Effect of Application Amounts on In Vitro Dermal Absorption Test Using Caffeine and Testosterone

Highly Biocompatible Lamellar Liquid Crystals Based on Hempseed or Flaxseed Oil with Incorporated Betamethasone Dipropionate: A Bioinspired Multi-Target Dermal Drug Delivery System for Atopic Dermatitis Treatment

Purpose

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease that severely impairs patient's life quality and represents significant therapeutic challenge due to its pathophysiology arising from skin barrier dysfunction. Topical corticosteroids, the mainstay treatment for mild to moderate AD, are usually formulated into conventional dosage forms that are impeded by low drug permeation, resulting in high doses with consequent adverse effects, and also lack properties that would strengthen the skin barrier. Herein, we aimed to develop biomimetic lamellar lyotropic liquid crystals (LLCs), offering a novel alternative to conventional AD treatment.

Methods

In screening studies, pseudoternary phase diagrams alongside polarized light microscopy (PLM) and viscosity measurements were utilized. Next, the selected LCCs underwent comprehensive characterization via PLM, small-angle X-ray scattering, differential scanning calorimetry, and rheological analysis. Lastly, their performance was evaluated and compared with the commercially available reference medicine in chemical stability study, in vitro permeation testing, in vitro safety assessment using cell proliferation assay, inverted light microscopy, and Raman mapping of keratinocytes, besides gap closure assay performed by live-cell imaging.

Results

Formulation (L/T)Ho30, containing the highest amount of lecithin/Tween 80 mixture (21%) and hempseed oil (28%), demonstrated lamellar microstructure with high skin hydration potential and favourable rheological features for skin administration. Moreover, in comparison with the reference medicine, it stood out by providing suitable chemical BD (betamethasone dipropionate) stability, improved 3-fold BD permeation, and excellent biocompatibility with over 85% cell proliferation at all tested concentrations, ensuring keratinocytes' integrity, as well as promoting skin healing with gap closure observed after 36 hours.

Conclusion

Unique multi-target drug delivery strategy depicted in newly developed bioinspired lamellar LCCs structurally resembling stratum corneum intercellular lipids, with incorporated BD drug, and composed of multifunctional components that synergistically strengthen skin barrier, was presented here and shows a promising approach for improved AD treatment.

Analytical Method Development and Dermal Absorption of 4-Amino-3-Nitrophenol (4A3NP), a Hair Dye Ingredient under the Oxidative or Non-Oxidative Condition

The chemical 4-amino-3-nitrophenol (4A3NP) is classified as an amino nitrophenol and is primarily utilized as an ingredient in hair dye colorants. In Korea and Europe, it is exclusively used in non-oxidative or oxidative hair dye formulations, with maximum allowable concentrations of 1% and 1.5%, respectively. Despite this widespread use, risk assessment of 4A3NP has not been completed due to the lack of proper dermal absorption data. Therefore, in this study, both the analytical method validation and in vitro dermal absorption study of 4A3NP were conducted following the guidelines provided by the Korea Ministry of Food and Drug Safety (MFDS). Before proceeding with the dermal absorption study, analytical methods were developed for the quantitation of 4A3NP through multiple reaction monitoring (MRM) via liquid chromatography-mass spectrometry (LC-MS) in various matrices, including swab wash (WASH), stratum corneum (SC), skin (SKIN, comprising the dermis and epidermis), and receptor fluid (RF). These developed methods demonstrated excellent linearity (R2 = 0.9962-0.9993), accuracy (93.5-111.73%), and precision (1.7-14.46%) in accordance with the validation guidelines.The dermal absorption of 4A3NP was determined using Franz diffusion cells with mini-pig skin as the barrier. Under both non-oxidative and oxidative (6% hydrogen peroxide (H2O2): water, 1:1) hair dye conditions, 1% and 1.5% concentrations of 4A3NP were applied to the skin at a rate of 10 μL/cm2, respectively. The total dermal absorption rates of 4A3NP under non-oxidative (1%) and oxidative (1.5%) conditions were determined to be 5.62 ± 2.19% (5.62 ± 2.19 μg/cm2) and 2.83 ± 1.48% (4.24 ± 2.21 μg/cm2), respectively.

