IN-VITRO BONE BIOCOMPATIBILITY OF POLY(ANHYDRIDE-CO-IMIDES) CONTAINING PYROMELLITYLIMIDOALANINE

Poly(anhydride-co-imides) are currently under study for applications i nvolving bone. The cytotoxicity of a series of poly(anhydride-co-imide s) with osteoblast-like cells (MC3T3-E1) was evaluated. The imide comp onent of the copolymers was based on pyromellitylimidoalanine and the anhydride component was based on either sebacic acid or 1,6-bis(carbox yphenoxy)hexane. Cell adhesion and proliferation on the sur faces of t he polymer discs were observed by environmental scanning electron micr oscopy. During the first 24 hours of attachment, the cells showed norm al morphology when cultured on copolymers containing 1,6-bis(carboxyph enoxy)hexane. The cells did not adhere to the polymers containing seba cic acid, probably due to the rapid degradation of the polymer surface s. Concurrently, the effects of polymer breakdown products on osteobla st-like cells were evaluated by studying their proliferation (cell num bers), viability (dye exclusion), morphology (light microscopy), and p henotypic expression. The morphology of osteoblast-like cells cultured in the presence of the polymer breakdown products pyromellitylimidoal anine and pyromellitic acid was found to be similar to that of the sam e cells grown on tissue culture polystyrene and consisted of a charact eristic polygonal shape. With use of a monoclonal antibody to osteocal cin, these cells were shown to demonstrate preserved osteoblast phenot ype with growth over a 21-day period. In addition, the cells reached c onfluency after 3-4 days, similar to cells grown on tissue culture pol ystyrene. This in vitro evaluation showed that the poly(anhydride-co-i mides) evaluated are non-cytotoxic and may be viable biomaterials for orthopaedic applications.