Fig. 4

Cell viability after fabrication and the total cell number in the constructs. a The live cells were stained with Calcein AM (green dots), and the dead cells were stained with PI (red dots). The images in a, b, and c represent the construct with the homogeneous cell distribution in Group B on the first day after biofabrication; the images in d, e, and f represent the superficial zone of the construct with the cell density gradient in Group B after 1 week of in vitro culture; the images in g, h, and i represent the middle zone of the construct with the cell density gradient in Group B after 2 weeks of in vitro culture; and the images in j, k, and l represent the superficial zone of the construct with the cell density gradient in Group A after 3 weeks of in vitro culture (scale bars: 100 μm). b Total cell numbers in constructs in Groups A, B, and C after 3 weeks of in vitro culture