3D Printing of bioinks including living cells

3D Printing is a versatile process tool in rapid prototyping as well as additive manufacturing of complex structures. Due to its capability of depositing cells with precision at desired positions, it is considerably interesting the use 3D-printable bio inks including living cells for tissue engineering purposes. The bioinks are mainly constituted of biopolymers, capable of chemical or physical gelation, which can provide a cell friendly environment and keep the cells alive and functional while printing.

During the extrusion process, which is a common way of printing scaffolds in 3D, the cells may experience different flow kinematics including spatial variations in strain and strain rate. This results in different tensile or shear stresses and the cells may be damaged while passing through the needle. The intensity of the damage depends on the details of the flow kinematics and the corresponding stresses, i.e. the syringe and nozzle geometry, the rheological properties of the ink and may also vary from cell-type to cell-type. The consequences can show up right after printing or at some time later during cultivation, e.g. dead cells, deterioration of cell functions or differentiation capability.

Tissue engineering through 3D printing is a promising technique for regenerative medicine and has a potential still only partially explored. The cell damage flow-induced mechanical stresses is a parameter that needs to be studied in order to develop strategies for the optimization of cell viability and successful 3D-printing of scaffolds with living cells.