Cochlear implants as in vivo sensors (CIAS) – Electrochemical monitoring of the intracochlear microenvironment and electrode stability

• Applicants: Dr. Nicole Roßkothen-Kuhl, Ph.D.; Dr.-Ing. Andreas Weltin
• Subject Area: Otolaryngology, Phoniatrics and Audiology ; Biomedical Systems Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 539251872

Motivation. The cochlear implant (CI) is the most successful neuroprosthesis to date with more than 1 million implanted patients worldwide. The main function of the CI is to electrically stimulate the auditory nerve of deaf or near-deaf patients by means of platinum electrodes in the cochlea. In addition to acting as a stimulator of the auditory system, CIs can also be used to measure impedances as well as responses of the auditory nerve. To date, however, it is not possible to monitor changes in the biochemical microenvironment of the implant, although it is known that foreign body responses can be induced in the cochlea as a result of CI insertion. Objective. Our goal is to extend clinical CI electrodes with the function of a permanent in vivo sensor by developing novel electrochemical measurement protocols to permanently monitor the microenvironment and electrode state of the implant. In long-term experiments on CI-supplied rats, the intracochlear microenvironment will be monitored from the time of implantation, through the starting point of stimulation, to long-term implantation, and correlated with implant function and auditory perception. In addition, we aim to characterize the stability and degradation of CI electrodes. This includes the development of optimal sensor protocols as well as a stable reference electrode concept by using the CI electrodes themselves to enable long-term translation to the clinic. Our expertise. To achieve these goals, we are forming an interdisciplinary research team of neurobiologists, engineers and physicians. In preparation for this project, we were able to demonstrate for the first time the use of standard CI electrodes as in vivo chemical sensors in acute animal experiments to monitor intracochlear oxygen changes. Our unique approach. Building on this, we aim to realize our project goals – monitoring the intracochlear microenvironment, assessing electrode stability and its correlation with implant function and auditory perception – through a unique combination of innovative techniques such as novel electrochemical measurement methods, an animal model to study the effect of acute and chronic CI stimulation on the auditory system, deafness models and a unique behavioural setup to study auditory perception in CI rats. Vision. Our long-term vision is an optimal implantation process and permanent monitoring of CI electrode status, as well as early detection of pathological processes in human patients to improve CI safety and functionality and thus the quality of life of their users. Monitoring health status through next-generation neuroprostheses will reduce the burden on patients, e.g., through imaging procedures, especially for children.

• DFG Programme: Research Grants