Direct injection of chondrocytes in a minimally invasive way has been regarded as the significantly potential treatment for cartilage repair due to their ability to fill various irregular chondral defects. However, the low cell retention and survival after injection still limited their application in clinical transformation. Herein, we present chondrocyte-laden microspheres as cell carriers based on a double-network hydrogel by the combination of the chitosan and poly(ethylene glycol) diacrylate (PEGDA). The microfluidic technique was applied to prepare size-controllable chitosan/PEGDA hydrogel microspheres (CP-MSs) via the water-in-oil approach after photo-crosslinking and physical-crosslinking. The chondrocytes were laden on CP-MSs, which showed good cell viability and proliferation after long-term cell cultivation. The in vitro investigation further demonstrated that chondrocyte-laden CP-MSs were injectable and the cell viability was still high after injection. In particular, these cell-laden microspheres were self-assembled into a 3D cartilage-like scaffold by a bottom-up strategy based on cell-cell interconnectivity, which suggested that these injectable chondrocyte-laden microspheres showed potential applications as chondrocyte carriers for bottom-to-up cartilage tissue engineering.
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