VITAMIN-E AS AN ANTIOXIDANT FOR POLY(ETHERURETHANE UREA) - IN-VIVO STUDIES

Poly(etherurethane) elastomers are useful materials in medical devices because of their mechanical properties and biocompatibility. However, it is necessary to stabilize these elastomers against the oxidation o f their ether soft segments. Synthetic antioxidants such as Santowhite (R) and Irganox(R) are often satisfactory; however, particularly for b iomedical applications, it was of interest to test the natural antioxi dant vitamin E in poly(etherurethane urea) (PEUU) elastomers in vivo. The alpha-tocopherol form of vitamin E was added to PEUU at 5% by weig ht. Biaxially strained PEUU specimens with and without vitamin E were tested in vivo in the cage implant system. The influence of vitamin E on PEUU biostability was analyzed by attenuated total reflectance-Four ier transform infrared (ATR-FTIR) spectroscopy and scanning electron m icroscopic (SEM) characterization of the PEUU surface. ATR-FTIR result s showed that vitamin E prevented chemical degradation of the PEUU sur face up to 5 weeks implantation, and at 10 weeks 82% of the ether rema ined. In contrast, without an antioxidant, only 18% of the ether remai ned after 10 weeks. No surface pitting or cracking was observed by SEM on PEUU with vitamin E; PEUU without antioxidant ruptured owing to ex tensive pitting and cracking. It was concluded that the antioxidant pr operties of vitamin E prevented oxidation of strained PEUU elastomers in vivo. The influence of vitamin E on PEUU biocompatibility was chara cterized by exudate leukocyte counts, density of leukocytes adherent t o the PEUU, and morphology of adherent leukocytes. These results indic ated decreased leukocyte counts in the exudate and less active adheren t cells on the PEUU with vitamin E compared to PEUU without antioxidan t. A proposed cell-polymer feedback system demonstrates how vitamin E improves both biostability and biocompatibility of PEUU elastomers in vivo. (C) 1996 John Wiley & Sons, Inc.