Preparation of cellulose nanofiber-reinforced gelatin hydrogel and optimization for 3D printing applications

Gelatin (GEL) obtained from animals is famous for its biocompatibility and biodegradability. However, its poor mechanical properties limits possible applications as bio-inks to fabricate tissue scaffolds through three-dimensional (3D) printing. In this work, a high strength hydrogel based on cellulose nanofibers and GEL (CNF/GEL) was designed for 3D printing. Scanning electron microscopy and breaking strength results indicated that a CNF filling content of 10% was the best content in the CNF/GEL hydrogels. The rheological properties of the samples with different solid contents were investigated, and the 10%-CNF/GEL-5 hydrogel was proposed for 3D printing. Then, a printing strategy with optimal conditions, including a crosslinking procedure for obtaining a 3D scaffold, was proposed. The biocompatibility of G-10%-CNF/GEL-5 was also investigated using CCK-8 and Hoechst 33342/PI double-staining assays. These results confirmed that the 10%-CNF/GEL-5 composite hydrogel has potential to be used as a 3D bio-ink for application in tissue repair.