Collagen-based bioinks for regenerative medicine: Fabrication, application and prospective

In the field of regenerative medicine, the importance of 3D bioprinting is self-evident and nonnegligible. However, 3D bioprinting technology also requires bioink with excellent performance as support material to fabricate a multi-functional bioinspired scaffold. Collagen-based bioink is regarded as an ideal 3D bioprinting ink for its excellent biocompatibility, controllable printability and cell loading property. It is an important breakthrough in regenerative medicine with the progress of collagen-based bioink, which fabricates bioinspired scaffolds with different functions and is applied in different repair scenarios. This review summarizes the different applications of collagen-based bioink and classifies them as soft tissue and hard tissue according to the target region. The applications of target region in soft tissues include skin, cartilage, heart and blood vessels, while in hard tissues include femur, skull, teeth and spine. When the collagen-based bioink is applied in repairing soft tissue, the requirements of function are higher, while the mechanical properties must be further improved in repairing hard tissue. We further summarize the characteristics of collagen-based bioink and point out the most important properties that should be considered in different repair scenarios, which can provide reference for the preparation of bioinks with different functions. Finally, we point out the main challenges faced by collagen-based bioink and prospect the future research directions.