keratin Expression By Nail Consistency: An Immunohistochemistry Study

The nail plate is one of the essential structures of the nail apparatus and is highly keratinized, making it difficult to handle this tissue experimentally. Different types of nail consistency were identified by applying distal pressure to the nail plate. To analyze the relationship between the keratins expressed in the nail plate and nail consistency, we chose a sample of 32 adult individuals (age 49.81±3.21 y) with the same number of each sex, who had a similar percentage of nail consistency types (56.25% hard consistency nails and 43.75% soft consistency nails). Immunohistochemical analyses showed that hard consistency nails contain more keratin 17 than soft consistency nails (P=0.026). These novel results allow nail consistency to be defined by the differential expression of keratins in the nail plate, and have potential clinical implications for the diagnosis of possible nail disorders and/or systemic disease.

Investigation of the Dual-Stage Method of Active Er:YLF Laser Drug Delivery Through the Nail and Laser-Induced Transformations of the Drug Extinction Spectrum

BACKGROUND AND OBJECTIVE

A novel dual-stage method for active laser drug delivery (DSLADD) in the treatment of nail diseases is being presented. This method includes sequentially performed microporation of the nail with submillisecond pulses of Er:YLF laser radiation through a layer of an aqueous solution of drug deposited on the nail surface (Stage 1) and exposure this layer to the same laser radiation to deliver drug under the nail plate (Stage 2). The delivery of methylene blue (MB) as one of the possible drugs in the treatment of nail diseases is investigated. The influence of the thickness of the MB layer, as well as the energy and number of applied laser pulses, on the rate of active laser delivery is discussed. To illustrate the possible effect of delivery on the drug delivered, special attention is paid to the deformation of the extinction spectrum of MB solution after laser irradiation.

STUDY DESIGN/MATERIALS AND METHODS

Diode-pumped Er:YLF laser was used for DSLADD. The process of DSLADD under the nail plate was investigated using digital video microscopy. For different values of the thickness of MB solution layer applied to the nail plate and the energy of laser pulses, the number of laser pulses required to create a single through a microchannel in the nail plate and the number of laser pulses required to deliver the solution to the ventral side of the nail plate after its microporation were registered. The mass and the dose of MB solution penetrated under the nail plate, and the rate of MB solution delivery through a single microchannel was determined. Investigation of the influence of Er:YLF laser radiation parameters on the extinction spectrum of the drug was performed using a fiber spectrometer. The extinction spectra of the 0.001% aqueous solution of MB were recorded before and after exposure to a different number of Er:YLF laser pulses with the energy of 1-4 mJ.

RESULTS

It was found that the minimum number of laser pulses required for active Er:YLF laser drug delivery under the nail corresponds to the MB layer thickness of 100 μm and the laser pulse energy of 4 mJ. It is shown that in this case, the rate of active laser delivery of MB solution reaches 0.26 ± 0.03 mg/pulse. The radiation of the Er:YLF laser affects the shape of the extinction spectrum of the aqueous solution of MВ, which is associated with the transition of the dye from the monomeric to dimeric state. Depending on the laser pulse energy, the fraction of a certain conformational state in the aqueous MB solution can decrease or increase, stimulating a possible change in its photodynamic and antiseptic activity.

CONCLUSION

For the first time, a novel DSLADD through the nail has been described and investigated in vitro. It was demonstrated that at Er:YLF laser pulse repetition rate of f = 30 Hz, microporation of the nail plate and drug delivery through a single microchannel will be about 1.5 s. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Iontophoresis to Overcome the Challenge of Nail Permeation: Considerations and Optimizations for Successful Ungual Drug Delivery

