ABSTRACT
Recent developments in three-dimensional (3D) bioprinting technology enable the efficient fabrication of thick and complex tissues. Numerous 3D-bioprinting techniques have been developed to create sophisticated structures in a wide range of scales (from micrometer to centimeter) with various biomaterials (Datta et al. 2017; Ozbolat et al. 2017). Unlike traditional 3D printing that prints inorganic materials and needs minimal postprocessing after the completion of printing, bioprinting involves more complicated components such as suitable cells and printable biomaterials, and also requires substantial postprinting procedures. To develop tissue-specific functions, long-term culture with appropriate stimuli is necessary for most of the engineered tissues.
Vascularization of engineered tissues plays an important role in maintaining the tissue viability during the long-term postprinting maturation (Khademhosseini and Langer 2016; Kaully et al. 2009; Lovett et al. 2009; Phelps and Garcia 2010). Vascular networks with perfusion provide an adequate supply of nutrient and oxygen, thus maintaining viability and preventing necrosis of thick tissues during the maturation period. Vasculatures embedded within engineered tissues also provide backbone structures to recapitulate architectural features of the counterpart native tissue, and enable easy integration into the host circulatory system after the transplantation.
