In vivo bone regeneration promoted by G3@nCe/GelMA hydrogel evaluated at the 12th week of implantation. (a) Graphical illustration showing the implantation of G3@nCe/GelMA hydrogel constructs in rat critical-sized bone defects. (b) Representative 3D reconstructed μCT images and (c) Quantification of the neo-bone formation using BV/TV in specific regions of interest. (d) Representative images of HE-stained tissues. Scale bar: 200 μm. (e) Representative images from MT staining. Scale bar: 200 μm. (f) Immunofluorescence of tissue samples showing the expression of various bone-related proteins (Col-I, OPN, OCN, & CD31). Scale bar: 200 μm. The annotation G stands for the residual hydrogel, OB for old bone and NB for new bone. (g) The quantitative analysis of various bone-related proteins (Col-I, OPN, OCN, & CD31 using ImageJ. All data expressed as mean ± SD (n = 5; ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001).