Electrochemical Detection of Neurotransmitters: Toward Synapse-based Neural Interfaces

A synapse is an intercellular junction specialized for an electrochemical information process between presynaptic and postsynaptic neurons. At the chemical synapses, chemical neurotransmitters released from presynaptic membrane bind to receptors on the membrane of opposed postsynaptic neurons. The act of neurotransmitters not only instantly determines the types of neuronal signal, excitatory and inhibitory, but alters the genetic environments for long-term memory construction. As such, studies on neurotransmitters and the event of their release are essential to the understanding of neural function and plasticity in the brain. Electrochemical tools are powerful and suitable for the investigation of neural systems. Two major branches of electrochemical method, amperometry and fast-scan cyclic voltammetry (FSCV), are actively evolving for the detection of neurotransmitters in extreme conditions. Consequently, novel electrode materials and geometrical designs have been developed to overcome the limitations of selectivity and lifetime of the electrodes. Wireless and implantable systems have been developed for in vivo experiments. This review will focus on electroanalytical approaches for the direct measurement of the electrooxidizable neurotransmitters, while envisaging possibilities of synapse-based neural interfaces.