Functional stability of activated graphene-based electrodes after sterilization with ethylene oxide

Abstract

Neural implants are devices placed in the central or peripheral nervous system to electrically interact with the nervous tissue in order to monitor or treat neural diseases. To provide the highest benefit for patients with the minimum risk, advanced materials and devices have been developed to record and stimulate neural activity with high resolution and safety. The materials used at the interface between the devices and the neural tissue set a limit in spatial resolution of the neural signals transduction. This is the case of EGNITE (Engineered graphene for neural interfaces), a new electrode technology based on a carbon-based material. With this promising technology is possible to miniaturize the electrodes to micrometric scale while keeping high definition recording and efficacy in stimulation. The technology has been successfully tested in vitro and in vivo in rodents and large animals. However, it has been never tested in humans. To reach clinical studies and according to the ISO10993 the devices will need to go through a sterilization step, for example with ethylene oxide. This step, which could modify the performance of the electrode, has been never tested on the EGNITE technology. Thus, this thesis aims to assess the electrochemical properties of EGNITE electrodes after a sterilization process with ethylene oxide. Here, 22 devices from 2 different designs were studied in two experimental phases. During the first phase, the electrochemical properties of EGNITE electrodes were studied and discussed. In the second phase, 6 devices were sent to sterilize and their electrochemical properties were characterized, before and after the sterilization process. The obtained results were analysed with a software created for this thesis, which allow us to get conclusions at different statistical levels. The results of the experiments performed in the frame of this thesis suggest that the electrochemical properties were not modified beyond the accepted range and the functionality was kept after the sterilization process. However, a second round of experiments is needed to statistically verify the lack of electrochemical changes at the electrode level.