The purpose of this project is to study the interaction between biomaterials and the physiological environment and to determine the suitability of specially-prepared biomaterials for use in various contexts. Polymers, metals and ceramics are important for use in catheters, heart-assist pumps, electrode insulation and similar implant applications. Variations in these materials as well as physically induced stress and environmentally accelerated degradation can severely reduce their effectiveness for long-term use as surgical devices. Previous studies undertaken by this project have shown a relationship between the molecular chain structure and resistance to hydrolysis. Recent evidence suggests that physical forces such as stress induced during fabrication can promote a form of stress corrosion. In vitro test data and SEM photomicrographs of surgical explants of various polyurethane classes show that premature failure is often the result of a combination of forces acting on the polymer at stress risers. Polymer systems and composites capable of time dissolution offer significant advantages in the development of devices that allow natural tissues to take over as healing progresses. Tissue ingrowth into porous materials provides greater stability for specific implants. A strong correlation exists between these in vitro and in vivo observations over short and long term periods of study. A polymer system has been developed that can be used to produce vascular stenosis to varying degrees for the purpose of study, control and treatment of various physiological disease states. This system relies upon the controlled dissolution characteristics 6f biodegradable polymers and hydrogels.
