In vitro skin models in the optimization of skin formulations

Transdermal drug delivery is assumed to have a growing importance in drug development recently, thus it is crucial to optimize the penetration properties of drug into through the skin. Most of the current developments rely on the use of appropriate ex vivo animal or artificial models. However, the limited availability of human skin and the increasing restrictions in connection with animal testing encouraged the searchfor suitable artificial skin models.

For the review, we have searched the databases of scientific and medical research to collect the available publications about the in vitro skin models. Furthermore, we overviewed the methods of the DataBase service on ALternative Methods to animal experimentation (DB-ALM) database and the guidelines of Organisation for Economic Co-operation and Development (OECD).

In vitro skin models have advantages like reproducibility, relatively low cost, easy storage, uncomplicated handling, and they offer a possibility for rapid screening and faster optimization of skin formulations. Furthermore, their composition can be easily modified which allows studying the relationship between certain pathological conditions and barrier function. However, the limitations of these models are needed to be taken into account.

This review attempts to provide an overview of the most frequently used models, focusing on their limitations and advantages. Accessibility, easiness of the application, cost and the respective limitations have to be considered in order to choose the most appropriate in vitro model for the particular objective.