Iontophoresis is a widely used drug delivery technique that has been used clinically to improve permeation through the skin for drugs and other actives in topical formulations. It is however not commonly used for the treatment of nail diseases despite its potential to improve transungual nail delivery. Instead, treatments for nail diseases are limited to relatively ineffective topical passive permeation techniques, which often result in relapses of nail diseases due to the thickness and hardness of the nail barrier resulting in lower permeation of the actives. Oral systemic antifungal agents that are also used are often associated with various undesirable side effects resulting in low patient compliance. This review article discusses what is currently known about the field of transungual iontophoresis, providing evidence of its efficacy and practicality in delivering drug to the entire surface of the nail for extended treatment periods. It also includes relevant details about the nail structure, the mechanisms of iontophoresis, and the associated in vitro and in vivo studies which have been used to investigate the optimal characteristics for a transungual iontophoretic drug delivery system. Iontophoresis is undoubtedly a promising option to treat nail diseases, and the use of this technique for clinical use will likely improve patient outcomes.Graphical abstract.

Predictive Model of Nail Consistency Using Scanning Electron Microscopy with Energy-Dispersive X-Ray

Simple Summary

Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) is a useful technique to analyse elemental composition in the nail plate. The dorsal, intermediate, and ventral layers are differentiated by the levels of the elements present in each layer. The level of calcium in the dorsal layer is the main predictive variable in calculating the predictive model of consistency. This model will provide further knowledge of the factors that determine nail consistency in individuals and help health professionals to better understand nail characteristics and objectively determine nail consistency.

Abstract

The nail plate is made up of tightly packed keratin-rich cells. Factors such as the special distribution of the intermediate filaments in each layer (dorsal, intermediate, and ventral), the relative thickness of the layers, and their chemical composition define the characteristics of each nail. The main objective of this study is to determine nail consistency by calculating a predictive model based on elemental composition analysis using scanning electron microscopy. Nail consistency was determined in 57 participants (29 women and 28 men) in two age groups (young people and adults). Elemental composition was analysed in each layer using scanning SEM-EDS, and nail plate thickness was measured by image analysis. A total of 12 elements were detected in nail plates, of which carbon, nitrogen, phosphorus, sulphur, and calcium showed significant differences between layers (p-values ≤ 0.01). The level of calcium in the dorsal layer was the main predictive variable in calculating the predictive model of consistency, with 75.4% correctly classified cases. Elemental analysis in each layer of the nail plate by SEM-EDS can be used to develop a predictive model of nail consistency that will help health professionals to objectively determine nail consistency.

Raman Spectroscopy, X-ray Diffraction, and Scanning Electron Microscopy as Noninvasive Methods for Microstructural Alterations in Psoriatic Nails

Psoriasis is a chronic inflammatory disease associated with immune system dysfunction that can affect nails, with a negative impact on patient life quality. Usually, nail psoriasis is associated with skin psoriasis and is therefore relatively simple to diagnose. However, up to 10% of nail psoriasis occurs isolated and may be difficult to diagnose by means of current methods (nail biopsy, dermoscopy, video dermoscopy, capillaroscopy, ultrasound of the nails, etc.). Since the nail is a complex biological tissue, mainly composes of hard α-keratins, the structural and morphological techniques can be used to analyze the human fingernails. The aim of this study was to corroborate the information obtained using Raman spectroscopy with those obtained by scanning electron microscopy (SEM) and X-ray diffractometry and to assess the potential of these techniques as non-invasive dermatologic diagnostic tools and an alternative to current methods.

