Lateral drug diffusion in human nails

Halogenated class of oximes as a new class of monoamine oxidase-B inhibitors for the treatment of Parkinson's disease: Synthesis, biochemistry, and molecular dynamics study

Oximes are the promising structural scaffold for inhibiting monoamine oxidase (MAO)-B. Eight chalcone-based oxime derivatives were synthesized by microwave-assisted technique, and their ability to inhibit human MAO (hMAO) enzymes were tested. All compounds showed higher inhibitory activity of hMAO-B than hMAO-A. In the CHBO subseries, CHBO4 most potently inhibited hMAO-B with an IC₅₀ value of 0.031 μM, followed by CHBO3 (IC₅₀ = 0.075 μM). In the CHFO subseries, CHFO4 showed the highest inhibition of hMAO-B with an IC₅₀ value of 0.147 μM. Compound CHBO4 had the highest selectivity index (SI) value of 1290.3. However, CHBO3 and CHFO4 showed relatively low SI values of 27.7 and 19.2, respectively. The -Br substituent in the CHBO subseries at the para-position in the B-ring showed higher hMAO-B inhibition than the -F substituent in the CHFO subseries. In both series, hMAO-B inhibition increased with the substituents at para-position in A-ring (-F > -Br > -Cl > -H in order). Compound CHBO4 (-F in A-ring and -Br in B-ring) was 12.6-times potent than the substituents-reversed compound CHFO3 (-Br in A-ring and -F in B-ring; IC₅₀ = 0.391 μM). In the kinetic study, K_i values of CHBO4 and CHFO4 for hMAO-B were 0.010 ± 0.005 and 0.040 ± 0.007 μM, respectively, with competitive inhibitions. Reversibility experiments showed that CHBO4 and CHFO4 were reversible hMAO-B inhibitors. In the cytotoxicity test using the Vero cells by the MTT technique, CHBO4 had low toxicity with an IC₅₀ value of 128.8 µg/mL. In H₂O₂-induced cells, CHBO4 significantly reduced cell damage by scavenging reactive oxygen species (ROS). Molecular docking and dynamics showed the stable binding mode of the lead molecule CHBO4 on the active site of hMAO-B. These results suggest that CHBO4 is a potent reversible, competitive, and selective hMAO-B inhibitor and can be used as a treatment agent for neurological disorders.

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.

In Silico Drug Screening Based Development of Novel Formulations for Onychomycosis Management

Onychomycosis is a prominent fungal infection that causes discoloration, thickening, and mutilation leading to the separation of the nail from the nail bed. Treatment modalities for onychomycosis may include oral, topical, or combination therapy with antifungals and at times may require chemical or surgical intervention. The burden of side effects of antifungals is enormous, and therefore using molecular docking-based drug selection in context with the target keratin protein would ensure better disease management. Ciclopirox, Amorolfine HCl, Efinaconazole, Tioconazole, and Tavaborole were submitted for assessment, revealing that Amorolfine HCl is the best fit. Consequently, two formulations (Nail lacquer and nanoemulgel) were developed from Amorolfine HCl to validate the in silico screening outcomes. The formulations were further fortified with over-the-counter ingredients vis-a-vis with vitamin E in nail lacquer and undecylenic acid in nanoemulgel for their prominent roles in improving nail health. Both the formulations were systematically designed, optimized, and characterized. Amorolfine HCl containing nanoemulgel (NEG) was developed using undecylenic acid as an oil phase and thioglycolic acid as a penetration enhancer. The quality parameters evaluated were particle size, the zeta potential for nanoemulsion (NE) (78.04 ± 4.724 nm and −0.7mV, respectively), in vitro cumulative drug release (96.74% for NE and 88.54% for NEG), and transungual permeation (about 73.49% for NEG and 54.81% for NE). Nail lacquer was evaluated for the drying time, non-volatile content, and blush test. In vitro cumulative drug release of the developed nail lacquer and comparator marketed formulations were around 81.5% and 75%, respectively. Similarly, the transungual drug permeation was 6.32 μg/cm² and 5.89 μg/cm², respectively, in 24 h. The in silico guided preparation of both formulations containing Amorolfine HCl and over the counter ingredients is amenable for therapeutic use against onychomycosis and will be evaluated in the in vivo model.

Nail Melatonin Content: A Suitable Non-Invasive Marker of Melatonin Production

Melatonin plays multiple physiological roles in the human body. Evaluation of melatonin production by the determination of urinary 6-sulfatoxymelatonin in 24-h samples has important drawbacks which hinder the successful evaluation of melatonin production in large cohorts. Here, we evaluated the potential of nail analysis for estimating melatonin production. Firstly, mass spectrometry methodology for the determination of melatonin in nails was optimized and successfully validated. The method was found to be linear in the range 6.5-830 fg/mg with intraday and interday accuracy in the range 100-104 %, precision below 15 % and a LOD of 3.5 fg/mg. Secondly, nail melatonin concentrations from 84 volunteers (age 5-96) were determined. The expected correlation between melatonin and age was obtained (correlation coefficient -0.615; p < 0.001). Additionally, we showed that fingernails are preferable to toenails to determine nail melatonin content. Finally, fingernails collected for 180 days after melatonin administration (two volunteers, 1.9 mg/night during 5 days) were analyzed. Nail melatonin concentrations immediately rose after administration and went back to pre-administration values after ≈100 days in both volunteers. Our results suggest that melatonin determination in nails is a suitable non-invasive tool for the estimation of global melatonin production. Due to the easy collection and storage of nails, the long-term information obtained and the multiple functions of melatonin, nail melatonin content might complement dim light melatonin onset, which is commonly measured from plasma/saliva samples, paving the way for melatonin research.

