Clinically Relevant In Vitro Model for Chronic Electrical Stimulation and Long-Term Evaluation of Cochlear Implant Electrode Functionalization

Cochlear implants (CIs) electrically stimulate auditory neurons for many hours daily, exposing implant materials to chronic electrical stimulation (ES). Clinically relevant in vitro models are therefore essential for preclinical evaluation of CI electrode functionalization. We developed an in vitro set-up that simulates CI use by enabling chronic, acoustically evoked ES, impedance monitoring, microscopic inspection of electrode arrays, and ISO 10993-12–compliant supernatant sampling. CI processors were stimulated for 16 h per day, while receivers and electrodes were operated under physiological conditions in an incubator. Custom-made components allowed parallel testing of three CIs, full immersion in artificial perilymph, and in situ observation. The system was stable over several weeks and yielded clinically comparable impedance values.