Portable X-ray fluorescence of zinc applied to human toenail clippings

Zinc is an essential trace element in humans. Zinc deficiency can result in a range of serious medical conditions which include effects on growth and development, the immune system, the central nervous system, and the gastrointestinal system. Diagnosis of zinc deficiency is often precluded by the lack of a noninvasive and reliable biomarker. Zinc concentration in nail is considered an emerging biomarker of zinc status in humans. Whether zinc in nail accurately reflects zinc status is beyond the scope of the current study, but is an important research question. The development of a portable method to quickly assess zinc concentration from a single nail clipping could be a useful advance. In this study, single toenail clippings from 60 individuals living in Atlantic Canada were measured for zinc using a portable X-ray fluorescence (XRF) technique. These samples were obtained from the Atlantic PATH cohort, part of the largest chronic disease study ever performed in Canada. Each toenail clipping was measured using three 300 s trials with a mono-energetic portable XRF system. Results were then assessed using two different approaches to the XRF analysis: (1) factory-calibrated zinc concentrations were output from each trial, and (2) energy spectra were analyzed for the characteristic X-rays resulting from zinc. Following the measurement of zinc using the non-destructive portable XRF method, the same clippings were measured for zinc concentration using the "gold standard" technique of inductively coupled plasma-mass spectrometry (ICP-MS). A linear equation of best fit was determined for the relationship between average XRF output zinc concentration and ICP-MS zinc concentration, with a correlation coefficient r = 0.60. Similarly, a linear equation of best fit was found for the relationship between a normalized XRF energy spectrum zinc signal and ICP-MS zinc concentration, with a correlation coefficient r = 0.68. Individual ICP-MS zinc concentrations ranged from 32 μg/g to 140 μg/g, with a population average of 85 μg/g. The results of this study indicate that portable XRF is a sensitive method for the measurement of zinc in a single nail clipping, and provides a reasonable estimation of zinc concentration. Further method development is required before portable XRF be considered a routine alternative to ICP-MS for the assessment of zinc in nail clippings.

Formulation of Tioconazole and Melaleuca alternifolia Essential Oil Pickering Emulsions for Onychomycosis Topical Treatment

Onychomycosis is a disease that affects many adults, whose treatment includes both oral and topical therapies with low cure rates. The topical therapy is less effective but causes fewer side effects. This is why the development of an effective, easy to apply formulation for topical treatment is of high importance. We have used a nanotechnological approach to formulate Pickering emulsions (PEs) with well-defined properties to achieve site-specific delivery for antifungal drug combination of tioconazole and Melaleuca alternifolia essential oil. Silica nanoparticles with tailored size and partially hydrophobic surface have been synthesized and used for the stabilization of PEs. In vitro diffusion studies have been performed to evaluate the drug delivery properties of PEs. Ethanolic solution (ES) and conventional emulsions (CE) have been used as reference drug formulations. The examination of the antifungal effect of PEs has been performed on Candida albicans and Trichophyton rubrum as main pathogens. In vitro microbiological experimental results suggest that PEs are better candidates for onychomycosis topical treatment than CE or ES of the examined drugs. The used drugs have shown a significant synergistic effect, and the combination with an effective drug delivery system can result in a promising drug form for the topical treatment of onychomycosis.

Once Weekly Application of Urea 40% and Bifonazole 1% Leads to Earlier Nail Removal in Onychomycosis

Introduction

Onychomycosis is a chronic nail fungal infection resulting in nail damage and a decreased quality of life. Chemical avulsion of the nail with urea and bifonazole -removes fungally infected debris, increasing antifungal treatment efficacy and penetration. Previous clinical ob-servations describe patients who applied their urea and -bifonazole ointment less frequently, achieving earlier nail removal. In this study, we analyzed the relationship between duration of urea and bifonazole application and time to nail avulsion.

Methods

χ² tests, multiple regression analysis, and ANOVA were performed to analyze the similarities between treatment regimens (daily, every 3 days, or once a week), association of regimens or patient characteristics to nail removal, and compare time to nail removal between each regimen, respectively.

Results

Daily application of ointment and sealing resulted in an average length of time (±SD) to nail removal of 18.7 days (±6.8 days); once every 3 days resulted in nail removal at 12.7 days (±6.2 days) and once per week at 11 days (±4.46 days) (p < 0.001). Age was the only patient factor that affected duration to nail removal.

Conclusion

Once weekly application of ointment with sealing for a 1-week duration is associated with a decrease in time to complete chemical avulsion of the nail by approximately 1 week.

