Synthesis of functionally graded MgCO3 apatite accelerating osteoblast adhesion.

As a means of improving the biological properties of materials for use as bone substitutes, functionally graded carbonate apatite containing Mg, FGMgCO3Ap, was synthesized at 60 degrees C and pH 7.4 using a gradient magnesium supply system. X-ray diffraction analysis of FGMgCO3Ap showed a poorly crystallized apatitic pattern, similar to that of human bone. ESCA analysis clearly showed the negative gradient distribution in Mg1s intensity (atomic concentration) of magnesium from the crystal surface toward the inner core. When the FGMgCO3Ap crystals were mixed with collagen, the resulting FGMgCO3Ap-collagen composite, irradiated with UV light for 4 h, retained their features in the saline solution. After washing away the nonadhesive cells, a cell adhesion assay showed that the optical density of the FGMgCO3Ap-collagen composite was higher than that of the CO3Ap-collagen composite. SEM observation showed that the osteoblast-like cells adhered well to the surface of the FGMgCO3Ap-collagen composite. Staining with hematoxylin-eosin and alizarin red confirmed the existence of a great many more cells and a thicker extracellular matrix layer on the FGMgCO3Ap-collagen composite than on the CO3Ap-collagen composite. This result demonstrated the acceleration effect of magnesium ions on osteoblast adhesion on the FGMgCO3Ap-collagen composite. Copyright 2002 Wiley Periodicals, Inc.