Flexible neural recording electrodes based on reduced graphene oxide interfaces

Conventional recording neural electrodes are made of stiff materials such as metal or silicon which triggers unwanted inflammation and does not provide intimate contact with brain tissue. Flexible neural electrodes have therefore been increasingly investigated to address these issues. In this study, we introduce reduced graphene oxide (rGO) recording electrodes in the format of 3-dimensional flexible membranes (rGO-3D) and 2-dimensional thin films (rGO-2D) for long-term and acute recordings, respectively. The rGO electrodes supported the functional development of cultured primary neurons and displayed good recording capabilities similar to conventional glass pipette and Pt ball electrodes in ex vivo and acute in vivo experiments. In vivo biocompatibility studies demonstrated the migration of neural processes onto the rGO-2D surface and within the rGO-3D electrodes, with the latter forming an intimate interpenetrating network. This study not only generates new knowledge to balance conductivity and porosity of rGO coatings but also provides in-depth evaluation of the physical and biological properties of such interfaces.