3D microextrusion-inkjet hybrid printing of structured human skin equivalents

Fabrication of human skin equivalents is one of the challenging issues in many areas, including biology, medicine, cosmetics, and ethics. However, conventional skin models have problems with their quality, reproducibility, and production methods. One effective solution for this issue is bioprinting, which solves the limitations of conventional manufacturing. In this study, we tried to fabricate a skin equivalent with a layered structure by coupling two printing techniques. We performed pneumatic microextrusion technique to generate a stable dermal layer composed of collagen and primary human dermal fibroblasts. This was followed by piezoelectric inkjet printing of primary human epidermal keratinocytes to apply an epidermal layer with high viability and uniformity. Shear viscosity of collagen ink containing dermal fibroblasts was measured to optimize printability. The epidermal bioink, composed of only media and epidermal keratinocytes, was also examined under various conditions to improve the inkjet printing process. The culture conditions, including the bioink and culture media, were also validated in terms of cell viability. After approximately 2 weeks of submerged dermal culture and more than 2 weeks of air?liquid interface culture, we performed histological staining and immunostaining to assess our printed skin models. This hybrid process could be used to implement a simple and reproducible printing method for generating multilayered skin models and also make it possible to regulate epidermal layer by adjusting inkjet printing parameters. We expect that this method would provide additional varieties of skin models with further investigation. ? 2021 Elsevier B.V.11Nscopu