Figure 5.

Biomedical applications of gradient-bioprinted tissue-like constructs. (a) Two examples showing cell density gradients of GFP-HUVECs bioprinted in an arbitrarily controllable manner at any desired density in any given single printing session. The intensity analysis for each example shows the consistency of output intensity pattern (green) and the velocity ratios of input bioink flows (red). (b-d) Gradient bioprinting of cells within the 10 wt.% GelMA hydrogels. (b) A circle pattern with MDA-MB-231 cells (blue) showing the cell density gradient in the radial direction and the quantitative analysis of the fluorescence intensities. (c) The vascular network structure with the cell density gradient in the horizontal direction encapsulating HUVECs (green) and the quantitative analysis of the fluorescence intensities. (d) A construct containing RFP-HUVECs and GFP-HUVECs showing the positive gradient of red cells and the negative gradient of green cells from left to right, and the quantitative analyses of the fluorescence intensities. (e) The photograph captured on EDD 14 of the CAM assay implanted with the printed VEGF-gradient scaffold and its corresponding image processed with the traced vessels. Bar graphs showing the quantitative values of the total vessel lengths and vessel numbers. (f) C2C12 myoblasts stained with F-actin/nucleus (red/blue) cultured on a bioprinted stiffness-gradient hydrogel presenting various morphologies. The quantifications of single-cell areas and cell aspect ratios (major axis to the minor axis) of C2C12, as well as the compressive modulus of 10–30 wt.% GelMA hydrogel. *P < 0.05, **P < 0.01, ***P < 0.001; one-way ANOVA (e, compared with the control group of 0 μg mL⁻¹ VEGF; f, compared with the group of 10 wt.% GelMA), mean ± s.d. (e, n = 3; f, n = 10).