Inkjet Printing of a 3D Microstructured Human Skin Equivalent

Abstract

Needs for highly mimetic human skin models are becoming larger than before these days as animal testing in the cosmetics field is gradually being banned in many countries starting from European Union since 2013. Fabrication of artificial human skin equivalents with the increased representativeness is required to substitute the gap of the conventional animal testing. The skin is the largest organ of the body with the structural and functional complexity. Microstructures of dermis which help sustaining dermal-epidermal junction are the one of the key features among the existing complexities in skin such as appendages, vasculatures, immune cells, and pigment. However, conventional skin equivalents are made simply by stacking dermis and epidermis layers, lacking the detailed microstructures of human skin. Here, we present a 3D human skin model with microstructured dermis. The piezo-type inkjet printer enabled the controlled displacement and density of Type I collagen, dermal fibroblasts, and epidermal keratinocytes with high accuracy. We found that the degree of collagen contraction varies with the density of printed dermal fibroblasts. We used this phenomena to form papillary microstructures in the dermal layer. Various forms of microstructures were fabricated by changing local density of dermal fibroblasts or shapes of patterns. Epidermal keratinocytes were also inkjet printed as a densely packed monolayer within a controlled region preventing slipping away from the surface of the dermal collagen area. We believe that the inkjet-bioprinted 3D human skin equivalents with microstructures will play a critical role as a bridge between in vitro human models and in vivo tissues by replacing animal testing.