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Disorders of keratinization and other genodermatoses
Published in Rashmi Sarkar, Anupam Das, Sumit Sethi, Concise Dermatology, 2021
Epidermal differentiation and keratinization are complex processes, and various genetic mutations can disrupt the usual course of maturation. The resultant altered epidermis is unable to perform its normal functions or serve as an effective barrier. There is an increase in transepidermal water-loss, making the skin dry and prone to irritation. Impaired immunity to microbial infections can result in frequent infections. The defective epidermis is also considerably less compliant and pliable compared to normal epidermis, and this can often cause blistering over pressure points or limitation to movements accompanied by pain and fissuring. However, the greatest impact of these disorders is possibly because of the significant cosmetic disability that they cause. The skin is of primary importance in determining the appearance of an individual, and abnormal skin can hamper the socio-economic and emotional aspects of the life of the affected individual.
Transepidermal Water Loss
Published in Enzo Berardesca, Peter Elsner, Klaus-P. Wilhelm, Howard I. Maibach, Bioengineering of the Skin: Methods and Instrumentation, 2020
Fernanda Distante, Enzo Berardesca
The term TEWL generally refers to the total amount of water vapor loss through the skin. However, it is a true reflection of stratum corneum barrier function only in the absence of sweat gland activity. Transepidermal water loss may be considered a process of passive diffusion which obeys the usual diffusion laws of physics relative to passive diffusion processes.3 It may be expected, therefore, that the rate of water vapor diffusion across the stratum corneum would depend directly on the ambient relative humidity, the stratum corneum barrier integrity, and temperature, and inversely on the stratum corneum thickness, which determines the penetrability through the stratum corneum.3,4
Structure and Function of Human Skin
Published in Marc B. Brown, Adrian C. Williams, The Art and Science of Dermal Formulation Development, 2019
Marc B. Brown, Adrian C. Williams
It is readily apparent that skin structure varies to some degree over the human body; clearly the stratum corneum is thicker on the palms of the hands and soles of the feet (i.e., the load-bearing areas of the body) than on the lips or eyelids. However, the relative permeability of different skin sites is not simply a function of stratum corneum thickness, since different permeants exhibit varied rank orders through different skin sites. Wester and Maibach (1999), in reviewing regional (site to site) variations in permeability, showed that variations in drug absorption can be seen for sites with a similar thickness of stratum corneum, and that some areas with different stratum corneum thickness provide similar levels of drug absorption. In addition to stratum corneum thickness, the corneocyte surface area varies, and follicular density and the volume of pores differs from site to site. Regional variations in cutaneous blood flow and transepidermal water loss have also been reported.
A novel technique to evaluate nail softening effects of different urea formulations
Published in Pharmaceutical Development and Technology, 2021
Hiep X. Nguyen, Yujin Kim, Tejas D. Kekatpure, Emily Lesica, Ajay K. Banga
In contrast to skin transepidermal water loss, which has been a common term in the scientific field (Nguyen et al. 2018), Transonychial Water Loss (TOWL) was reported in markedly fewer studies (Murdan et al. 2008; Sattler et al. 2012). TOWL measurement could be regarded as a simple, rapid, and noninvasive method to evaluate the hydration and integrity of nail. In this study, an increase in TOWL values might indicate a higher hydration level and a softer structure of bovine hoof membrane. The water content of the membrane could be either enhanced by the absorption of water molecules from the receptor fluid or decreased due to the water evaporation from the membrane surface. We observed TOWL values increased when the study duration was 10 or 18 h: 1.45 ± 2.05% to 50.86 ± 24.53% for 4xU-O-N1; 21.13 ± 0.93% to 24.23 ± 7.54% for 4xU-O-N2; and 35.32 ± 5.55% to 26.70 ± 3.42% for 4xU-C-S1. However, a prolonged study (24 h) allowed more water to evaporate to result in a decrease in TOWL values by 15.8 ± 0.92% for 4xU-O-N1, 15.22 ± 2.36% for 4xU-O-N2, and 8.24 ± 0.13% for 4xU-C-S1 (Figure 7). This observation suggested that an appropriate study duration (10 or 18 h) was preferred to study the effect of topical formulations on TOWL values of bovine hoof membranes. However, when topical formulations with the same urea concentration (4x, % w/w) were studied for a duration of 10 or 18 h, we still obtained inconsistent and statistically different readings of TOWL values (Figure 7). Thus, this study lacked a reliable correlation between TOWL values and the urea concentration in the formulations applied on the membranes.
Evaluation of the changes in sebum, moisturization and elasticity in acne vulgaris patients receiving systemic isotretinoin treatment
Published in Cutaneous and Ocular Toxicology, 2021
Güllü Gencebay, Özge Aşkın, Server Serdaroğlu
Stratum corneum serves as a physical barrier that decreases the transepidermal water loss. The moisture level of stratum corneum depends on its composition of amino-acids, ammonia, urea and piridolin carboxylic-acid which is known as the natural moisturising factor. An intact epidermal barrier is of utmost importance for skin hydration. The skin sebum levels, skin moisture levels, the skin pH and the epidermal permability are the most important factors for the skin homoeostasis27–31. A study has compared the skin physiology of 300 healthy individuals and showed that the transepidermal water loss was lower in young males compared to young females. Furthermore, the same study showed that the skin hydration was higher in young males compared to young females32. Our study demonstrated that the average moisture level of the skin increased 79% after the cumulative oral isotretinoin therapy. This result is in parallel with previous literature showing that increased lipids leading to disturbed epidermal barrier and declined skin hydration27–31. On the other hand, Kmiec et al. demonstrated that transepidermal water loss increased and hydration decreased with systemic isotretinoin therapy23.
Fabrication and characterization of dissolving microneedles for transdermal drug delivery of allopurinol
Published in Drug Development and Industrial Pharmacy, 2021
Jianmin Chen, Xinying Liu, Siwan Liu, Zemin He, Sijin Yu, Zhipeng Ruan, Nan Jin
Here, we reported a kind of DMNs for transdermal drug delivery of AP. The DMNs were fabricated by using a suspension solution casting method with PDMS molds. The fabrication process, morphology, mechanical strength, skin penetration performance, and in vitro release of DMNs were extensively investigated. Additionally, ex vivo diffusion in mouse skin and in vivo transdermal delivery in hyperuricemic mice of DMNs encapsulating AP were also evaluated. Moreover, the transepidermal water loss (TEWL) of skin and the recovery of the skin after the treatment of DMNs were studied. To our best knowledge, this is the first work to fabricate and study DMNs for transdermal drug delivery of AP.