Analytical method development and dermal absorption of 2-amino-5-nitrophenol (2A5NP), a hair dye ingredient under oxidative condition

Although 2-amino-5-nitrophenol (2A5NP) is one of the ingredients of hair dye, there has been no information on the dermal absorption rate of 2A5NP. 2A5NP is managed at less than 1.5% in Korea and Japan. In this study, analytical methods were developed and validated using high-performance liquid chromatography (HPLC) in various matrices of wash, swab, stratum corneum (SC), skin (dermis + epidermis), and receptor fluid (RF). Validation results were acceptable based on Korea Ministry of Food and Drug Safety (MFDS) guideline. The HPLC analysis showed a good linearity (r2 = 0.9992-0.9999), a high accuracy (93.1-110.2%), and a good precision (1.1-8.1%) in accordance with the validation guideline. Franz diffusion cell was used to determine dermal absorption of 2A5NP using mini pig skin. 2A5NP (1.5%) was applied to skin at 10 μl/cm2. For certain cosmetic ingredients such as hair dye with short exposure time, an interim wash step (after 30 min) was added during the study. After application for 30 min and 24 h, skin was wiped off with swab and SC was collected using tape stripping. RF was sampled at 0, 1, 2, 4, 8, 12, and 24 h. Total dermal absorption rate of 2A5NP (1.5%) was determined to be 13.6 ± 2.9%.

A Comparative Analysis of Biological and Synthetic Skin Models for Drug Transport Studies

Ethical restrictions as well as practical or economic issues related to use of animal and human skin has been the main reason the growth in the number of investigations with alternative models. Reconstructed skin models, for example, have been useful to evaluate the in vitro toxicity of compounds; however, these models usually overestimate the amount of drug permeated due to impaired barrier properties. In this review, the performance of synthetic and biological skin models in transport studies was compared by considering two compounds with different physicochemical properties. The advantages and limitations of each skin model are discussed in detail. Although synthetic and reconstructed skin models have shown to be useful in the formulation optimization step, they present many limitations: (1) impaired barrier properties; (2) lack of follicular transport; (3) no metabolism in synthetic membranes; (4) differences in terms of lipid organization; (5) more affected by formulation constituents. Therefore, animal and human tissues should still be prioritized in drug transport studies until new advances in alternative models are achieved. Investigations of the impact of cell-culture conditions on skin formation, in turn, bring perspectives related to the development of unhealthy/injured skin models (an aspect that still deserves attention).

Negligible Toxicokinetic Differences of Glyphosate by Different Vehicles in Rats

Glyphosate is a non-selective herbicide. Although glyphosate is not acutely toxic, the intake of glyphosate-based herbicides has caused many accidents. Some studies have suggested that surfactants might be the cause. The purpose of this study was to compare the toxicokinetic (TK) properties of glyphosate according to different vehicles in rats. Glyphosate (1%) was dissolved in distilled water (DW), polyoxyethylene tallow amine (POEA), and Tween 20. After a single oral treatment of glyphosate (50 mg/kg), blood was collected at time intervals, and glyphosate concentrations in the target organ (liver and kidney) were determined 24 h after final blood collection. All samples were analyzed using LC-MS/MS. The TK parameters of glyphosate were similar in the DW and Tween 20 groups. However, there were significant differences in Tmax and volume of distribution (Vd) between the DW and POEA group (p < 0.05). Glyphosate was absorbed about 10 times faster in POEA group rather than DW, and exhibited a higher distribution. However, other important TK parameters of T1/2, AUC, and Cmax were not statistically different among the different vehicle groups. Although glyphosate concentration in the liver was significantly higher in the POEA group than in the DW group, there was no significant difference in the kidney. These results indicate that the toxicokinetics of glyphosate are not significantly affected by POEA. It can be concluded that POEA toxicity itself can be attributed to the acute toxicity of glyphosate-containing products.

