Growth and adhesion of osteoblast-like cells derived from neonatal rat calvaria on calcium phosphate ceramics

The effects of biocompatible ceramics on the growth and adhesion of osteobl ast-rich rat calvarial cell cultures were investigated. Osteoblast-like cel ls and mouse fibroblast-like L-929 cells were cultured on composite sinters of hydroxyapatite (HAP) and beta-tricalcium phosphate (TCP) culture carrie rs, whose Ca/P molar ratios were adjusted to values of 1.50, 1.55, 1.60, 1. 64 and 1.67. The growth rates of both. cell types were accelerated on the T CP-HAP ceramics as compared to those on polystyrene plastic (LUX) or bioine rt zirconia ceramics. The population of osteoblast-like cells reached a den sity of 2.28 x 10(5) cells/cm(2) on 100% HAP (Ca/P ratio 1.67) at 9 d of cu lture, while the corresponding cell density was 1.66 x 10(5) cells/cm(2) on LUX and 1.26 x 10(5) cells/cm(2) on zirconia. Adhesion of the osteoblast-l ike cells on TCP-HAP ceramics was similarly increased as compared with that on LUX or zirconia ceramics. The adhesion of L-929 cells on TCP-HAP cerami cs was found to be weaker than that on cultures on LUX or zirconia ceramics . The time-dependent variations in the alkaline phosphatase activity of the osteoblast-like cells showed that the osteoblastic phenotype was potentiat ed by culturing the cells in calcium-rich media. The surface analyses of th e Ca/P ratio and the microstructure by XRD and FTIR suggest that the Ca-ric h surface was newly formed by recombination on the surface layer in the cul ture medium containing fetal bovine serum. These results suggest that the s urface of TCP-HAP ceramics, especially that of 100% HAP ceramics, are effec tive for accelerating growth and differentiation of osteoblast-like cells. This is most probably due to the chemical and physical instability and comp osition of 100% HAP, which promote the formation of a Ca-rich layer at the cell-material interface and provision of Ca ions to the osteoblast-like cel ls.