3D bioprinting of photo‐crosslinkable silk methacrylate (SilMA)‐polyethylene glycol diacrylate (PEGDA) bioink for cartilage tissue engineering

Articular cartilage damage poses huge burden on healthcare sector globally due to its extremely weak inherent regenerative ability. Three-dimensional (3D) bioprinting for development of cartilage mimic constructs using composite bioinks serves as an emerging perspective. However, difficulty in development of suitable bioink and chemical crosslinking associated inherent toxicity hamper widespread adoption of this technique. To circumvent this, a photo-polymerizable hydrogel-based bioink which helps in recapitulation of the complex cartilage microenvironment is pertinent. Herein, a photo-crosslinkable bioink containing different concentrations of silk methacrylate (SilMA) and polyethylene glycol diacrylate (PEGDA) was mixed with chondrocytes for biofabrication of 3D bioprinted cartilage constructs. The rheological properties, printability of bioink and physico-chemical characterization of printed hydrogel constructs were examined along with cartilaginous tissue formation. The printed SilMA-PEGDA hydrogel constructs possessed proper internal porous structure and demonstrated most reliable rheological properties, printability along with good mechanical, and degradation properties suitable for cartilage regeneration. Live/dead staining showed cytocompatibility of the 3D-bioprinted SilMA-PEGDA constructs. Moreover, a marked increase in cell number and DNA content was observed within the cartilaginous tissue as indicated by cell viability and DNA content quantitation. Biochemical evaluation confirmed the neocartilage formation within SilMA-PEGDA bioprinted constructs as revealed by enhanced deposition of cartilage specific extracellular matrix-sulphated GAG (sGAG) and collagen type II (>2-fold increase, p < 0.001) with time. Finally, immunohistochemical analysis indicated expression of collagen type II and aggrecan which corroborated with cartilaginous tissue formation. Taken together, we conclude that SilMA-PEGDA bioink could be suitable candidate for bioprinting chondrocytes to support cartilage tissue repair and regeneration.