Formation of a keratin layer with silk fibroin-polyethylene glycol composite hydrogel fabricated by digital light processing 3D printing

Silk fibroin (SF)-incorporated 4-arm polyethylene glycol acrylate (PEG4A) was used as a bioink for digital light processing three-dimensional printing. A visible range of light was adopted for the process to assure the safety of the cells in the bioink. Fibroblast cells were embedded in the printed hydrogels, and the keratinocyte cells were cultured at the surfaces of the hydrogels. The proliferation of cells with the bioink materials, PEG4A and SF-PEG4A, and the toxicity of these materials, were verified by live/dead and alamarBlue assays. The primary human keratinocytes on the SF-PEG4A hydrogel scaffold generated a keratin layer by the tissue culture at the air-liquid interface, promoting maturation and stratification. SF-polyethylene glycol hydrogels showed higher cell proliferation and cell spreading, and the thicker keratin layer was formed with SF-PEG4A hydrogels compared with PEG4A hydrogels.