Abstract
Stratum corneum (SC) represents the outermost layer of the skin, being an effective barrier against the entry of molecules and pathogens. Skin research has given particular focus to SC as it hampers effective drug delivery for cosmetical and therapeutical purposes. Following recommendations to develop alternative models to animals, the SC isolated from skin obtained from medical procedures or from pigs has gained extensive attention. Yet, there is still missing a standard and simple procedure accepted within the scientific community to avoid application of different isolated SC methodologies, a fact that may hamper progress in skin research. Considering this challenge, the present study evaluated different experimental conditions aiming to establish a useful and sustainable solvent-free procedure for the obtention of a realistic SC model. The studied trypsin digestion parameters included concentration, incubation period and temperature. Isolated SC was characterized using histological analysis and calcein’s permeability, after the procedure and during a 6-week storage period. Data recommend trypsin digestion at 4 °C for 20 h as the most effective procedure to isolate SC from pig ear skin. This work contributes to standardize the SC isolation procedure, and to obtain a valuable and reliable SC mimetic model for skin drug development.
Highlights
Transdermal drug delivery is assumed as one of the most attractive routes for administration of active ingredients
Despite the fact that no major differences have been detected in the morphology of the stratum corneum (SC) layer isolated considering the different experimental conditions, the permeation results described above evidenced that condition A represents the most advantageous set of parameters to obtain a realistic SC mimetic model
To better understand the transformation that occurred in the pig ear skin during the chosen SC isolation protocol, fresh skin portions have been collected in different timepoints of the procedure for subsequent histological analysis
Summary
Transdermal drug delivery is assumed as one of the most attractive routes for administration of active ingredients. Even though the skin is a complex organ composed by several layers [2], many stratum corneum (SC)-based models have been proposed (reviewed in [1]) These approaches are simpler than full-thickness skin mimetic models, they represent a valuable approximation for the prediction of drugs permeation across the skin. The functions of SC include the prevention of excessive water loss from the skin, maintenance of body temperature, hinder the entry of xenotoxic chemicals as well as the invasion of pathogens [7] In line with this facts, many in vitro and ex vivo models mimic mainly the SC since it is commonly considered the most important barrier for the study of the permeation of the drugs and thereby, understanding the drug permeation process across this layer is usually the most relevant step in drug discovery
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