3D printing of high-strength photo-crosslinking flaxseed gum bioink for cartilage regeneration

Three-dimensional (3D) bioprinting provides a new possibility for personal customization of cartilage tissues. Although biocompatible, most natural biopolymer inks have poor mechanical strength to bear repeated extrusion, incomparable with load-bearing cartilage. By utilizing a heteropolysaccharide called flaxseed gum (FG), a strong photo-crosslinked methacrylated FG (FGMA) bioink was synthetized and integrated with stem cells for cartilage defect therapy. As a hybrid bioink, FGMA has favorable 3D printability and shown to exhibit high mechanical strength and superior fatigue resistant ability. 4% FGMA2 (MA substitution = 8.1%) has the modulus of about 41 times of GelMA and could maintain its structure integrity under 60% deformation after 2000 cycles. FGMA2 has a degradation period of about 66 days, similar to that of GelMA. In vitro study shows that FGMA2 has excellent biocompatibility with stem cells and chondrogenic potential, both beneficial to cartilage regeneration in the cartilage lesion model. More importantly, in vivo study demonstrated that the regenerated neo-cartilage tissue by FGMA2 displayed the similar morphology and matchable mechanical strength to the natural cartilage after 8 weeks. In conclusion, FGMA has demonstrated this potential as a high-performance bioink for 3D printing for tissue/organ regeneration.