Advancement of the Electrochemical Performance of Stainless-Steel EEG Electrodes by Functionalizing with Carbon Nanotubes and Antibiofouling Molecules

Understanding brain function and neurological disorders are essential to develop therapeutic strategies such as neuropharmacological medications and implantable biomedical tools to treat brain-related disorders. Implantable neural electrodes can deliver in-depth knowledge of brain activity and disorders by recording real-time brain signals. Epilepsy is an electrophysiological brain disorder caused by genetic factors or a brain injury. Electroencephalography (EEG) is a standard technique that provides more specific information about epilepsy. Both invasive and non-invasive EEG electrodes are used to study epilepsy and possess high temporal resolution. Invasive EEG electrodes are useful for localizing the brain's regions where epilepsy arises. EEG electrodes are mainly metal-based electrodes. Stainless steel, platinum, gold, tin, and silver are commonly used metals. Electrode material plays a critical role in the accuracy of the brain signal measurements and consistent performance in chronic applications. Stainless steel EEG electrodes are successfully used in EEG signal monitoring in vivo; however, stainless steel can undergo chloride-induced corrosion and biofouling over time. Corrosion and biofouling can negatively affect the impedance of the EEG electrodes resulting in poor signal recording and inconsistent performance. The current study reports the advancement of the performance of stainless-steel EEG electrodes by functionalizing with vertically aligned carbon nanotubes (CNTs) and zwitterionic phenyl phosphorylcholine (PPC) molecules. CNTs are conductive and biocompatible nanomaterial which have been successfully used for neural interfacing applications. The results show that the electrochemical performance of the EEG electrodes was significantly improved after functionalization with vertically aligned CNTs. Electrochemically grafting of zwitterionic PPC molecules onto CNTs further improved electrochemical performance and introduced anti-biofouling properties.