tecoflex and biomer

A series of novel polyurethane elastomers based on methylenediphenyl diisocyanate, 1,4-butanediol and the macrodiols, poly(hexamethylene oxide), poly(octamethylene oxide), and poly(decamethylene oxide) were implanted subcutaneously in sheep for periods of 3 and 6 months. The specimens that were subjected to 3 months of implantation were strained to 250% of their resting length, while those implanted for 6 months had no applied external strain. SEM examination of the explanted specimens revealed that the novel materials displayed resistance to environmental stress cracking. Proprietary materials, Pellethane 2363-80A, Biomer and Tecoflex EG-80A, which had been implanted under identical conditions, showed evidence of significant stress cracking. The extent of stress cracking in the 3-month strained experiment was similar to that from the 6-month unstrained experiment. Stress cracking was also observed in Pellethane 2363-55D, when implanted for 6 months (unstrained). Neither changes in molecular weight nor in tensile properties provided a clear indication of early susceptibility to degradation by environmental stress cracking.

Topics: Animals; Biocompatible Materials; Butylene Glycols; Equipment Failure; Foreign-Body Reaction; Glycols; Hardness; Male; Microscopy, Electron, Scanning; Molecular Weight; Polymers; Polyurethanes; Prostheses and Implants; Sheep; Stress, Mechanical; Surface Properties; Tensile Strength

Several analytical pyrolysis methods, namely pyrolysis mass spectrometry (Py-MS), time-resolved pyrolysis mass spectrometry (TRPy-MS), and pyrolysis short column gas chromatography mass spectrometry (Py-GC/MS) were used to analyze polymers of clinical interest both before and after implantation. A sample of Biomer, a poly(ether urethane urea) used in the Utah artificial heart, was analyzed using these methods. Two poly(ether urethanes) (Tecoflex and Pellethane) and a poly(dimethylsilicone) (Silastic) sample were analyzed using Py-GC/MS. The direct Py-MS of Biomer identified the components used in the manufacture of Biomer. Py-GC/MS of Biomer, Tecoflex, Pellethane, and Silastic also identified the components used in their manufacture. The analysis of explanted Biomer detected the presence of adsorbed cholestadiene, the reaction of chloride ions with a stabilizer, and the presence of a siloxane contaminant. The cholestadiene was detected on the outside housing of an artificial heart which had been implanted for 297 days. The cholestadiene was detected at low levels and was identified by library search on the MS data system. The siloxane contaminant was also identified by the MS data system. All of the methods demonstrated required only short instrumental analysis times (10 min or less). Data analysis required much more time, but much of the data analysis can be automated.

Topics: Biocompatible Materials; Gas Chromatography-Mass Spectrometry; Hot Temperature; Mass Spectrometry; Polymers; Polyurethanes; Prostheses and Implants; Silicone Elastomers; Silicones