3d Printing Of Mechanically Stable Calcium-Free Alginate-Based Scaffolds With Tunable Surface Charge To Enable Cell Adhesion And Facile Biofunctionalization

For the 3D printing of bioscaffolds, the importance of a suitable bioink cannot be overemphasized. With excellent printability and biocompatibility, alginate (Alg) is one of the most used bioinks. However, its bioinert nature and insufficient mechanical stability, due to only crosslinking via cation interactions, hinder the practical application of Alg-based bioinks in the individualized therapy of tissue defects. To overcome these drawbacks, for the first time, an epsilon-polylysine (epsilon-PL)-modified Alg-based bioink (Alg/epsilon-PL) is produced. The introduction of epsilon-PL improves the printability of the Alg-based bioink due to increasing electrostatic interactions, which enhances the self-supporting stability of the as-printed scaffolds. The presence of the functional crosslinking -COOH and -NH2 groups in Alg and epsilon-PL under mild conditions further enhances the mechanical stability of the scaffolds, far exceeding that of Alg/Ca2+ scaffolds. The surface charge of the prepared scaffolds is finely tuned by the feed ratio of Alg to epsilon-PL and postimmobilization of different quantities of additional epsilon-PL, with a view to enhancing cell adhesion and further biofunctionalization. The results indicate that chondroitin sulfate, an extracellular matrix component, and vascular endothelial growth factor can be successfully applied to biofunctionalize the scaffolds via electrostatic adsorption for enhanced biological activity.