When technology enables hearing
Our senses are our constant companions in everyday life. For most people, hearing is something they take for granted, whether they’re in a conversation or listening to music. But what if everything around you is silent? What if you could never hear your favorite song or the voice of your favorite person again?
A cochlear implant allows people to relearn how to hear as long as their auditory nerve is still healthy. This greatly improves the quality of life for people with hearing loss. It’s important to note that these implants can be implanted in children as young as five months old. However, the implants currently last only about 20 years, meaning that the issue of reimplantation will eventually arise. For patients, this entails both physical and psychological stress. The risks of surgery, the danger that the implant will not be accepted by the body, or that damage will be caused during explantation are just a few of the possible complications.
Corrosion damages the implants
In addition to the medical aspects, the degradation of platinum due to electrochemical corrosion is the reason for the limited longevity of these implants. The individual electrodes responsible for stimulating the auditory nerve are made of platinum and are constantly exposed to electrical impulses. This leads to degradation of the platinum, which not only impairs function but can also trigger inflammatory reactions due to platinum deposits in the tissue.
Researchers at the Institute of Materials Science (IW) at Leibniz University Hannover are addressing precisely this problem. They are investigating the exact mechanisms of this platinum corrosion, the factors that exacerbate it, and how it can be prevented in the future.
In collaboration with the Department of Otorhinolaryngology at Hannover Medical School (MHH), the IW is working on subproject A05, “Sensory Cochlear Electrode,” within the SIIRI Collaborative Research Center to determine how implants can be designed in the future to maximize their longevity. Through the Collaborative Research Center/Transregio 298 SIIRI (Safety-Integrated and Infection-Reactive Implants) engineering solutions are applied to medical challenges in order to develop durable, smart implants.
Sensory gold electrode as an early warning system
Currently, patients with cochlear implants must undergo regular medical examinations, for example, to adjust the stimulation parameters. This may become necessary if the patient’s subjective perception of hearing with the implant deteriorates. The adjustment is non-invasive and is performed using electrochemical impedance spectroscopy and software specifically developed for this purpose. If a patient can no longer perceive certain frequency ranges well, the parameters must be readjusted. This is usually a sign that the electrode contacts are degrading due to corrosion or that tissue has grown over them.
In the SIIRI Collaborative Research Center, the research group at the IW is developing a gold electrode capable of detecting degradative processes. In this process, one of the platinum electrodes will be coated with gold in the future. A functional coating will be applied to this gold layer that can capture the platinum from the inner ear fluid, the perilymph. The platinum deposits on the surface of the gold and can be bound through chemical functionalization. If the impedance of these electrode contacts is then measured from the outside using electrochemical impedance spectroscopy, the researchers at the IW can very quickly determine whether corrosive processes have occurred. If this is the case, ENT specialists adjust the stimulation parameters accordingly so that the implants remain functional for longer. The major advantage here is that disruptive processes are detected early on, allowing for more controlled adjustments.
In addition to the degradation of platinum, inflammatory reactions also play an essential role in the implant’s functionality and the patients’ health. The research group at the IW, in collaboration with researchers from other subprojects within the SIIRI consortium, is developing an additional electrode coating that is coated with specific antibodies. This coating will be able to capture the proteins that are released during the inflammatory process.
Prototype for the cochlear implant of the future
While the IW has so far concentrated on researching the corrosion mechanisms and influencing factors of platinum degradation, the focus in the current second funding period of SIIRI is on the further development of the sensory gold electrode and the development of a functional and innovative cochlear implant prototype. The subproject team has already successfully demonstrated and published the functionality of the gold coating. In addition, this funding phase is entirely dedicated to transferring the technology to other implant systems, which means that the interdisciplinary collaboration – a hallmark of this Collaborative Research Center – will be further intensified.
For the third and final funding period, the researchers in the subproject plan to further develop and test the prototypes in collaboration with cochlear implant manufacturers in order to lay the groundwork for future regulatory approval. In addition, the developed models will be adapted to and tested on other implant systems, such as knee or hip implants. The interdisciplinary research conducted by Leibniz University and the Medical University offers unique opportunities to develop the implant of the future in Hanover, with the aim of further improving people’s quality of life.
