APATITE COATED ON ORGANIC POLYMERS BY BIOMIMETIC PROCESS - IMPROVEMENT IN ITS ADHESION TO SUBSTRATE BY GLOW-DISCHARGE TREATMENT

A dense, uniform, and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure: First, a substrate is set in contact with particles of bioactive CaCrSiO2-based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma so that a number of apatite nuclei are formed on the substrate. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5SBF) so that the apatite nuclei grow in situ. In the present study, organic polymer substrates were treated with glow-discharge in O-2 gas atmosphere, then subjected to the above-mentioned biomimetic process. The induction periods for the apatite nucleation on all the examined organic polymers were reduced from 24 to 6 h, with glow-discharge treatment. The adhesive strengths of the formed apatite layer to the substrates increased from about 4 to 10 MPa for poly(ethylene terephthalate) and poly-ether sulfone, and from 1 similar to 2 to 6 similar to 7 MPa even for poly(methyl methacrylate), polyamide 6 and polyethylene. It is supposed that highly polar groups such as carbonyl, ester, hydroxyl, and carboxyl ones formed by glow-discharge treatment increased the affinity of a silicate ion with the substrates to decrease the induction period, and also increased the affinity of the apatite with the substrate to increase the adhesive strength. The apatite-organic polymer composites thus obtained are expected to be useful as bone-repairing materials as well as soft tissue-repairing materials. (C) 1995 John Wiley & Sons, Inc.