Visualization studies of human skin in vitro/in vivo under the influence of an electrical field

Development of a Novel Simple Gel Formulation Containing an Ion-Pair Complex of Diclofenac and Phenylephrine

BACKGROUND AND AIM

Since the pharmacological effects of diclofenac (DF) are short-lived because of its short half-life, prolongation of the pharmacological effect in a topical formulation is needed for more appropriate clinical use. For the enhancement of dermal accumulation and prolongation of the pharmacological effect of drugs, the aim of this study was to develop a simple gel formulation containing an ion-pair complex of DF and phenylephrine (PHE), which induce constriction of the vascular smooth muscles.

MATERIALS AND METHODS

The ion-pair complex was prepared by mixing sodium DF and an ethanolic solution of PHE. The formed complex was characterized by powder X-ray diffraction (PXRD) and Fourier-transform infrared (FT-IR) spectroscopy. The ion-pair complex for the gel formulation was prepared by mixing an equimolar concentration of 50% 1,3-butylene glycol and distilled aqueous solution of 2% xanthan gum, which was characterized by proton nuclear magnetic resonance (1H-NMR). Skin permeation and accumulation of DF and PHE were evaluated by in vitro and in vivo studies.

RESULTS

From the results of PXRD and FT-IR, it was suggested that new crystalline peaks formed by the ion-pair complex and their complex interacted with the carboxyl group in DF and the amino group in PHE. In the gel formulation, the ion-pair complexes were detected by 1H-NMR. The ion-pair complex enhanced the accumulation of DF in the skin in the in vitro study. On the other hand, PHE accumulation in the dermis increased with the ion-pair complex, as exhibited by the in vivo study.

CONCLUSION

A new gel formulation containing the ion-pair complex of DF and PHE was developed, which improved the accumulation of DF in skin.

Review of Stratum Corneum Impedance Measurement in Non-Invasive Penetration Application

Due to advances in telemedicine, mobile medical care, wearable health monitoring, and electronic skin, great efforts have been directed to non-invasive monitoring and treatment of disease. These processes generally involve disease detection from interstitial fluid (ISF) instead of blood, and transdermal drug delivery. However, the quantitative extraction of ISF and the level of drug absorption are greatly affected by the individual's skin permeability, which is closely related to the properties of the stratum corneum (SC). Therefore, measurement of SC impedance has been proposed as an appropriate way for assessing individual skin differences. In order to figure out the current status and research direction of human SC impedance detection, investigations regarding skin impedance measurement have been reviewed in this paper. Future directions are concluded after a review of impedance models, electrodes, measurement methods and systems, and their applications in treatment. It is believed that a well-matched skin impedance model and measurement method will be established for clinical and point-of care applications in the near future.

Controlled delivery of ropinirole hydrochloride through skin using modulated iontophoresis and microneedles

The objective of this study was to investigate the effect of modulated current application using iontophoresis- and microneedle-mediated delivery on transdermal permeation of ropinirole hydrochloride. AdminPatch® microneedles and microchannels formed by them were characterized by scanning electron microscopy, dye staining and confocal microscopy. In vitro permeation studies were carried out using Franz diffusion cells, and skin extraction was used to quantify drug in underlying skin. Effect of microneedle pore density and ions in donor formulation was studied. Active enhancement techniques, continuous iontophoresis (74.13 ± 2.20 µg/cm(2)) and microneedles (66.97 ± 10.39 µg/cm(2)), significantly increased the permeation of drug with respect to passive delivery (8.25 ± 2.41 µg/cm(2)). Modulated iontophoresis could control the amount of drug delivered at a given time point with the highest flux being 5.12 ± 1.70 µg/cm(2)/h (5-7 h) and 5.99 ± 0.81 µg/cm(2)/h (20-22 h). Combination of modulated iontophoresis and microneedles (46.50 ± 6.46 µg/cm(2)) showed significantly higher delivery of ropinirole hydrochloride compared to modulated iontophoresis alone (84.91 ± 9.21 µg/cm(2)). Modulated iontophoresis can help in maintaining precise control over ropinirole hydrochloride delivery for dose titration in Parkinson's disease therapy and deliver therapeutic amounts over a suitable patch area and time.

