Effects of Freezing on Functionality and Physicochemical Properties of A 3D-Human Skin Model

Abstract

Short AbstractThree-dimensional skin substitutes reconstructed by tissue engineering have strong potential to emulate skin conditions in vivo, although their production necessitates a relatively long period of time. Storage of cryopreserved substitutes among time, using some kind of banking system, would be a conceivable solution to make their utilization more appealing for dermopharmaceutical testing. This study evaluated the effects of freezing at -20 °C over a period of 2 months on the structural and physicochemical properties of skin substitutes produced by tissue engineering. IntroductionLocated at the interface between the human body and the exterior environment, skin is the first line of defense against pathogens, chemicals, and harmful mechanical stimuli [1]. Due to its large surface area and its structural and functional complexity, regenerating a complete human skin represents a big challenge. Over the past years, different human skin substitute models have evolved in order to treat victims of severe burns and chronic cutaneous wounds [2]. Skin substitutes are useful in both applied and fundamental fields of research. They can be grafted as skin replacement in clinical applications or used for various types of skin tests, such as dermopharmacology and toxicology studies [2,3]. Skin substitutes properties must be as close as possible to those of normal skin [4].Over the past decade or so, the use of animals in fundamental and applied research has been subject to social debates, and this has led to the creation of more restrictive legislations, such as the addition of the Seventh Amendment to the European Union's Cosmetic Directive [4]. Utilization of skin substitutes to perform tests allowed for the elimination, or at least reduction, of controversial animal testing. Moreover, as animal skin differs in many ways to human skin, well representative skin substitutes could improve the validity of performed tests [5]. In order to increase efficiency, rapid access to skin substitutes is critical. Therefore, optimized storage methods are needed [6].Cryopreservation is an approach that has been under much investigation recently. The impact of various freezing conditions has been tested on animal and human skins. Among all tests performed, permeability analysis is one of the most commonly used in the literature. This test is based on the fact that skin, despite its crucial involvement as a barrier against exogenous material, remains permeable to most substances. AbstractBackground: Three-dimensional skin substitutes reconstructed by tissue engineering have strong potential to emulate skin conditions in vivo, although their production necessitates a relatively long period of time. Storage of cryopreserved substitutes among time, using some kind of banking system, would be a conceivable solution to make their utilization more appealing for dermo pharmaceutical testing. This study evaluated the effects of freezing at -20 °C over a period of 2 months on the structural and physicochemical properties of skin substitu...

Freezing Weakens the Barrier Function of Reconstructed Human Epidermis as Evidenced by Raman Spectroscopy and Percutaneous Permeation

“…Micro-emulsions enhance partitioning into both the aqueous and lipid phases of the SC, hence circumventing the effect of freezing on the aqueous permeation pathways. These considerations may explain our results and Pouliot's, who showed an approximately 10-fold increase in benzoic acid (log K ow = 1.9) permeation though an in-house full-thickness skin equivalent stored at −20 • C for 2 months compared to fresh samples [12], being contrary to Hoffman and Müller-Goymann's results, who reported no effect of freezing in nitrogen (24 h and 6 months) on the permeation of ibuprofen (log K ow = 3.8) from a commercial cream through a full-thickness skin equivalent [11]. Hence, to fully describe effects of storage conditions on a given reconstructed skin model, a study covering a range of permeant hydro-/lipophilicities and vehicles is necessary.…”

“…On the other hand, Pouliot showed an approximately 10-fold increase in the cumulative amount of benzoic acid permeated though an in-house full-thickness skin equivalent stored at −20 • C for 2 months compared to fresh skin equivalents. ATR-FTIR measurements, however, revealed no effect of freezing on the SC lipid conformation of the skin equivalents [12].…”