Electrochemical in vivo oxygen sensing on cochlear implants

Cochlear implants (CIs) are the most frequently implanted neuroprostheses. Despite the clinical success of CIs, the processes actually occurring at the electrodes post-implantation remain unknown, and the majority of research is limited to endpoint analyses. Electrochemical methods offer the possibility of using implant platinum electrodes as sensor electrodes for in vivo measurements without the need for implant modifications. We demonstrated this possibility by sensing oxygen concentrations in a CI-supplied rat model using combined chronoamperometry and active potentiometry, supported by in vitro oxygen and hydrogen peroxide calibrations. Exploiting CIs as electrochemical in vivo sensors promises valuable insight into reactions of the microenvironment to the implant, such as inflammation and encapsulation. Furthermore, electrochemical methods such as cyclic voltammetry and reciprocal derivative chronopotentiometry offer the possibility of monitoring electrode conditions in situ.