Poly(ethylene glycol) hydrogels cross-linked by hydrolyzable polyrotaxane containing hydroxyapatite particles as scaffolds for bone regeneration

Poly(ethylene glycol) (PEG) hydrogels cross-linked by a hydrolyzable polyrotaxane containing hydroxyapatite particles (PRX-HAp) were developed as scaffolds for bone regeneration. Five scaffolds with various composition of the polyrotaxane, PEG and HAp particles were prepared to examine cell adhesion in vitro using rat primary cultured osteoblast. Cells were observed to attach well on a PRX-HAp that have the same weight ratio of the polyrotaxane and HAp particles at 7 days after seeding. These results indicate that HAp particles are necessary for cell adhesion and survival, but a higher ratio of the particles is not suitable for cell adhesion. The composites of rat osteoblast and the PRX-HAp were implanted subcutaneously in syngeneic rats and harvested at 5 weeks after implantation. In histological analysis, osteoblast-like cells became arrayed along the surface of the PRX-HAp, and osteoid-like tissues were observed in the region between a queue of osteoblast-like cells and PRX-HAp. These images are similar to intramembranous ossification, and it is expected that bone regeneration occurs on the surface of the PRX-HAp. This study strongly suggests the great potential of the PRX-HAp as scaffolds for bone regeneration.