Advanced 3D-Printing Bioinks for Articular Cartilage Repair

Chondral lesions caused by stressors, such as injury or inflammation, lead to osteoarthritis (OA). OA is a degenerative joint disease that has become a challenge worldwide. As the articular cartilage is incapable of self-regeneration due to the absence of vessels and nerves, novel cartilage repair techniques are urgently needed. Three-dimensional (3D) bioprinting, which allows the precise control of internal architecture and geometry of printed scaffolds, has stepped up to be a promising strategy in cartilage restoration. With regards to 3D bioprinting, bioinks with proper chemical and mechanical properties play one of the most critical roles in designing successful cartilage tissue constructs. In particular, hydrogels as 3D hydrophilic cross-linked polymer networks are highly recommended as bioinks because of their fine biocompatibility, easy fabrication, and tunable mechanical strength. Herein, we highlight the widely used polymers for hydrogel preparation and further provide a non-exhaustive overview of various functional modified additives (such as cells, drugs, bioactive factors and ceramic) to exploit the unique properties suitable for bioprinted cartilage. Finally, a prospective on future development for 3D-bioprinting in cartilage repair is elucidated in this review.