Composition and structure of apatite formed on organic polymer in simulated body fluid with a high content of carbonate ion

Apatite layer was formed on polyethyleneterephthalate (PET) substrate by th e following biomimetic process. The PET substrate was placed on granular pa rticles of a CaO, SiO2-based glass in simulated body fluid (SBF) with ion c oncentrations nearly equal to those of human blood plasma to form apatite n uclei on their surfaces. The apatite nuclei was then grown into a continuou s layer by subsequently soaking the substrate in SBF under air or CO2 atmos phere in which CO2 partial pressure in the ambient was adjusted to 14.8 kPa to increase the content of carbonate ion to a level nearly equal to that o f blood plasma. The increase in the content of carbonate ions in SBF change d the Ca/P atomic ratio of the apatite from 1.51 to 1.63, content of CO32- ions from 2.64 to 4.56 wt %, and lattice constants a from 94.32 to 94.23 nm and c from 68.70 to 68.83 nm, respectively. The Ca/P ratio and lattice con stants of the apatite formed in SBF under CO2 atmosphere were approximately identical to those of bone apatite, i.e. Ca/P atomic ratio 1.65, content o f CO32- ion 5.80 wt % and lattice constants a 94.20 and c 68.80 nm. This in dicates that an apatite with composition and structure nearly identical to those of bone apatite can be produced in SBF by adjusting its ion concentra tions including the content of carbonate ions to be equal to those of blood plasma. (C) 2000 Kluwer Academic Publishers.