Cold sub-atmospheric and atmospheric pressure plasma for the treatment of Trichophyton rubrum onychomycosis: An in-vitro study

Previous studies have suggested the applicability of cold atmospheric pressure plasma for the treatment of onychomycosis. Whether delivering cold plasma in sub-atmospheric pressure would be beneficial for this purpose is yet to be established. The current study aimed to evaluate efficacy of cold sub-atmospheric and atmospheric pressure plasma in Trichophyton rubrum growth inhibition. Bovine nails infected with T. rubrum were treated by a cold air plasma device, which enables utilizing plasma in sub-atmospheric pressures (Low = 100 millibar; High = 300 millibar) or atmospheric pressure. The infected foci were exposed to the plasma source directly or indirectly. Treatment with high sub-atmospheric pressure setting achieved T. rubrum growth reduction of 94.0% and 73.0%, for direct and indirect exposure to the plasma source, respectively (P < .001). Low sub-atmospheric pressure setting achieved similar T. rubrum growth reduction of 86.2% for direct exposure to the plasma source (P < .001), but only marginally significant 58.8% reduction rate for indirect exposure to the plasma source (P = .056). None statistically significant fungal growth reduction was attained with the use of atmospheric pressure setting. Cold plasma was shown to effectively inhibit T. rubrum nail growth, with sub-atmospheric pressure setting achieving better outcome than atmospheric pressure.

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.

Emerging Optical Techniques for the Diagnosis of Onychomycosis

Onychomycosis is the most prevalent nail infection. Although it is not a life-threatening condition, it impacts the quality of life for many patients and often imposes a challenging diagnostic problem. The causative agents are dermatophytes, yeasts and non-dermatophytic moulds. Accurate and early diagnosis, including the identification of the causative species, is the key factor for rational therapy. Still, early diagnosis is not optimal as the current gold standard for the differentiation of the infectious agents is culture-based approaches. On the other hand, noninvasive optical technologies may enable differential diagnosis of nail pathologies including onychomycosis. When light penetrates and propagates along the nail tissue, it interacts in different ways with the components of either infected or healthy nail segments, providing a wealth of diagnostic information upon escaping the tissue. This review aims to assess alternative optical techniques for the rapid diagnosis of onychomycosis with a potential to monitor therapeutic response or even identify the fungal agent non-invasively and in real time in a clinical setting.

EEMCO Guidance for the in vivo Assessment of Biomechanical Properties of the Human Skin and Its Annexes: Revisiting Instrumentation and Test Modes

Biomechanics of the skin is an important subject in skin research. It has been studied for many decades involving various technologies and methods to characterize and quantify mechanical properties of the skin under different in vivo conditions. The present EEMCO paper reviews the current rel-evant information, providing practical orientation to researchers dedicated to in vivo assessment of biomechanics of skin and its annexes. We discuss the available non-invasive instruments, including their principles and variables. A correspondence between the descriptors nomenclature proposed by Agache and the designation for the suction-based standard instruments is proposed. The addressed properties include skin softness/stiffness, firmness, elasticity, elastic and viscoelastic properties, extensibility, resilience, anisotropy, acoustical shock wave hardness, friction (in relation to topographic properties), thickness, fiber/stress mechanics (bending, cyclic, tensile, fatigue, or torsion), and hardness. We provide the relation of these properties to biomechanical descriptors and in some cases to SI units. Practical guidance for the proper use of these instruments, limitations, and possible interpretations are provided, while discussing the meaning of descriptive or "phenomenological" variables. For studies intended to quantify the effect of an intervention with regard to mechanical properties, we recommend a minimum of 30-40 participants, based on normal distribution of the data sets. Some important limitations are recognized, including the lack of standardization of procedures and calibration of instruments, which compromises the relevance and real nature of the descriptors/parameters obtained with these devices. The present work highlights an approach to a better practice and a science-supported biomechanical assessment of human skin, hair, and nails.

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.

