A novel murine model for the in vivo study of transdermal drug penetration

Methods for the characterisation of dermal uptake: Progress and perspectives for organophosphate esters

Organophosphate esters (OPEs) are a group of pollutants that are widely detected in the environment at high concentrations. They can adversely affect human health through multiple routes of exposure, including dermal uptake. Although attention has been paid to achieving an accurate and complete quantification of the dermal uptake of OPEs, existing evaluation methods and parameters have obvious weaknesses. This study reviewed two main categories of methodologies, namely the relative absorption (RA) model and the permeability coefficient (PC) model, which are widely used to assess the dermal uptake of OPEs. Although the PC model is more accurate and is increasingly used, the most important parameter in this model, the permeability coefficient (Kp), has been poorly characterised for OPEs, resulting in considerable errors in the estimation of the dermal uptake of OPEs. Thus, the detailed in vitro methods for the determination of Kp are summarised and sorted. Furthermore, the commonly used skin membranes are identified and the factors affecting Kp and corresponding mechanisms are discussed. In addition, the experimental conditions, conclusions, and available data on Kp values of the OPEs are thoroughly summarised. Finally, the corresponding knowledge gaps are proposed, and a more accurate and sophisticated experimental system and unknown Kp values for OPEs are suggested.

Effect of High-Dose Topical Minoxidil on Erythrocyte Quality in SKH1 Hairless Mice

Simple Summary

In any animal species, involuntary exposure to unknown agents may increase genetic material damage. This genetic damage can also induce the appearance of diseases such as cancer or other pathologies, including problems that can be passed on to the offspring of the damaged individual. For instance, living organisms may be affected due to the use of medications or exposure to certain chemical, physical, or biological agents which cause cell failure. This impaired function acts as an indicator that helps identify and evaluate damage in order to avoid or minimize it. In this work, excessive doses of a cosmetic drug for topical use in dermatological treatments, known as minoxidil, produced defects in the blood of hairless mice, particularly in red cells, indicating loss of DNA, a situation that may compromise life or the offspring by causing damage to their genetic material. It is important to consider that compounds may be tissue- or species-specific, although we cannot rule out the possibility that similar damage could occur in other animal species. Thus, excessive exposure to this compound should be prevented.

Abstract

SKH1 hairless mice are widely used in carcinogenesis and dermatology research due to their bare skin, as exposure to different agents is facilitated. Minoxidil is a cosmetic drug that is recognized as a mitogenic agent, and mitogens are suggested to have carcinogenic and mutagenic potential by inducing cell division and increasing the possibility of perpetuating DNA damage. Therefore, we hypothesized that the application of high doses of minoxidil to the skin of hairless mice would increase the number of micronucleated erythrocytes (MNEs) in peripheral blood. The objective of this study was to evaluate the topical administration of high doses of minoxidil on peripheral blood erythrocytes of SKH1 mice by means of micronucleus assay. Minoxidil was administered on the entire body surface of mice every 12 or 24 h. Minoxidil dosing every 24 h increased the number of micronucleated polychromatic erythrocytes (MNPCEs), and dosing every 12 h increased the number of MNEs and MNPCEs, as compared to baseline and the negative control group. No decrease in polychromatic erythrocyte frequencies was observed in the minoxidil groups. Therefore, topical application of high minoxidil doses to mice can produce DNA damage, as observed through an increase in the number of MNEs, without producing cytotoxicity, possibly due to its mitogenic effect.

Development of ibuprofen-loaded nanostructured lipid carrier-based gels: characterization and investigation of in vitro and in vivo penetration through the skin

An ibuprofen-loaded nanostructured lipid carrier (IBU-NLC) was developed for enhanced skin penetration to improve the treatment of osteoarthritis and other musculoskeletal diseases. The mean particle size was 106 nm, with a spherical morphology, a smooth surface, and a zeta potential of -18.4 mV. X-ray diffraction studies revealed the amorphous state of the lipid matrix. Both Raman spectroscopy and Fourier transformation infrared analysis indicated no major shifts in the spectra of the formulations, which suggest rapid drug dissolution from the nanoparticles. The drug loading was 9.85%, and the entrapment efficiency was 98.51%. In vitro release of the NLC dispersion, in vitro permeation, and in vivo animal studies of IBU-NLC gel all confirmed that the permeation of IBU was significantly better than that of a reference after 6 hours. In conclusion, IBU-NLC gel is of great potential to enhance drug permeation through the skin and hence the efficacy of the treatment of chronic joint inflammation.

Animal models for percutaneous absorption

Animal models are important tools to predict human in vivo percutaneous absorption/penetration. Monkey, pig, rat, rabbit, guinea pig, hairless rodents, such as hairless rat, hairless mouse, hairless guinea pig and hairless dog, are among the most used animals for this purpose. Each animal model has its own advantages and weakness or limitation. To better correlate animal data with human skin absorption, we need to be familiar with each animal model's characteristics as well as experimental method and condition. We reviewed the original papers published after 1993 that described permeability of both animal skin and human skin. It showed that monkey, pig and hairless guinea pig are more predictive of human skin absorption/penetration and common laboratory animals, such as rat, rabbit, guinea pig, generally overestimate human skin absorption/penetration.