(Invited) Chemistry of Robust Neural Interfaces

Wednesday, 4 October 2017: 16:40
National Harbor 11 (Gaylord National Resort and Convention Center)
P. A. Takmakov (US FDA)
Neural implants of the future will be able to acquire and process signals from the nervous system to develop patient- and situation-specific electrical neuromodulation for therapeutic effects. This approach provides fantastic opportunities for dynamic, flexible and personalized treatments. However, realization of this vision requires robust neural interfaces between medical devices and biological tissue. Device failures because of the body’s immune response as well as adverse effects associated with neuromodulation are significant challenges. We are developing in vitro platforms to (1) establish root causes of these issues and (2) provide methods and techniques for rapid development of robust neural implant technologies.

One “side-effect” associated with neuromodulation is irreversible electrochemical reactions that can introduce harmful chemical species during charge injection. The exact nature of these reactions is not well understood. In this work, an in vitro platform for quantification of these reactions that is suitable for use with any specific stimulation protocol has been developed. It was observed that charge injection with imbalanced waveforms leads to decrease in dissolution of platinum. This finding suggests a reduction in irreversible electrochemical reactions, which is contrary to accepted belief.

The second aspect of a robust neural interface is related to current reliance of a new generation of neural implants on microfabrication technology, which does not necessarily yield devices with high tolerance for a biological environment. This calls for extensive R&D work on developing reliable devices. Testing of new implant designs in chronic animal experiments is slow and expensive. To facilitate innovation, reactive accelerated aging (RAA) platform has been developed. RAA is an in vitro system that simulates the biological environment, particularly attack of an implant by the immune system by exposing the device to elevated temperature and hydrogen peroxide for a short duration. RAA was used to discover failure modes for commercial devices that included dissolution of metal, delamination or substantial loss of insulation with further violation of its electrical and barrier properties. RAA was validated by comparing to failures modes that have been observed after chronic implantation in rodent brain.