Neurotransmitters-Key Factors in Neurological and Neurodegenerative Disorders of the Central Nervous System

Neurotransmitters are molecules that amplify, transmit, and convert signals in cells, having an essential role in information transmission throughout the nervous system. Hundreds of such chemicals have been discovered in the last century, continuing to be identified and studied concerning their action on brain health. These substances have been observed to influence numerous functions, including emotions, thoughts, memories, learning, and movements. Thus, disturbances in neurotransmitters' homeostasis started being correlated with a plethora of neurological and neurodegenerative disorders. In this respect, the present paper aims to describe the most important neurotransmitters, broadly classified into canonical (e.g., amino acids, monoamines, acetylcholine, purines, soluble gases, neuropeptides) and noncanonical neurotransmitters (e.g., exosomes, steroids, D-aspartic acid), and explain their link with some of the most relevant neurological conditions. Moreover, a brief overview of the recently developed neurotransmitters' detection methods is offered, followed by several considerations on the modulation of these substances towards restoring homeostasis.

An electrochemical sensor based on an anti-fouling membrane for the determination of histamine in fish samples

Electrochemical determination of histamine (HA) is quite challenging owing to the high oxidation potential and electrode fouling from HA oxide polyhistamine, which leads to poor sensitivity and unrepeatable measurement. In the present work, a simple, sensitive and repeatable electrochemical measurement of HA was developed based on a Nafion and multi-walled carbon nanotube (MWCNTs) composite membrane modified glassy carbon electrode (GCE). Compared with the bare GCE, the Nafion and MWCNT composite membrane modified electrode significantly enhanced the oxidation peak current and reduced the peak potential to 1.12 V (vs. SCE). Moreover, the characterization of the modified electrode by XPS and EIS showed that polyhistamine scarcely deposited on the composite membrane of the modified GCE, which made it possible to realize repeatable electrochemical measurement of HA. The electrochemical oxidation behavior of HA on the modified electrode was studied by differential pulse voltammetry (DPV). The oxidation peak current has linear and natural log-linear relationships with HA concentration in the range of 20-200 μmol L^-1 and 0.5-10 μmol L^-1, respectively. The detection limit was 0.39 μmol L^-1 (S/N = 3). The modified electrode could be used to determine 100 μmol L^-1 HA ten times repeatedly; the peak currents in consecutive runs were all above 95% of the initial response. This method was also successfully applied to the determination of HA in fish samples and recoveries ranged from 98.2 to 101.2%.

"Nano": An Emerging Avenue in Electrochemical Detection of Neurotransmitters

The growing importance of nanomaterials toward the detection of neurotransmitter molecules has been chronicled in this review. Neurotransmitters (NTs) are chemicals that serve as messengers in synaptic transmission and are key players in brain functions. Abnormal levels of NTs are associated with numerous psychotic and neurodegenerative diseases. Therefore, their sensitive and robust detection is of great significance in clinical diagnostics. For more than three decades, electrochemical sensors have made a mark toward clinical detection of NTs. The superiority of these electrochemical sensors lies in their ability to enable sensitive, simple, rapid, and selective determination of analyte molecules while remaining relatively inexpensive. Additionally, these sensors are capable of being integrated in robust, portable, and miniaturized devices to establish point-of-care diagnostic platforms. Nanomaterials have emerged as promising materials with significant implications for electrochemical sensing due to their inherent capability to achieve high surface coverage, superior sensitivity, and rapid response in addition to simple device architecture and miniaturization. Considering the enormous significance of the levels of NTs in biological systems and the advances in sensing ushered in with the integration of nanotechnology in electrochemistry, the analysis of NTs by employing nanomaterials as interface materials in various matrices has emerged as an active area of research. This review explores the advancements made in the field of electrochemical sensors for the sensitive and selective determination of NTs which have been described in the past two decades with a distinctive focus on extremely innovative attributes introduced by nanotechnology.