3D Printing Biologically-inspired DNA Based Gradient Scaffolds for Cartilage Tissue Regeneration.

Cartilage damage caused by ageing, repeated overloading, trauma, and diseases can result in chronic pain, inflammation, stiffness, and even disability. Unlike other types of tissues (bone, skin, muscle, etc.), cartilage tissue has an extremely weak regenerative capacity. Currently, the gold standard surgical treatment for repairing cartilage damage includes autografts and allografts. However, these procedures are limited by insufficient donor sources and the potential for immunological rejection. After years of development, engineered tissue now provides a valuable artificial replacement for tissue regeneration purposes. 3D bioprinting technologies can print customizable hierarchical structures with cells. The objective of the current work was to prepare a 3D-printed three-layer gradient scaffold with lysine functionalized rosette nanotubes (RNTK) for improving the chondrogenic differentiation of adipose-derived mesenchymal stem cells (ADSCs). Specifically, biologically inspired RNTKs were utilized in our work since they have unique surface chemistry and biomimetic nanostructure to improve cell adhesion and growth. Different ratios of gelatin methacrylate (GelMA) and poly (ethylene glycol) diacrylate (PEGDA) were printed into a three-layer GelMA-PEGDA gradient scaffold using a stereolithography-based printer, followed by coating with RNTKs. The pores and channels (~500 µm) were observed in the scaffold. It was found that the population of ADSCs on the GelMA-PEGDA-RNTK scaffold increased by 34 % compared to the GelMA-PEGDA scaffold (control). Moreover, after three weeks of chondrogenic differentiation, collagen II, glycosaminoglycan, and total collagen synthesis on the GelMA-PEGDA-RNTK scaffold significantly respectively increased by 59%, 71%, and 60%, as compared to the control scaffold. Gene expression of collagen II α1, SOX 9, and aggrecan in the ADSCs growing on the GelMA-PEGDA-RNTK scaffold increased by 79%, 52%, and 47% after three weeks, compared to the controls, respectively. These results indicated that RNTKs are a promising type of nanotubes for promoting chondrogenic differentiation, and the present 3D printed three-layer gradient GelMA-PEGDA-RNTK scaffold shows considerable promise for future cartilage repair and regeneration.