Improving alginate printability for biofabrication: establishment of a universal and homogeneous pre-crosslinking technique.

Many different biofabrication approaches as well as a variety of bioinks have been developed by researchers working in the field of tissue engineering. A main challenge for bioinks often remains the difficulty to achieve shape fidelity after printing. In order to overcome this issue, a homogeneous pre-crosslinking technique, which is generally applicable to all alginate-based materials, was developed in this study. With this technique it was possible to markedly enhance the printability of a 2 % (w/v) alginate solution, without using a higher polymer content, fillers or support structures. It was possible to print 3D porous scaffolds with a height of around 5 mm. Furthermore, the rheological behavior of different pre-crosslinking degrees was studied. Shear forces on cells as well as the flow profile of the bioink inside the printing nozzle during the process were estimated. A high cell viability of printed NIH/3T3 cells embedded in the novel bioink of more than 85 % over a time period of two weeks could be observed. Furthermore, also the Young's Modulus of selected hydrogels, as well as the chemical characterization of alginate in terms of M/G ratio and molecular weight, were determined.