Engineering of Uniform Epidermal Layers via Sacrificial Gelatin Bioink‐Assisted 3D Extrusion Bioprinting of Skin

Abstract To reconstruct an ideal full‐thickness skin model, basal keratinocytes must be distributed as a confluent monolayer on the dermis. However, the currently available extrusion bioprinting method for the skin is limited when producing an air‐exposed cellular monolayer because the cells are encapsulated within a bioink. This is the first study to use sacrificial gelatin‐assisted extrusion bioprinting to reproduce a uniform and stratified epidermal layer. Experimental analyses of the rheological properties, printability, cell viability, and initial keratinocyte adhesion shows that the optimal gelatin bioink concentration is 4 wt.%. The appropriate thickness of the bioprinted gelatin structure for achieving a confluent keratinocyte layer is determined to be 400 µm. The suggested strategy generates a uniform keratinocyte monolayer with tight junctions throughout the central and peripheral regions, whereas manual seeding generates non‐uniform cellular aggregates and vacancies. These results influence gene expression, exhibiting a propensity for epidermal differentiation. Finally, the gelatin‐assisted keratinocytes are bioprinted onto a dermis composed of gelatin methacryloyl and dermis‐derived decellularized extracellular matrix to establish a full‐thickness skin model. Thus, this strategy leads to significant improvements in epidermal differentiation/stratification. The findings demonstrate that the gelatin‐assisted approach is advantageous for recreating reliable full‐thickness skin models with significant consistency for mass production.