The present invention features devices for treating hearing loss, methods of making the devices, and methods for treating hearing loss. The devices include cochlear implants with biological cells placed at least on one or more of the electrodes of the implant. The cochlear implants then bypass dead or damaged hair cells in the cochlea by directly stimulating the auditory nerve fibers leading to the perceptions of sound. The biological cells can extend processes from the implant to the brainstem, creating a bridge that transmits electric signals from the electrode to the brainstem more efficiently than traditional cochlear implants. Methods of making the implants include applying a composition containing biological cells to an electrode of a cochlear implant, and treatment methods include implanting a cochlear implant that carries biological cells on one or more electrodes into a human who has experienced profound hearing loss (e.g., sensorineural hearing loss).