FRESH 3D Bioprinting of Alginate – Cellulose – Gelatin Constructs for Soft Tissue Biofabrication

The fabrication of three-dimensional (3D) bioprinted free-standing, low viscous, cell-laden hydrogels with good resolution, low cytotoxicity, and mechanical properties, comparable to native soft tissues, is a current challenge in tissue engineering. Recently, a new syringe extrusion approach, called Freeform Reversible Embedding of Suspended Hydrogels (FRESH), has been introduced to enhance 3D-bioprinting of soft hydrogels. Printing is conducted with the material embedded in a thermo-reversible gelatin bath, which acts as supporting material and can also initiate in-situ crosslinking when proper crosslinker agents are added. This work is the first to develop a 3D FRESH printable, low-cost, polymeric hydrogel composed of sodium alginate (SA), carboxymethylcellulose (CMC), and gelatin. A factorial design is investigated to identify best printing parameters. Printability Pr and CAD fidelity indexes are defined as responses of interest against scaffold resolution and shape fidelity. Results show a free-standing scaffold with a printability index, Pr ~ 1, a compression Young’s Modulus of about 4 kPa, and a cellular ATP content of stromal cells up to 50% compared to a 2D cell culture after 14 days. These promising results demonstrate the potential of such hydrogel to print soft constructs, applicable for neural or skin tissue engineering applications.