Assessing zinc from a nail clipping using mono-energetic portable X-ray fluorescence

A mono-energetic X-ray beam from a portable X-ray fluorescence device was used to excite characteristic X-rays from zinc in a series of nail clipping phantoms. Twenty nail clipping phantoms having equal zinc concentrations of ~40 µg/g, but with different physical characteristics, were measured individually for 300 s using a small diameter (~1 mm) X-ray beam. Energy spectra obtained from the measurements were analyzed using PyMca software. Zinc signal size varied widely between the different clippings, with a relative standard deviation of 41% observed in the combined signal from zinc Kα and Kβ characteristic X-rays. Three different normalization approaches were introduced to account for variation in the amounts of sample interrogated by the X-ray beam. All three approaches produced similar results, and successfully reduced the relative standard deviation to between 12% and 13%. A clear trend was still observed, however, between the normalized zinc signal and the thickness of clipping measured. To account for this effect, normalized signals were adjusted to calculate "thickness-corrected" values. The relative standard deviation of these thickness-corrected values was 6.2%. Reproducibility of measurement from individual clippings was excellent, with relative standard deviations on the order of 1%, with or without normalization. Overall, this new method of measuring zinc in nail shows promise for the assessment of zinc status in humans using a portable device. The method is sensitive, rapid, and requires only a single nail clipping.

Terbinafine hydrochloride nail lacquer for the management of onychomycosis: formulation, characterization and in vitro evaluation

AIM

The present investigation's intention was to develop an optimized nail lacquer (NL) for the management of onychomycosis.

MATERIALS & METHODS

The NL was optimized statistically adopting 3² full factorial design having different polymer ratios and solvent ratios. The formulations were assessed for drug permeation drying time and peak adhesive strength of the film. Characterization was done using techniques including attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), x-ray diffraction (XRD), etc.

RESULTS & CONCLUSION

The formulation that had 1:1 polymer ratio and 80:20 solvent ratio was chosen as the optimized formulation. In vitro permeation studies showed better penetration (∼3.25-fold) as well as retention (∼11-fold) of the optimized NL formulation in the animal hoof as compared with the commercial formulation. The findings of in vitro and ex vivo studies elucidated the potential of the optimized formulation. [Formula: see text].

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.

Microstructural alterations in the onychomycotic and psoriatic nail: Relevance in drug delivery

Despite the important nail alterations caused by onychomycosis and psoriasis few studies have characterized the microstructure of the diseased nail plate and the diffusion and penetration of drugs through this altered structure. This work aimed to characterize the microstructure of the healthy, onychomycotic and psoriatic human nail using Raman spectroscopy, scanning electron microscopy, optical microscope profilometry and mercury intrusion porosimetry followed by analysis of the structure with PoreCor® software. The results showed that onychomycotic nails have higher porosity and lower amounts of disulphide bonds compared to healthy nails. This suggests that the presence and action of fungi on the nail plate makes this structure more permeable to water and drugs. Psoriatic nails had increased porosity compared to healthy nails but lower than fungal infected specimens. In vitro permeation studies showed that diseased nails were more permeable to ciclopirox (onychomycosis) and clobetasol (psoriasis) although drug permeation was highly variable and likely to be influenced by the degree of alteration of the nail structure. On the whole, this work provides new and valuable information about the microstructure and porosity of diseased nails and a plausible explanation of the increased drug permeability observed in this work and elsewhere.

Estimating uptake of phthalate ester metabolites into the human nail plate using pharmacokinetic modelling

There is a lack of knowledge regarding uptake of phthalate esters (PEs) and other chemicals into the human nail plate and thus, clarity concerning the suitability of human nails as a valid alternative matrix for monitoring long-term exposure. In particular, the relative importance of internal uptake of phthalate metabolites (from e.g. blood) compared to external uptake pathways is unknown. This study provides first insights into the partitioning of phthalate-metabolites between blood and nail using pharmacokinetic (PK) modelling and biomonitoring data from a Norwegian cohort. A previously published PK model (Lorber PK model) was used in combination with measured urine data to predict serum concentrations of DEHP and DnBP/DiBP metabolites at steady state. Then, partitioning between blood and nail was assessed assuming equilibrium conditions and treating the nail plate as a tissue, assuming a fixed lipid and water content. Although calculated as a worst-case scenario at equilibrium, the predicted nail concentrations of metabolites were lower than the biomonitoring data by factors of 44 to 1300 depending on the metabolite. It is therefore concluded that internal uptake of phthalate metabolites from blood into nail is a negligible pathway and does not explain the observed nail concentrations. Instead, external uptake pathways are more likely to dominate, possibly through deposition of phthalates onto the skin/nail and subsequent metabolism. Modelling gaseous diffusive uptake of PEs from air to nail revealed that this pathway is unlikely to be important. Experimental quantification of internal and external uptake pathways of phthalates and their metabolites into the human nail plate is needed to verify these modelling results. However, based on this model, human nails are not a good indicator of internal human exposure for the phthalate esters studied.

