APATITE COATING ON ORGANIC POLYMERS BY A BIOMIMETIC PROCESS

Dense and uniform layers of a biologically active carbonate-containing hydroxyapatite can be formed on various kinds of organic polymers by the following biomimetic method, First, a substrate is set in contact with particles of CaO-SiO2-based glass soaked in a simulated body flui d (SBF) with ion concentrations nearly equal to those of human blood p lasma for forming the apatite nuclei on the substrate. Second, the sub strate is soaked in another solution highly supersaturated with respec t to the apatite, e.g., with ion concentrations 1.5 times those of SBF (1.5SBF) for making the apatite nuclei grow on the substrate in situ. The induction period for the apatite nucleation, which is defined as the time of the first treatment required for forming enough of the apa tite nuclei to make the continuous layer after the second treatment, w as almost 24 h for most of the examined polymers. The adhesive strengt h of the formed apatite layer to the polymers was as high as 3 to 4 MP a far poly(ethylene terephthalate), poly-ether sulfone, and poly (viny l alcohol) hydrogel. This type of apatite-organic polymer composite is expected to be useful for repairing not only living hard tissues but also soft ones.