POLY(ANHYDRIDE-CO-IMIDES) - IN-VIVO BIOCOMPATIBILITY IN A RAT MODEL

The degradation and tissue compatibility characteristics of a novel cl ass of biodegradable poly(anhydride-co-imide) polymers: itylimidoglyci ne-co-1,6-bis(carboxyphenoxy)hexane] (TMA-gly:CPH) (in 10:90; 30:70 an d 50:50 molar ratios) and itylimidoalanine-co-1,6-bis(carboxyphenoxy)h exane] (PMA-ala:CPH) (in 10:90 and 30:70 molar ratios) were investigat ed and compared with control poly(lactic acid/glycolic acid) (PLAGA in 50:50 molar ratio) matrices, a well-characterized biocompatible polym er, in rat subcutaneous tissues for 60 days. Polymers were compression -molded into circular discs of 14 mm x 1 mm in diameter. On post-opera tive days 7, 14, 28 and 60, histological tissue samples were removed, prepared by fixation and staining, and analyzed by light microscopy. P LAGA matrices produced mild inflammatory reactions and were completely degraded at the end of 60 days, leaving implant tissues that were sim ilar to surgical wounds without implants. TMA-gly:CPH (10:90 and 30:70 ) matrices produced mild inflammatory reactions by the end of 60 days, similar to those seen with PLAGA. TMA-gly:CPH (50:50) produced modera te inflammatory reactions characterized by macrophages and edema. PMA- ala:CPH matrices elicited minimal inflammatory reactions that were cha racterized by fibrous encapsulation by the end of 60 days. In vivo deg radation rates of poly(anhydride-co-imides) were similar to PLAGA. Bot h PMA:ala:CPH and TMA-gly:CPH matrices maintained their shapes and deg raded at a constant rate over the period of two months. These polymers , possessing good mechanical properties and tissue compatibility, may be useful in weight-bearing applications in bone. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.