Platinum is currently used as electrode material in neuronal electrodes, e.g., the cochlear implant (CI). Apart from the stimulation of neurons by the electrode contacts, it is also important to restore and sustain healthy conditions in the cochlea. Neuroprotective and neuroregenerative drugs can be used to support remaining neurons and to induce the outgrowth of dendrites. For optimal application, these drugs should be released locally, i.e. employing an implant-associated drug delivery system. Due to the inertness of the materials from which the cochlea electrode is manufactured - platinum and silicone - the construction of such a system is not trivial. 

Here, we present a novel nanocomposite material, composed of nanoporous platinum (NPPt) and nanoporous silica nanoparticles (NPSNPs) as a novel implant-associated local drug delivery system which is generated as a coating on the surface of the CI electrode. NPPt exhibits high conductivity and favourable electrochemical properties. NPSNPs which are embodied in the pore system of the platinum offer a high surface area, large permanent porosity and a high versatility with regard to easily adjustable surface properties in order to accomplish a high drug loading.

For the generation of the NPSNP@NPPt material on the surface of the electrode contacts, a hard template approach was used utilizing silica-polystyrene core-shell nanoparticles as template particles. Platinum was deposited electrolytically between the particles and the polystyrene was removed. SEM investigations showed the successful synthesis of the desired structure of the nanocomposite. Cell culture investigations of the new material show a good cytocompatibility. Current work focuses on the chemical modifications of the NPSNPs in order to introduce specific surface functionalities which allow efficient loading and controlled delivery of drugs.