Enhanced bone regeneration by porous poly(L-lactide) scaffolds with surface-immobilized nano-hydroxyapatite

Novel porous poly(L-lactide) (PLLA) scaffolds with surface-immobilized nano-hydroxyapatite (N-HAp) were synthesized for effective bone regeneration. N-Hap-bearing surface phosphate functionalities were immobilized chemically on the pore surface of amine-treated PLLA scaffolds. Thermogravimetric analysis (TGA) showed that 24 wt% of N-HAp had been immobilized on the scaffold pore surface. Field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) confirmed that N-HAp was exposed markedly on the pore surfaces of scaffolds compared to the conventional scaffold fabricated by a bulk-mixing process of PLLA and N-HAp. The PLLA scaffold with surface-immobilized N-HAp had a higher surface Ca atomic ratio (4.6%) than that on the pore surface of the bulk-mixed PLLA/N-HAp scaffold (Ca = 0.4%). The porous PLLA scaffolds with surface-immobilized N-HAp provided favorable environments for enhanced in vivo bone tissue growth, which was estimated by hematoxylin and eosin (H&E) staining for organic bone tissues and alizarin red S staining for inorganic bone minerals. These results suggest that the N-HAp immobilization approach may produce many useful scaffolds with pore surfaces featuring excellent bone tissue-regenerative properties.