Physicochemical properties and biocompatibility of the bi-layer polyvinyl alcohol-based hydrogel for osteochondral tissue engineering

Osteochondral defect regeneration was a great challenge because of limited self-repaired ability for its sophisticated hierarchical inner structure. Hereon, the bi-layer hydrogel with robust osteochondral interfacial bonding was formulated under fully physical crosslinking, which was consisted of polyvinyl alcohol/collagen II for cartilage layer and polyvinyl alcohol/biphasic calcium phosphate/carbon nanotubes for bone layer. The bi-layer hydrogel with irregular pore distribution showed decreased pore size from top to bottom. The tensile modulus of bi-layer hydrogel reached to 7.14 ± 3 MPa and the stretched fracture surfaces were always appeared in the upper hydrogels, proving bi-layer hydrogels' well interfacial bonding strength. Furthermore, hydrogels' biocompatibility was evaluated using two kinds of cells in vitro, and the repair performance was also assessed in vivo test. The results demonstrated the bi-layer hydrogel owned favorable cytocompatibility and could induce the formation of osteochondral regeneration. Additionally, the max load at defect section reached to 67.24 ± 36.06 N after 12 weeks regeneration, verifying well bonding strength between the neotissue and native adjacent tissues. This work revealed the favorable bi-layer hydrogel owed great potential in repairing osteochondral defects. [Display omitted] •A biomimetic bi-layer hydrogel was fully physical crosslinked for osteochondral TE.•The porous hydrogel owned well interfacial bonding strength without any glue.•The bi-layer hydrogel could promote the formation of osteochondral regeneration.•The neotissue had well bonding strength with native adjacent tissues.