A New Silicone Carbonate Polyurethane Copolymer

摘要

Polyurethanes (PU) have long been used for biomedical applications due to their excellent mechanical properties and reasonable biocompatibility. However, polyether urethane elastomers are susceptible to biodegradation1. Silicones are known to be extremely biostable and biocompatible, making silicone segments an ideal replacement for the polyether soft segments of polyurethanes. As a result, a new silicone polyurethane copolymer, Elast-Eon™ 2A, was developed by AorTech Biomaterials in Australia2. St. Jude Medical Cardiac Rhythm Management Division (SJM-CRMD) began marketing this material as Optim® insulation (Optim) in its pacemaker and defibrillator leads in 2006. Optim combines the toughness of polyurethane with the biostability of silicone into a single material. Optim has a hardness of ~90A while silicones used as insulation can have hardnesses in the range of 60~80A. AorTech recently developed a silicone carbonate polyurethane copolymer called EcSil™ which has a hardness of ~74A. This study compared several mechanical properties useful in establishing the appropriateness of a material for use in pacing and defibrillation leads. Additionally, the biostability of EcSil to Optim was compared using both an accelerated in vitro metal ion oxidation (MIO) and in vivo environmental stress cracking (ESC) methods.