A photocurable and thermocurable composite hydrogel and the application in a contraction resistant full-thickness skin model

Three-dimensional (3D) organotypic skin in vitro has attracted increasing attention for drug development, cosmetics evaluation, and even clinical applications. However, the severe contraction of these models restricts their application, especially in the analyses based on barrier functions such as percutaneous penetration. For the full-thickness skin equivalents, the mechanical properties of the dermis scaffold plays an important role in the contraction resistance. In this investigation, we optimized a hydrogel composed of gelatine methacrylamide (GelMA), hyaluronic acid methacrylate (HAMA), and type I collagen (Col I), adjusted the elastic moduli to 2.27±0.08 kPa to fit the skin cells growth and resist contraction as well. This optimized hydrogel exhibited a swelling ratio of 23.25 ± 0.94% and demonstrated satisfactory cell viability in fibroblasts cultures. Then, we mixed this hydrogel with fibroblasts of liquid-liquid culture to construct the dermis, on which seeded keratinocytes were seeded for another 14 days of air-liquid culture to form cornified epidermis, and a commercialized hydrogel Ava-FT-Skin was used as control. This optimized skin model could maintained its integrity for a prolonged period of 28 days. Differentiated epidermis presented basal, spinous, granular, and cornified layers, meanwhile, epidermis markers like keratin-10, keratin-14, involucrin, loricrin, filaggrin, and dermis markers vimentin were expressed distinctly in the right distribution. Furthermore, penetration of a 607 Da Cascade blue-labelled dextran was calculated and compared to the Avatarget skin model, both of which could prevent more than 99% of the fluorescent molecule. We consider that this full-thickness skin model could be widely used in pharmaceutical and cosmetic industries, especially in penetration detection, contributing to the excellent contraction resistance.