Changes in nail keratin observed by Raman spectroscopy after Nd:YAG laser treatment

Lasers and photodynamic therapy have been considered a convergence treatment for onychomycosis, which is a fungal infection on the nail bed and nail plate. Laser therapies have shown satisfactory results without significant complications for onychomycosis; however, the mechanism of clearing remains unknown. In this work, we investigated changes in the chemical structure of nail keratin induced by Nd:YAG laser using Raman spectroscopy. Toe nails with onychomycosis were treated with 1064 nm Nd:YAG laser. After laser treatment, the disulfide band (490-590 cm^-1 ) of nail keratin was rarely observed or was reduced in intensity. The amide I band (1500-1700 cm^-1 ) also showed changes induced by the laser. The α-helical (1652 cm^-1 ) structures dominated the β-sheet (1673 cm^-1 ) in nontreated nail, but the opposite phenomenon was observed after laser treatment.

An investigation of how fungal infection influences drug penetration through onychomycosis patient's nail plates

The treatment of onychomycosis remains problematic even though there are several potent antifungal agents available for patient use. The aim of this investigation was to understand whether the structural modifications that arise when a patient’s nail become infected plates influences the permeation of drugs into the nail following topical application. It was hoped that through improving understanding of the nail barrier in the diseased state, the development of more effective topical treatments for onychomycosis could be facilitated. The permeation of three compounds with differing hydrophobicities, caffeine, terbinafine and amorolfine (clog D at pH 7.4 of −0.55, 3.72 and 4.49 respectively), was assessed across both healthy and onychomycosis infected, full thickness, human nail plate sections. Transonychial water loss (TOWL) measurements performed on the healthy and diseased nails supported previous observations that the nail behaves like a porous barrier given the lack of correlation between TOWL values with the thicker, diseased nails. The flux of the more hydrophilic caffeine was twofold greater across diseased in comparison with the healthy nails, whilst the hydrophobic molecules terbinafine and amorolfine showed no statistically significant change in their nail penetration rates. Caffeine flux across the nail was found to correlate with the TOWL measurements, though no correlation existed for the more hydrophobic drugs. These data supported the notion that the nail pores, opened up by the infection, facilitated the passage of hydrophilic molecules, whilst the keratin binding of hydrophobic molecules meant that their transport through the nail plate was unchanged. Therefore, in order to exploit the structural changes induced by nail fungal infection it would be beneficial to develop a small molecular weight, hydrophilic antifungal agent, which exhibits low levels of keratin binding.

Efinaconazole Topical Solution, 10%: Factors Contributing to Onychomycosis Success

To provide an adequate therapeutic effect against onychomycosis, it has been suggested that topical drugs should have two properties: drug permeability through the nail plate and into the nail bed, and retention of their antifungal activity in the disease-affected areas. Only recently has the importance of other delivery routes (such as subungual) been discussed. Efinaconazole has been shown to have a more potent antifungal activity in vitro than the most commonly used onychomycosis treatments. The low keratin affinity of efinaconazole contributes to its effective delivery through the nail plate and retention of its antifungal activity. Its unique low surface tension formulation provides good wetting properties affording drug delivery both through and under the nail. High antifungal drug concentrations have been demonstrated in the nail of onychomycosis patients, and effectiveness of efinaconazole topical solution, 10% confirmed in two large well-controlled multicenter Phase 3 clinical studies in patients with mild-to-moderate disease.