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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. [ABSTRACT FROM AUTHOR]

Early reports have demonstrated the feasibility of oxidized dextran/gelatin (OD/GEL) hydrogel for tissue engineering applications and the printability of OD/GEL hydrogel for 3D printing scaffolds, but adequate insight into fabricated OD/GEL scaffolds is lacking. In the present study, we prepared (cellulose nanocrystal) CNC/OD/GEL hydrogels and fabricated CNC/OD/GEL scaffolds by 3D printing. The properties of CNC/OD/GEL hydrogels were investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. The process of 3D printing of hydrogels was optimized, and the influence of the OD and CNC contents on the printability of CNC/OD/GEL hydrogels was investigated by studying the width of the printed filaments. The uniaxial compression test was performed to study the effects of the OD and CNC contents on the breaking strength and elastic modulus of CNC/OD/GEL scaffolds. In addition, the uniaxial compression test was also performed to determine the optimum mass ratio and crosslinking time of OD and GEL. The effects of the CNC content on scaffold shrinkage, scaffold swelling and scaffold porosity were further studied. The biocompatibility of a CNC0.4OD2G2 scaffold was also investigated by Cell Counting Kit-8 (CCK-8) and Hoechst 33342/PI double-staining assays. Collectively, the results confirmed the good potential of the CNC/OD/GEL hydrogels as 3D bioink for application in tissue repair. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing, used to fabricate modular and patient-specific scaffolds with high structural complexity and design flexibility, has drawn wide attentions in the tissue engineering area. However, one of the key problems hindering the application and development of 3D printing in TE area is the poor mechanical property of bio-inks. In this work, we aimed to design a high-strength hydrogel system based on dialdehyde cellulose nanocrystals (DAC) and gelatin (GEL) as a new bio-ink for 3D printing of scaffolds. The DAC were prepared and used as a natural crosslinker to interact with the GEL through a Schiff base reaction. The mechanical test results indicated that the breaking strength of the optimal 4:8-DAC/GEL sample was almost 41.3-fold greater than that of the GEL hydrogel. According to the rheological test results, the 4:8-DAC/GEL sample incubated for 3 h was proposed as a bio-ink for 3D printing. Then, the printing conditions, including the printing pressure and nozzle speed, as well as additional crosslinking conditions for a freshly printed scaffold, i.e., the crosslinking time and temperature, were optimized. Crosslinked scaffolds with adjustable porosity and good fidelity were successfully obtained. The biocompatibility of 4:8-DAC/GEL was also investigated by CCK-8 and Hoechst 33342/PI double-staining assays. Collectively, these results confirm the good potential of the 4:8-DAC/GEL hydrogel as a 3D bio-ink for application in tissue repair. [ABSTRACT FROM AUTHOR]