Rheological behavior, 3D printability and the formation of scaffolds with cellulose nanocrystals/gelatin hydrogels

Recently, the CNC/GEL (cellulose nanocrystals/gelatin) composite hydrogel has been used as a biomaterial for 3D printing of tissue engineering scaffolds. Rheological properties of hydrogel have been regarded as one of the most important factors affecting printing quality, especially the viscosity recover time. However, there is still a lack of comprehensive research on the rheology property of the CNC/GEL hydrogel in the process of 3D printing. In this study, the CNC was isolated from Humulus japonicus, and a CNC/GEL hydrogel system was prepared. The rheological properties of CNC/GEL hydrogel were evaluated using a rotary rheometer. The viscosity recovery time of the CNC/GEL hydrogel was measured using a special method. The optimal ratio of hydrogel was obtained by rheology experiment and mechanical test. The flow field distribution of the hydrogel in the flow passage of 3D printer was analyzed using fluent simulation. The rheological parameters of a hydrogel can be adjusted by changing the printing conditions. Thus, the effect of printing conditions on the formation of CNC/GEL filaments was also investigated. Finally, the biocompatibility of the printed CNC/GEL scaffold after crosslinking treatment was verified using CCK-8 and Hoechst 33342/PI double-staining assays. The present study shows a new approach for the analysis of rheological properties of CNC/GEL and also provides some suggestions for 3D printing of CNC/GEL scaffolds.