Fig. 14.

4D biofabrication ofacrosslinking gradient in cell-laden bone-like tissues. (a) Schematic illustration of the 4D biofabrication process to form structures with different crosslinking degrees on the upper and lower sides: hydrogel precursor containing photocurable polymer, photoinitiator (PI), and UV absorber was placed between two quartz plates, followed by UV irradiation to obtain hydrogels with crosslinking gradient and hence self-bending ability by responding to water. (b–e) Photographs showing bending structures fabricated with different SMHs. (f) Bending degree of the cell-laden OMA structures during 4 weeks of in vitro culture in osteogenic medium. (g) An image of Live/Dead staining showing the cell viability after 4-week in vitro culture. (h–j) Quantification of (h) DNA content, (i) ALP activity normalized to DNA content, and (j) calcium content normalized to DNA content in the cell-laden hydrogels at varying time points. (k) Alizarin red stained scaffolds after 4-week in vitro culture. NC (negative control): cell-laden hydrogels obtained in the presence of a UV absorber and cultured in cell growth medium, EG (experimental group): cell-laden hydrogels obtained in the presence of a UV absorber and cultured in osteogenic medium, PC (positive control): cell-laden hydrogels obtained in the absence of a UV absorber and cultured in osteogenic medium. Reproduced with permission [133]. Licensed under a Creative Commons CC BY license.