Biocompatibility of polyimide-based neural interfaces for chronic implant applications

Abstract

Neural interfaces provide functional re-establishment of the central nervous system, as well as accessibility to monitor physiological responses at a cellular and molecular level. An ideal device is electrically, mechanically, and biologically compatible in long-term applications. Reducing the foreign body response and scar tissue formation caused by the surrounding tissue of the implant makes the device most biocompatible, while not hindering the electrical interface of the device. Technological advances in polymer materials are leading to improved designs of neural implants with the utilization of flexible polyimide, which decreases the relative micromotion strain. However, the flexibility of polyimide causes the device to buckle during insertion; therefore a biodegradable polymer, polyglycolic acid (PGA), is added to the polyimide device in order to temporarily enhance the structural rigidity. In this study we detail the successful biocompatibility demonstrated with both uncoated and PGA coated polyimide devices to provide new design strategies for neural implants used in chronic applications.