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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]

As one of the most abundant wild herbs in nature, the Humulus japonicus stem (HJS) is a new low-cost source of cellulosic material. In this work, cellulose nanocrystals (CNCs) were isolated from HJS using acid hydrolysis. The influence of high temperature pretreatment (HT pretreatment) on the properties and yields of these HT-HJS (HJS fibers after HT pretreatment at different temperatures) and HT-CNCs (CNCs prepared from the HT-HJS) was studied. The results showed that there was no variation of the chemical structure among the HT-HJS and HT-CNCs. The thermal stabilities and crystallinities of the HT-HJS were higher than bleached HJS. The average diameters of the HT-CNCs were significantly smaller while the average aspect ratios of them were obviously bigger than the CNCs, and the biggest average aspect ratio of HT140-CNCs (63.40) was almost twice of CNCs (32.00). Compared with the CNCs (70.05%, 212.8 °C), the crystallinity and initial degradation temperature also showed increase for the HT-CNCs and increased up to maximum of 86.93% and 227.5 °C for the HT160-CNCs. [ABSTRACT FROM AUTHOR]