Abstract
Poly(methylmethacrylate)(PMMA) is the most frequently used bone void filler for vertebral augmentation in osteoporotic fracture. PMMA bone cement not only exhibits strong mechanical properties but also can be fabricated according to the shape of bone defect. However, the adhesion between the PMMA-based cement and the adjacent bone is usually weak as PMMA bone cement is inherently bioinert. The combination of bioceramics and polymers as composites may increase cell attachment and improve biocompatibility. The nano-hydroxyapatite(HAP) not only plays a significant role in maintaining the properties of the natural bone but also offers a favorable environment for osteoconduction, protein adhesion, and osteoblast proliferation. However, when nano-HAP is blended with PMMA, defects and cracks may form at the polymer/ceramics interface, resulting in uneven distribution of stress and subsequent inferior mechanical strength. The lack of affinity between nano-HAP and polymer may also produce aggregation and uneven distribution of nano-HAP. These problems may be resolved by using surface-modified HAP nano-crystals prepared by chemically grafting poly(ε-caprolactone)(PCL) on nano-HAP surface so as to increase the affinity of polymer/ceramic interphases . Thus, incorporation of surface-modified nano-hydroxyapatite (EC-HAP) may not only improve the interfacial adhesion between cement and bone and between nanoparticles and cement, but also increase biocompatibility. In this research, PMMA mixing with 0~30 wt% EC-HAP were examined. Surface morphology, degradability, mechanical properties and cellular responses were investigated in vitro. The PMMA cement with EC-HAP exhibited superior mechanical properties and stability. Furthermore, the introduction of EC-HAP could promote the adhesion and proliferation of cells on the surface of EC-HAP/PMMA. The bioactivity of the PMMA cement with 20 wt% EC-HAP had the best osteogenic bioactivity. The results showed that the surface-modified HAP/PMMA has potential as bone substitute.