RECENT ADVANCES IN BIOMEDICAL POLYURETHANE BIOSTABILITY AND BIODEGRADATION

This paper summarizes our recent efforts to better understand the effe cts of antioxidants, the effects of strain-state, mechanistic studies of soft segment cleavage by reactive oxygen radicals, and the effects of different soft segment chemistries on the biostability/biodegradati on of polyether polyurethanes (PEUUs). In vivo cage implant system stu dies and in vitro cobalt ion/hydrogen peroxide studies have been carri ed out on PEUUs and the polymers have been analysed by attenuated tota l reflectance and Fourier transform infrared (ATR-FTIR) spectroscopy, and scanning electron microscopic (SEM) characterization of the PEUU s urfaces. The natural antioxidant, vitamin E, has been shown to inhibit biodegradation and enhance biostability of PEUUs. Studies of the effe ct of stress state on PEUU biodegradation demonstrate that stress can inhibit biodegradation. While polyether soft segments may be cleaved b y the presence of reactive oxygen radicals, the presence of oxygen has a profound effect in accelerating biodegradation. The biodegradation of polyurethanes may be inhibited by substituting different chemistrie s such as polydimethylsiloxanes, polycarbonates, and hydrocarbon soft segments for the polyether soft segments. To safety utilize polyuretha nes in long-term biomedical devices, the biodegradation mechanisms of polyurethane elastomers must be fully understood and subsequently prev ented. (C) 1998 SCI.