Bone tissue engineering via application of a collagen/hydroxyapatite 4D-printed biomimetic scaffold for spinal fusion

The fabrication of biomimetic scaffolding is a challenging issue in tissue engineering. Scaffolds must be designed with micrometer precision to enable cell proliferation and tissue growth, requiring customization based on the type of tissue being developed. Biomimetic scaffolds have attracted interest for their potential in spinal fusion applications. By providing a structured environment to promote osteogenesis, these materials offer a robust and minimally invasive means to fuse vertebrae. The present study describes the successful preparation of a biomimetic collagen/hydroxyapatite hierarchical scaffold, with each strut having several microchannels via 3D printing, leaching, and coating processes (i.e., one-way shape morphing, 4D printing). The biophysical properties of the scaffold were analyzed, as were its various cellular activities, using human adipose stem cells. This biomimetic microchannel scaffold demonstrated great potential for osteogenic activities in vitro and significantly increased new bone formation and ingrowth of blood vessels in vivo in a mouse model of posterolateral lumbar spinal fusion. These in vitro and in vivo results suggest that the microchannel collagen/hydroxyapatite scaffold could act as a potential bone graft substitute to promote high rates of successful fusion.