3D-reactive printing of engineered alginate inks

Alginate is a common component of bioinks due to its well-described ionic crosslinking mechanism and its tunable viscoelastic properties. The extrusion-based 3D-printing of alginate inks requires additives, such as gelatin and Pluronic, pre or post- printing crosslinking processes and/or coextrusion with crosslinkers. In this work, we aim to provide a diffent printing approach of alginate-based inks, introducing the 3D-reactive printing. Indeed, the control over the crosslinking kinetics and the printing time allowed printing different inks while maintaining unaltered their final composition to identify a suitable formulation in terms of printability. Alginate solutions were crosslinked with insoluble calcium salts (CaCO3) inducing dynamic modification of their microstructure and viscoelastic properties in time. The monitoring of fibers printability and internal microstructure, at the different time points of the ink gelation, was performed by means of a well-defined set of rheological tests to engineer a priori inks properties for the a posteriori 3D-printing process. This new perspective allowed 3D reactive printing of alginate fibers with predermined properties, without involving post-extrusion crosslinking steps and additives.