A chondroitin sulfate based injectable hydrogel for delivery of stem cells in cartilage regeneration

Chondroitin sulfate (CS), as a popular material for cartilage tissue engineering scaffolds, has been extensively studied and reported for its safety and excellent biocompatibility. However, the rapid degradation of pure CS scaffolds has brought a challenge to regenerate neo-tissue similar to natural articular cartilage effectively. Meanwhile, the poly(ethene glycol) (PEG) -based biopolymer is frequently applied as a structural constituent material because of its remarkable mechanical properties, long-lasting in vivo stability, and hypo-immunity. Here, we report that the combination of CS and hyperbranched multifunctional PEG copolymer (HB-PEG) could synergistically promote cartilage repair. The thiol functionalised CS (CS-SH)/HB-PEG hydrogel scaffolds were fabricated via thiol–ene reaction, which exhibits rapid gelation, excellent mechanical properties and prolonged degradation properties. We found that rat adipose-derived mesenchymal stem cells presented great cell viability and improved chondrogenesis in CS-SH/HB-PEG hydrogels. Moreover, the injectable hydrogel scaffolds reduced stem cell inflammatory response, consistent with the well-documented anti-inflammatory activities of CS.