High surface area carbon microelectrode for neural microstimulation and neurochemical sensing

Brain disorders are recognized as a relevant global healthcare issue. Among the greatest challenges that are part of scientific world, understanding the functioning of the human brain, especially if injured, has been an object of interest and continuous study for years. Its enormous complexity has always fascinated research especially for the disorders and pathologies that afflict it in order to be able to know it’s organization and progress with the development of tools aimed at favoring diagnosis and treatment protocols, not yet defined today. The most important goal, refers to provide a clear communication with the brain to restore its damaged neural functions and to treat psychiatric and neurological disorders. Mental health disorders such as depression, bipolar disorders or schizophrenia and neurodegenerative disorders such as Parkinson, affect and compromise the lives of millions of people worldwide. For this reason, attention has been focused on the development of technologies capable of monitoring, recording, stimulating, highly selective and sensitive. In particular, neural engineering has focused on the design of neural interfaces such as electrodes, to enable bidirectional access to the brain, i.e. to record electrophysiological and chemical signals and stimulate the neurons. An ideal microelectrode, must be miniaturized and achieve a robust and suitable incorporation with the environments of the nervous systems. The relevant application of this cutting-edge technologies deals with neurotransmission which, if malfunctioning, causes negative effects to the brain. The study of these tools focuses on measures of neurotransmitter development, in vitro and vivo, in different areas of the brain to highlight the mechanisms that are created when affected by injury. The main objective of this thesis is testing the electrochemical performance of high surface area carbon (HSAC) microelectrodes manufactured using an innovative laser technique (LINC) and on substrate flexible polyimide. In order to obtain a sensor suitable for an application of this type, experiments are conducted in vitro to analyze and evaluate it’s strengths as well as its limits since an electrode must respect various requirements for it to be reliable and performing. First, the electrochemical properties of the LINC electrodes have been evaluated, through Electrochemical Impedance Spectroscopy and Cyclic Voltammetry. Subsequently, the experiments branched out on two different purposes: stability for microstimulation and sensitivity for neurochemical sensing of dopamine. As for the former, long-term electrochemical stability has been explored and quantified under aggressive and daily electrical stimulation. Regarding the second purpose, LINC electrodes obtained with different conditions were tested to evaluate the sensitivity of different dopamine concentrations, using Square Wave Voltammetry. Finally, doped microelectrodes of different heteroatoms, mainly boron and sulfone groups, were tested and investigated for dopamine sensitivity and with the aim of exploring different ideas for the realization of these promising microelectrodes. Excellent performances have been obtained following the experiments carried out and although the methods examined have not yet been implemented in vivo, they are promising sensors for future experiments in vivo and revolutionary in the diagnosis and treatment of brain disorders.