6 Conclusions
A carrageenan-based bioink gel system was established using 1.5% w/v carrageenan to induce rapid gelation of the silk and injectability during printing, allowing the formation of self-standing gel constructs. The printability of carrageenan-based hydrogel was found to improve with increasing concentrations of alginate and MCNTs in the composite hydrogels, and it was found to be the best with the alginate concentration of 1.5% w/v and MCNT concentration of 0.05% w/v. We optimised the printing parameters based on the rheological properties and applied them on kc-s and kc-c composites. Using this approach, we demonstrated excellent structural strength and printability of the carrageenan composite without significant negative effects on the cell viability (>93% average cell viability). With respect to shear force gradients in different areas of the gel filament, we found that despite the different printing pressures, the average cell survival rate of the printed gel also had a certain gradient, and the difference in each area was approximately 5%. This shear force gradient affects the microstructure of the gel filaments and can induce cell growth while responding to the material’s response to shear stress. The carrageenan-based bioink system was found to be compatible with HUVECs loaded in the gel matrix, kc-s, and kc-c, supporting better cell growth relative to carrageenan gel. It could achieve precise adjustment of the pore size, porosity, and pore distribution of the hydrogel structure by optimising the printing parameters and realising the precise preparation of the internal structure of the 3D hydrogel-based tissue engineering scaffold. Finally, with the optimal printing conditions, the carrageenan composite hydrogels (kc-s and kc-c) demonstrated the potential as a prospective bioink for fabricating purposes and as a promising 3D-printed scaffold with remarkable mechanical properties, while maintaining the structural and biological activity, in the field of tissue engineering and regenerative medicine.