Transungual Delivery, Anti-Inflammatory Activity, and In Vivo Assessment of a Cyclodextrin Polypseudorotaxanes Nail Lacquer

A new cyclodextrin polypseudorotaxanes nail lacquer (Regenail^®) containing biotin, methyl sulphonyl methane (MSM), and dimethylsilanediol salicylate was developed and evaluated in vitro and in vivo. The product was developed to improve nail status and diminish signs of pathological nail alterations. A reference product (Betalfatrus^®) was used for comparative purposes. An in vitro permeation experiment in hooves showed high MSM and biotin absorption. The content of sulfur and silicon in hooves was also found to be higher compared with the reference product. MSM was tested in human keratinocytes, exhibiting a good cytotoxicity profile and anti-inflammatory activity by the reduction in IL-8 and TNF-α under LPS stimuli. A clinical study was performed to check product safety and efficacy against nail brittleness and alterations such as Beau's lines and onychorrhexis. A reduction in both alterations and in surface roughness without alteration of nail structure was observed, with a good level of patient acceptance and satisfaction.

Calcium and Silicon Delivery to Artificial and Human Nails from Nail Polish Formulations

A deteriorating nail standard is a growing problem as the global prevalence of diabetes is increasing. Systemic treatment with mineral supplements may not be recommended, mainly due to the high doses required to deliver optimal therapeutic concentrations. In this work, we evaluate nail polish formulations for the local delivery of strengthening elements to the nail plate. Specifically, we assess calcium and silicon release from nail polish base coat formulations containing three different concentrations of White Portland Cement to water, as well as to artificial and human nails. The delivery of calcium and silicon to the dorsal nail plate was determined by inductively coupled plasma optical emission spectrometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. To the best of our knowledge, this is the first study showing that such dual elemental delivery to human nails can be achieved from nail polish formulations. Hence, this work may form the basis for new inventions where therapeutic functionalities can be integrated with the mechanical and cosmetic properties of a base coat nail polish. Future permeability studies are required to verify long-term effects on the nail standard, induced by the formulations under study.

Optimization of Drug Permeation from 8% Ciclopirox Cyclodextrin/Poloxamer-Soluble Polypseudorotaxane-Based Nail Lacquers

Cyclodextrin/poloxamer-soluble polypseudorotaxane-based nail lacquers have demonstrated significant capacity for promoting the permeation of drugs into the nail plate. Furthermore, previous studies have shown that the use of hydroalcoholic blends as vehicles promotes drug permeation. The work described herein studies the effect of the type of alcohol used in the lacquer preparation, and the composition of the vehicle is optimized to obtain soluble doses of 8% and to promote the diffusion of ciclopirox base and olamine across the nail. Permeation studies on different types of alcohols show that optimum results are achieved with short-chain alcohols, and that results become less satisfactory the higher the number of alcohol carbons. In addition, solubility and penetration studies on the bovine hoof have enabled the composition of the lacquer to be optimized for both forms of ciclopirox. The results suggest that optimized lacquers have better ciclopirox diffusion and penetration properties than the commercial reference lacquer. Lastly, in vivo studies in which optimized ciclopirox olamine lacquer was applied for 45 days to the nails of healthy volunteers showed that it caused no negative effects or changes to the nail surface. These results demonstrate the significant potential of cyclodextrin/poloxamer-soluble polypseudorotaxane-based nail lacquers for the ungual administration of drugs.

Iontophoresis for drug delivery into the nail apparatus: exploring hyponychium as the site of delivery

In present studies, a hyponychium pathway (from ventral side of the nail plate) was investigated as a potential route of drug delivery into the nail apparatus using iontophoresis as an active physical method. In vitro transport studies were performed across the human nail plate using sodium fluorescein as a marker substrate for 24 h. After transport studies, the amount of sodium fluorescein extracted from an active diffusion area of the nail plate in case of iontophoresis was found to be ∼54-folds more to that of passive. The amount of sodium fluorescein retained in the peripheral area of the nail plate after application of iontophoresis was found to be ∼30-folds more relative to passive. Ex vivo transport studies were performed on excised human cadaver toe using terbinafine hydrochloride as a model drug for three days (8 h/day). The amount of terbinafine retained in the nail plate after application of iontophoresis (3.43 ± 1.34 µg/mg) was ∼20-folds more when compared with passive (0.17 ± 0.10 µg/mg). The amount of drug extracted from the nail bed and nail matrix was 1.73 ± 0.12 µg/mg and 0.55 ± 0.22 µg/mg, respectively. On the other hand, there was no detectable amount of terbinafine found in the nail bed and nail matrix in case of control (passive delivery). These studies show that the iontophoretic drug delivery through hyponychium region to other parts of the nail apparatus could be a potential way of onychomycosis treatment.

Diffusion of uncharged solutes through human nail plate

Passive diffusion data for uncharged solutes in hydrated human nail plate are collected and compared to the predictions of two theories for diffusion of uncharged solutes in dense keratin matrices. Quantitative agreement between the experimental data and the theories examined is poor. Concerns with both the experiments and the theories are identified and discussed. It is evident from the analysis that magnitude of the experimental nail permeability data may be questioned, as may the extrapolation procedures used to estimate the properties of dense fiber arrays from more dilute systems. Despite these caveats, it can be inferred that the microstructure of the nail plate is more complex than that assumed in the described models. The influence of residual lipids is implicated. More rigorous experiments and theoretical analysis of mass transport in the nail plate system are warranted. Successful completion of these tasks could lead not only to better predictions of transungual drug delivery, but also to better models of skin permeability, if hydrated nail plate can indeed serve as a model for the corneocyte phase of (partially hydrated) stratum corneum.