APATITE COATED ON ORGANIC POLYMERS BY BIOMIMETIC PROCESS - IMPROVEMENT IN ADHESION TO SUBSTRATE BY HCL TREATMENT

A dense, uniform and highly biologically active bone-like apatite laye r can be formed in arbitrary thickness on any kind and shape of solid substance by the following biomimetic method at normal temperature and pressure: first, a substrate is set in contact with particles of CaO- SiO2-based glass soaked in a simulated body fluid (SBF) with ion conce ntrations nearly equal to those of human blood plasma. Second, the sub strate is soaked In another solution with ion concentrations 1.5 times those of SBF (1.5 SBF). In the present study, organic polymer substra tes were treated with 1 M HCl solution, then subjected to the above me ntioned biomimetic process. The induction periods for the apatite nucl eation on polyethyleneterephthalate, polymethylmethacrylate, polyamide 6 and polyethersulfone substrates were reduced from 24 to 12 h with t he HCl treatment. The adhesive strength of the formed apatite layer to the polyethyleneterephthalate, polymethylmethacrylate and polyamide 6 substrates were increased from 3.5 to 7.0 MPa from 1.1 to 2.8 MPa and from 0.6 to 3.1 MPa, respectively, with the HCl treatment. It is supp osed that highly polar carboxyl group formed by the HCl hydrolysis rea ction of ester group in polyethyleneterephthalate and polymethyl meth acrylate or amide group in polyamide 6 increased the affinity of the s ubstrates with a silicate ion to decrease the induction period, and al so increased the affinity of the substrate with the apatite to increas e the adhesive strength. The apatite-organic polymer composites thus o btained are expected to be useful as bone-repairing materials as well as soft-tissue-repairing materials.