Graphene Encapsulated Copper Microwires as Highly MRI Compatible Neural Electrodes

Magnetic resonance imaging (MRI) compatible neural electrodes are important for combining high-resolution electrophysiological measurements with more global MRI mapping of brain activity, which is critical for fundamental neuroscience studies, as well as clinical evaluation and monitoring. Copper is a favorable material to use in MRI because it has magnetic susceptibility close to water and tissues. However, the cytotoxicity of copper precludes its direct implantation for neural recording. Here, we overcome this limitation by developing a graphene encapsulated copper (G-Cu) microelectrode. The toxicity of copper is largely eliminated, as evidenced by the in vitro cell tests and in vivo histology studies. Local field potentials and single-unit spikes were recorded from rodent brains with the G-Cu microelectrodes. Notably, the G-Cu microelectrodes show no image artifacts in a 7.0 T MRI scanner, indicating minimal magnetic field distortion in their vicinity. This high MRI compatibility of our G-Cu probes would open up new opportunities for fundamental brain activity studies and clinical applications requiring continuous MRI and electrophysiological recordings.