Effect of Surface Grafted Hydroxyapatite on the Improved Performance of Hydroxyapatite/Poly(ε-caprolactone) Scaffold

Hydroxyapatite nanoparticles (HAP) were surface-grafted with poly(ε-caprolactone) (PCL) using two types of hydroxyl groups: inherent hydroxyl groups within HAP and hydroxyl groups of poly(2-hydroxyethyl methacrylate) (PHEMA) grafted on the HAP surface by atom transfer radical polymerization (ATRP). The grafting efficiency and the amount of grafted polymer were evaluated by thermal gravimetric analysis (TGA). The colloidal stability testing suggested that the surface-grafted HAP retained higher dispersibility in methylene chloride than pure HAP nanoparticles did. Moreover, the dispersity of the modified particles was significantly improved with the increasing amount of PCL grafted. The composite scaffolds of PCL and surface-grafted HAP exhibited enhanced compressive strength and modulus, which was attributed to the increased interfacial interaction between PCL and surface-modified HAP. In particular, it was found that the compressive modulus of the surface-grafted HAP with 47.2 wt% PCL was 91.6% higher than that of pure HAP mixed with PCL scaffold.