IN-VIVO BIOCOMPATIBILITY AND BIOSTABILITY OF MODIFIED POLYURETHANES

Modified segmented polyurethanes were examined for biostability and bi ocompatibility using an in vivo cage implant system for time intervals of 1, 2, 3, 5, and 10 weeks. Two types of materials were used: polyet her polyurethanes and polycarbonate polyurethanes. Two unmodified poly ether polyurethanes (PEUU A' and SPU-PRM), one PDMS end-capped polyeth er polyurethane (SPU-S), and two polycarbonate polyurethanes (SPU-PCU and SPU-C) were investigated in this study. Techniques used to charact erize untreated materials were dynamic water contact angle, stress-str ain analysis, and gel permeation chromatography. Cellular response was measured by exudate analysis and by macrophage and foreign body giant cell (FBGC) densities. Material characterization, postimplantation, w as done by attenuated total reflectance-Fourier transform infrared spe ctroscopy (ATR-FTIR) in order to quantify biodegradation and scanning electron microscopy (SEM) to qualitatively describe the cellular respo nse and biodegradation. The exudate analysis showed that the acute and chronic inflammatory responses for all materials were similar. Lower FBGC densities and cell coverage on SPU-S were attributed to the hydro phobic surface provided by the PDMS endgroups. The polycarbonate polyu rethanes did not show any significant differences in cell coverage or FBGC densities even though the macrophage densities were slightly lowe r compared to polyether polyurethanes. By 10 weeks, biodegradation in the case of PEUU A' and SPU-PRM was extensive as compared to SPU-S bec ause the PDMS endcaps of SPU-S provided a shield against the oxygen ra dicals secreted by macrophages and FBGCs and lowered the rate of biode gradation. In the case of polycarbonate polyurethanes, the oxidative s tability of the carbonate linkage lowered the rate of biodegradation t remendously as compared to the polyether polyurethanes (including SPU- S). The miner amount of biodegradation seen in polycarbonate polyureth anes at 10 weeks was attributed to hydrolysis of the carbonate linkage . (C) 1997 John Wiley & Sons, Inc.