Contents I. Introduction
Neurotransmitters are endogenous chemical messengers that enhance, transmit and transduce signals between neurons [1]. They govern neurophysiological brain functions, including mood and cognition [2]. In addition, they regulate sleep [3], learning and memory [4], and diverse other brain functions. Altered neurotransmitter concentrations have been reported in several neural disorders including Alzheimer’s [5], Parkinson’s [6], Huntington’s [6], seizures [7], traumatic brain injury (TBI) [8], and mental disorders including major depressive disorder (MDD) [9], anxiety [10], obsessive-compulsive disorder (OCD) [11], schizophrenia [12], and other disorders [13]. Thus, quantitative neurotransmitter detection within the brain has the potential for novel monitoring and research in a wide variety of brain disorders [14]. Notwithstanding progress in neurotransmitter detection in the brain, is currently limited to the temporal and spatial resolution of current neurochemical sensing methods [15]. For example, conventional methods typically possess low temporal resolution, including brain microdialysis [16] (dependant on the speed of sample collection, generally /min), and high-pressure liquid chromatography (HPLC) [17] as it requires 5–15 min of collection [12]. In addition, capillary electrophoresis (CE) [18] and imaging mass spectrometry [19] are not real-time, time consuming, expensive and require specific sample preparation [14]. Furthermore, safety concerns make many traditional analysis techniques unviable when measuring neurotransmitter concentrations within the brain [16]. One class of techniques which is now showing potential for neurochemical monitoring is electrochemical evaluation.
