Surface Crystal and Degradability of Shape Memory Scaffold Essentialize Osteochondral Regeneration

Abstract

The minimally invasive deployment of scaffolds is a key safety factor for theregeneration of cartilage and bone defects. Osteogenesis relies primarily oncell-matrix interactions, whereas chondrogenesis relies on cell–cellaggregation. Bone matrix expansion requires osteoconductive scaffolddegradation. However, chondrogenic cell aggregation is promoted on therepellent scaffold surface, and minimal scaffold degradation supports theavascular nature of cartilage regeneration. Here, a material satisfying theserequirements for osteochondral regeneration is developed by integratingosteoconductive hydroxyapatite (HAp) with a chondroconductive shapememory polymer (SMP). The shape memory function-derived fixity andrecovery of the scaffold enabled minimally invasive deployment andexpansion to fill irregular defects. The crystalline phases on the SMP surfaceinhibited cell aggregation by suppressing water penetration and subsequentprotein adsorption. However, HAp conjugation SMP (H-SMP) enhancedsurface roughness and consequent cell-matrix interactions by limiting cellaggregation using crystal peaks. After mouse subcutaneous implantation,hydrolytic H-SMP accelerated scaffold degradation compared to that by theminimal degradation observed for SMP alone for two months. H-SMP andSMP are found to promote osteogenesis and chondrogenesis, respectively, invitro and in vivo, including the regeneration of rat osteochondral defectsusing the binary scaffold form, suggesting that this material is promising forosteochondral regeneration.