2.2. Preparation of bioink and cells for 3D bioprinting
Carrageenan, which is mainly composed of κ-Carr (Solarbio Inc., Beijing,
China), it was mixed at 1.5% w/v concentration with sodium alginate
(Solarbio Inc.) solution[36], and the concentration of the alginate
solution was fixed at 0.5% w/v, 1% w/v, and 1.5% w/v in this study.
MCNTs were purchased from TIMENANO Inc. China and fixed at 0.5% w/v,
1% w/v, and 1.5% w/v). Calcium chloride (CaCl2,
Solarbio Inc.) was used as the cross-linking agent for sodium alginate
solution. The preparation method of carrageenan composite hydrogel is as
follows: (1) kc: κ–carrageenan (1.5 g) was dissolved in
double-distilled water (100 mL) in a 3-necked round bottom flask and
stirred under a constant flow of nitrogen for 4 h. (2) kc-s: carrageenan
(1.5 g) and sodium alginate were dissolved in double-distilled water
(100 mL) in a 3-necked round bottom flask and stirred under a constant
flow of nitrogen gas for 4 h. (3) kc-c: 0.05 g of MCNTs were placed into
50-mL deionised water and subjected to ultrasonic dispersion for 10 min
to obtain a carbon nanotube water dispersion system. A certain amount of
carbon nanotube dispersion solution was added to the carrageenan
solution to obtain a carrageenan/MCNT hydrogel system (carrageenan
concentration 1.5% w/v, carbon nanotube concentration 0.01% w/v). All
of the prepared hydrogels were aseptically processed before use.
Particularly, in this case, we used a high pressure for 1 h and
ultraviolet light for 2 h. To prepare the cell-loaded biological ink, we
mixed human umbilical vein endothelium cells (HUVECs; Beijing Oligobio,
Beijing, China) into a hydrogel for printing.