FRESH bioprinting technology for tissue engineering - the influence of printing process and bioink composition on cell behavior and vascularization.

The rapid and tailored biofabrication of natural materials is of high interest for the field of tissue engineering and regenerative medicine. Scaffolds require both high biocompatibility and tissue-dependent mechanical strength to function as basis for tissue-engineered implants. Thus, natural hydrogels such as fibrin are promising but their rapid biofabrication remains challenging. Printing of low viscosity and slow polymerizing solutions with good spatial resolution can be achieved by freeform reversible embedding of suspended hydrogels (FRESH) bioprinting of cell-laden natural hydrogels. In this study, fibrin and hyaluronic acid were used as single components as well as blended ink mixtures for the FRESH bioprinting. Rheometry revealed that single materials were less viscous than the blended bioink showing higher values for viscosity over a shear rate of 10-1000 s