Environmental fate and toxicity of androgens: A critical review

Androgens are released by humans and livestock into the environment and which cause potent endocrine disruptions even at nanogram per liter levels. In this article, we reviewed updated research results on the structure, source, distribution characteristics and the fate of androgens in ecological systems; and emphasized the potential risk of androgens in aquatic organism. Androgens have moderately solubility in water (23.6-58.4 mg/L) and moderately hydrophobic (log Kow 2.75-4.40). The concentration of androgens in surface waters were mostly in ng/L ranges. The removal efficiencies of main wastewater treatment processes were about 70-100%, except oxidation ditch and stabilization ponds. Sludge adsorption and microbial degradation play important role in the androgens remove. The conjugated androgens were transformed into free androgens in environmental matrices. Global efforts to provide more toxicity data and establish standard monitoring methods need a revisit. Of the day available, there is an urgent need for comprehensive consideration of the impact of androgens on the environment and ecology.

Pharmacokinetics and the Dermal Absorption of Bromochlorophene, a Cosmetic Preservative Ingredient, in Rats

The cosmetic industry has flourished in recent years. Accordingly, the safety of cosmetic ingredients is increasing. Bromochlorophene (BCP) is a commonly used cosmetic preservative. To evaluate the effects of BCP exposure, in vitro dermal absorption and in vivo pharmacokinetic (PK) studies were conducted using gel and cream formulations. The Franz diffusion cell system and rat dorsal skin were used for tests according to the Korea Ministry of Food and Drug Safety guidelines for in vitro skin absorption methods. After the dermal application (1.13 mg/cm²) of BCP in the gel and cream formulations, liquid chromatography–mass spectrometry (LC–MS/MS) was used to evaluate the amount of BCP that remained unabsorbed on the skin (WASH), and that was present in the receptor fluid (RF), stratum corneum (SC), and (epi)dermis (SKIN). The total dermal absorption rate of BCP was 7.42 ± 0.74% for the gel formulation and 1.5 ± 0.9% for the cream formulation. Total recovery in an in vitro dermal absorption study was 109.12 ± 8.79% and 105.43 ± 11.07% for the gel and cream formulations, respectively. In vivo PK and dermal absorption studies of BCP were performed following the Organization for Economic Cooperation and Development guidelines 417 and 427, respectively. When intravenous (i.v.) pharmacokinetics was performed, BCP was dissolved in glycerol formal and injected into the tail vein (n = 3) of the rats at doses of 1 and 0.2 mg/kg. Dermal PK parameters were estimated by the application of the gel and cream formulations (2.34 mg/kg of BCP as an active ingredient) to the dorsal skin of the rats. Intravenous and dermal PK parameters were analyzed using a non-compartmental method. The dermal bioavailability of BCP was determined as 12.20 ± 2.63% and 4.65 ± 0.60% for the gel and cream formulations, respectively. The representative dermal absorption of BCP was evaluated to be 12.20 ± 2.63% based on the results of the in vivo PK study.

An OECD TG 428 study ring trial with 14C-Caffeine demonstrating repeatability and robustness of the dermal absorption in vitro method

The dermal absorption potential of ¹⁴C-Caffeine applied as a 4 mg/mL concentration (10 μL/cm² finite dose) was investigated in six laboratories under Good Laboratory Practice conditions using an OECD TG 428-compliant in vitro assay with flow-through cells and split-thickness human skin. Potential sources of variation were reduced by a standardized protocol, test item and skin source. Particularly, skin samples from same donors were distributed over two repeats and between labs in a non-random, stratified design. Very similar recovery was achieved in the various assay compartments between laboratories, repeats and donors, demonstrating that the assay can be robustly and reliably performed. The absorption in one laboratory was 5-fold higher than in the others. This did not clearly correlate with skin integrity parameters but might be associated with an accidental COVID-19 pandemic-related interruption in sample shipment. It is possible that other factors may affect dermal absorption variation not routinely assessed or considered in the current method. The mean receptor fluid recovery, potential absorption (recovery in receptor fluid and skin except tape strips 1 and 2) and mass balance of caffeine was 6.99%, 7.14% and 99.13%, respectively, across all and 3.87%, 3.96% and 99.00% in the subset of five laboratories.