Directly coaxial 3D bioprinting of large-scale vascularized tissue constructs.

Three-dimensional (3D) bioprinting of soft large-scale tissues in vitro is still a big challenge due to two limitations, (i) the lack of an effective way to print fine nutrient delivery channels (NDCs) inside the cell-laden structures above the millimetre level; (ii) the need for a feasible strategy to vascularize NDCs. Here, a novel 3D bioprinting method is reported to directly print cell-laden structures with effectively vascularized NDCs. Bioinks with desired tissue cells and endothelial cells (ECs) are separately and simultaneously printed from the outside (mixed with GelMA) and inside (mixed with gelatin) of a coaxial nozzle. As a result, the printed large-scale tissue consists of sheath-core fibers. At the same time, when the core fibers are dissolved to generate channels, the ECs deposit and adhere to the channels automatically. With this method, 3D cell-laden, vascularized tissue constructs (⩾1 cm) with a long-term culture (⩾20 d) are firstly reported. Specifically, vascularized cancer tissue constructs and osteogenic tissue constructs were generated. Considering the above advantages, this advanced bioprinting strategy has significant potential for building large-scale vascularized tissue constructs for applications in tissue engineering, and possibly even in regenerative medicine and organ repair.