Hybrid Printing Using Cellulose Nanocrystals Reinforced GelMA/HAMA Hydrogels for Improved Structural Integration.

3D printing of soft-tissue like cytocompatible single material constructs with appropriate mechanical properties remains a challenge. Hybrid printing technology provides an attractive alternative as it combines a cell-free ink for providing mechanical support with a bioink for housing embedded cells. Several hybrid printed structures have been developed, utilizing thermoplastic polymers such as polycaprolactone as structural support. These thermoplastics demonstrated limited structural integration with the cell-laden components, and this may compromise the overall performance. In this work, a hybrid printing platform is presented using two distinct hydrogel inks that share the same photo-crosslinking chemistry to enable simple fabrication and seamless structural integration. A mechanically reinforced hydrogel ink is developed comprising cellulose nanocrystals and gelatin methacryloyl/hyaluronic acid methacrylate (GelMA/HAMA) as the structural component, and GelMA/HAMA as the cytogel containing a mouse chondrogenic cell line, ATDC5. Hybrid printed constructs with encapsulated cells are fabricated using the two optimized inks, and the structural integration of the constructs is evaluated by cyclic mechanical compression. Finally, the cell viability of encapsulated ATDC5 cells in the hybrid printed structures is evaluated.