Coaxial hydro-nanofibrils for self-assembly of cell sheets producing skin bilayers.

Bilayered skin sheets were fabricated with coaxial hydro-nanofibrils for three-dimensional (3D) cultivation in a biomimetic environment. Polycaprolactone (PCL) was electrospun and hydrolyzed to release fragmented nanofibrils (NF) in an alkaline condition. Methacrylated gelatin (GelMA) was adsorbed and photo-tethered on the surface of the fibrils to prepare coaxial NF composed of hydrophilic shells and hydrophobic cores. GelMA layers on the NF were characterized by X-ray photoemission spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetric analysis. The GelMA showed higher decoration level on NF compared to native gelatin. GelMA-decorated NF significantly enhanced cell proliferation rate and phenotypic expression of human dermal fibroblasts, when spontaneous formation of cell sheets was observed for seven days. HaCaT cells were layered on top of the fibroblast sheets and further cultivated in air-water interfaces to prepare bilayered skin sheets. After 21 days of incubation, the top layers of the bilayered sheets showed higher expression of pan-keratin and the dermal cells showed higher proliferation in GelMA-decorated NF.