Development and Evaluation of a Human Skin Equivalent in a Semiautomatic Microfluidic Diffusion Chamber

Abstract

There is an increasing demand for transdermal transport measurements to optimize topical drug formulations and to achieve proper penetration profile of cosmetic ingredients. Reflecting ethical concerns the use of both human and animal tissues is becoming more restricted. Therefore, the focus of dermal research is shifting towards in vitro assays. In the current proof-of-concept study a three-layer skin equivalent using human HaCaT keratinocytes, an electrospun polycaprolactone mesh and a collagen-I gel was compared to human excised skin samples. We measured the permeability of the samples for 2% caffeine cream using a miniaturized dynamic diffusion cell (“skin-on-a-chip” microfluidic device). Caffeine delivery exhibits similar transport kinetics through the artificial skin and the human tissue: after a rapid rise, a long-lasting high concentration steady state develops. This is markedly distinct from the kinetics measured when using cell-free constructs, where a shorter release was observable. These results imply that both the established skin equivalent and the microfluidic diffusion chamber can serve as a suitable base for further development of more complex tissue substitutes.

Skin-on-a-Chip Technology for Testing Transdermal Drug Delivery—Starting Points and Recent Developments

“…HaCaT immortalized human keratinocytes were implanted on the mesh and placed in the sample holder, which attached to the membrane to form a confluent monolayer. During the measurements, the transport of caffeine across the artificial skin equivalent was compared with the human excised skin samples, the results of which showed similar transport kinetics [58] (Figure 6). [58].…”

“…During the measurements, the transport of caffeine across the artificial skin equivalent was compared with the human excised skin samples, the results of which showed similar transport kinetics [58] (Figure 6). [58]. The difference between concentration readings from the marked mesh-only and SE samples is significant (p = 1.2 × 10 −7 , n = 12 in each group).…”

“…In modern societies, many different stringent laws and regulations have been introduced to meet this demand, including a ban on the use of animals in cosmetic experiments in the European Union since 2013. As a result, there has been a significant increase in the demand for alternatives that can fully elicit the role of animals in pharmaceutical and cosmetic research [58].…”

“…Transdermal transport measurements using skin equivalent (SE) and human skin. Caffeine concentration in the collected fractions was measured by spectrophotometry and is shown as a function of time[58]. The difference between concentration readings from the marked mesh-only and SE samples is significant (p = 1.2 × 10 −7 , n = 12 in each group).…”

Characterization and ex vivo evaluation of excised skin samples as substitutes for human dermal barrier in pharmaceutical and dermatological studies

“…There are in vitro models (such as artificial membranes with lipophilic or non-lipophilic characters), cell-based skin cell monolayers (such as HaCat cells) 1 and commercially available human reconstructed epidermis or full thickness living skin tissue models. These in vitro models have several advantages (stability, good reproducibility, no ethical issues), but they cannot mimic properly the full cellular composition of the living skin tissue.…”