Collagen/bioceramic-based composite bioink to fabricate a porous 3D hASCs-laden structure for bone tissue regeneration.

To successfully achieve the porous cell-blocks, a bioink is a prerequisite requirement. However, although various hydrogel-based bioinks have been applied, a hydrogel/bioceramic-based composite bioink consisting of cells has not been actively investigated owing to its poor printability and low initial cell-viability. In this study, a new bioink consisting of fibrillated collagen, cells, and bioceramic (β-TCP) is suggested to attain a 3D porous cell-laden composite structure with high cellular responses, in aspects of initial cell viability, proliferation, and differentiation using preosteoblasts (MC3T3-E1) and human adipose stem cells (hASCs). By manipulating the processing conditions and weight fractions of the ceramic in the bioink, a 3D porous cell-laden composite structure can be fabricated successfully. The cell-laden composite structure revealed that the printed structure was mechanically stable, the laden cells were satisfactorily viable, and even cell proliferation/differentiation was well performed. Moreover, the cells in the composite structure exhibited significant osteogenic activities compared to the pure collagen bioink (control), and higher levels of osteogenic gene expression of the hASC-laden composite structure were observed without using an osteogenic medium than those of the control using an osteogenic medium, indicating that the laden β-TCP triggered osteogenic differentiation of the hASCs.