Enhanced Bone-Regenerative Performance of Porous Hybrid Scaffolds by Surface Immobilization of Nano-Hydroxyapatite

Nano-hydroxyapatite (N-HAp)has shown the pivotal role in producing bone-regenerative materials since it has similarity to natural bone minerals in terms of size, morphology, and the composition. Currently, the combination of biopolymers and N-HAp is recognizedas an attractive approach in generating hybrid scaffolds for bone tissueengineering. Surface engineering is an important issue since it determines whether cells can effectively adhere and proliferate on porous scaffolds. We aim to develop a synthetic approach to porous 3D scaffolds by immobilizing N-HAp on pore surfaces. The discrete nano-level anchoring of N-HAp on the scaffold pore surface is achieved using surface-repellent stable colloidal N-HAp with surface phosphate functionality. This rational surface engineering enables surface-anchored N-HAp to express its overall intrinsic bioactivity,since N-HAp is not phase-mixed with the polymers. The porous polymer scaffolds with surface-immobilized N-HAp provide more favorable environments thanconventional bulk phase-mixed polymer/N-HAp scaffolds in terms of cellular interaction and growth. In vitro biological evaluation using alkalinephosphatase activity assay supports that immobilized N-HAp on pore surfaces of polymer scaffolds contributed to the more enhanced in vitro osteogenicpotential. Besides, the scaffolds with surface-exposed N-HAp provide favorable environments for enhanced in vivo bone tissue growth, estimated by characteristic biomarkers of bone formation such as collagen. The results suggest that newly developed hybrid scaffolds with surface-immobilized N-HApmay serve as a useful 3D substrate with pore surfaces featuring excellent bonetissue-regenerative properties. Acknowledgement. This research was supported by a grant (code #: 2009K000430) from 'Center for Nanostructured Materials Technology' under '21st Century Frontier R&D Programs' of the Ministry of Education, Science and Technology, Korea.