Rapid printing of bio-inspired 3D tissue constructs for skin regeneration

It is still a challenge for existing bioprinting technologies to fabricate organs suitable for implantation, mainly due to the inability to recapitulate the organs' complex anatomical structures, mechanical properties, and biological functions. Additionally, the failure to create 3D constructs with interconnected microchannels for longrange mass transportation that limits the clinical applications of 3D printing technologies. Here, a new method was developed to print functional living skin (FLS) using a newly designed biomimetic bioink (GelMA/HA-NB/LAP) and digital light processing (DLP)-based 3D printing technology. The FLS possess interconnected microchannels that facilitates cell migration, proliferation and neo-tissue formation. The GelMA/HA-NB/LAP bioink, composed of gelatin methacrylate (GelMA), N-(2-aminoethyl) 4 (4 (hydroxymethyl)-2-methoxy-5-nitrosophenoxy) butanamide (NB) linked hyaluronic acid (HA-NB) and photo-initiator lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP). The bioink demonstrated its rapid gelation kinetics, tunable mechanical properties, good biocompatibility and tissue adhesion. The DLP-based 3D printing technology provides a rapid method to precisely position clusters of human skin fibroblasts (HSFs) and human umbilical vein endothelial cells (HUVECs) with high cell viability to form FLS. The FLS promotes skin regeneration and efficient neovascularization by mimicking the physiological structure of natural skin, and it can also be easily handled and implanted onto the wound site due to its strong mechanical and bio-adhesive properties. Moreover, in vivo study demonstrated that the living skin exhibited instant defense function and had superior performance in promoting dermal regeneration with skin appendages in large animals. This study provides a rapid and mass production method of functional living organs for future clinical applications.