APATITE COATED ON ORGANIC POLYMERS BY BIOMIMETIC PROCESS - IMPROVEMENT IN ITS ADHESION TO SUBSTRATE BY NAOH 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 substrate surface by the following biomimetic method at ordinary tempe rature and pressure. First, a substrate is set in contact with particl es of bioactive CaO SiO2 based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. Second, the substrate is soaked in another solution wit h ion concentrations 1.5 times those of SBF (1.5 SBF). In the present study, organic polymer substrates treated with 5 M NaOH solution were subjected to the above mentioned biomimetic process. The induction per iods for the apatite nucleation on polyethyleneterephthalate (PET), po lymethylmethacrylate (PMMA), polyamide 6 (PA6), and polyethersulfone ( PESF) substrates were reduced from 24 to 12 h with the NaOH treatment. The adhesive strength of the formed apatite layer were increased from 3.5 to 8.6 MPa, from 1.1 to 3.4 MPa, and from 0.6 to 5.3 MPa with the NaOH treatment, for PET, PMMA, and PA 6, respectively. It was assumed that highly polar groups, such as carboxyl and sulfinyl ones formed b y the hydrolysis of an ester group on PET and PMMA and of an amide gro up on PA 6, or of a sulfonyl group on PESF with the NaOH treatment, at tached a large number of hydrated silica dissolved from the glass part icles, to accelerate the apatite nucleation, and also to form a strong bond with the apatite. The apatite-organic polymer composites thus ob tained are expected to be useful as bone-repairing as well as soft tis sue-repairing materials. (C) 1994 John Wiley & Sons, Inc.