Effects of silica on the bioactivity of calcium phosphate composites in vitro

In the present study, silica-calcium phosphate composites (SiO2-CaP composites) were developed by mixing the starting materials (SiO2 and CaHPO4) in different ratios with the addition of 0.1% w/v NaOH solution. The phase composition of the SiO2-CaP composites was determined by XRD and FTIR. After thermal treatment at 350 degrees C/1 h and at 1000 degrees C/ 3.5 h; all SiO2-CaP composites composed of beta-quartz, alpha-cristobalite and beta-Ca2P2O7. The presence of calcium phosphate enhanced the transformation of beta-quartz into alpha-cristobalite at 1000 degrees C. SEM observation indicated favorable attachment and spreading of neonatal rat calvaria osteoblasts onto the surface of silica-rich SiO2-CaP composites. After attachment, these cells produced significantly higher amount of protein and expressed higher AP activity than cells attached to silica-poor samples. Results of the study suggested that the silica-based composites are more bioactive than calcium phosphate-based composites. Silica promoted the expression of osteoblast phenotype by both solution-mediated effect and direct interaction with the surface of the substrate. (C) 2005 Springer Science + Business Media, Inc.