Effect of iontophoresis on in vitro transdermal absorption of almotriptan

The aim of the present work was to characterize the in vitro transdermal absorption of almotriptan through pig ear skin. The passive diffusion of almotriptan malate and its iontophoretic transport were investigated using current densities of 0.25 and 0.50mA/cm(2). In vitro iontophoresis experiments were conducted on diffusion cells with an agar bridge without background electrolytes in the donor compartment. Although both current densities applied produced a statistically significant increment with respect to passive permeation of almotriptan (p<0.01), that of 0.50mA/cm(2) proved to be the best experimental condition for increasing the transport of almotriptan across the skin. Under these experimental conditions, the transdermal flux of the drug increased 411-fold with respect to passive diffusion, reaching 264±24μg/cm(2)h (mean±SD). Based on these results, and taking into account the pharmacokinetics of almotriptan, therapeutic drug plasma levels for the management of migraine could be achieved via transdermal iontophoresis using a reasonably sized (around 7.2cm(2)) patch.

A new method for non-invasive measurement of skin in the low frequency range

OBJECTIVES

The purpose of our study was to estimate skin structure and conductivity distribution in a cross section of local tissue using non-invasive measurement of impedance data. The present study was designed to evaluate the efficiency of skin depth information through computer simulations. The multilayer tissue model was composed of epidermis, dermis tissues, and subcutaneous.

METHODS

In this study, electrical characteristics of skin models were used for conductivity of 0.13 S/m, 0.26 S/m, 0.52 S/m, permittivity of 94,000 F/m, and a frequency of 200 Hz. The effect of the new method was assessed by computer simulations using three-electrode methods. A non-invasive electrical impedance method has been developed for analysis using computer simulation and a skin electrical model with low frequency range. Using the three-electrode method differences through the potentials between measurement electrodes and reference electrodes can be easily detected. The Cole electrical impedance model, which is better suited for skin was used in this study.

RESULTS

In this study, experiments using three-electrode methods were described by computer simulation based on a simple model. This electrical impedance model was fitted and developed in comparison with our model for measurement of skin impedance.

CONCLUSIONS

The proposed electrical model for skin is suitable for use in interpretation of changes in impedance characterization of the skin. Using the computer simulation method, information on skin impedance depth can be more accurately developed and predicted.

In vitro cutaneous application of ISCOMs on human skin enhances delivery of hydrophobic model compounds through the stratum corneum

This study aimed to investigate the effect of a novel kind of immune-stimulating complexes (ISCOMs) on human skin penetration of model compounds in vitro to evaluate their potential as a delivery system, ultimately for transcutaneous vaccination. Special focus was on elucidating the mechanisms of penetration. Preparation of ISCOMs was done by dialysis and subsequent purification in a sucrose density gradient. The penetration pathways of acridine-labeled ISCOMs were visualized using confocal laser scanning microscopy (CLSM). Transmission electron microscopy (TEM) was used to evaluate the ultrastructural changes in the skin after application of the ISCOMs with or without hydration. Transcutaneous permeation of the model compound, methyl nicotinate, was evaluated in diffusion cells. The prepared ISCOMs were 42-52 nm in diameter as evaluated by dynamic light scattering with zeta potentials of -33 to -26.1 mV. TEM investigations verified the presence of ISCOM structures. Penetration of acridine into skin was greatly increased by incorporation into ISCOMs as visualized by CLSM. Permeation of methyl nicotinate was enhanced in the presence of ISCOMs. Ultrastructural changes of the intercellular space in the stratum corneum after exposure of ISCOMs were observed on micrographs, especially for hydrated skin. In conclusion, cutaneous application of ISCOMs leads to increased penetration of hydrophobic model compounds through human stratum corneum and thus shows potential as a transcutaneous delivery system. The increased penetration seems to be reflected by a change in the intercellular space between the corneocytes, and the effect is most likely caused by the components of the ISCOMs rather than intact ISCOMs.

Permeability of model stratum corneum lipid membrane measured using quartz crystal microbalance

The stratum corneum (SC) is the outermost layer of the epidermis. Stacked intercellular lipid membranes found in the SC play a crucial role in regulating water transport through the skin. Despite the importance of this role of the SC lipid membranes, only a few studies have presented quantitative methods to measure the permeability of water in SC lipid membranes. In this work, we present a new method to determine the water permeability of a model SC lipid membrane using a quartz crystal microbalance (QCM). We investigate a model SC lipid membrane comprising an equimolar mixture of brain ceramide (CER), cholesterol (CHO), and palmitic acid (PA), and use QCM to determine the diffusivity (D), solubility (S,) and permeability (P) of water vapor in the model SC lipid membrane.