Figure 1.

The procedure of the biphasic biomimetic calcium phosphate coating. (a) Step 1: the biomaterial is immersed in a fivefold concentrated simulated body fluid for 24 h at 37°C, 150 r.p.m. with stirring. A fine, dense layer of amorphous calcium phosphate (ACaP) thereby formed serves as a seeding substratum for the deposition of a more substantial crystalline layer. (b) Step 2: after freeze-drying, the crystalline layer will be produced by immersing the ACaP-coated biomaterials in a supersaturated calcium phosphate solution for 48 h at 37°C, 60 r.p.m. with shaking. The samples are then freeze-dried. If the crystalline layer is to be functionalized by the incorporation of bioactive agents such as bone morphogenetic protein-2 (BMP-2), then these agents are introduced into the latter medium at a certain concentration. Circles, amorphous seedling layer; ellipsoids, BMP-2; diamonds, crystalline protein-carrying layer.