Studying neural interfaces in the Hybrid retinal implant project

Neuromodulation based on tissue integrated micro-electronic devices holds a great potential in restoring the functionality of degenerated organs. Specifically, retinal prostheses which are aimed at vision restoration for patients with retinal degeneration diseases, which are the leading cause of blindness in the western world (age macular degeneration and retinitis pigmentosa). These diseases are characterized by the gradual loss of photoreceptors cells, while the inner retinal layers are relatively preserved. In such cases electrical stimulation of the remaining viable neurons can enable vision restoration. Notwithstanding the promising reported results, the current retinal implants still provide low visual-acuity due to inherent limitations.

Our group is pursuing a novel retinal prosthesis concept, the hybrid-retinal implant, comprised of a high-density electrode array with 3D well like structures embedded with glutamatergic neurons aiming to neural activation threshold reduction by increasing the cell-electrode electrical-coupling. Thus, putatively increasing the spatial resolution while preserving the retinal neural circuits processing.

Herein we present the conceptual device validation through the fabrication process of such polymer-metal devices, followed by a thorough study of the implant biofunctionalization aiming to promote cell-adhesion, using various surface treatments. Next, we present in-vitro evidence of activation threshold reduction through electrophysiological investigations in both cell cultures and subretinal stimulation. Finally, the implant integration with the host retina is presented by OCT and histological assessment after in-vivo implantation in rat retinas.

This device has the potential to overcome the current retinal prostheses limitations and to increase the visual acuity of patients suffering from retinal degeneration.