Study of polymer-apatite composites as model systems for calcification andnovel biomaterials

Using the biomimetic method, we prepared hydrogel-hydroxyapatite (HAp) comp osites and polyurethane (PU)-HAp composite. The hydrogel-HAp composites wer e studied as model systems of calcification. PU-HAp composites were used as implantable materials for studying soft-tissue compatibility of HAp. HAp l ayers were formed on/in certain types of nonionic hydrogels that have hydro xyl groups on their side chains. The hydrogels used were poly(vinyl alcohol ) (PVA), poly(2-hydroxyethyl methacrylate) (PHEMA), poly (glucosyloxyethyl methacrylate) (PGEMA), and agarose. Under an optical microscope, one could observe the formation of thin and continuous HAp layers on the top surface of the PVA, PHEMA, and PGEMA gels. On the other hand, intermittent HAp laye rs were observed on the surface of the agarose gel. The swelling ratio and the bound water content of these hydrogels were measured as an essential ch aracter in HAp formation. There were relations among the HAp formation, the swelling ratios, and the bound water content. PU-HAp composites were impla nted subcutaneously into rats. HAp which formed on the PU could exhibit goo d tissue regeneration activity. The effect of HAp was comparable to that of fibronectin, collagen and RGD peptide. HAp-polymer composites will become novel biomaterials in the near future.