A bioink blend for rotary 3D bioprinting tissue engineered small-diameter vascular constructs.

3D bioprinted vascular constructs have gained increased interest due to their significant potential for creating customizable alternatives to autologous vessel grafts. In this study, we developed a new approach for biofabricating fibrin-based vascular constructs using a novel rotary 3D bioprinter developed in our lab. We formulated a new bioink by incorporating fibrinogen with gelatin to achieve a desired shear-thinning property for rotary bioprinting. The blending of heat-treated gelatin with fibrinogen turned unprintable fibrinogen into a printable biomaterial for vessel bioprinting by leveraging the favorable rheological properties of gelatin. We discovered that the heat-treatment of gelatin remarkably affects the rheological properties of a gelatin-fibrinogen blended bioink, which in turn influences the printability of the ink. Further characterizations revealed that not only concentration of the gelatin but the heat treatment also affects cell viability during printing. Notably, the density of cells included in the bioinks also influenced printability and tissue volumetric changes of the printed vessel constructs during cultures. We observed increased collagen deposition and construct mechanical strength during two months of the cultures. The burst pressure of the vessel constructs reached 1110 mmHg, which is about 52% of the value of the human saphenous vein. An analysis of the tensile mechanical properties of the printed vessel constructs unveiled an increase in both the circumferential and axial elastic moduli during cultures. This study highlights important considerations for bioink formulation when bioprinting vessel constructs. STATEMENT OF SIGNIFICANCE: There has been an increased demand for small-diameter tissue-engineered vascular grafts. Vascular 3D bioprinting holds the potential to create equivalent vascular grafts but with the ability to tailor them to meet patient's needs. Here, we presented a new and innovative 3D rotary bioprinter and a new bioink formulation for printing vascular constructs using fibrinogen, a favorable biomaterial for vascular tissue engineering. The bioink was formulated by blending fibrinogen with a more printable biomaterial, gelatin. The systematic characterization of the effects of heat treatment and gelatin concentration as well as bioink cell concentration on the printability of the bioink offers new insight into the development of printable biomaterials for tissue biofabrication.